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Page i Frontispiece Page ii Title Page Page iii Page iv Table of Contents Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Main Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 26-1 Page 26-2 Page 26-3 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 32-1 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 62-1 Page 62-2 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 80-1 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 94-1 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112 Page 113 Page 114 Page 115 Page 116 Page 117 Page 118 Page 119 Page 120 Page 121 Page 122 Page 123 Page 124 Page 125 Page 126 Page 127 Page 128 Page 129 Page 130 Page 131 Page 132 Page 133 Page 134 Page 135 Page 136 Page 137 Page 138 Page 139 Page 140 Page 140-1 Page 141 Page 142 Page 143 Page 144 Page 145 Page 146 Page 147 Page 148 Page 148-1 Page 149 Page 150 Page 151 Page 152 Page 153 Page 154 Page 154-1 Page 155 Page 156 Page 157 Page 158 Page 159 Page 160 Page 161 Page 162 Page 163 Page 164 Page 165 Page 166 Page 167 Page 168 Page 169 Page 170 Page 171 Page 172 Page 173 Page 174 Page 175 Page 176 Page 177 Page 178 Page 178-1 Page 179 Page 180 Page 181 Page 182 Page 183 Page 184 Page 184-1 Page 185 Page 186 Page 187 Page 188 Page 189 Page 190 Page 191 Page 192 Page 193 Page 194 Page 195 Page 196 Page 197 Page 198 Page 199 Page 200 Page 201 Page 202 Page 203 Page 204 Page 205 Page 206 Page 207 Page 208 Page 209 Page 210 Page 211 Page 212 Page 213 Page 214 Page 215 Page 216 Page 217 Page 218 Page 219 Page 220 Page 221 Page 222 Page 223 Page 224 Page 225 Page 226 Page 227 Page 228 Page 229 Page 230 Page 230-1 Page 231 Page 232 Page 233 Page 234 Page 234-1 Page 235 Page 236 Page 237 Page 238 Page 239 Page 240 Page 241 Page 242 Page 243 Page 244 Page 245 Page 246 Page 247 Page 248 Page 249 Page 250 Page 251 Page 252 Page 253 Page 254 Page 255 Page 256 Page 257 Page 258 Page 259 Page 260 Page 261 Page 262 Page 263 Page 264 Page 265 Page 266 Page 267 Page 267b Page 268 Page 269 Page 270 Page 271 Page 272 Page 273 Page 274 Page 275 Page 276 Page 277 Page 278 Page 279 Page 280 Page 281 Page 282 Page 282b Page 283 Page 284 Page 285 Page 285b Page 286 Page 286b Page 287 Page 288 Page 289 Page 290 Page 291 Page 292 Page 293 Page 294 Page 295 Page 296 Page 297 Page 298 Page 299 Page 300 Page 301 Page 302 Page 303 Page 304 Page 304b Page 305 Page 306 Page 307 Page 308 Page 309 Page 310 Page 311 Page 312 Page 313 Page 314 Page 315 Page 316 Page 317 Page 318 Page 319 Page 320 Page 321 Page 322 Page 322b Page 323 Page 324 Page 325 Page 326 Page 327 Page 328 Page 328b Page 329 Page 330 Page 331 Page 332 Page 333 Page 334 Page 335 Page 336 Page 337 Page 338 Page 339 Page 340 Page 341 Page 342 Page 342b Page 343 Page 344 Page 345 Page 346 Page 347 Page 348 Page 349 Page 350 Page 351 Page 352 Page 353 Page 354 Page 355 Page 356 Page 356b Page 357 Page 358 Page 359 Page 360 Page 360b Page 361 Page 362 Page 363 Page 364 Page 364b Page 365 Page 366 Page 366b Page 367 Page 368 Page 369 Page 370 Page 371 Page 372 Page 373 Page 374 Page 375 Page 376 Page 377 Page 378 Page 378b Page 379 Page 380 Page 380b Page 381 Page 382 Page 383 Page 384 Page 385 Page 386 Page 387 Page 388 Page 389 Page 390 Page 390b Page 391 Page 392 Page 392b Page 393 Page 394 Page 395 Page 396 Page 397 Page 397 Page 398 Page 399 Page 400 Page 401 Page 402 Page 403 Page 404 Page 405 Page 406 Page 406b Page 407 Page 408 Page 409 Page 410 Page 411 Page 412 Page 413 Page 414 Page 415 Page 416 Page 417 Page 418 Page 419 Page 420 Page 421 Page 422 Page 423 Page 424 Page 425 Page 426 Page 427 Page 428 Page 429 Page 430 Index Page 431 Page 432 Page 433 Page 434 Page 435 Page 436 Page 437 Page 438 Page 439 Page 440 Page 441 Page 442 Page 443 Page 444 Page 445 Page 446 Back Cover Page 447 Page 448 |
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jl ~ ---~ DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY SOGEORGE OTIS SMITH, DIrzCTOo WATaR-SUPPLY PAi a 819 GEOLOGY AND GROUND WATERS OF FLORIDA BY * GEORGE CHARLTON MATSON AND SAMUEL SANFORD PreparM d in cooperation between the United 8tate Oeological Survey andthe Florid Geological Surey, under the direction of Thomas Wayland Vaughan - .8. WASHINGTON GOVERNMENT PRINTING OFFIOB 1918 L 671 (j12 S S S S S" SRODUC ION...................................... r I.---GOCIAPHY ............................... North and central Florida, by G. C. Mtn... Nature of country........................... R elief ................. ... .. ... .. Dr nage ........................ ........ River................................ ak and wnp...................... Topographic provinces.................... Characteristic feature -. Soils. Upland or lake region............ ... .. ..-....1 _.......... Underground drainage................ .................. Caverns............................... ......... Sink holes............... ........................ Natural bridges..................................... Spring ..... ......... ...... .................. :. ..... feature ........... ..... .......... Lakes........ ....... ......... .... ......... Sand dune ............. ..... .. ........ ......... Iowland....................... ..... ..... St and ponds......... ............................. idg ..... ........... ........................ nddune................ ........ ................ Terraces................... ....................... General feature.................................... ewbe y ter ............. .. ....... ........... ala pop terrace................................. Penacola t e.e............ ................ The coast................................. ................. Coral reef-................... .. ........................ Submerged continental border ................ .......... Bar .......................................... Sounds............... ............. Inlet ............... .... ... ................ Tidal runways.......................................... Cape .............................. ......... .......... Origin and character................... ............ Soil types.................. ......................... th Florida, by auel Sanford ........................ Lo tion a d ................ ................ ...... G e l feature .................................. ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pags. 17 21 21 21 21 23 23 25 25 25 25 25 26 26 28 29 30 30 s0 o30 31 31 31 31 31 32 33 34 35 35 35 37 37 38 38 38 39 39 40 42 42 42 ... 2 OONENTS PARr I.--GnoonGA r-Continued. southern Florida, by Samuel Sanford--Continued. The mainland ............ ...............-- -----....-----... -- 4 Subdivisio.ns .................. .. ...... ................--- 4 Pineland ..................... .. ....................... 4 rea and dis t ........................... *...... 4 Dunes.......................... ......... ......----- .... 4* Chara te.. ..... .... . ....... - .... 4 Distribution .. ............. ....... ----..--- --. 47 Rolling snd plains............... -- ...- --...... -- Fla .la d .. .......... .............. ........... - - - ock ri~d ....... ..............................- ..... - s e........... ... ..... - ........................ Controlling condition..................................... CE glad s .......... ............. ................ - - - Extent........................ ...... --............- .....- - Elevation and drainage.............. .................. TeF ori r ............................................... Bedr ck... ............ .. ...... ..... ................- - Oc rigin ....... ........ .......... ...............--. N e l F o ..............rd................................. .......... Cypress wamps ............. -................ -5 - C tl e ....mp............. .............................. ----- The keys ..... ......... .....-- -- -.......... -- --.. .-----. .- neral character............... ... .......... *------ - The orida reef............ .... ... ... ........... 1 The uhore line. .............-.....- ---- --.. ------- Ocean currents.. .......... -. --- --- - - ParT II.-GEOLOOY ............----- -------*- *...**........***- Northern d central Florida, by G. t ......................... Geologic record.......... -.....--........... .-.-..---.- 6 Geer ucc on of formations ...... ..................... Tertiry sysem................... ................ 71 Ohlgocene re....... - - - - - se- - - - - - - e - - 71 oSubd ivis iones..... ....- .... - - - - .. 71 Viclbug group.............--..-...---.....-... ----. .. 71 Nomenlature ....................................... 71 Maiannand Peninular" limestones................. 73 Stratigraphicposition............................ 73 Litholie cha e ............................... 73 Thickness.................... ................... 73 hy ph expr on ........................... 74 aleotologi character............ ... ........ 74 tr ctu ......... .. .... .....--- -....... ...... 74 Aral distribution ............... ... -........... 7 Ocala limestone........-..--------.--... ----- ------... 79 Nomenclature ................ ---- ----------..... 79 Stratrap position ........- - - - - --- ..... so logie character............- - ....... 81 Thicees. ....... ....----- ------.----. -.... 81 hyographi expreion.......................... 81 P~aleontoloi.cha ..cter.........- - - - -....... gg truture..........--...------------- -- --... 82 Areal distribution...........-..-..--- -----........ 8 "Miliolite limestone" .,......--.-...-..--...... a CONTENTS. PAar Il.---GoLooY--Coltnue Northern and central Flrida, by 0. Matson--Ontinued Tertaia sytem-Oontinued. Ohgocene aerce-~-Continued ion group...................................... o enclature....................................... wthrn i for tion................................ General character.............. ........... tigrphic potion............................... Lithologic character............................... Thiknes i ............................... Paleontologicarac.. ........................... S curer .......... ........................... Areal distribute ....... ........ ............. athoohee formation.............................. Nomenclature.................................. tratigraphic potion........................... Litolgic c arac.... ............ ................. Thicknes..... .............................. Phyiographic exre ......... ................ Paleontologic character........................... Structure... ...... ............... .......... al dtribution ................................ Tampa formation........................... ..... C ctr and nomenclature ........................ Aiphc position............................. Lithologic character............................ Thick;n~ .....e........... .. ..... .............. Phlysographic expr on .......................... aleontologic charaer............... .......... S~tulcture ................... ................. trl dteri........................................ Alu Bluff fo ti ................... .............. S rtigraphic position................. ........... Lithologic charactr............... ........... e kneh .. ....... .......... . .............. Physiographic expre son......................... aleontologic character............................ r .......... ........ .......... Structure. ................................... Area distribution................................ Chipola marl member............... ........... Oak Grov d memb .......................... Shoal River marl menmber..... .................- scene ar............................. Nomenclature and abdivi .......... a~nuville formation.................... Sra phc potion................ Lithole ch mter.............. hicka e .... ................... Phyj grphie expreion............. leontologic charact.............. Stiucture........ ................. Sdribution ................... 85 86 87 87 88 89 89 89 89 90 95 108 108 98 94 96 95 96 98 96 102 102 105 108 104 104 104 105 108 108 108 109 110 111 111 111 111 117 119 120 121 121 123 128 128 126 125 126 126 128 .................. ...... -............- ..................- ...... ............ - ..................- .................. I ............... .................. - ........ ........ 4 CONTENTS. PART II.--GtocLo--.Continued. Northern and central Florida, by G. C. Mato--ontinued Tertiary sytem-Continued. iocene ei--Continued. P Choctawhatche marl .................................... 127 Stratigraphic position .................................. 127 Lithologic character................................. 128 Thickne ....... ......... ... ............... ...... 129 Phyiographic expr on............................... 129 Paleontologic character .............................. 129 Structure............................ ............ 130 Real distribution................... .............. 130 iocene erie.......................... ......... ....... 133 Calooeahatchee l...... .....................a.... 134 Nomenclature....................... .............. 134 Stratigraphic position ................................ 134 Litologic character................................. 135 Thicknee ........ ....... ... .. .............. 135 Physiographic expreion.............................. 135 Paleoto c character............................... 135 Structure................ ....... ................ 135 eal di ribution ................ ..................... 136 Nahu mar....................... .............. 138 Discrimination ........................................ 138 Stratigraphic position ................................. 139 Lithologic character.................................. 139 Thickno e ........ .... .. ..................... 139 Physiographic expreion ............................ 139 Paleontologic character............................ 139 Structure................................. .... 140 Aral ditribution ................. ................. 140 Alachua clay .............................................. 141 Depo tion .......... ........................... ... 141 Stratigraphic position ................... .......... 142 Lithologic character ................................... 142 ThicLk ea ................ ...... ............ .... 142 Physiographic expreion.............. ............. 142 Palontologic character.. .......... ............ 142 Structure........................ ........... .......... 143 Areal distribution ..................................... 143 Bone' gravel........................................ 144 Nomenclature..................... ................ 144 Stratigrphic poitio...... ..... ............ 145 Lithologic character................................ 145 Thicknes........................... ............... 145 Phyogrphic expre ............................. 146 Paleontologc cha racter..... ....................... 146 Structure... .................. .. ....... ............ 146 Areal ditribution.................................... 146 Pliocene (?) erie .............................................. 146 afaytt (7) fo ation...........-....-.....- .......... 146 Correlation.............. ........ .............. 146 tratigraphic position.................---............ 147 CONTENTS. PART I I.-G-EOLOG, -Continued. Northern and central Florida, by C. Matn---Continued. Tertiary ystm--Continued. Plicene (?) seris--Continued. Lafayette (?) formation-Continued. Lithologic character................................. Thickn es ... .......... .... ....................... Phyiographicexpression............................. Pal~ontologc character ................... .......... Structure...... .......... ... .... ............... Areal distribution.................................. u atera ry system ................................................ Subdiviions........................... ..... ............... Pleistocene ri............... ......................... Subd vision ...................................... ....... Fo liferou marls....... .......... ................ Gray nd ....................................... "Planorbi marl" ................................ Coquina..... .............. .............. "Venretiu rock ............................... Yellow clay...................... ... ........... Stratigraphic position .............................. Thile ....l.. ................... ............... Phyiogphic expression.............................. alontologie character ................ .. ............ structure. .............................................. eent eies .. ........................................ Alual deposits................ ... .. .......... ncustrine deposits............... .....-_. "Veretu rock"....................................... Coter reefs................ ...... ................... Coral e ............ ... ........ ........... Baho l deposit. ................... ................. E ian dep .. ......... ........ .... ................ Human remains... -- -- ------ Structure........................................ Early ivet ................... .......... General character................................ Southern Florida, by Samuel Sanford................... Str igr phy.................. .................... Peitocene formation...................... haractr and dtribuion ................... Well records.................. ........ Distribution of wells................... Palm Beach........................... Indian Key Channel..................... Key V ................ ............. nigh Key .......................... Big ine Key............................ Key Wet................. ........... Buck ey.............................. Oligocene series............................ Miocene and Pliocene series.................. Page. 147 148 148 148 148 148 150 150 151 151 151 1564 165 156 156 156 157 158 158 158 158 159 159 160 160 160 160 160 161 162 ..... 163 ........ 163 ........ 165 ........ 167 ........ 167 ........ 167 ........ 167 ........ 167 ........ 167 ........ 168 ........ 168 ........ 169 ......... 170 ........ 170 ........ 170 ........ 172 ........ 173 .... 173 CONTENTS. PART II.-- soL--oor---ntinued southern Florida, by Samuel -nord-Continued. Stratigrphy---Continued. Pleitcene erine ............... ................. .......... Unexposed formation ............................... Exposed fornation.............. ...... ............. General character.................................... Pal Beach limetone................................. Synonymy........................................ S raphi position.............................. Lithologic ha ter............................. Thickneee.. ............... .................. Physiographic expresion........................... Paleontologiichara r................... ........ Areal ditribuion............................... Structure. ................. .... .... ......... Miami oolite................ ...................... ynonymy.................... ................. ~tratiS phic p~ition .............................. Lithologic charcter.............................. Thlicrmne Phyaig .p .... ........... ....... Physiographic expremion.................... Paleontologic character..................... real ditri . . ution.. . . . . . . . . SCrreationu ............................ Correltion.................................. Origin ............. . ....... y WeOt polite ............................... itol . . . . ........................ Thickness............................. ..... Phyiogrphic epreeiion..................... aleontologic character .............. Origin. ................................... Chemical character .......................... Key Largo linmetone.......................... Synonymy... ............... ........... trataphic iion .................... .. Lithologic character....... .............. Thicl .............. ............ Phyographic exp ion.................. Paleontologic character..................... Areal distribution................. ...... tma River etone........................ Synonynmy................................. tratigrphic iion ....................... Lithologie character......................... Thicknl e ...................... ........ ... Areal ditribution........................ Origi ... ............ ........ .......... orrelaion of Pleistcne fo aon .......... .... Lithology of Pleistocene beds....................... Coq ina........................................ Sand. ..........s........ ......... ......... Pa4. 174 174 175 175 175 175 176 176 176 176 177 177 177 177 177 178 178 171 .... 179 ...... 179 .... 180 ...... 180 ...... 180 ...... 180 ...... 180 ...... 180 ...... 18 ...... 184 ...... 181 ...... 181 ...... 182 ...... 18 ...... 182 ...... 184 ...... 184 ...... 18 ...... 186 ...... 186 ...... 187 ...... 1 ...... 190 ...... 191 19...... 189 ...... 191 ...... 191 ... .. 19 CONTENTS. Pr II.--- oLooT-Continued southern Florida, by Samuel Sanford-Continued tiraphy---Continued. Pleistocene aerie-Continued. Lithology of Pleiatocene beda--Continued. Pte. Malde................. .......... 194 M .ara.......................... ....................... 194 Bume aryri .............. ........... ........ ... 19 Thner l of there .............................. 194 Recent seri.. .............. ...... .. ................... 195 General cha.. ct....... .......................... 196 eat ............. ~..... .... .................. 19 r .... ................... ........... ...... ... .. 196 Sad c ............................................ 198 Cora ............................ .. ............ 19 m .rock.. ............... ....... .. ............... 198 Outer b. ................. ...... .................... 198 Geolic history, by G. C. aton and Samuel Sanford.................... 199 Data ........................................................... 199 Oligcene epoch. ........................ ...... ............... 199 Vickburg epoch............................................. 199 Emegence........................... .. ..................... 201 Aplchicol epoch ................. ................... 202 ioene epoch....................... ......... .............. 203 Phyogphic changes........................................ 203 Depo ition..................... ......... ...... ............ 204 PlH ne epch................................................. 205 Phyographic changes........................ ............. 205 Deposttion......................20.. ........... 20 leitoene eoch ................................................ 207 Uplift ................................... ................. 207 Subo.rgnen ............... ......... ................... 209 Terrace....................... .......... ........... 210 Southern Florid........................................... 211 ecent epoch.. ... ............ ........ ...... ................... 212 Northern and central Florida ................................... 212 herFlorida........................................... 214 To.pc.ap.hi ch. n.............. ..... .............. 216 PA R III.--U B OE n wATEIn ...................................... 219 Gnel featur, by G. C. aton................... ............ 219 Soure............................................. ....... 219 Amount......................................................... 221 In the erth a whole......................................... 221 In Florid............ ................................... 221 Evap .... ............................. ...... .......... 222 epth ... ... .. .... ..................... ... .............. .. 224 W ate tble...................... ... ........ ................ 224 Depth of able p ....................................... 225 Cicuatio ......................... . ... . ............. 227 Reov ry ........................... ......... ... ............... 228 Natural recover......................................... 228 eepage..................... ....... .. ..... ....... 228 paing....................................---- ...........--- 228 8 CONTENTS. PAur II. UNEc RGROUND WAe -Continued. General features, by G. C. Maton--Contnued. Recovery--ontinued. . Artificial recovery ........ .................... ............. 229 W ells.......................... ... ........... ..... .... 229 Typest............................................ 229 Position........... ........... ... ........... 230 Methods of well making................................. 231 Dug wells....................................... 231 Bored wells....................... ............... 231 Driven wells ...................................... 232 Drilled well ...................................... 232 Methods of raising water .............................. 233 Central and northern Florida, by G. C. Matson........................... 234 Artesian water.................................................... 234 Artesian requisites ............................ .............. 234 Head.................... ......... ...... ..... 235 Controlling factors............................. ........... 235 Head in Florida ............................... .......... 236 Eat coast .............................. ............ 236 Interior ............................... ................ 237 Southern Florida ...................................... 237 W et coast.................. .... .. .............. 237 Chang.... ............ ....... .... ................ 237 Natural causes...................... .............. 237 Artificial causes ................. ........... 239 Artesian fallacies .......................................... 241 Occurrence ................... .... ................. 242 Water-bearing materials ..................... ................ 242 Character ............ .. ..... ................ 242 Sand and gravel ............... ..................... 242 Clay........... .................... .............. .. 242 Shell ma.rl .............. .... .............. 243 Limestone................ .... .................. 243 Wter-beaing formations ..................................... 243 Governing conditions...................................... 243 Oligocene seri e............. ................... 248 Importance 4......................... ........... 248 Limestones of the Vickburg group ..................... 248 Chattahoochee formation......... .................... 249 Hawthorn formation................................. 249 Tampa formation....................................... 250 Alum Bluff formation ............................... 250 Miocene series ..................................... 251 Chaacter.............. ............................ 251 ksonville formation.................................. 251 Choctawhatchee marl................................. 251 Pliocene seriea......................................... 252 General conditions................................. 252 Nahua and aloo atchee ma ....................... 252 Alachua clay.......................................... 252 Bone Valley gravel.................................... 253 Pliocene (?) series...................... ............... 253 Lafayette (?) formation............... ............. 253 Pleistocee and cent series ............................ 253 CONTENT8S9 PAr III--UNDEROuND WATr -Continued. Cental and northern Flord-Continued. Pag Public water sppli ........................................... 254 8urfe and undrgrond waters of southern Florida, by Samuel Snford.. 25 ource ........ ..... ......... .... ...... ..... ................ 255 Water bl................................................... 255 Spring .............. .... ...... ........ .............. ... .. 256 Water-bearing fo tio ......................................... 258 Oligocene.............. .. .... ........................ 258 iocene and Pliocena ............... ................. 258 Pleitocene ........................ ......... ....... .... 258 rtean water ..................... ........................ 259 Quality......................... ................. ............. 259 laios of sh and alt water underground...................... 261 PAr IV.--CorUmr D o rI N ..................... .............. 263 Alchu County, by G. Maton...................................... 263 General features,..... ............. ... ....... ............. 263 Geology ....................... ............... 263 Water supply............... ..... ........................ 285 Source ................................. ................ 265 uality............... .............. ...... .... .......... 2 Development ............................................... 26 county, by G. C. Matson.................. ............... 267 General fe ture .................... .............. ........... 287 Geology...... ........... ............ 267 Water upply............................... .................... 268 Source. ........ ........ ........... .............. 268 Quality...................... ................ 268 Development................... ............... 268 Bradfod County, by G. a n................... ........... 269 General features ............... .......... ... .............. 269 Geologic fo on ............................................. 269 Water supply....................................2.............. 270 urce ..................... ............................ 270 Quality................... ........ ... ................. 270 Development .................................. ............... 270 Brard County, by G. C. M on.................................... 273 General ftur ................... ........... ............. 273 Geology .. ............. .... .... ............................ 273 Water upply................................... ............... 275 ySurce.................................... ............. 275 Quality................ .............. ...... ......... ......... 275 Dvelopmnt.. ................................................. 275 un County, by G. Matson.................................... 277 General feature................. ........ .................. 277 ter...................................................... 278 a upply..................................................... 278 Source...................................................... 278 Qu ... ..... .... ... ... .......................... ........ 278 Development .................... .............................---- 279 iru County, by G. C. Matson...... ................................- 280 Gen rl featr .......................... ....... ..... ..... ....... 280 Geology........................................................... I...280 1l CONITNTh. PART IV.-COUNTY DESCRIBE rONS--Continued. Citrus County, by G. C. Matson--Contnued p W after supply ............................................ ..... 281 Source.............. ...... ............ ... ... ......... 281 Quality .............................................. ....... 281 Development ................................. .............. 281 Clay County, by G.. C Mton.............................. ......... 283 General feature ................................... .............. 283 Geology ............................................ ............ 283 W after supply.. ..... .... ................ ........... .... 28 Source.................................................. 284 Quality ..................................................... 284 Development .................................................. Col County, by G C. Matso.................................... 2 General feature....................... ..................... 28 Geology................ .................................... 28 aterupply................................................... 287 DSource. ...................n............................. 287 Quality ....................................... ............... 287 Developmentt.................................................... 287 e County, by S el Sanford....................................... 288 General featuree........................ ....................... 288 Geology ...................................................... 288 ter supply ........................................ ............ 289 e Sur.ce ....... ... ......................... ........... 289 Sprin ...... .................... .... ....... 289 W ell.......... ....... ........... ..... .... ................. 289 Artesian prospect............................................. 292 De oto County, by .. .Matson..................................... 294 General featule................. ............. ............... 294 G ology..... .......... .. ...... ............. ............ 294 atr pply...................... .................... ......... 295 oure................... .... ............................... 295 evelopmey.................................................... 295 etelomen ..................................................... 29 uv outy, by C. ... ......................................... 2. S Sources....................................... ....... 29 quality ......................... ...... ............ .. Dever lyopm.......................................... ...... a iaount......... ......M....................................... 0 General fat................................................... 0 Devoyelopment.......... .................................... 0. E ol uty, by C. ............................ ................. 01 W.er upy. ...................................... ......... 0. e ogy ................ .................................... ... Water lu .................................................. 34 o ................... .................. ................. 304 Quality... .................... .......................... 304 Development.............. ............................... 304 Franklin County, by G. Matson .................................... 05 General f ur ................... .............................. )5 Geology ........................ ....................... .......... 805 CONTEN~. 11 PAEr IV.--CorTnt pnlaaflro-s-Conti ued P in County, by G. C. Mataon--ontinued. ge. Wtrupply................................................... 30 Source........ ........ .................. ............... 306 Quality .... ............. .... ..... ...... ... ............ 306 Development......... ............ ..................... 306 en County, by G. Maton...................................... 308 Generfatur ...................... .......... ........ ...... 308 Geology ................................... ...... ............. ter supply ........................... ........................ 310 Source...... ........ .. ..... .. .. ........ ........... 310 uality.......................... ............................. 310 Development................................................ 310 H iton County, by G. C. on.................................. 312 Gene ftu ................................................. 312 Geology .... ............. ....... .... .. ... ...... ............... 312 Water supply........................ ....................... 313 Sour e........................... .......... ................ 313 Quality........................... .......... .............. 313 Development......... ....... .......... ............ 313 ndo County, by G. C. Mt ............... ... ............ 316 G eral featu .................................................. 316 Geo.logy. ..... ........................... ................ 316 ter uppl........................ ....... ................ 317 orce.................... ....... ...................... 317 Quality................................ ...... ............. 317 evelopment........................ ........ ............... 317 l o Couty, by G. C. Maton................... ............... 319 General .u ................. .. ...... ..................... 319 og............................ .............. 320 after upply................................... ................ 322 Source ............... ......... ....... ............ 322 Qualiy....... .......................... ................ 322 Development..... ....................... ................. 322 So ty, by ..... ...................................... 325 ral featu ........................................ ........... 32 Gology ..................... .......................... 326 water pply................................................. 326 oure ................ ................................... 326 Qulity... .................................. ................... 326 Development................................. ..... ....... 326 SCounty, by G. C. Matson.................................... 827 General u ..................................... ........... .. 327 l y ...... ... ... ............ ......... ........ ... 327 Wter supply........... ......... ....... ... .............. 328 source ................................................... 28 Qur ity..................................................... 328 Development........................... ................ 328 efferson County, by G. C. .................a.................. 30 General feature..................... ......... ........... Gology .......................... ..... ............ 330 t y ................................................... 331 Water upply........ ..... 1 ource ......................... ............................ 831 Quaity ................ ..................... ...........-... 31 )evelpen,,,....,...,..,......,,.,..,..,.v.,...,,.......,-, Q3, 12 co1VNT~ S PAST IV.---CONTY DEscOR los--Continued. P Laayette County, by G C. Matson .......................... ....... 335 General feature.................... ..... ....................... 335 Geology. .................................. ........... ......... 335 Water supply.............................. ................ 335 Source ................. ................... .............. 35 Quality.......................................... ....... ... 335 Development ............ .......................... 335 Lae County, by G. C. Matson ......... ............. .. 338 General features .................................... ......... 33 aGeology.. ........... ....... ........ 338 Water supply..................... ............... ....... 341 Source....................... .............. .......... 341 341 Development........... ............. ........... 341 General feature .............. .......................... .... ... 344 T -)cc .............. ........ ................................. 344 Ge ou ey a ............................................. 344 Source and quality .................. ... ....................... 344 Development ..... ................................. 345 Arteiaprospects ........ ...... ................ ........ 350 Leon County, by G. C. Maton ................................ ..... 350 General feature ................... ........................ 350 Geology-...... .. ... .. ..... ..... ......... 350 Water supply ............................. ...... .. 351 Source .................. ................ .......... 351 Quality .............. ....... ..... ..... .. 352 Development .............................................. 352 Levy County, by G. C. M ........M.......................... ... 354 General l futures ................................... 354 Geology.............................. .... 354 W water supply ..................................................... 354 Source......... ............ .......... ................. .. 354 Quality.................. ........... ....... 354 Development.............. ................... ....... 55 Liberty County, by G. Matsn ................. ............. .... 357 General featu ................................. .... ........ 357 Geology ............. ... .................. .................... 357 Water supply............................... ........ 358 Source ...... ....................... 358 Quality ...................... ........... 358 Development................................ ............. 358 Madison County, by G. C. Matson...................................... 359 General features............................ .. ....... ........ 359 Geology............................... .......... .. 359 Water supply.............................. 359 Source. ...................... .. ....... ....... ........... 359 Quality................ .... ................................. 360 Development .............................. ..... 360 Manatee by G. C. Matson .................. ......... ..... 362, General features.............. ..... ................... ........ .. 362i Geology .......... ...... .. ...- ....... ....... ...... 362 CONTENTS. Prr IV.----CouNT DEsCRIPToN-Continued. Manatee County, by G. C. Matson-Continued. Water supply.................................. Source........... .... ..................... Quality ................... ....... Development............. .................. Marion by G. C. Matson ...................... General features ...................................... Witter upply.~........................................ Water supply......... Source ................ ......... ....... Quality........ ...... ............... Development....................... Monroe County, by Samuel Sanford ............ ....... General features.................... ...... Geology ........................ Water supply ............... ..... ....... ..... Source and quality .............. .......... Development..................... ... Na u County, by G. C. Matron ............ .... General feature .......... ......... ... .. Geology........ ......... .. .. ...... Water supply .............. ..................... Source................... .............. Quality............. . Development............... ......... . Ora by G. C. Matson....................... General feature ................ ........ .. Geology. .............. . W after supply.................... ........ Source......................... ....... Quality........., ................. Development .............. .. .... Osceola by G. C. Maton............................. General feature .......... ...... ...... ........ Ge oloy........ ..... ................. Water upply------ ....... ...... Source ....... ....... ...... ..... Quality.............. ......................... Development ................. .. .............. Palm Beach County, by Samuel Sanford................... General features................. ....... Geology ..... ............. Water supply .......... ..... .. ....... ... Source......... ........ .. .......... Artesian prospects ........................... Pasco by G. C. Maton............................ General feature................................... Geology- ..... .......... W after aupply...................................... ... Source................ ................... ....... Quaty.......... ..................... .. ... Development ........... ................. Pinellas County........................................ Page. ............ 363 ............ 363 . ......... 363 .... .... 363 .. ..... 365 ........ 365 365 .. ..... 366 ............ 366 ........ ... 366 ............ 366 ....... ... 370 . ...... ... 370 ........ 370 ..... . 370 ............ 370 ... 371 ....... 373 ........... 373 ............ 373 .. 374 ....... 374 S......... 374 ....... 374 ....... 376 ...... 376 ... 376 ........ 377 ......... 377 .. ...... 377 .......... 377 ......... 379 ....... 379 ..... . 379 ....... 380 ............ 380 ........ ... 380 S........ 380 ........... 381 ... 381 ..... . 381 ........... 382 ...... . 382 ....... ... 384 .. ...... 385 ........ 385 385 . .......... 386 ...... 386 . .......... 386 ..... .... 386 ......... 387 14 CONTETS. PART IV.-Coi~r DEox roN e---Continued. P Polk County, by G. C. Maton ......................................... S General fature................. ... ................. ......... 388 Geology ............... .. .... ..... ...... ....... ........ 38 Water eupply.................................................. 38 Source................... .................. ............. 3. Quality....................................... ............ 39 Development....................... ..................... 39 Putnam County, by GC.. aton ..................................... 3)1 General fet ................................. ........ ... 91 Geology................. ........... ..... ............ ... 31 Water supply......................... ......... .......... 3 Source.. ..................... ..... ...... ...... 3 Quality......................................................... 3 Development ................................................ 3 St. John County, by G. C. Matson ............... .............. .. 394 General feature ................ ............ ............... ecology .............. .. ............ ............ 3 W after supply....................... ............................. 3 Souce ....................................................... X39 Quality.................. ................... ..... 397 Development ............... ............. ............... 39 St. Lucie County, by G. C Maton................... ............... 3 neal featu ................................................ 39 Geology ......................................... ............... 39 W after supply ....................... .............................. 39 Source ................. .................. .. ............ 3 Quality........................ ........... .... ........... 399 Development ................................................ 39 Sant Rosa County, by G. C. Maton ................................... 401 General feature ................................. ................. 401 Geology................ ............................. 401 Water upply............... ... .... ............................ 401 Source.................. ... ..... ....... 401 Quality................. ........................... .......... 401 Development................................. .... .......... 401 umter County, by G. C. Matson ...................................... 40 General tur.... ......... ........... .. .......... .. 440 Geology.... .. ............. ............. ............ .. 404 W after supply .................. .................................. 406 Source .................................... .... ............... 406 Quality ......... .......... ... ......... .. -... .......... 406 Development...... ................................ ....... 4 Suwannee by G. C. Maton ................... ............. 40B general features................................ ............ 408 Geology............... ....... ........ ............ .... .. Water supply...................................................... 48 Source ..................--.. ..-.. ..........-................. 40 Quality ....... ... ..... ..... .............................. 408 Development ........................... ...................... 40 Taylor County, by G. C. Matson ...................................... 415 General features..................................... ......... 413 Geology................. ........................................ 413 CONTE TS. 15 PARr IV.--Cou r r D7scR oN--Continued Taylor County, by G. C. Mal-on- n~u e. Water supply..................................... .......... ..... 413 Sourc ..... ........................ ... 9 .................... 413 Quality.............. ..................... ................. 413 Develop en .................................................. 414 Voli unt, by G C. Maton........................................ 416 General feature ................................... ............ 416 Geolagy........................................... ............. 416 W te pply..................................... ....... ....... 418 Sourc........... ........................ ............... 418 Qudity.............. ..................................... 418 Develop nt.............................................. 418 Wakulla County, by G. C. Mat.on.................................... 420 Genea f ur .......... ............. . . . . ... ... ......... 420 Ideology ................................ ................... 420 Water supply..................................... ............. 421 Source...................................................... 421 Quality ....................................... 421 Development........................ ..................... 421 Walton County, by G. C. Maton................................... 422 General ftur............... ......... ........ ............ 422 eol ............ .................................... ... 423 after uppl ... ............................... .... ............ 424 ource.......... ......... ....... .... .... .............. 424 uaelty....................................................... 424 Development................................ ............... 424 W ington County, by G. C. Maton.................................... 426 General featuret.. ................................... 426 Geolo ................ ................................... 426 Wate supply ............................... .... .............. 428 Source......................................................... 428 Quality....................................................... 428 Development ......................... ... ............... 428 IND X ........................................................................... 431 Inss (tables) facing p~es 254, 266, 27, 282, 284, 288, 294, 300, 304, 322, 328, 42, 348, 366, 80W, 384, 308, 378, 880, 890, 892, 406, 418. 76884-wa 319--13--2 ILLUSTRATIONS. PLT I General topogrphi and geologic map of Florid ............ In pocet II. Map of part of Wlliton quadrangle, showing ink hols.......... III. A, nk hole, Alachua County; B, ink hole containing pond, 10 mil ut t of Vernon, hington County.................. 2 IV. A, Sink of Sata Fe River; B, e ink f Oclahatchee Lake, 7 or 8 ilesouthof Le Prk, ........................... 2 V. Generlid ap of Pletocene terrace of Flori............ In pocket VI. A, Pleistocene te ad escpment boring St. Mars River on Florida ide, opposte Tradr Hill, Ga.; B, Old well of Spansh type, St. Augustine............... .............. ...... 32 VII. A, Beach ridge of coral and shell nd, Knighta Key; B, Calareous nd on reef rock........................... .............. 6 VIII. A, Mangrove key, waters edge; B, Root groth of magrovs south d of Key Vaca.............................. ... ....... 63 IX. A, etin in quarry aa Lime Co. at Ocala; B, QuarryofOl Lime Co. (old Phil quarry), mile southeast of Ocala........ 80 X. A, iestneof Tampa ormation expose along Smile Creek, a quarter of a mile below Atlantic Coast Line Railway bridge, Hills- borough County; B, Limestone of Chattahoche formation on Withlacoochee River at New Bridge (or Horn Bridge), 3 miles below Georgia & Florida Railway bridge, Lowndes County, Ga.. 94 XI. A, Contact of Nashua marl and Plestoene sand, a quarter of a mile below Nashua, on St. Johns River; B, Clay unconformably over- lying Nashua marl in pit about half a mile south of De Leon Spring ttio.............................................. o M XII. A, Congloerate of Lafyett (7) formation, rstg on andstone of uncertain ge, top of Rock Hill, Wahingtn County; B, Rock c in coquina quarry, Anataia Island...................... 148 XIII. A, Coquina rock on Gulf sde of Key; B, Turtle Mound, an ancient hell mound on North Indian River.................. 15 XIV. A, Reef rock, Key limestone, showing erion; B, Quarry in Mimi oolite .................................................. 178 XV. A, eef rock, Key Largo limtone, coral head; B, Mud cracks in cr tl ye of Key West oolite .............................. 14 XVI. A, Well at Quincy, illstrting type of bored well and bucket in use in Gadedn County; B, Flowing well at New Smyrna, with pro- on for shutng off water when not in u.................. 2 XVII. A, Waterwheel for pumping wtr, Calooslache River; B, Wekiva Spring, showing prig d bthho ............ ........ 234 FIro v 1. Section nea edge of Everglades west of Fort uddale........ 58 2. Relatn of undergroundwater level to Silver and Blue srng.... 224 3. elation of underground-water level to surface contour in Buwannee and Columbia counti.................................... 22 4. Profile acros peinsula of Florida in latitude 29 N.............. 25 5. Diagra showing importance of choosing proper locaons for well.23 6. Condition governing the occurrence of artan water in ome pats of Florida ....... ................................. 234 7. Vari n of water level in Johnson well ner Sa Bernardino, Cal.. 240 GEOLOGY AND GROUND WATERS OF FLORIDA. By G~CzO CHARuLTON MAT ox and SAMUEL SANFORD. INTRODUCTION. The geology of Florida has been a subject of investigation for many yes, for the delightful winter climate of the State early attracted to it many scientists who attempted, with varying degrees of success, to solve some of the geologic problems The investigations however, have thus far resnlted i only one comprehensive stratigraphri report, although many papers have appeared in scientific journals, notably in the transactions of the Wagner Free Institute of Science and the American Journal of Science. Te print report, like all similar reports covering large areas, contains data derived from many sources. The authors have care- flly stud the earlier literature and have compared the different views presented, which are here summarized, credit being given to the several investigators. The work of W. H. Dal, of the United States Geological Survey, has been especiay helpful. Mr. Dall made ex- tnive investigations of the pleontology of the Stat and, in 1892, published a treatise covering nearly a hundred pages, in which he outlined the conditions as they were then known, A later report by Mr. Dall is primarily paleontologic, but contains also a summary of the geology and the stratigraphy of the State. The paleontologic studies of T. Wayland Vaughan, of the ... States Geological Survey, under whose immediate supervision this report has bn prepared, in connection with the work of Mr. Dall, have also been of great value, because they have formed a basis for all subsequent work. Mr. Vaughan examined and identified the fossils collected during the progress of the work, and he has very generously placed at the disposal of the writers his own extensive notes, accumu- lated during many years. The work of other geologists, prominent among whom are Dr. Eugee A. Smith, Prof. Angelo Heilprin, and Prof. Alexander Agassiz, has added much to the writers' knowledge of the golog of Florida. 'urrltis pBrs-o 1. U aOl. Burvey No. 84, 1a89, pp. 8-157 ' Co rati to tr TIrtisry auna of rForida: Trans. W e r Inst. ., vol. 3, pts. 1-4, 189-10. 17 GEOLOGY AND GROUND WATERS OF FLORIDA After the discovery of phosphate in Flrida George H. Eldridge was sent by the - States Geological Survey to make detailed investigations of the deposits. He obtained much valuable data but unfortunately did not live to prepare his final report. His note- books have been available, however, and have occasionally been drawn upon by the writers. Aside from incidental references to underground waters in Florida, brief summaries of the water resources have been published by the United Geological Survey and by the Florida Agricultural Ex- periment Station. -of the scattered references to Florida waters are of historic interest only, but some of the records of deep-well boring are important. Four lists of these are worthy of special mention The first two were compiled by Darton,' the third by Fuller, Lines, and Veatch, and the fourth by Fuller and Sanford. Summaries of the underground-water resources of Florida have been published by Fuller and Sellards. A report on the ground waters of central Florida has bee published by the State Geological Survey.~ The investigations leading to the present report were made possible primarily by the passage of the act incorporating the new s' sur- vey. The United States Geological Survey was then engaged in mak- ing a systematic investigation of the geology of the Atlantic Coastal Plain of the United Stats and with the financial cooperation of the new survey was enabled to make a more comprehensive study than could have been carried out in a single season by either bureau alone. In October, 1907, F. G. Clapp, then employed by the Federal ur- vey, began a field' *:~ of the stratigraphy and underground water resources of northern and central Florid. In November of the same year he was joined by G.. Maton, andthe two remained in the continuously until May 1, 1908, visiting nearly every town in the northern and central sections and gathering as much data as time would permit At the same tie Prof. E. H. Sellars, State geolo- gist, and his assistant, Herman Gnter, visited 16 counties in central Florida and gathered data on the water supplies. The funds available for field expenses having been exhautd, Clapp and Matson returned to the office about May 1, 1908. 1 Darton, N. H., Pr inary li t of dep borngs n the United States Water-Supply Paper U . Gel. survey No. 67, pt. 1 ,, 1pp. 21-22; and Waterupply Paper No. 149, 1905, pp. 25-26. Fuller, M. L, Line E. F., and Veatch, A. C., Rord ofdpwe d- killing for 1904: Bul. U. 8. GeoL ury No. 2r, 1906, pp. 44-45. SFuller, M. L., and Snr, Sarel, Record of deep well drilling for 1901: Bull U. eol. Survey No. 2O, 1906, pp. 47-60, 19-199. SFuller, M. L., Contributions to the hydrology o eastern United State, 19i: Water-Supply Paper U 8. survey No 02,1904, pp. 18, 2, 38-275; and Underground water of eastern United States: Water-Bupply Paper U. 8.ol, urvey No. 14, 1905, pp. 159163. ellard, E. H., GOouartnc and ae of artefn water: Bull. Florda Ar Ex. Station No. 59, 19H, pp. 1-13. S ellard, E. H., A prelminry report on toh underground waer supply of central lorida: Bull. Florid eta. I rvy No. 1, 1908, pp. i 103. ACKNOWLEDGMENTS. On July 1, 1908, Mr. Clapp resigned from the United States Geo- loi Survey, anId the work of preparing the manuscript for the report on the northern and central pats of the State was intrusted to Mr. Matson. Before tendering his resignation Mr. Clapp prepared the topographic mp of the State and drew up a tentative outline of the paper published in the Second Annual Report of the Florida Ge- logical Survey. Shortly after the appearance of the State report Thomas Wayland Vaughan published a paper . "A contribution to the geologic history of the Floridian plateau,"' containing a r6sui6 of the geo- logic history and valuable information concerning the influence of depth and temperature of ocean waters, and the action of ocean currents in the development and history of the peninsula of Florida. The geologic information contained in the earlier papers has been incorporated in the present report with such revisions as were deemed essential to make it stable for a Water-Suppl Paper. The remIts of field work by Mr. Matson while in the employ of the General Land Office during the winters of 1909-10 and 1910-11 have been utili in the preparation of additional discussions of the Pleistocene geology. Some important changes in both the text and map of the earlier report have also been made possible by Mr. Matson's recent field work. The base map accompanying both reports was prepared by the United Sttes Geological Survey. At the time when the field workfor thi report was begnI Samuel Sanford was engaged in geologic work for the Florida East Coast Railway, and the task of investigating the geology of the keys and of the southern end of the State was intrusted to him. The interest and cooperation of the people of Florida have rendered thi work a pleasure, and the authors wish here to make public acknowledgment of the numerous favors and courtesies extended them in the field and office. Several persons deserve particular men- ion, among them being Dr. J. N. MacGonigle, of Miami; Mr Goff and several other officials of the Florida East Coast Railway, for affording opportunities to visit the extension of the rairoad during the process of its construction. Mr. Frank Clark, of Gaines ville, f wished introductions which greatly facilitated the investiga- tions; Dr. DeWitt Webb, of St. Augustine, and Dr. Crill, of Palatka, hwae interest themselves in the work. Many well drillers have furnished logs and records, adding valuable data to the knowledge of te stratigraphy. Capt. Alexander : of Eau Galli; Mr. H C. Haven, of De Lan; Mr. W. D Holcomb and Mr. Edward Pettigrew, f Manatee; Mr. H. W. Pearce, of Arcadia; Mr. H. Walker, of St. 'sa C., and Clapp, F. 0., A peinary report on the eoltogy of Florida, with special refeh ato th araphy: eond Ann. Rept Florida Oeol. Svey, 10, pp. 28-173. ;Pk C ie InsittAon of Whgto No. 13, 110, ppM 9-186. 20 GEOLOGY AD GROUND WATERS OF FLORA Augustine; Mr. Wnm. E. Hughes, of Charleston, S. C.; J. E. Ingraha, of the Florida East Coast Railway; J. C. Merdith, forerly constuc~ ing engineer, and W. J. Krome, constructing engineer, of the Key West extension, rendered special assistance. Many others, who can not be mentioned on account of lack of space, have given substantial assistance. A number of citizens have inter- ested themselves in acting as guides and in furnishing speimns and samples from wells. The officials of the Atlantic Coast line Railroad, the Seaboard Air Line Railway, the Florida East Coast Railway, and the louisville & Nashville Railroad, in Jacksonville, Wilming Norfolke,and uiille, have allowed access to their profs and other records, which gave valuable information for use in the construction of the topographic map of the Stat. (See P. I.) PART I.- -)EOGRAPHY. NORThRN AND CENTRAL FLORIDA. By G. Ma~on. NATUBR OF CO TRY, The area described in this report comprises all the State of Florida. (See PI. I, in pocket.) It forms a part of the province commonly known as the Coastal Plain-a broad tract of relatively low land which extends from New York to Mexico, rising gradually from the coast to a height of a few hundred feet and for the most part appear ently flat or gently rolling. In Florida the shores are low and swampy, variations in the altitude amounting to only a few feet several miles. Farther inland the surface is more rolling, and is in some places hilly, but the ref is nowhere great. Most of the sur face is sandy, though in a few localities the soil contains consider able clay. The sandstones, clays, sales, and limestones of the older formations are nearly everyhere only a few fet beneath the surface. Although Florida is a region of comparatively slght relief, its sur- face presents considerable diversity, ranging frm a nearly level plai in the coastal region and the Everglades to a deeply dissected upland in the northern part of the State, where it is trenched by steep-walled valleys, and to a highland in the peninsula, where it shows many more or less rounded depressions separated by narrow divides Altitudes within the State range from sea level to more tha 200 feet above at places on the ridge that forms the center of the ula and to about 300 feet above, at the western end of the State near the northern boundaries of Gadsden, Walton, Santa Rosa, and Escambia counties. The topographic map (Pl. I) is intended to show the approximate areas of land which lie above and below certain altitudes. The datum plane is mean sea level, and the contour lines connect points of equal altitude at intervals of 50 feet. The map bodies the results of the earlier topographic surveys, the river surveys of the United States Army Enginers, and the several railroad surveys, together with a large number of barometric determinations made dung the field work Although the exact location of the contours is in places more or ls uncertain, it is believed that they are sufficietly accu- 21 GEOLOGY AND GROUND WATERS OF FLORDA. rate to give a good idea of the relative area of decent titudes and to present a general plan of the broader topographic ftur of the Stat. The small scale of the map made it necessary to omit such minor detail as sink hole, valleys of small streams narrow ridg, and small more or less isolated elevations. The United States Geo logical Survey has already published detailed maps of seven contigo- ousU quadranglee (Arredondo, t, OitrDt Dunnellon, Oeala, Paunsoffke Tsala Apopka, and Williston), comprising an area of about 1,800 square miles, situated in the central part of the peninsula, and to these the reader is referred for lcal information The southern part of the peniula, comprig an area about 150 miles long and over 100 miles in average width, lies in general ss than 50 feet above sea level. Narrow strips of lowlad also borde the tlantie and Gulf coasts. The valleys of the streams do not rise above the 50-foot contour for a considerable distance from the cost, and one of them (St. Johns River) i nowhere more than 30 feet above tide. The uplands of the peninsula and the adjcnt part of north Flor- ida are separated into two more or le distinct parts by Ocklaw~ River. Begining southwest of Arcd, a belt of high land, very irregular in shape, extends northward o Smm o the Atlntic Coast Line Railroad, and separates the Kissimmee River drainage basin from that of the stress bt to the wet. At Lakeland, Broos- ville, and several other points this upland rises more than 200 feet above sea level. Another broad, irregular upland, stretching northward from Ockls- waha River to the Georgia line, includes a considerable tracr tmor than 150 feet above sea level and forms the divide between the Atlantic and Gulf drainage basins. Its narrowest part is along the western boundaries of Clay and Duval counties, where it forms the long northsouth divide known as Trail Ridge. This upland included Lake City, at an altitude 201 feet above sea level, and Highland on Trail Ridge at an altitude of 210 feet. Near the Georgia line the upland broadens into the Okefenokee swamp, which occupies a large areain Georgiaandextends a short distance into Florida. The wtern slope of the highland is cut by Santa Fe River and its tributaries, and its eastern slope is deeply dissected by the tributaries of St. Johns and St. Mays rivers. Near the State line in the northern and western part of Florida Ii a narrow upland which has been deeply dissected by several streams. On its seaward side this highland in many places descends rather abruptly to the low coastal region. Its highest points are near the northern line of the State, where considerable areas rise above the 250-foot contour Notable examples of this upland are seen in Gadsden County and in the counties west of Choctawhaches River. GEOGnAPHY OF ORTH ERN AND CENTRAL FLORIDA. T"allhassee, the ecpital of the State, stands about 205 feet above sea leIvl, on a remnant of the upland which has been isolated by erosion. East of Apalachicol River the railroad stations at Monticello, Mid- way, and Q y are all reported to be over 200 feet above se level, and west of this river are some of the highest points in Florida. Between Argyle and Deerland, and at several points north of Cret- view, all on the Louisville & Nashille Railroad, the profiles show that considerable tracts rise above the 200-foot contour. Argyle, DI IFuiak Springs, and MIb head are also above 250 feet It ap- per probable that at some localities near the Alabama line the sudrfae may be somewhat higher. According to the list of altitudes furnished by the Seaboard Air Line Railway, Mount Pleasant is 301 feet above sea level. This is the highest accurately determined point record in Florida The change in relative positions of land and sea which have affect the drainage of Florida are so closely interoven with the general geologic and physiogrphi history that their full discussion is left tiller. (Se pp. 199-218.) Heret t is only necsry to note the general eharacer of the streams and to state briefly the factors which have produced existing conditions. Some of the rivers ae confined to the coastal lowlands, where they uassmed their courses in consequence of the initial slope of the land as it emerged from the sea, they are therefore known as consequent stores. The channels of many of them are winding. herever there were depressions in the sands lakes were formed, and some of the consequent stream consist of a chain of such lakes joined by more or less welldefined channels. To this class belongs the Kissimme- Caloosahatchee system with its numerous lakes Consequent streams that have removed the thin mantle of surficial sand and cut into the older formations belong to the class known as superimposed streams. Thus Caloosahatchee River, which in parts of its coupre has eroded a channel through the surface formations into the underlying Plioene marls, is superimposed upon these older formations. In like manner St. Johns River north of Sanfor has been superimposed upon the PlioEene and probably the :.' ... rocks. manatee and Aucilla rivers have in parts of their courses been super- imposed upon the Oligocene formations In Florida there are many other examples of consequent and superimposed streams and many rivers which, like the St. Johns, are in part consequent and in part snperimpoeed. The rivers that cross both the older and younger geologic formations existed before the sands that form the surface of the lowlands were GEOLOGY AND GROUND WATERS OF FLORIDA deposited, and originally they entered the sea at the edge of the present highland belt Where they crossed the highland these streams now have broad, deep valleys floored with a deposit of alluvium and bordered by many prominent bluffs. In their course across the upland they take directions determined by the slope of the surface, but in most places they have removed the srficial formations and cut deeply into the r rocks upon which they are super~nm posed. As the coastal belt emerged from the sea by successive addi- tions to its landward margin, these streams gradually extended their channels across this new land and hence became in part what is commonly known as extended streams. On the Coastal Plain they flow in broad shallow trenches bordered by low bans of sand, a in some places they have removed the Pleistocene sand and eroded channels in the underlying limestones and marl. The most impor- tant extended streams of the State are Escambia, Blackwatr, Yellow, Choctawhatchee, Apalachicola, Ochlockonee, Aucila, Withlacoochee, Hillsboro, Peace, and St. Marys rivers. With the possible exception of Eseambia River, all these streams are in part superimposed upon the Pliocene or older geologic formations. after the deposition of the younger gologic formations and the extension of the streams across the newly emerged land, slight sub mergence caused a shortening of the streams and permitted the sea water to ascend the river channels for several miles from the coast In this way the lower parts of the stream valleys were transformed into estuaries which contain bracsh water and are affected by the tides. The exact length of those estuaries or tidal portions of the riers differs in different streams, and even in a single river it may change with the strength and direction of the wind, strong onshore minds raising the height of the water and forcing the sea water farther upstream and offshore winds having an opposite effect. LAKEs AND SWAMPS. Although the State of Florida is crossed by many large riv it contains numerous tracts of land which are very imperfectly drained and are occupied by lakes or swamps, some of them being of consider- able size The most noteworthy undrained area is in the southern part of the peninsula where the Everglades and adjacent lowlands form a nearly impenetrable wilderness. In ts lowland tract lies Lake Okechobee, one of the largest and most interesting lakes in the south tlantic States. According to Sanford the Everglades nowhere rise more than 25 feet above sea level, and the slope of the surface is so gentle that much of the water which falls during the rainy season is held for a time in broad, shallow ponds and marshes that carry excel- let growths of saw grass and other aquatic plants. These plants, GEOGRAPHY OF NORTHERN AND CENTRAL FLORIDA by their partial decay under water, have formed extensive peat and muck deposits several feet in thickness. Smaller swamps and marshes are found in all parts of the State but are especially numerous in the belt of lowland that borders the coast. In the highlands occupying the northern portion of the State they are smaller and less numerous. In the coastal belt there are also many small laks andI ponds, some of them permanent but most of tem lasting only during the raiy season. Few exceed 2 or 3 feet in depth. In the central part of the peninsula and in some localities near the northern boundary of the State are lakes and swamps which appear to be the result either of unequal depression of the surface sands or of solution of the subjacent limestone and consequent lowering of the surface. (See p. 74.) Some of the lakes are shallow and resemble the of the coast belt, but others are deep basins partly or holy enclosed by a rm of rock Many of the smaller swamps contain peat or muck, but few of the depois attain any great thickness and many of them form only a thin coating of partly decomposed vegetable matter mingled with more or less sand. CHARACTERISTIC FEATURES. Florida may be divided into thr topographic provinces-the upland region of the peninsula (commonly known as the "lake" region), the lowland, and the coast Lakes, of cure, are not con- fined to the upland or "lake" region Generally speaking, however, they are grouped in two more or less distint areas, those lying in rock basins occupying the upland and those lying in shallow depres- sions in the sand in the coastal and southern lowlands, though many in the highlands lie in depressions in the sand and some small ones in the lowlands are known to occupy rock basins. The highland area of the peninsula, however, where rock basins predominate, has commonly been known as the lake region, and for convenience this designation is retained. UPLAND OR LAKE REGION. The lke region comprises a type of topography common to all lnestone areas that have been sufficiently elevated to permit the formation of large underground stream. The character of the surface well shown by Plate II, which s a part of the Williston sheet of the topographic atlas of the United States. The numerous depresons shown in the plate are known as sink holes, and in order 26 GEOLOGY AND OBOUN WATBS OF FLOIDA. to understand their origin it is nece.y to consider the veop of the underground drainage. Cavrn.-Ths region is underlain at no gret depth by sev~ hundred feet of porous limetone of Vckburg age. W re r water bearing carbonic acid derived from decaying organic matt enters thi rock, it gradually dissolvesthe limetone and foe underground channel. A large part of the mineral attr th removed by the undergrund watr is carried to the surface and entering the river, is tranported to the sea. Selards est the amount of slid mater removed in thi manner, baking his c culations on the amount of mineral mattr contain in o iio the waters of eight of the large sprigs of the State. The sp emerge from caverns in the underlying limestone and are fed by t rain falling on the surrounding areas. The percentage of mine matter in solution was detrmied by analysis and the volume flow was etimated. By this method Sellards estimated that Sklv Spring brought to the surface 340 pounds of mineral matt minute. The figures for the other springs were different, but were large. With a conservative etiate of the average miner content of the spring water (219 parts per million) and the assui tion that about one-half the rainfall of Florida entered the and removed this amount of material, Sellar reached the conclu- sion that the amount of solution was sufficientto remove about 400 tons per square mile each year. If evenly distributed this would lower the surface of the limestone about a foot in 5,000 or ,000 year. The concentration of this solution along certa beds or channels of active circulation would permit the formation of large underground passages cotmparatively brief geologic tiae, and it has dissolved out man cnnelse known as cerns, which are already hundreds of feet in diameter and several miles in length kA levd surface and a porous soil, such as that of the lake rion, favor the development of caverns because most of the rainfall sinks into the earth instead of flowing off over the surface Snk holee.-As solution progressed the cavern roofs became weakened at numerous pointe and collapsed, forming the depression known as sink holes. (See P. II.) In some areas these depression are so numerous that they occupy a large part of the surface an< give the region its charateristic topography Splendid example of ancient sinks, such as the Devils Mill Hopper, are to be found i different parts of the State, and the formation of sinks in differei parts of the lake region by the collapse of cavern roofs is within th memory of persons now living. A good example of a recently former SBlrdt H., A prallmtay report on then wnadtrth ilay oiccntl Florida;: Bull. Flar Geol Survey No. I, 198, pp. 47-48. a Idem, p. 1. I ~ ~ :." ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0i 3o 3, II II 11 ,13. I WATER-SUPPLY PAPER 819 PLATE III A. SINK HOLE, ALACHUA COUNTY. B. SINK HOLE CONTAINING POND, 10 MILES SOUTHEAST OF VERNON, WASHINGTON COUNTY. U. L GEOLOGICAL SURVEY WATER-SUPPLY PAPER 819 PLATE IV A. SINK OF SANTA FE RIVER. B. DRAINAGE SINK OF OCLAHATCHEE LAKE, 7 OR 8 MILES SOUTH OF LAKE PARK, GA. U. & GEOLOGICAL SURVEY GEOGRAPHY Op NORTHERN AND CENTRAL FLORIDA. sink is to be een on the road between High Springs and the "sink" of Santa Fe River. A second example is a new sink near Alachua sink, Alachua County, where a action of the surface 100 feet in diameter has recently dropped over 30 feet, leaving an open hole filled with water. (See P. III, A.) In the phosphate region, a large quantity of water, which has been used in mining operations, is allowed to enter the ground. That this water may have a notice- able effect in wekening the roofs of the underground-drainage chan- nels is shown by the following quotation from the unpublished notes of George H. Eldridge: ice the mining of phophate h been underken many sinks have been formed near the settling ponda or along the line of drainage from the mine washers The writer has in the morning ped over a stretch of appF ntly firm road which on hi return at night had given way to a chasm 40 fet acres, in which earth, shrub, and te had ben engulfed and into which watr was pouring down to an under- ground p ge in the weird conceivable way. At one of the Southanpton mines the floor of the old pit and an adjoinig ar of overlying sand has sunk A verl feet, Saving rift in the rh 4 or 5 f acr If the bottom of the sink does not contain an opening the water that accumulates after rainfall will in most places escape to the underground stream by seepage, but if the amount of rainfall is too great to be carried away in this manner it accumulates in lakes or ponds The level of the standing water in such ponds fluctuates, rising after each rainfall and gradually sinking during dry weather. Hundreds of lakes in Florida belong to this class. Soee sinks have openings in the bottom which connect .. t under ground streams, and into these openings the surface streams plunge, carrying loans of sedinent and other dbris. This sediment probably aids the underground stream in enlarging its channel by mechanical wear, but sometimes it accumulates in such quantities as partly or wholly to close the passage, causing the surface water to form a l e or pond. (See l. HI, B.) Examples of open sinks receiving thedischarge of surface streams are common, conspicuous among thm being the sink of Santa Fe River (PI. IV, A), the sink of Chipola ier, the lake sink in Jefferson County, the sink of Oelahatchee S(PI. I, B, and the Alachua sink ner ainesville. SAachu sink is important because it illustrates some of the e which sink holes unro. n the erl d of the State, sink, which receives the drainage of a large stream crossing e Prairie, appears to have beeninabout the same condition i to-day; later, owing to the closing of the outlet," perhaps by Sand other rubbish, a a l lake was formed. About 1891 the sink reopened and the basin was drained, effectually ending the steamboat traffic that had developed on the lake rtrasi, WRlia, TMveis, 1791, pp, 187 t q. - D o; w. H.,COrrlaitn pmpe-eoo Bull. U.B. GBo. dvoy No. 84, IMB, pp. 94-8. GEOLOGY AND GROUND WAT~ S OF FLORDA In some parts of the averns the water enters through the ope- ings in the limestone and evaporates, leaving a deposit of calcium carbonate. By gradual accretion these deposits may form lamg pendants (stalctites) hang from the roof or wall. Wen the water falls to the floor of the cavern and evaporates, it remaining carbonate builds up projections known as stalagmites. The deposits in caverns are frequently highly ornamental and form the chief attraction for visitors. Sometimes the underground stre'-ams form new passages and abandon portion s of their old channels, andit i the abandoned channels that are commonly visited by traveler. In Florida only a few caverns have been explored and none are reported to be high ornamented. The most important caverns noted during the field work are located near Marianna, Ocala, and Alachua. The one near Alachu is known as Warren Cave and is said to be well worth visiting. NaLtural" bridges.-Where the underground s t ammerges, it form a spring, and as the roof of the cavern falls it leaves an open chann through which the spring drains to some surface stream. By a continuation of this process, the underground stream is transformed into a surface stream Where a segment of the roof of the under ground channel remains after the parts above and below have fallen, a natural bridge results ..: ... bridges may also be foredin another manner where the river water gradually works its way to an underground passage, establishing an underground stream beneath the floor of the surface channel. As such a channel is gradually enlarged by solution and mechanical wear, more river water passes through it. Finally, the surface channel may be unoccupied except during high water, or if the underground passage is large enough the surface channel may be entirely abandoned A surface channel may also be produced across a natural bridge whenever the underground passage is partly obstructed There are many natural bridges in Florida, small ones bing reported near Homosasa, north of Clarksvie, in northern Walto County, and in many other localities. Large natural bridges occur on Chipola River above Marianna, on Santa Fe River northeast of High Spring, and on several other rivers The natural bridge on Chipola River is submerged during high water, and a broad shallo surface channel crossing the natural bridge near High Springs said to carry a portion of the flood waters of Santa Fe River (PI. IV, A). The breadth of the surface channel near High Spring suggests that the natural bridge of Santa Fe River may have been formed by the second method outlined above. The natural bridge of Chipola River was submerged at the time the field work was done in that vicinity, so that no obse~ nations could be made. However, GEOGRAPHY OF NORTHERN AND CENTRAL FLORMDA the broad valley of the river above the bridge indicates that the upper part of the rivr has been a surface stream for a long period As natural bridges in such rocks are not apt to endure for long periods, it appears probable that this one may also have been formed by the second method. The great development of underground d nage in many parts of the State has given rise to many springs at places where streams emerge from subterranean chIannels The number of suh springs is very gret. In sz they vary from mere seeps to discharges which give rise to creeks and rivers large enough to float good-sied passen- ger and freight steamer. The best known and large is the Silver Spring in Marion County, which gives rise to a large stream of remarkable cleaess and beauty. The water emerges from a basin over 35 feet deep in a stream (Silver Spring Run) that is about 50 feet in ::. :. width and more than 9 feet in minimum depth in the center of the channel The water is so lear that objects lying on the bottom are distinctly viible. Among the other large springs of the region are Weldva Spring, the source of the river of the same name; Sulphur Spring, near Tampa; Suwannee Sulphur Spring, near Suwannee; Blue Spring, near Juliet Stcation; Blue Sprig, near Orange Juncion; Green Cove pring, on St. Johns River; Ithatu ee Spring, near Fort White; Poe Spring, near High Sprin; Crystal River Springs, the source of crystal River; Weekewachee Spring, near Bayport; and Newland Spring, near Falnouth. A these springs are well known and many of them are very large. They are supplied with water by the lneseones of the Vicksburg group, which are everywhere porous and in many places cavernous. A spring at Tarpon Sprigs is worthy of special mention because it appear to be in part supplied with water from a small lake. The water emerges at the bottom of the bay a few feet below mea tide eveL On the opposite side of the town is a small lake which is with- ut surface outlet and apparently occupies a sink hole. Usually the low of this spring is comparatively insignificant, but at times the discharge is enormous. Observations made upon the lake ust before and aIftr one of these outbursts of the sprin appear to show .at the lake discharges water into the spring through some under- pound channel, for the surface of the lake is said to have been owered several inhes while the spring was flowing rapidly. Aside from tlhe large springs mentioned many others yield large quantities of water, and springs of moderate size exist in nearly all parts of the State. Some of the smaller springs are supplied with water from the superficial sands, but many of them derive their mpplie from the limestone.. GEOLOGY AND GROUND WATERS OF FLO A zzIONAL FZTURZS In west Florida and in parts of pn ular and north Florida the surface confguration has been largely determined by the erosion of surface streams. However, sink hole topography is common as far west as Walton County, and many of the depression are occupied by small lakes. From Leon County westward the major streams cross the upland in wide, level-floored valleys bordered by well-defined bluffs. The depth of these valleys is due to the erosive action and the width to the meandering of the streams. Most of them contain a deposit of sand and mud, which rises but little above the level of the streams ad is partly overflowed when the lattr are high. The small streams of the uplands flow in narrow valleys with step walls and high gradients. In most of these valleys erosion has not extended far from the main streams and many of the divides between the principal rivers are comparatively level. Near the rivers the areas of level land become smaller and the number and depth of the valleys increase until the surface is largely reduced to steep slopes. It is also worthy of note that the amount of dissection increases toward the south. Thus most of the largest level tracts of upland are found near the northern line of the State. At its southern edge the upland in places descends quite abruptly to the coastal belt bordering the Gulf of Mexico. In some places, however, the transition to the coastal lowlands is by a gradual slope. The uplands are for the most part covered by a few feet of gry sand, wlich masks the minor inequalities of the erosion topography Moreover, it is in many places d cult to determine whether shallow depressions are sink holes or are merely irregularities in the surface of the sand However, the sinkhole origin of deep depression such as the lake at De Funiak Springs appears to be unquestionable. BAND DUNME. Sand dunes and ridges are common, especially along the souther edge of the uplands, but few of them are more than a few feet in height. Wind-blown sands are probably much more widespread than is indicated by the surface topography, the heavy precipitation, together with the abundant vegetation, preventing the development of extensive dunes. LOWLAND. The coastal region of Florida comprise a belt of lowld little of which rises above the 100-foot contor and much of which is only a few feet above high tide. Its emergence from the sea took plat GEOGRAPHY OF NORTHERN AND CENTRAL FLORIDA. after the drainage of the uplands had been well developed and the rivers gradually extended their channels across it as new areas were added to the land. sTREAM ANWD POND8. The Pleiocene sands, which form a large part of the surface in the coastal region, slope gently toward the sea and are in places crossed by small streak flowing in shallow valleys. Minor irregularities in the suEace of the sand have resulted in the shallow lakes and ponds that cover large areas during the rainy se n The difference in elevation between the bottoms of many of these ponds and the surface of the surrounding ares is less than 2 fet. artea-o Scattered throughout the coastal region are small areas of higher land which in some places resemble sand ridgs anin other places are ve irregular in form. Some of them contain a core of rock covered by a thin mantle of sad, but many appear to be composed entirely of sand. These areas represent the higher parts of the original sea floor and their positions were determined by the inequalities in the surface of the underlying rock or by unequal deposition of the sands. A large part of the surface of Florida is covered by a few feet of gray sand. Along the coast this sand has in some places reduced the original inequalities of the surface and in others has increased them by forming sand dunes and ridges. However, few of the dunes and ridges are more than a few feet in height and hence they have ittle effect on the topography. General fe res -Bordering the coast and extending into the vl- leys of all te large streak are a series of terraces resenting generally level surfaces bordered by low, seaward-faci scarps. These plains have been grouped into three divisions and as they represent succes- sive stages in the Pleistocne physiographic history of Florda they will be discussed at some length They form brad plain but little diseed by stream valleys and are so poorly drained that marshes and lake are common. The surface of the lowermost terrace ranges in altitude frm sea level to about 40 feet abo it, and includes both ecent and Pleistocene deposit; the second terrace ranges from 40 to 60 ft above sea level; and the third from 60 to 100 feet above the sae datum plane. They are own, respectively, as the Pen- acola, the T"ala Apopka, and the Newberry terrace, the firt-named ng the youngest. (See P1. V, in pocket.) These terraces are for the most part constructed of lithologically similar materials, and this fact together with the absence of char- 76E -wSP 819-18--8 GEOLOGY AND GROUND WATERS OF FLORIDA. aeristic fossils makes it necessary to rely on the topography for their discrimination. The general distribution of the terraces shown on Plate V. This map doe not show their occurrence in detail, for, in the absence of suitable topographic maps, it is in any places difficult to decide on the correlation of more or less isolated plains. The failure to delineate narrow terraces along some of the stie s is nectss~ because of the small sc~e of the map. The Pleitoene terraces were formed during submergence of portions of the land beneath the ea. The maximum amount of submergence was sufficient to permit the sea to encroach on the land less than 100 feet above the present level of the sea. The relations of the land and water remained nearly uniform at some stages long enough to permit the waves to erode and redeposit the materials from the underlying formations. The erosive action of the waves of the Pleistocene sea produced low seaward-facing carpa (see PI. VI, A) and at the same time the materials eroded from the older formations were redeposited in the form of plains that T locally several miles wide. The surfaces of these plains ae not everywhere level, but few inequalities exceed 2 or 3 feet, except where subsequent erosion has changed the topography The Pleistocene terraces were originally slightly irregular and the result of unequal deposition on an eroded surface. The mot strik- ing topographic features are the sink holes in the limestone that lie near the surface in the west-entral part of the peninsula. Some of the minor variations are the low sand ridges, lying nearly parallelto the coast, which were built by the waves of the Pleistocene sea Their recognition is exceedingly difficult because in most places they rie less than 5 feet above the ladjaent surface Depreions of varying size and shape are numerous, but they are seldom noticed except during the rainy season, when they are transformed into ponds and imarshes. The Pleistocene terraces extend up the river valleys, where they are composed in part of estuarine ad in part of fluviatile mteralI; the two types merge into each other and are not everywhere dis- tinguishable. Inasmuch as the deposition of fluviatie sediments shifted seaward during freshet and landward when the rivers were low and sluggish, the fluvitile deposit should dovetail with the estuarine. New berry terace.-The Newberry terrace, which is composed of ight-ghray or yellow sand with local deposits of clay, forms a plain rising from about 70 feet to more than 100 feet above sea level. Its formation was brought about by an encroachment of the sea upon the land and its size depends upon the amount of erosion and deposi- tion accomplished during that submergence, less whatever portion ha been subsequetly removed by erosion. Before te me of WATER-SUPPLY PAPER 810 PLATE VI A. PLEISTOCENE TERRACE AND ESCARPMENT BORDERING ST. MARYS RIVER ON FLORIDA SIDE, OPPOSITE TRADERS HILL, GA. B. OLD WELL OF SPANISH TYPE, ST. AUGUSTINE. U. GEOLOGICAL SURVEY GEOGRAPHY OF NORTHE-N AND CENTRAL FLORIDA this eneroachment Florida had suffered considerable erosion and the Tertiary forations had been subjected to some tilting and folding, so that the materials composing the terrace rest on the eroded surfaces of formations ranging in age from the Vicksburg to the Pliocene, and their relation to the Tertiary foratons is every- where unconformable. eathering had been active before the invasion of the Pleitocene sea, and the terae consists largely of the weathered portions of the subjacent rocks. Limestone is generally absent, the prevailing aterals being sand wth some clay and a little chert, especily where the underlying rocks belong to the Vicksburg group. No fossils have been found in the posed portions of the Newberry terrace, and it is doubtful if it contains many. Some of the Pleisto- cene shells obtained from well borings at Ki nsimmee probably came from the layers near the base of this terrace, but they are not unle. those found in the younger Pleistocene terraces. The fluviatile por- ions of the ternace are somewhat coarser than the marine portions and contain a much larger proportion of colored sands and clays, especially in the northern part of the State. The Newberry terrace encircles te Tertiary formations, forming an almost unbroken band about them. Its presence at several points i northern and southern Aachua counties has led to the belief that a Pleistocene strait separated the higher portion of the peninsula from the upland to the north, thus transforming the central portion of the peninsula into an island Other smaller areas to the west wre probably separated fro the central area by narrow straits. However, these conclusions need to be confirmed by more deiled observations than have as yet been possible. At the Georgi boundary the materials of the Newberry terrace and probably those of the Tsala Apopka terrace, merge into the deposits of the Okefenokee formation. Few exposures give adequate sections of the Newberry terrace and well records rarely shed much light on its thckess A few exposures in the phosphate rock region show that the sands range from 1 to 20 feet in thickess. However, the maximum thickness of the sands and clays forming this terrace may exceed 100 feet in some of the valleys where considerable erosion preceded the Pleist- cene submergence. Tsla Apopika terrae.-The Tsals Apopka terrace is composed chiefly of sand, with clay at some localities. These deposits, resting unconformably upon Tertiary formations, form a plain rising 40 to 60 feet above sea level. The encroachment of the sea at the time of SVe~tch, Otto, and S hnon, L. W., GOeoy of th coastal in of Georgia: BuB. eorgia GeoL re 5 io.2B, i, p. . GEOLOGY AND GROUND WATERS OF FLORIDA. the formation of the stla Apopka terrace was not so extensive during the development of the Newberry terrace. The stratigraphic relations of the materials compried in the two terraces have not been observed, though the materials composing the Tsala Apopka terrace may rest upon the eroded edges of the Newbey terrace. The Tsala Apopka terrace materials have been observed resting upon eroded surfaces the of ertiary age at the type locality, in the Tsala popka lake region, and at many other places. As in the cas of the Newberry terrace, the underlying beds include the differ ent formations from the Oligocene to the Pocene. Sand is the principal constituent of the Tsala Apopka terrace, although some clay is found in places and fragments of chert occur where the underly beds are of Oligocene age. In general, the sands are gray, but in northern Florida red and yellow hands are found in many of the stream valleys. The deposits composing the Tsala Apopka terrace probably average 25 to 30 feet in thickness but this; t is uncertain beuse ood exsus are rare. The Teala Apopka terrace is well developed in the icinity of the lake of that name, and it extends southward nearly to Punta Gord, thence east and north along the west side of St. Johns River valley An area of the terrae lies east of St. Johs River, but its outlines are very imperfectly known. The Payne Prairie plain, as well as the plain partly occupied by Orange Lake, are regarded as portions of this : and a broad branch extends up Ocklawaha Rive. The upland portion of the State is surrounded by this terrace, and it probably extends beyond the State line in the valleys of the princi- pal streams. Pensacola terrace.-The Pensacola terrace is a broad plain, rising less than 40 feet above sea level, and apparently including two dii- sions, one being less than 20 feet above, and the other from 20 to 40 feet above sea level. There has been no attempt to differentiate these two subdivisions, and on the map (Pl. V) they are not spa- rated from the deposits. This terrace merges with the plain that forms the surface of the Satilla formation in Georgia The Pen sacola terrace presents topographic conditions similar to those of the Satilla plain, but the composition of the materials entering into the construction of the two plains are unlike The Pensacola terrace is largely constructed of sand with local beds of clay but in the southern portion of the State includes im- portant limestone beds, several of which are described by Sanford. A large amount of coquin underlies the sand that forms the sur- face of the terrace from St. Augustine southward. Aside from the limestone the terrace materials are sand, except at a few localities I Veatoh, Otto, and Bphan, L. W., OGology of the Coasta Pi o Georgia: BulL Georgia Od. Survey No. 26, 1911, p. 4. GEOGRAPHY OF NORTHERN AND CENTRAL LORIDA, where they include mar containing shells of land and marine animals. The '.''. -.... of the sands and limestone is variable, ranging from less tan a foot to more than 100 feet, the average being probably greater than n any other Pleistocene terrace. Where the base of the terrace materials is exposed, it is found resting unconformably upon the older beds, but good exposures are rare The Pensacola terrace occupies a wide belt surrounding all the older formations,. t extends the entire length of St. Johns River valley and ocupies uan area nearly 150 miles long in the southern end of the peninsula. The Eveglades and adjacent marshy lowlands, together with the depressions occupied by numerous lakes, lie within the area included in the Pensacola terrace. The area occupied by is terrae on the west side of the peninsula is smaller than on the east because the winds and currents of the west coast are less favor- able for adding to the land area than those on the east coast. On the southern edge of western Florida terrace broadens near some of the large streams and in areas where the direction of the winds is favorable to the extension of the land seaward. The estuarine and fluviatie portions of the Pensacola terrace are so narrow that it is not practicable to show it along the river valleys except near the coast Along some of the larger streams this terrace may extend beyond the northern boundary of the State. THE COAST. The extensive coast line of Florida a great .'. of topo- graphic forms, for the most part shaped by waves, tides, shore cur- rents, and living organisms, chiefly corals. The configuration of the shore is dependent on the relative importance of these agencies. Coral reefs are restricted to an area near the southern end of the peninsula, and it was to ths area that much of the earlier geologic work was devoted Sanford discusses the formation of the Florida keys and the adjacent portion of the mainland in the light of his recent studies in that region. Here it is only necessary to call atten- tion to the fact that coral reefs have been of minor importance in the development of the peninsula; in fact there appears to be no reason to suppose that reefs have been on the west coast or north of the north line of Dade County on the east coast. SW BERGRD CONTMITAL, BORDER. Reference to the charts of the United States Coast and Geodetic Sur- vey shows that the depth of the water along the Florida coast is in few place more than 10 fathoms. Submarine contours (P1. V, in pocket) which have been compiled from the charts previously mentioned, GEOLOGY AXD GROUND WATERS OP FLORIDA. show the general relations of the submarine portions of the Floridian plateau to the lad surface. In 1910 these relations were fully. dis- cussed by Vaughan d and consequently only a few facts will be con- sidered in this report. From the present shore line the sea bottom slopes gently to a depth of 100 fathoms, and at that depth the descent becomes abrupt. The submarine area less than 100 fathoms in depth is regarded as a portion of the continental mass, and is more closely related to the land than to the deep-sea bottom beyond the 100-fathom line. An uplift of 600 feet would add to the land surface all the area inclosed by the 100-fathom curve. Reference to Plate V will show what a large increase in the land area would result from such an uplift. Within the area circumscribed by the 10-fathom contour are large areas where the water is shoal It would take an uplift of only 60 feet to bring the land enclosed by this curve above sea level. rom soundings this submerged ara is known to have a gentle slope sea- ward, and its outer margin is comparatively regular. This would give to the land surface a much more regular outline than it now has, and, according to Vaughan,2 would increase the area of the land about one-third. A study of Plate V shows that the position of the present land sur- face is excentric on the Floridian plateau as outlined by the 100- fathom curve. The 100-fathom curve is farther offshore on the west side of the peninsula than on the east side Not only does the land lie near the east edge of the plateau but in the vicinity of Jupiter and thence southward the land actually extends nearly to the 100-fathom contour. Two factors a r thought to be rI ponsble for the excentric position of the peninsula upon the continental shelf. First, there has been differential movement resulting in a depression of the west coast, carrying some of the land beneath the sea. This is shown by the narrowing of the belts of outcrop of the younger formations and the apparent absence of other formations on the west side of the penin- sula. Second, the east coast is being rapidly extended by the large amount of sediment supplied to it by waves acting under the influence of the strong northeasterly winds The effect of this is well shown by Cape Canaveral, as well as by the numerous bars that are trans- forming the coastwie straits into lagoons. Evidence is not wanting to show that such processes have been active in the past, for ancient bars and lagoons that have been filled wth sediments may be recog- nized at numerous places. I Vaughan, T. W., A contribution t ib geoo~ history ol the Floridian plateau: Pub. Carneg It. Washington No. I 1 910 pp. 07-4. * Id m, p. 109. GEOGRAPHY OF NORTHERN AND CENTRAL FLORIDA. In the shallow water at some distance from the shore the waves graduy build bars which rise nearly to the surface. As the material is derived from the sea bottom the bars vary it the character of the latter. At present te prevailing material on both the east and west coasts is sand, often considerably admixed with shells, and the bars now being formed consist largely of sand with a small pro- portion of shell fragment. In comparatively recent geologic time, the beach materials on some parts of the coast appear to have been largely shlls, which were built into bars and afterwards cemented to form coquina. Some layers of sand and a considerable percentage of silica in the coquina show that terrigenos material was never entiely absent, though it was often of minor importance. In the shallow water along the exposed shores, both of the mainland and the islands, currents are formed which transport the beach materials and build them into numerous forms. Among these are the bars which are found across the entrance of all the bays, constituting one of the important obstacles which confronts the Army engineers in their endeavor to make the rivers and harbors accessible to steamers. On the east coast where the prevailing currents move southward, the bars are commonly extended by additions to their southern ends. On the Gulf coast, the dominant currents appear to be in the opposite direction and the bars are usually building by successive additions to their northern ends, though an eastward current of some importace may be inferred from the position of the bar at the entrance to St. Andrews Bay. Behind the shore bars are narrow bodies of shallow water which, on the east coast, are commonly known as rivers though they might more appropriately be termed sounds. To this class long such bodies of water as Hali and Indian rivers. As the sounds become more nearly surrounded by the growing bars they change into lagoons which are in turn gradually filled with silt and ths transformed into marshes. Mosquito Lagoon and Lake Worth on the east coast are examples of lagoons, and marshes are numerous along both the east and west coasts. About 20 years ago an attempt was made to open a passage for steamship navigation by deepening the sounds and lagoons. This plan ias successful, but in recent years the channels have been allowed to bec obtructed by sand bars and oyster reefs In the last few years intret in this "inside" channel has been revived, and it is nw proposed to extend the passages northward to .. Jersey. GEOLOGY AND GROUND WAThS OF FLORIDA. Where drainage from the land nters a sound or partly inclosed bay, the water ecapes through a narrow passage in the bar known as an inlet As the bars are built under the influence of a prevailing cur- rent, the inlet is gradually shifted in the direction of growth, and after a t hne opening becomes so obsetuced that a ew inlet is forme during high water. Usually the lets are formed near the head of the bar and their direction of movement on the tlanc cost is southward and on the Gulf coast northward or westward. At Jupiter, on the east oast, an opening is somethes dredged near the north end of the bar and this opening gradually shifts toward the south It has been found that the inlet remains open much longer when the opening is made oward the northern end of the bar than when it is made farther south. TIDAL RTZWAXE. At ordinary high tide the level of the water in the bays and sounds is raised from 1 to 2 feet above the normal low-water level. If at the same time a strong wind is blowing toward the land the water rises much higher. When the tide recedes, a seaward current is formed which scours the bottom and sdes of the channels. Frequently the water pours through some low gap in a shore bar, thus elping to form a passage. Many of the inlets across the Florida bars are formed in this way. To the erosive action described above the name scour" is applied. Gulliver thinks that the channels near Cedar Keys present an example of tidal runways produced by tidal scour, and he designates them the "western Florida type." At the mouth of St. Johns River and elsewhere along the South Atlantic and Gulf coasts, the Army engineers have constructed dams to narrow the runway so that the effect of tu e tidal scour will keep open a channel deep enough to permit the entrance of large vessels. Many of the important capes of Florida appear to have be built of sand deposited by currents moving along the shore. Cape Cana veral on the east coast was formed where the easterly trend of the current caused the southward-moving current to move outward from the coast into the deeper water where the of the water was checked, causing it to deposit some of its load of sand. Fromthe outward end of the cape there projects a long narrow spit of sand, which rises nearly to the surface The seaward end of this spit is often bent into a hook by the action of the current. On the west coast the northward-moving current encounter the islands near the west end of St. Vincent Sound, and turning westward SOulliver, F. P., Shore-ln topography PIo. Am. Acadl Art and el., vol. 24, 18p9, pp. 1801. OROGRAPI-7 OF NORTHERN A'-D CENITRL FLO -IdA forms Cape San Blas. Cape St. George at the western end of the island of the same name, and Southwest Cape, west of Apalachee Bay, appear to have been formed in a similar manner All of these capes are gradually being extended seaward by the continual addition of material transported along shore by the currents. Many minor projections usually known as points have ofiinated in practically the same manner as the larger capes In 1898 Gllver studied the origin of Capes Canaveral and San Bias, and designated the current cuspate forelands." SOIL. ORIGIN AND CHARACTER. The soils of Florida are almost all derived from the sandy Tertiary and Pleistocene formations; and, since the gray Pleistocene sand is the most widespread of the surface deposits, it naturally gives rise to the so over the greater portion of the State. The sols of the Lafayete (9) formation occupy considerable areas in northern and weern Florida, and they form the subsoil in many localities where the Pleistocene sands are thin. Both theAlachua clay and the Piocene marls are so thinly covered in some parts of peninsular and west Florida that they form part of the subsoil. In some areas, where er- ion has been especially active, Pliocene and Pleistocene have both been removed, leaving the older geologic formations exposed to form the sis; but such areas are confined to the uplands of the penin- sula and west Florida On the uplands residual materials formed by the weatheriCg of the Olgocene formations lie so near the surface that they become a more or less important part of the soil or subsoil or both Peat and muck soil occupy a large area in the southern part of the peninsula and smaller areas in several parts of the State. Their greatest development is in the Everglades, but they are found in many oter localities where swanips exist. They consist of organic matter mixed with more or less inorganei material, such as sand and clay. These sois are of recent origin and are still being formed, especially over a large area south of Lake Okechobee, where the sur- face is very low and flat and the drainage imperfect. Pleistocene sands form the soil below the 100-foot contour in nearly all of pninsular Florida and extend to the margin of the uplands in northern and western Florida. The soils of the :.:.: .. (?) forma- ton are largely confined to the upland areas near the northern boundary of the State. hey do not form large unbroken tracts but occur in more or less isolated areas where the post-Pliocene sands are abset. In many localities the overlying sands are so thin that O -llver, F. P., op. cit., p. 180. GEOLOGY AND GROUND WATERS OF FLORIDA. the Lafayette (9) deposits form an essential part of either the soil or the subsoil, even where the surface materials are younger. Plcstocene marls and coquina, in a more or less decomposed state, form the suboil at numerous places along the east coast and along the west coast south of Bradentown Areas where these Pleistocn marls lie near enough to the surface to be considered part of the soil are much moe restricted than is their geologic distribution. In the central part of the peninsula, especially of Gaines- ville, the Alachua clay lies so near the surface that it forms a part of the subsoil, but so far as is now known it does not enter into the formation of the surface soil. Over much of the area where thi formation occurs it is too deeply buried to be considered a part of the soil. On the north bank of Manatee in the vicinity of Ellenton, there are some areas of land, valuable for truck gardening, wherethe residual lays left by the solution of the limestone of the Tampa formation form very good soils. In some places these clays contain more or less Pleistocene sand and numerous fragments of angular or subangular chert. Doubtless other localities exit where the residual products of this limestone lie near enough to the surface to form part of the soils, but the real distribution of these soils is not yet known. Decomposition products of the limestones of the Chattahoochee formation and the Vicksburg group form parts of the soils in locali- ties where younger deposits are absent, but over large areas they are too deeply buried beneath the younger geologic forma- tions to be important in soil formation It is the proximity to the surface of marls or residual products of the rocks of the Vicksburg group which is regarded as the source of the fertility of many of the "hammock" lands near the west coast, and it is doubtless the presence of such material near the surface which accounts for the excellent growth of timber in places on the peninsula where the sur- face soil is very poor. SOIL TYPES. In 1897 Whitney made a general examination of the Florida soils. He says: The principal type of soils examined were the first, second, and third quality of high pine land; the pine flats or so-called "flat woods"; the light hammock, the gray or heavy hammock, the mixed land, the heavy marl hammock; the pineapple land; the Etonia scrub, the spruce-pine scrub; and the Lafayette formation. Since the publication of Whitney's report, detailed soil surveys have been made in the vicinity of Gainesville and in Escambia County. 1 Whitney, Mlton, A p ly port on the so of FIrida: Burl Sos No. 13, U. S. ep Agr., 15 p. 7. OCOG Y OP 1--- --- A-M CENTRAL PFLORDA. In ths detailed work the soils were classified by their physical prop- ertie, origin, and topography, texture being considered the most important characteristic. The principal types recognized were sands, ine sands, sandy oarns, and fine sandy loams. Subordinate types were loams, silt loams, clays, mucks, and meadow. These types have, with some exceptions, been grouped into three series and cor- related with similar soils elsewhere in the Coastal Plain. Aside from thee general types are the Gainesville and Gadsden sands, so named by the Bureau of Soils of the Department of Agriculture, and some other types which have not yet been correlated. The ay and loam soils of Florida cover a very small area and are not of great important The clay soils are chiefly small tracts in the neighborhood of stress and are not tiled; in this connection it should be borne in innd that much of what is commonly called clay in northern and western Florida is to be classified as a sandy loam, be- cuse, though more or less plastic, it contains sand as its most impor- tant constituent. The sand or sandy loam soils, which cover the greater part of Florida, may be subdivided into a large number of al of which have certain general characteristics. When brought under cultivation their natural productivity is commonly low, but they sspond quickly to proper treatment and can be made to produce rge crops, which grow rapidly and mature early. These chara- ristics, when linked with a subtropical climate, make the produc- ion of early fruits and vegetables very profitable. In order to pro- cure the best results it is necessary to exercise skill and judgment in the treatment of the soils, and in some places to expend considerable money for fertilizers. There is apt to be a deficiency of moisture on some of the sands and sandy loams, and hence irrigation is. sometimes practiced. are used in nearly all parts of the State, the amount and ind used in the different localities being governed by the nature of the crop grown and the experience of the most successful farers. A striking example of the productivity of a sandy soil properly tilled s furnihed by the yield of pineapples from a ridge of sand near Fort Piere. The value of barnyard refuse and legumes as fertilizers is reogniz in some localities, but their use should be much more extnsve. Some recent experiments of the Department of Agicul- ture1 are of interest, as they show that lime, which is not generally ed on Florida soils, may add greatly to the productivity of certain types of the sand and sandy loam soils. The peat and muck soils of Florida have not been extensively used because tey are in swampy areas, which require drainage. Exten- sive drainage operations are in progress in the Everglades, and if these ar continued large areas of peat soil will be available for cultivation. disumy of fmb County, Florld: Field Operations Bur. Bois, U. S. Dept. Agr., 190, p. 38. G0L860Y AtID OROUbD WAERs OF FLOtRIbA The natural productivity of the peat and muck soils of Florida has seldom been determined, but, judging from the experience of farmers in other States, it is safe to predit that the gla so are destined to take rank among the best lands of the State for the production of certain crops. Moreover, experience in several other States has shown that such soils seldom require the addition of complete fertilizers, such as are used on sandy soil. In fact, the addition of small quan- tities of salts of potasim should usually be sufficient to cause a peat or muck soil to produce good crops, though possibly in some areas the addition of phosphates would be necessary These facts are i- portant, because it will cost much less to fertilize the peat and muck soils than is now being expended on the sandy soils. GEOGRAPHY OF SOUTHERN FLORIDA. By SAMUEL SANFORD. LOCATION AND AEA. The erm southern Florida is here made to include, for convenience of description, the portion of the peninsula with its bordering islands or keys lying south of a roughly northeast-southwest line extending from the north line of Palm Beach County on the east coast past the south end of Lake Okechobee to the mouth of San Carlos Bay on the west coast. The piece of mainland thus arbitrarily cut off is 140 miles in extreme length, north and south, and 120 miles in maximum width, east and west. Its area is about 7,300 square miles, of which 6,000 square miles are swamp or land so low as to be covered with water during the rainy season, from June to October, or, near the coast, by unusually high spring tides. The total number of the keys is unknown, but their area is here estimated at 300 square miles. (See P1. I, in pocket.) GENERAL FEATURES. Growing coral reefs extend along the Florida coast for over 200 miles and are found nowhere else in the continental limits of the .Because of the reefs and the teeming marine life of the surrounding waters, southern Florida has attracted attention for over 50 years and has been visited by a number of eminent scientists who have described and discussed the main features of the keys and the southeast shore of the mainland. Owing to the difficulties of travel in this region and its comparative remoteness and inaccessi- bility before the building of the Florida East Coast Railway, these visitors confined their observations' to the -' the shore line of the keys, and the edge of the mainland in the vicinity of Biscayne Bay. In 1907 and 1908 the writer had an opportunity to study in detail some features of the topography and geology and their relation to GEOGL AHY OF SOUTHERN FLOBIDA. underground waters that were not so evident in former years as they are today. Between 1896, the year of two important contributions to the geology of the region-the papers by Alexander Agassiz on the elevated reef and by Griswold 2 on the southern Everglades-and 1909, when the geology was described in detail in the second annual report of the State geologist, the railroad had been completed from Palm Beach to Miami and from Miami to Knights Key. At the mouth of Miami River, where only a few houses stood at the time of Griswold's visit, there is now a city of over 5,000 inhabitants, from which radiate miles of excellent macadam roads. What was then a barren wilderness now includes thousands of acres of truck farms and and grapefruit plantatios. The result to the geologist from this transforation is a great increasing te eaily obtainable rock evidence. Wells, quarries for road metal, and railroad borrow pits make the compiling of geologic data along the east coast vastly easer than it was in 1895. Even on the ."'. '" remote west cost, from Cape Sable north, there are more settlements to-day than there were then, and with the coming of the motor boat the exploration of the shallow and tortuous passages characterizing that coast has been much facilitated. The larger portion of the interior is included in the great saw-grass swamp of the Everglades. Though repeatedly crossed by troops in the Seminole War and well known to many white men, hunters of sligators and plume birds, living on its borders, this expanse of water and sedge-covered muck had until 1907 been visited by few geologist and traversed by none. Griswold's account of what he saw toward the south end of the Everglades remained for years the best description of the more noteworthy features of the topography and geology of the region. Now, however, the drainage and recla- marion work carried on by the State is yielding evidence that the individual explorer, from the physical difficulties to be overcome, could not possibly hope to obtain. In a general review of the salient of the topography of souther Florida it is convenient to consider the mainland, the keys, and the shore line separately. Taken as a whole the topography of the Florida mainland has all the aspects of "- :. Drainage is defective; sloughs, shallow ponds, and lakes abound. Most of the interior is a swamp; no well-defined river systems nor stream valleys exist; and some of the short river that flow from the Everglades into the Atlantic are, where bedrock comes a few feet above sea level, characterized by rapids in their upper courses, Ii, Alexander, The elevated reef of Florida: Bull. Mus. omp. Zool. Harvard Coll., vol. 28, No. 2, , pp. 2-51. Griold. L, Notes on the gOology of 8o n FIord: Bull Mm. Comnp. Zol. Hv ,d coll. S, o. 2, ISM, pp. 5-I. GEOLOGY AND GROUND WATRS OF FLORIDA This infantile aspect is due to two causes, one the actual recency of deposition of the beds, consohdated and unconsolidated, that con- stitute the land surface, and the other the slight elevation of the bed above sea level since deposition. The rocks have had relatively little time to decay, and there has been no elevation of the land high enough or long enough to give streams an opportunity to erode vT leys and establish well-marked drainage systems. The shoreline topography is more varied in places its forms a those of infancy and in places those of youth or adolescence, the differences in aspect being determined by the influence of opping factorsthose that tend to extend the land's edge irregularly and thos that smooth shore lines into long sweeps and easy curve. The relations between land and water on any coast are inconstant and ever varying only is the shore a line of battle between the forces that destroy and those that build up the land but geologic history shows that changes of level are the rule, that the lands or the oceans slowly rise or fall during long periods of time, parts of tese bottom becoming dry land and parts of the land being invaded by the ocean. In places these movements are rapid enough to be proved by human records. : :.... highlands border the ocean invasion is slow; where coasts are low it is relatively swift. The transitions of coast lines and the changes resting from slight elevations or deprens of coast are factors of high importance in contemplating the prnt shape of the land mass of southern Florida. As has been pointed out by Agassi D and others, the presen Florida mainland is but the top of a vastly greater submarine plateau, the southeastern and southern edges of which are near the present shore line, and the western edge many miles t tthe west. Hence, e may regard the present outline of the Florida mainland as a mer accident Though stable enough when measured in terms of human life, its ephemeral when compared with the duration of a gelog period. A -'--. : -- of 50 feet would cover all the area wondered in this except the tops of a very few sand hills and ridges; an elevation of 50 would extend the shore line bu little on the east, though making dry land of Biscayne Bay; on the south it would dry the Bay of Florida; and on the west it would extend the land for 30 miles west of the entrance to Shark River and 20 miles wet of Cape Romano. The keys orislands that fringe the coast of southern lorda, or fo the great arc that ends in the Tortugas, are of several types, but for the roger part re alihe mainland. Except for some beach ridges and dunes, the general elevation of the keys is less than 10 feet, and hundreds of keys are merely mud lat hidden by mangroves. GEOGRAPHY OF SOUTHERN FLORIDA SUBDIVISIONS. Although the surface of the south Florida mainland has slht relief, it yet shows considerable variety of type. A detailed study of its forms is beyond the province of this paper, but certain .surface features will be discussed at some length because of their intrinsic importance, because of the attention given them by previous writers, and because a. general understanding of the topographic types is essential in the study of the recently deposited formations and is nec- esary to a consideration of underground-water supplies. Southern Florida lies low. The average elevation of the surface is below 20 feet and over long stretches the ground is almost a dead level. The general slope of the surface is south, though elevations along the east coast may average 10 feet higher than along the west coast This is shown by the drainage of Lake Okechobee, the greater length of the west coast rivers, and the trend of the river courses, features that are considered individually on succeeding pages. In consequence of the slight relief, the imperfect drainage, and the resulting accumulation of surface water during the rainy season, small differences in elevation have a marked effect on vegetation and make it possible roughly to divde the mainland ito pineland and swamp. The pineland includes the hammocks, isolated patches whereon grow hardwood trees of several genera, and many of the prairies or grassy tracts; the swamp land includes the coastal swamps with their char- acteristic growths of sedges or black and red mangroves Owing to the low relief the line of demarcation between swamp and pinelad is extremely irregular. In many places it is not a line but a variable width of prairie, which may be 2 feet under water at the end of a rainy season, but which in most year gets so dry during the winter months that tomatoes and other garden truck can be grown on it at a profit without artificial drainage. As Maton has stated (p. 35), practically all of southern Florida lies witin the boundaries of the lowest of the three trraces or terrace plains that may be differntiated within the State. This lowest terrace, whih has a maximum altitude of 40 feet, Matson has designatd the Pensacola terrace. PINELANDS. AREA AND DISTRIBUTION. The pinelads of southern Florida are not remarable by reason of the size of the trees, the thickness of gowth, nor the yield of good timber per acre, but as they include the larger portion of the surface lying above wha may be termed normal water ev they are impres- GEOLOGY AND GROUND WATERS OF FLORIDA. ive from their extent. Their total area is a matter of conjectur for though the pinelands have been surveyed by the United States Land Offce, the township maps give an perfect idea of the actual extet of the tiber. In round figures perhaps 1,300 square are to be regarded as pineclad The pinelands of the eastern coast extend for the mot part s a narrow belt betweenthe Everglade and the coastal swamp from the north line of Palm Beach County to 12 miles outhwest of Homet This belt is widest at the north, where it may be 20 miles across, and i much narrower south of Jupiter Inet, where it is about 6 wide, varying in width from 2 to 8 miles and tapeg to its soth- western :.- ----!'. West of the Everglades the pinesare mor irregularly distributed; at Naples they grow to the shore of the Gulf; along the north line of Monroe County they grow in more or less disconnected areas separated by narrow and broad strips of cypre~ between Cape Romano and the mouth of Lostmans River they lie from 5 to 15 miles back of the outer face of the network of keys that constitute the apparent shore line South of Lostmans River ther is no pineland. As the trees grow on areas of very different ]pographic aspet, the pineland of southern Florida may be divided according to the character of its relief into dunes, rolling sand plai, rock ridges, and flat lands. DUNES. ..-Dunes as here considered are purely eolian accumu nations and do not include deposits of sand that owe their relief wholly or in part to the action of water, whether that of current or of waves. Dunes are sharply differentiated from beach rdges, those coastal accumulations of sand and other loose material in the shaping of which waves and ind-driven spray took part. Thus some of the ridges facing the ocean at Palm Beach are not considered to be true dunes. Moreover, in this discussion the term dune is applied to ridges that are at least 4 or 5 feet higher than the general level of the sand near by. The dunes are composed of medium fine quartz sand, varying in tint from pale yellow to orange or to light reddish brown. Th sand is rather angular and some of it can be broken down to finr grains by rubbing between the fingers. Fossil sells are rare, if at all; none were seen by the writer in a rather careful inspect tion of sections through several dunes. The different tints of the sand are not, according to the writer's observations, arranged in dis tinct bands, nor is the sand everywhere plainly stratifid. However, the color tends to increase with depth below surface, thus causing the gradation seen in a section through a dune to follow the suace contours. In many places the shades of yellow and brown are mottled GEOGRAPHY OF SOUTHERN FLORIDA or blotched. Streak of gray sand, possibly caused by the decay of pine tree roots, extend from the surface to varying depths into the yellow and reddish sands below. In some dunes the sands toward the center have been so cemented by iron oide as to form irregularly rounded masses of hard rock. perhaps the most noteworthy feature of the dunes of southern Florida is their quiescence. If cleared of pine timber and palmetto Esrub they grow good pineapples, but even when bare their sands are little moved by the prevailing winds. The blasts of a hurricane may affect them somewhat, but certainly nowhere in southern Florida is there any such movement as is characteristic of dunes in active growth; no leeward march overwhelms trees and threatens dwellings, and no such drift is in progress as can be seen at Cape Henry, Va., and at other points on the Atlantic coast Instead of burying forests the dunes of southern Florida, where not cleared, are covered with scrub or large pine trees. In short, they are quiescent. Evidently, therefore, the dune were formed during a time when conditions were different from those now prevailing-a time when the topographic and the climatic conditions favored sand drift. Though near the coast the dunes are not directly related to the present shore line, but, as shown by the ^ of swamp and the off-lying keys, to another shore line now below sea level. The significance of these facts as bearing on the post-Tertiary history of southern Florida wil be discussed later. Di-tri on-In southern Florida the larger dunes lie near the coast. East of the Everglades and Lake Okechobee they reach south to River as a discontinuous series of irregularly distributed mounds and ridges, in places separated by considerable intervals of flat or gently rolling country or by stretches of shallow water; but in few places do they extend more than a few miles inland and in few do they face the open ocean. South of New River there are, so far as the writer knows, no true dunes; certainly there are none on the 150-mile chain of keys that extends from Biscayne Bay to the Marquesas, the nearest approach to them being many low indistinct idges and mounds, nowhere 8 feet above mean sea level. These are most pronounced long stretches of beach facing breaks in the living coral reef, par- tiularly where the water near the shore has more than average depth, or rather where the seaward slope of the bottom is greatest. These low heaps of sand, from their position, may be the work of the waves quite as much as of the wind, and in fact most, if not all, of them are true beach ridgs. Their outlines may probably have been modified slightly by wind-borne sand, but their main features are cerly due to wave action, particularly to the waves that break on the exposed beaches during a hurricane, when tides 4 feet or more 768-warc 319--1--c-4 GEOLOGY AND GROUND WATE~B OF FLORIDA. above mean high water mark inundate the keys and facilitate the formation of unusually high inshore waves. Along the east coast the position of the more prominent dunes near the shore is indicated on the Coast Survey crts. A noteorthy succession of ridges extends in an approximately northnorthwst direction from 2 miles north of the dune on which stands Jupiter lighthouse, at the north side of Jupiter Inlet, to and past Hobe Sound station on the Florida East Coast Railway; just back of the staton the summit of one has a height of 63 feet above sea level. Back of the lighthouse at Jupiter the top of one dune is perhaps 45 feet high. North of Hobo Sound station the dune belt veers to the westward and dies away within 3 mles. There are no large dunes along the railroad from Hobo Sound to the north line of Pal Beach County, and, according to report, no large ones north of the northern end of the Hobe Sound belt and o high ground between it and Kissimmee. South of Jupiter Inlet dunes are numerous but occur as disconnected mounds or riges and not as continuous or ntiguous ridges A typical dune, 47 feet high, at West Pan Beach, according to report, contained masses of rock. There are dunes 20 feet high near Palm Beach. Isolated dunes and ridges near the shore between West Palm Beach and Jupiter are shown by the Coast Survey charts. South of West Palm Beach the dune belt lies farther inland, though generally parallel to the seashore, and the more prominent dunes have not been mat ed. There is a fine dune ridge near the east side of Lake Oborne, bout a mile west of Lantana station. Isolated dunes of dinihing height occur to the south, the southernmost one of any prominence known to the writer being Pine Island, in the Everglades back of Fort Lauderdale 6 miles from their eastern mar gin. The belt of country containuig the prominent dunes south of West Palm Beach probably in no place exceeds 5 iles in width. On the west coast of southern Forida, dunes are not nearly so numerous as on the east coast and are more irregularly distributed; like the east-coast dunes they are found near the shore rather than inland. The best-developed dune system seen by the writer on the west coast i the one that covers parts or the whole of several islands near Caximbas Pass. It extends east from the south end of Caximba Island in a disconnected line having somewhat the shape of the Greek letter 8, the total length being about 8 miles Just back of Caximbas post office, at th west end of the ste, there isa dune about 35 feet high. A ile to the northeast another ridge, having a maximum height of 60 feet, is said to be the highest in the system. There are no dunes on the islands near the muth of Caloosahatchee River, where from the coniuration of the present coat line they GEOGRAPHY OF SOUTHERN FLORTDA might be epecte, although a high beach ridge forms the backbone of Captiva Island. Between the mouth of the Caloosahatchee and Caximbas there are said to be two dunes, one on a small inner key near stereo, the other, much larger, on the mainland about halfway between Marco and Naples. South of Caximbas there are no dunes, not even back of the 10-mile stretch of sandy beach at Cape Sable, and there are none along the southern edge of the mainland from Cape Sable eastward. From this review it appears that though the distribution of the south Florida dunes is in some way related to the present coast line, the rlation is not a definite one. The high ridges lie back from the ocean and from the Gulf, yet extend only a few miles inland Those lying on keys rise out of mangrove swamps where dune building is now impossible; those near open water, like the dune back of Jupiter Light, general lie back of a protecting key and back of a fringe of mangroves. ROLLtNG BAND PLANI. By rolling sand plains is here meant sandy stretches of the main- land undulating in broad sales and low ridges. In the swals are shallow lakes or lagoons, wet prairies, or cypress swamps On the east coast these sand plains form a belt that extends, with a maximum width of 6 miles, from the north side of Palm Beach County nearly to Miami River. Out of this belt rise most of the dune mounds and ridges Inland the rolling sand plains merge imperceptibly into the monotonous level of the flatlands and the prairies bordering the Everglades; seaward they are bounded by swamps or by open water. On the west coast south of Caloosahatchee River the rolling sand plains are of relatively slight importance, though in them may be included the arable land, a succession of beach ridges back of the present shore line at Cape Sable, and the sandy keys, many of them not pine clad, that fringe the coast from Cape omano northward. Near the shore on the east coast the higher ground and the ridges of the sand plains are in many paces covered with a straggling growth of sprce pine. In the hollows are many fresh-water lakes, some several miles long. Most of these are less than 10 feet deep,. and some are so shallow that they disappear entirely for months during a period of defiient rainfall such as prevailed from November, 1906, to May, 1908. A few of the lakes may be over 10 feet deep, and the writer was told that Lake Osborne had a maximum depth at the end of a normal rainy season of 30 feet, extending some feet below sea level. However, the lakes, as a rule, are so shallow and the slopes of their banks so gentle that a survey of the rolling sand-plain country made in or shortly after a summer of normal rainfall would show vastly different relations of land and water from GEOLOGY AND GROUND WATERS OF FLORIDA. one made in early spring following a year of deficient precipitation. This accounts in part for lakes appearing on maps of souther Floida at many places where the visitor may find none The sand grains, like those of the dunes, are angular rather than rounded. They are gray at and near the surface, but become yd- lowish a short distance below, except in places where water stands during most of the year The decoloration of the sands near the surface is to be explained by the decay of lant roots, the action of soil bacteria, and the leaching effect of rain. The character of the sands and the elevation and prevailing trend, parallel to the coast, of the ridges indicates that the rolling sand plains are in part beach deposits and in part the work of the wind and that they are related to the dunes. FLATLANDS. The term "flatlands" is applied to the imperfectly drained pinlands lying between the rolling sand plains and the Everglad or thi bordering prairies and forming a dicontinuous strip of count which on the east coast extends from the north side of Palm Beach County to the vicinity of New River, in Dade County. Its greatest width back of Hob Sound is about 10 miles The flatlands have a soil of lightgray sad, resembling that of the rolling sand plains, and bear a thin growth of pine trees separated in places by expanses of prairie a mile or more wide, a difference of a foot in elevation determining the character of the vegetation In the rainy season prairies are shallow lakes. In the flatlands lie also exceptional sloughs or pond holes, some of which are a fourth of a mile or more across, and which, being 3 to 5 feet below the general level of the are never dry. In places these deeper hollows support good growths of cypress, and as the region of relatively permanent standing water, the Everglades, is approachd the pine and the cypress growths intermingle in most irregular fashion. In some places pines grow up t the edge of the prairie bordering the Everglades; in others a fringe of dwarf cypress separate pineland and swamp; and in still others considerable areas sup- port good growths of cypress. On the west coast the surface of the country between the Everglade and the Gulf is even more monotonously level than that of the east coast and the relations of swamp and dry land are more.irregular of the pine grows in patches and strips, in places miles in extent, separated by cypress swamps. In consequence, the tiber- clad flatlands of the west coast are described as pine islands and cypress strands. Prairies are scattered through or fringe the pine lands, and toward the Everglades and north of the Big Cpress geat stretches of prairie make excellent cattle ranges. GEOGRAPHY OF SOUTHERN FLORIDA. ROCK RIDGES The absence of rock outcrops over the greater part of that portion of the mainland included under the term southern Florida is striking, and indeed remarkable when one finds that in many places solid rock lies only a few feet below surface. To outcrops of any extent the term rock ridge is here applied, though it should be understood tat these rock ridges may not rise more than 2 feet above the level of the s undng country and probably nowhere have an elevation exceeding 25 feet bove sea level. The rock ridges of the east coast comprise the prominent otcrops of oolitie limestone that extend from 5 miles north of Miami to Homestead and separate the great saw-gras swamp of the Everglades from the fringe of mangrove swamps and salt prairie along the western shore of Biscayne Bay. This rocky country forms part of the Bis- cayne pineland The are of these outcrops is estimated at 200 square miles, but is really a matter of conjecture. The relations of rock ridge and prairie along the western edge of the pineland are extremely intricate, the elevation of the outcrops falling gradually to the level of the Everglades and the pineland tapering off in a serie of rocky keys or islands (of which Long Key is the that extend fully 15 miles beyond the southwest corner of the main body of the pineland. Over many square miles between Miami and Long Key and about Long Key the limestone forms the surface. ... :. of Miami the outcrops are mantled by sand before the elevation of the rock surface has become as low as 6 feet above mean sea level. North of New River, between the sea and the Everglades, except for the coquina near the beaches, outcrops of rock are few and scat- tered. In the Everglades some of the keys have a rocky foundation, such being reported nearly to Lake Okechobee, but so far as known the only ones that form bare rock ridges are Long Key and the keys related to it, none of which reach as far north as the latitude of On tJ west coast of southern Florida hard rock outcrops are more scattered than on the east but cover a much wider area. Throughout the pine island and cypress strands, limestone projects here and there through the sands and is found along the roads from Fort Myers to Fort Shakelford and from Fort Myers past Immoka to the head of Alens River. Moreover, narrow interrupted strips of bare rock, some of them several miles in width, run through the pinelands. A peculiar feature of the rock outcrops of southern Florida is the erosion of the surface. On the west coast, where the limestones are denser and finer than on the east coast, the rocks weather irregularly into rounded kobs and lumps a few inches to a foot above the general level of the surrounding sands, making it difficult to drive a wagon GEOLOGY AND GROUND WATERS OF FLOIDA. across bare expanses. In the rocky area of the east coast the softer oolitic limestone weathers into angular shapes, producing extremely rough surfaces and making walking a task that requires constant watchfulness. The ground is strewn with loose, sharply angulrr fragments (products of weathering and of the disruptive power of tree roots), and fixed angular masses a foot oro high, withre pointed summits and jagged outlines, vaguely suggest miniature pagodas. Hand in hand with this surficil erosion has gone underground solution. Next to the bristling rock surface, te most striking feature of the Bisayne pineland south of Miami is the .of innumer- able holes and hollows. The holes, which communicate with under ground solution channels, are of all sizes, varying from not over an inch across to 20 fet or more in diameter Besides the sharply out- lined holes, there are throughout the pineland countless shallow hol- lows 1 to 3 feet deep and 10 to 100 fet across.A fewof these hollo owe their origin to original conditions of deposition, some may be due to the overturning of trees and conequent upheaval of the rocks by roots, and others have been caused by the falling in of the roofs f subterranean watercourses. Few of these holes and hollows are large enough to be termed sinks. The large vertical-walled holes running down to permanent watex level form natural ells; the shallow hollows are best denominated potholes. Deep, or Devils, Lake, near the west eoast, 12 miles north of Everglade post offle, is, so far as the author knows, the only rock- rimmed opening n southern Florida that resembles the great s in the country to the north. It is about 500 feet across, is nearly circular in outline, and its reported depth is 90 feet. Although there is danger of exaggerating the activity of under- ground and surface water in eating away the soft limestone of the east coast, yet there are plentiful evidences of solution. The pothole and the hollow-sounding areas of rock, perhaps 25 feet across, wit as many as six or seven holes a foot or so in diameter showing the water beneath, that are found along te edges of the southern Ever glades; the springs below tide level at Cocoanut Grove and other points on the shore of Biscayne Bay; the Punch Bowl, a spri basn the deep holes in New River; and the shallow gorge of Arch Creek with its low rck bridge-all bear witness to the work that is being done. SWAMPS. OONTROLUNG CONDITION. As before stated, the swamp land of southern Florida includes the great saw-grass morass of the Everglades, the cypress swamps and strands around its edges or intermingled with the pinelad, and the salt meadows and mangrove swamps of the coast. The very sligh GeOGRiAPIY OF SOUTHERN ILORIDA. differences in elevation over long stretches of the mainland, the gradual slope of the rock surface below sea level, the rock rdges on the southeast, the confirmation of the upper surface of the bedrock, and the rapid growth of grasses and sedges are all factors in the distribuion of land that i permanently wet and of that which is, for a part of every year, dry. EVERG IA S. Aent.-It is difficult for a person who has not seen the Everglades to form even an aproimate idea of that far extending exanse of sedge, with its stretches of shallow water, its narrow wndig channels of deeper water, its scattered clumps of bushes, and its many islands. Photographs fail to convey the impressions of distance, of remotenss, and of virgin wildness which strike the visitor who for he first time looks out across that vast expanse. The Everglade the greater portion of southern Florida. They reach from Lake Okechobee on the north to the vicinity of hitewater Bay on the south and may have a maximum width of 60 es. They have not been surveyed and their exact area is undetermined, but it is estimated at 5,000 square miles The relief of the drier land is slight and the actul dividing line between saw grass morass and cypress swamp, prairie, pineland, and coastal swamp is extremely intricate. A difference of 2 feet in water level means the fference between shallow lake and dry land over hundreds of square miles. Hence, the relation between land and water shown on a particular map is not necessarily to be taken as absolute or ven general; it may only show the reaction as determined in the month or months and year of the survey. On the north the main body of the Everglades reaches tohe south er and southwestern sides of Lake Okechobee Arms extend farther north, but much of the eastern and most of the northern shore of the lake is bordered by cypress swamps, some of these con- taning the tallest and cleanest cypress to be found in Florida. East of the lake t Everglades fade away irregularly in the Alla- pattrah Flats, a region largely under water at the end of each rainy season, where intending strips of saw-grass swamp and grassy priie, set with patches of cypress and, more rarely, with hammocks of hardwood, stretch away in an almost dead level. Farter south the Everglades are bordered by praise and cypress swamp or at a few places reach nearly to the cost rocky pine-lad islands that extend southwestward from the main body of the Biscayne pine- land nearly to Whtwater Bay have a fringe of prairie, but east of them lies a saw-grass strait and to the south lie wide expanses of saw grass dotted with keys that disappear seaward among thickets of dwarf cypress or mangrove. On the west the Everglades from GEOLOGY AND GROUND WAThER OF FLORIDA. Whitewater Bay to Lostmans River reach the mangrove swamps tht fringe the coast. North of Lostmans River an arm of the Ever lades runs up between the mangrove swamp and the prairie board ing the pine islands and gradually disappear before reaching Ae River. Cypress swamp and prairie form the western bound of the maln body of the Everglades from Lostmans River to Caloostc River.A narow strip of small cyprs is said to exend along the western edge of the Everglades for 60 mis south of Sam Jones town legion and drainage erences in elevation are slit; few of the islands are more than 2 feet above hgh-waer level, and the slopes are so gentle as to be detected only by the movement of the water or by leveling The general slope south but, in spit f the water seen everywhere in the rainy season, i not uniform. w, ir ar rises, measured 2by inches only, serve to divernfy the watr and sedgecovered peat in thee r ot of t year. Thre a also sloughs-narrow winding strips of open water through the sedga- some of which extend for mies Often it is not posble to detect a perstent current in thee h pasag, wlhih, for the most p~ seem to lie north and south along the west side of the Everglade and nororthnrthwest and south-southeast along the east side. The water brought down by Kissinmee River escapes from lke Okechobee through a canal connecting with the Caloosahatchee and through the saw grass. The short streams around the southern edge of the lake, shown on most maps of Florida, do not flow into the lake but from it They close up within a few miles and the tick grot of saw grass makes the movement of water in any given direction very slow. Some of the water entering the lake reaches the Gul and some the Atlantic, the water moving as a mss slowly sout ward When the lake rises to about 22 feet above mean sea level it is said to overflow into the Everglades along its whole souther border. As evidence of the flatness of the Everglades, residents of the east coast state that when the canal leading from the lake was darnd at Lake Hicpochee in the year 1904, racing the level of the water above the dam 3 feet, more water came down the east coast rivem as far south as New River, and the marginal prairies were under water so late in the fall as to hinder seriously the growing of vegetables, but whether the dam caused all the trouble complained of is doubtful. Since Lake Okechobee overflows to the south and the waters e c; ing from it may reach either the Atlantic or the Gulf, the elevatin of its surface is in a way a measure of the elevation of the Everglade. Several determinations of its level have been made by Covernment engineers and surveyors. An elevation of 20.4 feet was found by a party of engineers in April, 1901, but an even lower level-19.8 feet- GEOOGRPHY OF SOUTHERN FLOIDA. Reported to have been found in March, 1908. High-water levels published by the Unite States Chief of Engineers are 22.4 feet in 1886 and 23.4 fet in 1878. Comparatively few determinations alongthe edges have been reported. Some determination along the stern margin are: West of Lantana, 18 feet; west of Hillboro Inlet, 14 fet; west of Fort Lauderdale, 3 to 9 feet; at the pool at the head of Miami River, 6.2 feet. South of the Biscayne pineland and Long Key the height of the Everglades is less than 6 feet. Wright1 says that the mean water level of the lake is 20.5 feet, that the low- water level is about 19 feet, and the greatest depth at low water is 22 feet, making the bottom at that point 3 feet below sea level. Willoughby in his trip across the Everglades from Harney River to Miami River found that the water on the west side had a slow move- ment southwest, aInd on the east side a similar movement southeast Ingraham, who crossed the Everglades from Fort Shackelford to Miami, found a southerly movement in a creek connecting Okaloa- koochee Slough and the Big lCpress but little current in the sloughs W. J. Krore, who made a careful survey of the southern Everglades for the Florida East Coast Railway, found a slight southerly current in the slough that forms the headwaters of Taylor River between the mainland ad Long Key. The writer, however, found no perceptible current in this slough near Paradise Key in June, 1908. Evdenly at times of high water there is a perceptible movement of the water of the Everglades down the slight slopes toward the nearest outlets. At times of extremely low water the sloughs may be so separated that except in the immediate vicinity of a river no current is perceptible. The normal difference between high and low water in the Ever- gdes is about 2 feet; the maximum difference may be twice as great. In the spring of 1908 it was possible to travel by wagon fror the Biseayne pineland to and about Long Key, whereas in the early winter of 190-7 one could cross the southern Everglades in a power boat. During the Seminole War successful pursuit of the Indians depended on a depth of water sufficient to permit the use of ship's boats. Bedrck.-The Everglades have been variously called a lake in a rock-jrim ed basin and a vast sik In the light of the facts accu- atd by of the War Department, the Disaton Co., the Florida Eas Coast ailway, and the -.:.: of Florida, and by the explorations of Ingraham, Willoughby, and others, both these design nations appear inexact. Bedrock apparently lies at or near the surface around the edges of the Everglades. Along the east side from Jupiter River to Hillsboro 3 0Wght, oJ 0., poirtf the Spoil t the Aegitlatuire of Florida on the Evergodes f Pitda, p h, 1i0.g GEOLOGY AND BOUND WATERS OF FLO1 DA River outrops are few. South of New River they are more numerous and from just north of Miami to Homestead the rock forms ba ridges with a maximum elevation of 15 feet aboe mean water level in the Everglades. This line of ridges bens at its southern end to the west and gradually disappears as a series of rocky keys running west and southwest and reaching nearly to Whitewater Bay. South of this rock idge, from Cutler on Biscaye Bay around the southern end of the mainland, past Cape Sable, Whitewater Bay, Ponce de Leon Bay, and the Ten Thousand Islands, there e no outcrops of bedrock above the ea level; nor are there any along the shore south of Sanibel Island. On the southwesen side of the Evergldes rock comes within a fot of low-water level in Rock Creek, an ar of of of the series of bays that together make up much of the lower 12 mil od Lostmans River Three miles northeast of this point rock outcrop in a pine island. hence northward many rock exposures are scat- tered through the flatlands. They can be seen at the head of Allens River and 11 miles to the east on the property of the Deep Lke Fit Co. The belt of country in which rock is exposed widens north ward and at Naples is fully 40 mies wide from east to west his region is monotonously level and the rise of the rock surface inland is slight. In short, bedrock outcrops around the main body of the Everglades from Jupiter River to For Shackelford with no important interruption except between Lstimans River and the west st of the rocky keys beyond Long Key. n this break rock does not on the average lie more than 5 feet below the level of low water. If allowance be made for the general slope of the water level toward the drainage channels on the east and west coasts, the hydraulic gradient amounts to 0.3 foot per mile for 30 miles northwest of Miam It is evident that the actual depth to bedrock in the middle of the Everglades is only 3 to 4 feet below a level line extend from rock rim to rim. As these points might be 40 miles apart, and s the depth below the line at the latitude of. averages less than 5 feet, the inappropriateness of theterm basin for the southern por- tion of the Everglades is evident. Nor is the term sink more accurate. The area is too large; the o floor too flat Potholes and small sinks are common in the rocky prairie south and southeast of the main body of the Everglades, and large sinks fied with mud may exist in the main expand, but their existence is not proved. Possibly, also, sinks of some size may exist between the line of rocky keys and the north shore of the Bay of Florida. Certain features of Bear and other lakes back of Flamingo suggest that they are sinks. Although the rock floor of the southern Everglades is nown to be amost flat, yet it is altogether possible that farther north there are true basins of considerable extent. The preliminary surveys for the G*OGBAPHY OF 80UTHr RN FLORA drainage work undertaken by the State at New River showed that bedrock slopd off more steeply at that place than to the south or the north, and a depth of 20 feet to bedrock improbable in a strip a few miles wide. Reports are current of an east-west rock ridge 8 or 10 mile south of Lake Okeehobee within 6 feet of the surface but are probably without substantial basis A rock ridge rises north from Long Key, reaching as far north as Miami, but according to report, sounding with a 10-foot pole on a line from Fort Shakelford to Miami, found no rock ti within 15 miles of Miami Hence there is a probabili that the Everglades cover a series of shallow rock hollows. Whether these hollows were as deep when first occupied by the Everglades as they are now, whether they represent original inequalities of deposition of the lime rock, or whether they are buried shallow valleys can not be determined from the evidence at hand It is probable, however, that the deepening and enlarging effect of underground solution has been exaggerated. Bedrock lies 10 feet below low-tide level at Jewflsh Creek, 18 fet below at Flamingo, 5 to 10 feet below in Whitewater Bay, 13 feet below at the mouth of Shark River, 13 feet below at the mouth of Lestnans River, 12 feet below on Chokoloskee Island, and 5 to 10 feet below at Everglade. Dredging in the canals west of Fort Lauderdale show rock (not oolite) near the surface 7 to 10 miles west of the town. Regarding the rock ridge reported in the Evergades south of Lake Okechobee, R. E. Rose, State che t, who is filiar with the results of the Disston surveys, in a letter to the writer says that no rock was found at 12 feet, the leng of the sounding rod, between a point 20 miles south of the lake and the lake, and that he has never found rock with a 10-foot rod near the south side of the lake. According to his recollection rock was found at 8 feet 20 miles south of the lake. The South Canal survey approaches the rock reef on the west (in T. 48 ., R. 35 E.) farther east the muck is deeper The light westward slope of the larger part of southern Flrida, to which reference has been made, is due to a recent tilting and to deeper accumulation of sand along the ocean than along the Gulf shore rather than to variations in bedrock level. The latter is effective only along the southeast side of the Everglades. Ogin of the Everg~ades.-The Everglades owe their existence primarily to an abundant rainfall and to the slight elevation of southern Florida. Even were there no basin-like structure whatever, and were the bedrock surface absolutely flat along an east-west line, the present rainfall, the slugs drainage, and the luxuriat growth of vgetation would result in a swamp forming aross the center of the peninsula from Lake Okehobee. In short, the Everglades emb le in origin the Dismal Swamp of North Carolina and Virginia. GEOLOGY AND GROUND WATEM OF FLORIDA The peat found throughout a large part of t Everglades reso on rock, sand, or marl In places sounding indicate more than one peat bed, with sand between. The relations of peat and sandto bedrock west of Fort Lauderdale are shown by a section along te drainage canal the. (Se fig. 1.) CYPRESS SWAMPSO Most of the many tract of cypress scattered over southern Florid all for no especial notice. Probably te finest cypress grows north east of Lake Okechobee, but the largest tract of good timber ae west of the Everglades; Okaloacoochee Slough and the Big Cyprt are the two most important. Both have extremely irregular outline with numerous arms forming strands among adjacent pine islands or prairies The southern boundary of the Big Cypress is not on most maps of southern Florida and on many its extent is greatly exaggerated, the name being printed across a region where cypre swamps, prairies, hammocks, and pineland are intermingled During the Everglades to the Gulf north of Cape Romano. The maximum east-west width of the swamp may be 40 miles. Ten miles east of the Cypress. Waters Sand Muc Ui.estone (Miami polite) fItU 1-Eection na edg of Eergtr swa weat of Fort tnites wde-, st Iw rlL Vertical scale, Inc 36 teet; hortiontal sde,1 at It -Iperiod nnof high water bostern pass through the rs fBti COASTAL SWAMPS. As a consequence of the low relief and the gradual slope of the east-west width of tie may be 40 mils. Ten mils Of the land below sea level, southern Florida has wide areas of coast swamp. These areas include (1) wet lands along lagoons or rivers lying back of the barrier beaches of the east coast, covered party by open marsh and partly by scrubby growths of mangrove, and (2) the more extensive swamps of the south and southwest coast, which die away in a network of channels and islands. On the west coast these mangrove covered islands and the mangrove swamps behind extend from Whitewater Bay, the southernmost arm of whi: c Cypress. COASTAL 8WAMP8. is separated from the Bay of Florida by less than 5 miles of wet prairie and swamp to Cape Romano North of arco the coastal I(The iel ) or river-; 1. ack of the of the partly by ol -mrsh and r fy by i -,ru D-t' iof v and (2) the 1r extensive Swampsg Of Lte and soL it coast, which die I i a net of On d islar tOnhi west iIt a j from ay, the -i-of is )d from the y Morida by 1, i than 5aile of wet prai a rjnd swamp, to Cape Romano. North of Maro the cosa GEOGRAPHY OF SOUTHERN FLORIDA. lands and the swamp land include pine islands, and in places north of Naples pines grow to the Gulf shore. The red manrove most frequently grows as a bushy tree, under 20 feet hih. The swamp that forms te southern fringe of the main- land from Chi Gut to 6 miles east of Flamingo has such low trees, as have many islands in Whitewater Bay and most of the patches of swamp along the main line of the Florida Keys from Biscayne Bay to theMarquesas. But in the Shark .: .. .. archipelago and the southern portion of that unmapped maze of land and water, the Ten Thousand Islands, the mangrove forms a noble forest, the trees growing to a height of 60 feet or over with clean smooth trunks 2 feet or ore in at the butt and without a limb for 30 feet from the ground. They rise from the Gulf like a agree wall and are one of the most string features of the shore line of southern Florida The majestic appearance of these trees compared with the look of those in White- water Bay can not be explained by any local peculiarity of climate. Rathr does it result from the aeration of the thick bed of soft gray mrl on which they grow by the swing of the tides, which here have amplitude than anywhere else on the whole coast of the peninsula, fully 5 feet. Northward, toward Cape Romano, the trees become smaller and along te inlets back of Caimbas they are as bushy as in Whitewater Bay. The maximum width of coastal swamp in southern Florida is un- known, since the boundary between coastal swamp and Everglades is a matter of After a season of' . rainfall the chan- nels leading from the latter carry fresh water and after a dry season salt water. Thus in May, 1908, the writer found sat water in Lost- ma River within the Everglades, 17 miles from the mouth of the river, while in October of the same year, after the heavy rainfall of the summer and early fall, the water was fresh to a point within 5 nile of the Gulf. GENERAL CHARACTER. The keys or islands that fringe the south Florida mainland differ greatly in sie shape, and surface features. Some are typical barrier beaches, long, narrow, lowlying banks of sand, crowned with coco- nut palms and buried in mangrove swamps to landward. -:'. are true mangrove islands, shoals formed by the efforts of tidal and wind- nduced currents where mangroves were able to take root and arrest a lterial thrown up by the waves. Other are sand banks so low- ying or so exposed as to support only a scanty growth of beach ses and weeds; and still . notably those in the main chain hat extends from Virginia Key opposite Miami to Key are of rock or hav a rock foundation reaching to or above mean sea level GEOLOGY AND GROUND WATERS OF FLORIDA and covered with various scrubby hardwood trees, palms, and even pines. Within this chain, fringing the mainland or dotted over the Bay of Florida are many keys in all stages of growth, from banks below sea level to banks just bare at low tide on which mngroves have got foothold and by their entangling roots are catching seaweed and drift wood, arresting the movement of calcareous sand and mud, and e- tively pushing out the shore line. Whitewater Bay, which lies bind Cape Sable and has an extreme northwes~outheast length of perh~ 20 miles, is full of these mangrove islands. .. of Whitewater Bay the Ten Thousand islands form a network of channels and of marl banks supporting a heavy growth of red and black mangrove. From Big Pass to Sanibel island an almost continuous beach of siliceous sand, broken only by narrow inlets, such as Johns Pass, Gordon Pass, Big Hickory Pass, and Big Carlos Pass, faces the Gulf. These passes lead to inner "bays" dottd with islands of many sizes, but with few features of especal interest. Though the islands along the coast of southern Florida may be readily divided into definite types, as barer beaches, rock islands, and mangrove islands, it is not possible to state from present infr- mation the relative importance of these types The decided differences of surface of the keys-bare rock or rock with a very thin veneer of leaf mold, sand, and marl-and the light differences of elevation above high tide, have resulted in great differ ences of vegetation. Near the water's edge and on flats or on rock beaches beow high- tide level grow mangroves; on the beach ridges coconut palms, not indigenous, flourish. Inland the low marl flat support grss sedges, and salt meadow weeds. The higher ground, caled hammock, supports a dense growth of scrubby hardwood trees, buttonwood, ironwood, and madeira, little of which attains a height of more tha 20 feet. Three of the keys,..' :....... Little Pine, and Big Pine, notably the .:.: carry patches of pine. The rock outcrops along the keys differ from those of most of the bare rock in the Biscayne pineland or in the flat lands of the west coast between the Everglades and Cape Romano. They are weathered, hence more even, and not jagged looking, except on spray- worn beach slopes. Angular blocks, disrupted by tree roots or by temperature changes, are scattered over them, but in places the sur- face is comparatively smooth over areas of 20 to 100 square yads Holes and hollows resembling those found in the Biscayne pind and formed in the same way abound, but the rock itsef has a ook of newness; its major inequalities are not the result of subaerial decay. It is like that of some of the low keys in the Everglades west of Lo Key. GEOGRAPHY OF SOUTHERN FLORIDA. Since the keys were elevated to their present height they have been subjected to forces tat ted to advance the shore line and to those that tend to push it back. The easily winds have played an important part in giving the eastern and southern faces of the keys teir present forms. Dferenes in time and height of tides in Florida Strit and the Bay of Florida, together with te area of the bay, reslt in trong current sweeping through the p asages between the keys, rticularly the openings wnt of Long Key. When northern blow the shallow waters of thee b ar milk-whit over large areas from the y stuff in suspenion. This is depoted, to be picked up with a change of wind or tide, or is carried to sea in such quantii as to show in the blue waters of the Gulf Stream 10 mes ousde the keys The bars and banks about the keys and in the Bay of Florida, the areas of marl ad calcareous sand above sea level, show the activity of waves and currents and ndcate how much material they have recently handled THE FLORIDA REEF. The shores of the main line of keys, extending from opposite Bi- cayne Bay to Key West and Boca Grande, are in plaes rocky and in oer places are bordered by flats of soft marl or calcareous sand On some keys the surface is bare rock; on others it is sand or marl; on very few do wide strips of land stand as muchas 6 feet above the highest spring tides (See P1. VII, A, B.) The longest key-Key Larg~ -is 30 mile in extreme length, buis nowhere over 3 miles wide, and its maximum width above the high spring tides is considerably less Big Pine Key is 10 miles long and high ground is nearly 2 miles wide with a greatest elevation of 10 fee. Key West is 4 miles long by 1 mile wide and its highest ground, which is near the center of the city of Key West, has an elevation of 13 feet. The highest measured points in the whole chain of keys are two small knolls 18 feet high, one on Windleys Island and the other on Plantation Key, just to the north. The knoll on Windleys island was quarried for fills and bllast along the railway line to Knih Key. The Florida Keys are separated by Bahia Honda Channel into two distinctly differentiated divisions. East of the channel the islands are narrow and le along a sweeping are cured toward the southeast. Outside this arc is the Florida Strait; ide it are the Bay of Florida, Barnes Sound, Blackwater Bay, Card Sound, and, Bicayne Bay. The western end at Bahia Honda is 35 miles from East Cape on Cape Sable, the nearest point of the Florida mainland. The rock uidge of Key Largo is not 2 miles from the edge of the mangrove swamp that fringes the end of the peninsula and from there northward the keys are within 8 miles of the mainland, GEOLOGY AND GROUND WATERS OF FLORDA. West of Baia Honda the keys form an archipelago rou trian- gular in outle. In this group, the westward prolongaton of the arc in which lie Bahia Honda and the keys to the east and northea is found in the southern shore ine of the keys; but the keys themsves, instead of lying parallel to this arc, have a prevailing north-northwaet, south-southeast arrangement, perpendicular to the arc. The caue of t striking dissimilarity in position are twofold, a difference in rock structuIre and a difference in the direction of the force which have shaped the islands. Bahia Honda and the keys east of it represent an uplifted cora rd more or les covered with sand and marl; hence their basement roc ridges have the trend of the cora patches of the old reef. The ke west of Bahia Honda consist of an oolitic limestone formed from depoe its in a broad expanse of shallow water hence thee was no orial ridgelike upbuilding, no pronounced trend to the rock structu Dif- ferences in resistance to erosion have resulted in irregularities of the rock surface, which, as along the old reef to the east, have been more or less covered with marl and alcareous sand. The prevailing north south trend of the passages separating the keys, hence the end of the keys themselves, is due to tidal currents, which owe their power to differences in time and height of the id of e Gulf and the Strait of Florida. The shaping of the great arc of the keys is the joint production of several factors. The old coral reef that forms its greater part built up from the bottom in water of a certain depth along a line that had the general direction of the outheastern and southern edge of the submarine plateau of the Florida peninsula. The cue of its western end was controlled more or less by the eastward flow of the Gulf Stream against the westerly movement of the prevailing ds. The writer did not visit the Tortugas, which have been describe by :. ... and by Vaughan, nor the Marquesas, an atol-like group of beach ridges and mangrove islands that s presumably under by the Key West oolite not more than 10 to 15 feet below sea The Marquesas are of Recent age, and according to Vaughan Tortugas are also. TOPOGRAPHY. The-shaping of the shore lines of any region is the joit work f tidal and wind-made currents, waves, and winds. he share of each of these agencies is determined by the efficiency permitted through antecedent conditions of coastal topography, the character of the shore-line materials, and the circumstances controlling the general of ocean currents and winds, and the work being done at any given time is in a measure controlled by the rise or fall of th land with reference to sea level. Thus shore-ine features have the aspects of infancy, adolescence, or maturity, according to the length U. S. G~OLOG3CAL SURYYY WATER-SUPPLY PAPER SIR PLATE VII A. BEACH RIDGE OF CORAL AND SHELL SAND, KNIGHTS KEY. Ar B. CALCAREOUS SAND ON REEF ROCK. WATER-SUPPLY PAPER 819 PLATE VII U LGEOLOIMCAL SURVEY NEW A WATER-SUPPLY PAPER 319 PLATE VWI A. MANGROVE KEY, WATER'S EDGE. B. ROOT GROWTH OF MANGROVES, SOUTH END OF KEY VACA. -1 U. S. GEOLOGICAL SURVEY GEOGRAPHY OF 8OUTHERE FLORIDA. of time the waves and currents have been working at a certain level and the effectiveness of their attack on the land. In the same region, s in southern Florida, adolescent features may be found where the attack i strong, and infantie where the attack is weak or ineffective. The south Florida mainland is low, its coasts dip gently beneath the water, and the shore-ne materials are nearly eve here uncon olidated. Under these conditions slight changes of level can swing shore lines over long distances, and the effectiveness of wave attack is easily modied by agencies, such as coral, which tend to build up and, or agenies, such as maroves, which tend to push out the shore. (See PI. VIII, A, B.) The region has no welmarked valleys and no large rivers; hence atnteeent drain ge has been of minor niportance in deter the work of waves and currents The streams are clear, they bring down little matter in suspension, their waters are not heavily miner- alzed, and they contbute comparatively little to the sea bottom; hence delta builin is inienifcant. At the same tine an intense amount of limy material is supplied by the remains of marine organ- iss, the agitation of the shallow near-shore water facilitates the depo- sition of calcium carbonate, and the effluent swamp waters contain organic compounds that may act as precipitants; hence banks of narl form near river entrances or outside of passages leading from lagoons, and where the banks are protected mangroves gain a foot- hold and iterrupt the sequence of forms that would reult from the unopposed action of waves and currents. Maps of the east coast show a shore line with adolescent features, such as uspate forelands, weildeveloped bay bars, and long beaches with gentle curves. The offsets and overlaps of the bars and beaches sow that the movement of sand is toward the south. This move- ment is ver marked at Jupiter Inlet. When the bay bar at the outh of the inlet is cut through at its north end to make a navigable nel, the drift of the sands makes the channel travel southward, as it approaches the south side of the inlet it shoals up and the ater flows over the bar in a shallow sheet. OCEAN CURRENTS. Vaughan has~ summarized the action of the forces that produced a Flridian Plateu and has called special attention to the or- ne of ocean currents, as follows: Importance of curenta in shaping the land area of Florda has been emphasized real eecone of the preceding dircuon. Before the history of the current of a n an be thoroughly undertood it i necessary to know the history of the Hat- azi of TNorth GCarol. The present Flonda countercurent seem due partly to nping~ement o the Gulf Srem nst the attem projection, resulting n a A rBn to the history of th FidI Plateau: Pb Carngie h Wihldgton No. 13, 1910. . 319 -6 765340-wsr 31O~--6 GEOLOGY AND GROUND WATERS OF FLORIDA. portion of the waters being deflected southward along the coat d of continung their northward journey. The Hatrter axi has existed as a dividing line between depitional areas apparently since Middle Cretaceous time, and it has been eitr region of sho water, or occasionally a land area, since later Eocene time. The Vick burn and Apalachicolan seas were both warm, tropical or subtpical in tempe ture. It is not definitely determinable at parent whether the warmth of these wa s due to currents directly from the Tropics or to wam return currents produced by the northward-flowing Gulf Strem having a portion of its waters diverted southard by impinging agat t a laient from the more northerly land area. In Miocene time it ia definitely known that a cold inshore current found its way southward to Florida and westward to Penacola. This current may be due to the Miocene submergence of the Hateras area sufficiently lowering the sea bottom off lht- terato permit the Gulf Stream to continue its course unobstructedly northwrsd Should this hypothesis be correct a reexamination of the faunas of the Miocene dept- it of northern North Carolina nd Virin and those of outh rn North Carol (the Duphln marl), South Carolina, Georgia, and Florida, with reference to synch~ny may be necemitated The Miocene outhwad current transported quantities ter- rigenous material and deoited it on the astern border of the Floridia Plateu. Sine Mocene time there have been constantly return currents of arm water (how- ever not so warm the Gulf Stam), and they, aided by wids and ides, have deit terrigenouh material on the eastward ide of the land areas wee ing a portion of it to the southern end of the Plateau. Thee current were active during Pliocene and Pleistocene times, and are still active to-day. The shape of the upper surface of the Floridian Plateau, the land areaof its ester side, the arrangement of the geologic formations of suceeessive ages, the directions of the st cou and the contour of the present coast line owe their peciii and characteristic to the concomitant operation of the forces producing dformtion and to oceanic current. The writer does not share Vaughan's view as to the exstnce of great return eddies of the Gulf Stream and their effectiveness in modifyig coast lines, either to-day or in time long past. The sand grains along the east coast of Florida have traveled southward not at great depths but in shallow water, along beaches and bars Such being the case, their travel as determined by the inshore waves and current, which are mostly tidal or wind induced. The anle of inidence of the waves along a stretch of beach is chiefly a mater of wind diection. Were the near-shore currents and waves to move material northward rather than southward, a return eddy of the Gulf Stream, a mile or more offshore, would have very little to do with the shaping of the shore line. Moreover, the writer doubts the stence of a great eddy of the for that Vaughan's words imply. Of course, the movement of such a body of water as sweeps through Florida Strit must be accompanied by eddying, but the writer in his observations along the keys saw no sign of any general, persistnt return eddy. The drift of sand and mud, as indicated by beaches, banks, and bars along the great are of the main line of the keys, is the work of local inshore currents that change continually in dire- ton and strength but are controlled by the tides and the more effective winds. A balance of effect is shown in the Marquesas, where waves from the east and waves from the west seem to be of nearly equal strength in piling up sand and mud. PART II.---GEOLOGY NORTHERN AND CENTRAL FLORIDA. By G. C. MAoN. GEOLOGIC R CORD. The processes which formed the ocks comprising the State of Florida have changed from tie to time, but they have always ben similar to those now operating along the coast. That the rocks are largely of marine ori is shown by the presence in many of them of shells of marie animals similar to those that live along the coast to-day When the sea was clear animal ife abounded and the shells accumulated to form limestones, but when the water was muddy sand and clay predominated in the deposits. Thus the roks of Florida record the conditions which existed during their deposition. I some places accumulations of clay, sand, and gravel appear to have taken place on land or in rivers and lakes, giving rise to nonmine formations, but these deposits are only a minor portion of the whole. Although the rocks of Florida may appear to indicate continuous sedimentation there is good evidence that deposition has at times been interrupted by periods when the land emerged from beneath the sea and was subjected to erosion. During these periods the action of air and water removed part of the materials already de- posited and left an uneven surface. When the land was again submerged beneath the sea other materials wre deposited upon the eroded surface. Such breaks are known as unconformities. The same forces which caused the land to rise above sea level sometimes operated to produce a slight compression of the strata. In this manner the peninsula was raised in the form of a broad ah several hundred feet above the floor of the deep sea This fact is not readily apparent, because the land surface represents only the higher portion of the arch. Minor folds of the strata are also nown in Florida, but they are mostly inconspicuous and are recog- nized with difficulty. GEEAL SUCCESSBBION OF FORMATIONS. The time that has elapsed since the oldest known rocks were formed in the New World is so long that any attempt to estimate its duration in years would be futile. The rcks deported during that time have been divided into several systems, of which only 85 GEOLOGY A"D GROUND WATERS OF FLORIDA the last two are represented in Florida. Of these two the most recent is known asthe Q te d the one immediately pre- cedigas the Tertiary. The rocks belonging to the Quatern system are subdivided into two series, known as the Recent and the Pleistoene. In Florida the Pleistone began with an uplift that carriedthe surface higher above sea level than it is at the present day Th uplift was followed by an interval of extensive erosion, which was terminated by a sinking of sufficient extent to carry the lowlands beneath the sea The degree of bmergence vared. Later another emergence raised the surface of the State somewhat above its present altitude. This change in level is regarded as the closing event of the Pleistocne epoch. During the Recent epoch slight chang have occurred, none of them being of sufficient magnitude to be compared with the movements during the Pleistocene. Duing both the Pleistocene and the Recent epochs sand, peat, marl, and coquina accumulated over nearly the entire State. The rocks blongig to the Tertiary system are commonly grouped into four series, of which the youngest is the Pliocene. The Pliocene of Florida has been subdivided into five formations which differ more or less from each other. They are known as the Lafayette (1) formation (Pliocene ), the Nashua and Caloosahatchee marl, the Alachua clay, and the Bone Valley gravel. The Lafayette (I) form- tion is commonly composed of red and yellow sands ad sandy delays, which cap the ls and uplands of north Florida The Nash and Caloosahatchee marla consist of sands and marls which contain shells of marine organisms. The Alachus clay is commonly sandy and locally cntainns many bones of large land animnas. The Bone Valley gravel is a phosphatic gravel, which is known as land pebble phosphate. Subsequent to the preparation of this manuscript some evidence was obtained that seems to warrant the tentative inclusion of the Bone Valley gravel in the Miocene. Though these formations are described separately and are represented by three different color on the geologic map (P1. I in pocket), it is probable that all of them except the Bone Valley gravel are largely contemporaneous. Next older than the Pliocne are rocks belonging to the Miocene series. These are divided into two formations, known as the Choc- tawhatchee marl and the Jacksonville formation, though probably deposited at about the same time. The former, which is a shell marl, is well exposed in north and west Florida; and the latter con- sists of limestone, delay, and sand, known chiefly from well records at Jacksonville and farther south along the east coast. The oldest rocks known in Florida belong to the Oligocene series. They comprise several formations arranged in two groups, known as the Apalachicola group and the Vicksburg group. Of these groups, GEOLOGY OF NORTHERN AND CENTRAL FLORIDA. the younger (Apalachieola) contains four formations-Alum Bluff, Chattahoochee, Hawthorn, and Tampa. The Alum Bluff formation is the youngest, but the other three are believed to be largely con- temporaneous. The Alum Bluff formation comprises the typical sands and delays which characterizethe formation along Apalachicol River and elsewhere, together with the Chipola marl, Oak Grove sand, and Shoal River marl members. The Vicksburg group includes three formations, known as the Ocala limestone, "Peninsular" limestone, and Marianna limestone. The limestones of the Vicks- burg group are especially important because they underlie the entire State, and furnish the artesian water in all the large areas where flowing wells are obtained. They are exposed in many of the build- ng-stone quarries and phosphate mines. The rocks belonging to the oldest epoch of the Tertiary (Eocene) are not exposed in Florida, but tey occur at the surface in the adjoining States and they doubt- les unerlie the limestone of the Vicksburg group. The following tale shows the general succession and character of the geologic formations of Florida. 'The nme of thi frn atos printed on the nmp (P, I) as Hawthorne, th spelling d in some grisly poblihed port, but a the gerphrt m~me f which It It derived s polled Hawthorn, t flnalte sb bmn dropped in the text. GEOLOGY AND GROUND WATERS OF FLORIDA. I ,i I I TM . A2A I I '. 11 _4 *inc~rodinuoolni(i pd ui |S i S 8 GEOLOGY OF NORTHERN AND CENTRAL PLORIDA. *LmR.iAw 70 GEOLOGY AND GROUND WATERS OF FLOBRDA. : I Ipt J: p 00 oo 56 "B I ' Le I qo i Ba j 0. ~ GEOLOGY OF rORTIERN AND CENTRAL FLORIDA. OLIGOCENE SERIES. The Oligocne rocks may be separated into two groups, called here the Vicksburg group and the Apalachicola group. These two groups were formerly regarded as Eocene and Miocene, respectively. As early as 1846 Conrad referred the ocks exposed at Ballast Point near Tampa, together with the prevalent rock of the peninsula, to the uppe division of the Eocene; and for many years the rocks here included in the Vicksburg group continued to be called Eocene by numerous writers, including Bailey,2 Tuomey," Smith,' and Dall. The deposits here called Apalachicola group were first differentiated from the Vicksburg in 1887, when Langdon 6 examined the Oligoeene beds of Apalachicola River and reported that they were Miocene. This name was retained for some time but it was modified by the use of "old or ubtropical Miocene" to distinguish it from the later Miocene. In 1896 Dall7 published a brief statement of the reason for regarding the socalled Eocene and the so-called "old Miocene" of Florida as Oligocene; and this designation has since been followed in many but not in all publications dealing with southern Coastal Plain geology. NOMENOLATURE. After the setting apart of the "old Miocene," there rem ned a considerable thickness of rock which was still regarded as Eocene and was known as the Vicksburg limestone.' This name had been used to include all the older Tertiary rocks of the peninsula, com- pring both the Vicksburgian limestone and the deposits here caled Apalachicola group, but with the increase of knowledge of the geology of the State it was gradually restricted to the older lime- stones. Subsequent study indicated that this group of older lime- stones, though presenting but slight ithologic variation, was divisi- ble on paleontologic grounds into two parts, the lower division (here i Conrad, T. A., O a on the geology of a part of east Florida, with a catalogue of recent shells ftb coast: Am. iour. Be., d sr., vol. 2,, -, pp. -4. SBailey, W, Am. Jour. Bt, 2 ser., vol. 10, 18, p. 282. *Tomeey, ., A noto of the geology of the rida kys: Am. Jour. Sel., 2d sr.,vol. 11, IM0, pp. 390 Smth, E. A., On the geoy Florida: Am. Jour. Sea., 3 sr., vol. 21, 1l81, pp. 28-I9. * D', W. H, d ., ad a, D., C pap: Bull U. eol. Survey No. 84, 12, SI~gdon, Dil, r Soe F a Moe: Am. Jour. Bl., Sd sr, vol. 38, B, pp. 322-3 ' Dall, W. H., Deeriptio of Tertry fasls from the Antll rn Proo U. Vt. Nat Mms., vol. 19, No. u, 1B96, pp. 3-05. SBull U.. G. eol. Surey No. 84,1843, pp. 101-104. E. A., On thegeology of ord Am. Jour. Sol., ad ser., vol. 21, 1881, pp. 202-301. GROLOGY AND GROUND WATEhB OF PLORIDA. lled "Peninsular" letone) being de ntd the "Vicksburg" limestone and the upper the Ocala limestone Still later, Dal pro sed the abandonment of the name Vicksburg as apple to stones of the peninsula of Florida and the substitution of the te~n "Peninsular" for the lower division above described. He stat: From the obserions on the typical Vicburgan by Col. Cy it e ble that the Orbitoidal limetone which forms the mam of the Floridian Pate, rd which hal been, in this work and m the literature generally, called the Viclua limestone may really form different horion together f the typic . ian and be intermediate between the latter and the nuimmulitic Ocals lmtone In order to promote cleaned nnd avoid confu~on, it is probably advable to adop a distinct name for the Orbitoidal phase or formation, for which I :.would : term Peninslar limestone. This is intended not as a permanent formation e but as a general trm for the fundamental platu leone of Florida, in whic close and thorough study may reslt in he dicinaton of more than one houo or zone, The reason for the change suggested by Dall is the fact that the fossnln which have been regarded as charact~rist of the Vicksbuar have been found to occur at other horizons, and hence their occ1p rence in the limestones which underlie the numutic rock of the peninsula can not be regarded as proof of equvalence of that ime stone with the limestone at the type locality at Vicksburg, Miss. The question of the correlation of the Florida formations is further complicated by the fact that two horizons are represented in the bluff at Vicksburg. To avoid further confusion, however, the lower Oligocene rocks in Florida, originally known as the Vicksburg stone, are here designated the Vicksburg group. The group is thought to comprise thre formations, here called the Ocala limestone, the "Peninsular" limestone, and the Marianna limestone. The "Peninsular" and Ocala limestone were recognized by Dal; and the name Marianna limestone was later given to the soft, porous, light-gray to white limestone of western Florida, which are characterized by an abundance of Orbitoides mantellt and other Foram inifera and many other fossils, prominent among which are F da poeudoni and P. perpZanua. At the type locality (Marianna, Jack- son County) this limestone is so soft that it can be cut into wi tha saw. It contains some beds of chert and many of the are slieci.ed. Lithologically the rock at Marianna resembles the Oeala limestone at Ocala and the "Peninsular" limestone but it differs from the former in the character of its fauna, especially in the absence of nummulites, and it is believed that it may represent a horizon below the "Peninsular" limestone of Dall. The close lithe S. WanrFress Inst. t, ol. 3, Ipt. 0, i 1h54. aseo, 0. C., ad clawp, Q., scn Ann. Rpt. Florida GaoL Survey, 190, p. B. GEOLOGY OF NORTHERN AND CENTRAL FLORIDA. logi resemblance between the Marianna limestone and the "Penin- sular" limestone, however, makes it possible to combine much of the discussion concerning these two formations. MAIANN A AND "PENINSU IR" LE mTONES. 8traiaph pot&ii. -The base of the "Peninsular" lestone is not exposed in Florda and there is no satisfactory evidence jt it has been reached in drilling wells hence the character of the sub- jacent formation is not known. Reference has already been made to the uncertainty concerning the exact correlation of the "Peninsu- 1ar" limestone of Florda. It wil thus be seen that no satsfatory conclusions can be drawn cocerning the relation which the "Penin- sular" limestone bears to the underling beds. Its relation to the overlying formations will be discussed in connection with those formations. The Marianna limestone is thought to be the stratiraphic equiv- alent of the upper part of the bluff at Vicksburg, Miss. Some well in west Florida enter beds of sand and clay that probably represent older formations, but the tratigraphic relation of the Marinna to these older beds can not be determined. In west Florida, where this fo action is recognized, it is unconformably oerlai by beds belonging to the Aptlachicola group or by post~Plocene formations it c caraoer-The M anna and the "Peninsular" forma- tions consist of soft, porous, white or lightgray limestone, in some places resembling marl, especially when partly decomposed. Some bands of darker-colored dense limestone are reported in wells, and nodules and layers of chert are common; chert beds are especiay prominent at certain horns. For the most prt the cherty beds are dker in color than the linestoe and range in thickess from a fraction of an inch to 15 feet. In some localities as many as six or seven successive beds of chert have been encountered in a single well, the heavier layers being, in general, the more persistent. It is usually chert which forms a nearly water-tight cap to the artesian water beds in these formations. Certain beds are abundantly fos- siliferous, containing innumerable specimens of Orbitoides and shells of mollusks, such as PeCten po1dloni. At several localities the rock is so soft that it can be cut into blocks with a saw. On exposure to the weather these blocks harden rapidly, making a building stone of very fair quality. Beds of sand, some of them 10 feet or more in thickness, are reported in some of the wells that penetrate this for- mation. In general these sand beds appear to be most numerous in the northwestern part of the State, but even there they are a minor part of the formation. Thik s.--The thickness of the "Peninsular" limestone and the Marianna limestone appears to be exceedingly variable. The 74 GEOLOGY AND GROUND WATERS OF FLORDA. sickness given by Foerate, from his investigations in southwestern Georgia and the adjacent part of Florida, s 220 feet, and probably this should be regarded as the approximate measure of the Marianna. The thitciess of the Vicksburg group is reported by Dall' to be 140 feet at Salt Mountain, Ala., and, on the basis of well borings, is esti- mated by the same wrier to be over 350 feet at Gaieville, 212 feet at Lake Worth, and 1,068 feet at St. Augustine. From recent exam- inations of well boring by Vaughan and Bassler limestone of Vick~ burg age is known to have a thickness of over 225 feet at Qncy, 250 feet at Alachua, and 325 feet at Bartow; apparently it thickens markedly southward from its exposures in Georgia and Alabama. It is hard to estimate just how much reliance can be placed on well records, because the drill may penetrate some distance into a formal tiion before characteristic fossils are obtained, and it is posibl for folks to drop from the side of the bore and thus ontiue to apple~ in the rilli far below the bae of the formation to which they belong. Of all the estates gien above the one at Ginville probably the most reliable, because the well is eaid to be asedto the bottom. PhyEl ographc ezpres~ .The "Peninsular" limestone ad the Marianna liestone are characterized by a topography due to slu- tion and marked by numerous underground streams, natural bridg~, ink holes, and large irregular depressions. That the underound streams in these formations attain considerable size is shown by a number of large springs which emerge apparently from definite channel&. The most noted natural bridge of the Marianna lie- stone is on Chipola River near Marianna but there are many other of smaller size, both in this formation and in the "Peninsular" lie- stone. Wherever the limestone lies near the surface, rounded hills and sink holes characterize the topography; the sinks form many lake basins in the central part of the peninsula. Paeonologi chaacte Both the "Peninsular" limestone and the Marianna limestone are characterized by an abundant fauna, the most prominent fossil being Orbitoides manelli, with which is associated Pelet poulEotzi and P. perphlua. Dall* says that the fauna of the "Peninsular" limestone includes about 222 species, of which 102 are restricted to it. With the imperfectly known fauna of the Ocala limestone it has 15 species in common; 9 species continue into the "silex bed" and limestone of the Tampa formation, and continue into the Miocene and down to the Recent fauna. Struure.The "Peninsular" limestone and the Mainnna lime stone have been affected by the earth movements which have pr- 1 oete, A. ., Am. Joa r. bL, 3d ser., vol. 48, 1890, p. 46. Bull. U. a. Ge Survey No. 84, 1S2, p. 103. Tr. Wer Free Int. Sol., voL 3, pt. 6, aLO, pp. 16 . GEOLOGY OF NORTH N AND CENTRAL FLORIDA 75 duced the present structure of the State. Their major structural feature consists of a broad anticline. The dips are low and are generally seaward. Local variations in altitude of the surface of these limestones are so pronounced as to suggest that there has been considerable local warping as well as a general arching Toward the southern end of the State the "Peninsular" lmestone dips southward beneath the Everglades, where it is probably buried under some hundreds of feet of younger sediments. Along the east coast this formation shows marked variations in depth; nowhere, however, does it rise to within less than 175 feet of the surface, and at Jackson- vle it lies at least 525 feet below the surface. At Tampa, on the west coast, the "Peninsular" limestone probably lie somewhat more than 100 feet below the surface, but farther north along the coast it may be exposed Apparently the dip of the Marina limestone toward the southwest in the long western exten- ion of the State is very rapid, for at Pensacola this limestone is buried more than 1,100 feet beneath younger sediments. Real disfriution..-As early as 1849 limestone of Viksburg age was noted by J. WW.Bailey, who obtained some "Orbitulites" from a cher at Pyles plantation, about 40 miles west of Palatk. The locality where these specimens were obtained is only a few miles south of Ocla. The same writer mentions the occurrence of similar rock at several points between Palatka and Tampa, but in no case does he give the exact localites. While collecting statistics for the Tenth Census, Smith gathered much valuable information relating to the geology of Florida. He presented evidence to show that limestone of Vicksburg age under lies nearly the entire peninsula of Florida, giving in part its real outcrop and noting the occurrence of Orbiltides masteli, Pe"em o i, and other characteristic fossils in exposures of the lime stone here called Marianna a few miles southeast of Campbellton, at the Bi Spring, east of Marianna, and at other localities which he does not name. From a limestone collected by him 6 miles from St. arks, in Wakulla County, Hilprin identifed Orb6iide maei, and pronounced the roc t be o Vicksburg; but the rock at St. Marks belongs to the Apalachicola group instead of to the Vicksburg group. Smith examined a marl which occurs at various points along the Gulf coast and decided that it also was of Vicksburg age. He states that it forms the basis of the "gulf hammock" land in the coastal counties from Wakul~as County nearly to Tampa Bay in fllaborough County. In describing the real extent of the Vicksburg, Smith included in it large areas of rock which are now known to belong to the upper Oligocene or Apalachicola group; for example, the lime- 1 EBa, i. W., Amn. Joir. BLt, 2 aer., vol. 2, 1i1, p. 88. tntih, E. A., On the elogy of Florida Am. Jounr. Sol, 3d se., vol. 21, 11i, ipp. 20-0. GEOLOGY AND GROUND WATERS OF FLO A. stone extending along Suwannee River for many miles and the ime stone at Tampa. He called attention to the fact that the limeston of the Vicksburg group prevail in the vicinity of Gaineville and that in many places they are composed largely of O ade .... Other localities included in the Vicksburg were ayn Pririe and Ocala. In addition to the locatie mentioned above, Smith reports lime stone of Vicksburg age at Live Oak and Lake City,in the northern part of the peninsula. At these localities, as in many other parts of the peninsula, the formation is overlain by a few feet of younger It is impmcticable with the data yet printed to determine exactly at how many of smith's localities the country rk belongs to the Orbitoide horion om o the, double, will eventually be own to be of later age, as wll be indicted later in i summary. Only those whee no doubt seems to exi will be species here. In Alachua County it is widespread, having been observed by Smith and Dll at Gainms- ville andwestward to and about Archer, though in many places overlain by solution ay residuum, rennantw, or even beds oflater age but moderte thckne Ii had bee identified at Silver Spring, 6 miles eat fom Ocala, by Le Conte,'as erly as 1861,' and subsequently the observation has been confirmed by Smith. Specimen of th rock have been collected by Willcox at Martin station, Marion County, abou8 miles noho Ocala, where the rock is very cherty; and at Jarve's spring, on the other border of Psco County; at Fort Foster, on the North Fork of the Hillsboro River, where, as in many other places, reli of the old Miocene beds overlie it. eve of the loli referred to by Heilprin must remain for the present on the doubtful list, but among them should hardly be counted the islet at the mouth of Homsam River, om which Mr. Wilicox obtained the Pygorhw hua (Raneli) goudi Bouv4, a nall echinode originally described from the buhmone (ante-Claibornian) of Georgia. It will be seen from this quotation ha later investigation indicate that the limestone at some of the localities mentioned by Smih is not of Vicksburg age. However, this should not be regarded as d treating fro the value of the earlier work, for with the increase of knowledge it is inevitable that formation lines should be shifted and that new formations should be discriminated. Miss Maury's summary of the Vicksburg indicates that it forms a large part of the country rock in north-central Florida, and she cits many of the localities mentioned by Dall and Bailey She mention especially the exposures seen in the vicinity of Gainesville, which are surrounded by rocks belonging to the divion here ca d Apalachi cola group. Attention is also called to the ocurrence of psum, which is regarded as the result of the action of sulphur on calcium carbonate, and the occurrence of phosphate rock, resulting from an analogous chemical action. 1BLll. U. S. Owl survey No. 4, IMBS, pp. 102-103 SAm. Jour. Sol., 2d ser., vol. 21, 181, pp. 1-12. SManury, C. The Oiligooene of western Europe and southern United States: Bull. No. 1 Am. Plotol- 00, voL a, 19a, pp. 4-O. GEOLOGY OF NORTHERN AND CENTRAL FLORIDA. During the progress of recent field work the occurrence of the Mari- anna limestone was noIted at Natural Bridge, in north-central Walton County, but there is no indication that it reaches the surface west of this county; indeed, from well records and exposures of other forma- tions, there is every reason to believe that in Escambia and Santa Rosa counties this formation lies some hun s of feet below the surface of the upland. East of Marianna the formation is exposed at several localities where it presents considerable variation in its lithologic characters tic. At some of these localties it is a soft porous white limestne, and at others it is a tough dense gay limestone However, some of this difference in texture may be accounted for by the fact tat the rock hardens on exposure to the air, and it is perhaps significant that the hard gray limestone is usually seen at natural exposures and the soft porous rock at quarrels Near the east edge of the town of Marianna a small exposure affords the following section: Se~ion No. 1, ear east edge of M anna Lfyette (?) formation: rst. Clay, red, andy; some bed8 of aand and gravel ..................... 25 aianna limestone: Clay, white, marly....... ............... ............. 5 Li e, hard, earthy, gray.................................. 2 Marl, blue, ith many ecten .......................... ........ 8 Lim tone, hard, gray............................ ............ 4 Stin No. (approximaely 0 feet below section No. 1). Limestone, had, gray, very fmiliferous; contains Orbttide man Feet telli, Pecn poulont, etc........... .. ........ .......... 5 Chert, dark gray............................................... Limestone, soft, porou, white; a few Orbitoids and other foeils... 30 The white limestone of this action is exposed in a quarry, where it is obtained by sawing. It is used locally for building, especially in the construction of chimneys. Upon exposure to the weather the rock hardens until it resembles the hard meber at the top of the section A well drilled at Marianna penetratd limestone, marl, and clay to the depth of 265 feet, where a bed of quicsand was encountered. An incomplete log of this well is given below Log of well at Marianna. ThlicknLs Depth. Feat. Fee. d n d y m (Plsto ee).............................. ..... Cay, red and yellow, amdy, nd nd (Iyettte(?))....................... 2B 21 fe, hir, d mril, lten gi btde; doubtl-s Ineludes action No. I at the at e d otf e l n... ........................ .................. ........ 45 661 Hurd rock (chrt); towed by a a bed of marl and limtone with cart (Mariann Ilimtnert (t))... 200 2664 78 G- EOLOGY AND GON WA; S OF FLOXR The log of this well does not afford any means of judging at wht depth te base of the M a limestone was reached, but it is possible that an underlying formation was entered some distance above the bottom of the wll At a locality 2 miles southeast of Chiply, the Marianna limestone outcrops in the edge of a sink, and about 6 miles southwest of Chiple and 1 mile north of Duncan it is exposed in some small quarries wha it had been obtand for buildingto t one of these qu1- es, belonging to F. G. Owens, the rock hs also been burned for lie, which was reported to be of oodquality. This quarry shows a 20 feet of porous white limetone, r ambling the rock in section No. 2 at Marianna. Near the surface it is very hard and durabk, but at greater depths it is much softer. Fossils occur throughout the section, but they are especiay numerous in the upper 5 feet, where the rock appears to be large composed of AOrbitides mate. A welldefined ridge at the quarry appears to consist of the Marianna limestone covered by a few feet of white Pleistocene sand and .. -.. lon, the presence of the Marianna being indicated by numerous boulders containing charactexrisi organic remas. A few miles northeast of unan, at Faling Water, a large ink exposes several feet of llght~gray limestone, probably belonging to the Marianna. At thi locality there appears to be a well-defin system of underground drainage, which is indicated at the by numerous sink holes. The bet exposure is seen where a sm~ stream plunges into one of these sink holes with a reported fall of over 70 feet. The rock, however, forms a nearly perpendicular cif and is not easily accessible At Natural Bridge, near the north line of Walton County, a light gray to yellowish-gray marl forms the arh ich spans a sm stream. The width of the channel is probably 20 feet and the.. of the bridge about one-fifth mile. The height of the exposure abov the level of the waer in te creek was estimated by Vaughan' to be 35 to 40 feet. When fresh the rock is soft and crumbles readily in the fingers, but when exposed to the weather it hardens rapidly and assumes the yellowish color mentioned above. It is quarried by sawing, and is locally known as "chimney rock," because it s used in the construction of himneys. A considerable percentage of clay, which occurs in fine particles distributed through the rock, indicates that the material is a marl rather than a limestone. Pee poulsoni is the most abundant fossil. From the lithologic characts of the rock, together with the occurrence of numerous specimens of the species mentioned above, the rock is considered to belong to the Marianna limestone. V 1hghan, T. W,unpubUishd noto. GEOLOGY OF NORTHERN AND CENTRAL PLORA. A quarter of a mile south of Bride, near a turpentine still, a silar marl outop in the bed of a small stream with a thicness of about 20 feet. This rock is slightly more compact than that described above and has a distinctly grayish or bluish color. Thee differences, however, are probably due to the fact that it has not suffered so much weathering as the rock at the '.. :.... Bridge, and its substantial equivalence with the latter can hardly be ques- ~onedL Numerous concretions of nearly pure carbonate of lime are scattered throughout this marl, but they do not appear to have any relation to the occurrence of the fossils. About 7 miles southwest of Marianna and nearly 1 mile from Kynesville, a number of fragments of limestone were obtained from a field, where they were said to have been turned up by the plow. They represent a very cherty phase of the Masanna limestone and are probably residual products of weathering. They consist of boulders up to 2 or 3 feet in diameter, which contain innumerable specimens of Orbitidc e madtelli and Pecten p~oni. At the phosphate mines in the vicinity of Groom, where a number of specimens of Orbitoides mantelli were collect, the rock has the lithologic characteristics of the "Peninsular" limestone. The collec- tion was made from boulders dredged from a mine, and it is difficult to decide whether it is "Peninsular" or Ocala limestone. The pres- ence of a number of specimens of Cassidulus suggests that limestone belonging to the Apalachicola group is also represented. In the absence of characteristic Nummulites in the collections, it appears not unely that the limestones of the Apalachicola group may here rest upon the "Peninsular" limestone. However, this conclusion is made subject to revision in case future collections from this locality should reveal the presence of fossils belonging to the Ocala limestone. The "Peninsular" limestone is known to outcrop throughout the central part of the peninsula, where it may be observed in numerous natural and artificial exposures. It has been encountered in many of the hard rock phosphate mines from Croom northward nearly to the north line of the State. It is also known to underlie a large part of the central lake basin of the peninsula, and it is encountered in wells along the east coast from Fernandina southward to beyond Palm Beach and'along the west coast south of Tampa. OCALA LD3rErONE. onmenclature.-The Ocala limestone was formerly regarded as part of the "Orbitoides limestone," but in 1882 Nummulites derived from waste products of the limestone were described by Heilprin. The specimens were obtained by Willcox from Chassahowitzka River, 1~Hpr Angdl, On the oc~acr of nummuliti depots to Florda and the ah~olation of Num- witsh a freh-water fauna: P. Phadeiphia Aciad Nat. Be., 1, pp. 189-195. 7~60-war 319-13---6 GEOLOGY AND GROUND WATERS OF FLORIDA. and their association with fresh-water forms of recent shells was rightly interpreted to mean that the Nummulites had been trans- ported from some other locality and redeposited with the younger shell. In 1884, Wilcox announced the occurrence of the nuini u- litic rock in place some distance above the original locality on Cha howitzka River, and Hefilprin, in commenting on the announcement, stated that the beds belonged to the Oligocene. The rock occurs at the old confederate iron works in Levy County where it was given the name "Lvyviile formation" by Johnson,' who described it as consisting of about 20 feet of soft porous building stone. He believe that it had been partly removed by erosion in the western part of the peninula, where it is much thinner than farther east, but expressed doubt to its having been deposited over the entire surface of the underly "Peninsular" limestone. Johnson mentioned several other localities where o this formation was recognized, among them being Paynes Prairie. He reported t~hast at a quarry on the Noonanville road near Santa Fe River the formations rested dictly upon the "Peninsular" limestone, the nummulic rock (Ocals limestone) being absent. Johnson's Levy- evil formation has usually been regarded as the substantial equivalent of the Ocala limestone; but it is not possible at present to verify the determination of the nummultes, and the rocks at Leville may really belong to some other formation. In subsequent publications by Hlprin this rock was called "Nummulitic" lm tone but in 1892 Dall proposed the name Ocal limestone. He states: Among th rock which until recently were not discriminated om the Orbitoides limese, and which appear in central Florid directly and conformably to ovrlie the latter, though no one hs dered their contact, i a yellowih riable rock con- Smany Foraminifer, conspicuous among which are two species of Numulites, N. til ozii and N. flortna Hp Thfis rock was first brought to notice by Mr. Joeph Wlllcox, and to Prof. Heilprin we owe a description of it which discriminates between it and the Vickbug or Orbitoides rock. The rock was early recognized as Eocene, though not di ted from the elier bd It is beet displayed at Ol, Fa., where it forms the country rock, and has been quarried to a depth of 20 feet without coming to the bottom of the beds. Stracigrapic position The Ocal limestone lies stratigraphically between the "Peninsular" limestone and the beds here designated the Aalachicola group. Lithologically, it bears a strong resemblance to the underlying "Peninsular" limestone, with which it also has close faunal relation. These facts have led to the conclusion that he two formations are conformable, and it has also been suggested that the Ocala limestone is a local phase of the "Peninsular" lime- 1 ene, new ser., mvol. 3, 1884, p. 907. J ohbon, L. C., Am. Jour. S, 3d ser., vol. 26, 18s, pp. 280-2i. Rl. G8o. Survey No. 4, 1802, pp. 10-104. WATER-8UPPLY PAPER 3a1 PLATE IX A. SECTION IN QUARRY OF OCALA LIME CO. AT OCALA. B. QUARRY OF OCALA LIME CO. (OLD PHILLIPS QUARRY) I MILE SOUTHEAST OF OCALA. U. L. GEOLOGICAL SURVEY GEOLOGY OF NORTHERN A- D ONTTAL FLOBIDA- stone. Although the two formations are probably conformable, the extensive distribution of the nummulites of the Ocal limestone shows that it represent a wideprad change in condition and is not to be classes as a mere local phase of the underlying beds. The Ocala limestone, as already note by Johnson, is in places wanting, so tt the overlying formations ret directly upon the "Paninsular" limestone. Lidogeic c~harater,-The Ocala limestone consists of a soft, porous, light-gray to whit limestone which bears a strong lithologic resemblance to the underlying 'Peninsular" limestone but is dis- tinguished from it by the included fossils. When slightly weathered, the rock becomes light yellow, and owing to its granular appearance soften rewarded as a sandstone The removal of the calcareous material by the leaching action of underground water leaves a pale yellow, more or less incoherent sand, containing a small percentage of calcium arbonate. When fresh, the Oeala limestone is so soft that it i easily broken, but many o surfaces become hardened by the deposition of calcium carbonate by water emerging along the outcrop. For this reason the rock locally appers to be hard and firm. Its porosity and ready solubility permit the formation of numerous underground channels which appear in som of the out- crops and are elsewhere inferred from the numerous sink holes. (See PI. IX, B.) The rock contains an abundance of organic remains which are commonly preserved as csts. Nodules and large masses of chert are also common and in some localities a large part of the rock has been slfi (e P X, A.) Thickess.-No defiant determination of the maximum thickne of the Ocala limestone has been made, and as yet no exposures have been observed which show the contact with the underlying "Penin- sular" limestone. All the information now available indicates that the thickness is variable and that the variation is probably in con- siderable measure due to subsequent erosion rather than to the inequalities of deposition. Dall states that at the type locality the Ocala limestone has been quarried to a depth of 20 feet without reach- ing its contact with the underlying "Peninsular" limestone. The greatest thickness noted during the recent field investigation was in a sin hole near Ocala, in which the formation is exposed to a depth re to a topography haractrzed by low hills, gentle slopes, sink holes, sinking streams and natural bridges. This limestone has had an important influence in the development of many of the lake Da, W. H.,ra ar e Ist. SoL, TOL a, pt. 6, 190, p. iMIt GEOLOGY AND GROUND WATERS OF FLOBXA. basins, and it forms the nature bridge over Santa Fe River High Spring. In the central portion of the peninsula underound streams are common and many large spring emerge from the Ocal limestone. PaneoologZc carter.-The Ocal limestone, like the underlying ''Peninsular" limestone, is characterized by a gret number of Foraminifera but it differs from the latter in the prince of Num- muliteso A few mollusk are said to be retrite toh formation, but as yet the fauna is very imperfectly no and future study may add to the number of fossils nown to be peuliar to it. Stritre.---The Ocala limestone shows the sae structural fear as the underling "Peninsular" limestone, both formations having doubtless been subjected to the same deformation sine their dposi tion. AreaL d~ iti .--It was in 1882 jhat Joeph Wilox dicove a rock in the vicinity of Chasahowitzka River which he submitted to Heilprin for idtification. The presence of Nummulites wsy regarded a an indication that a new fonsation had been dscovered. In 1886 Helprin added to the pulled list of locaities where the nummulitic fauna was known to occur a spot near Arredonda, about 6 miles southwest of Gainesville, where Nummadife8 floridamus had been collected by G. A. Wetherby and Joseph Wilcox. In 1902, after summarizing the results of previous investigations Dall* mentions certain new localities of the Oeaa limstone, as follows: Since then Mr. Willcox has obtained the rock in place 15 mile northeast of the original locality, from the shore of Wcss Bay, near Cedar Keys, and alo from , le banks of Wacama River, Levy County; from a "sink hole" at Pembeon erry on Withlcohee River, boup 10 mile ~et from Brookville, td ro at Bayport, rnando County, and at various places about Ocala f. Wetherby hps also sent specimens from a well 5 miles southwest of Gainesville, Alachus County, and Mr. L. C. John reports it from an old Confedte iron furnace, 3 miles north of Levyville, Levy County, where it is only 20 feet thick and is covered with a bed of bogiron ore, formerly worked. Pembe~ns terry is the most southern point t which it has been recognized at the sufce but at Bartw Polk County, it occurs covered by about 6 feet of later strtas From the character of its included organic remains the exposure at Martin stations regarded by Dall* as equivalent to the Ocala lime stone. At this locality the rock is more or less silieified and has been found useful for railroad ballast, road metal, and other purposes where durable material is needed. The Oeala limestone is extensively exposed at the type locality, where it has been quarried for the construction of roads and the SHeIlprin, Angelo, Pro.hadelphia Acadi NaT. SLt, 1882, pp. 18-1B. Abtract ton Am. Jour. Sch 3dse., vol. 24, 1882, p. 2. Heflprin, Anglo, Nohs on the Tetlarty galogy and peleontology of the ~outhen United 8tut: Am. Jour. S Ul., 3d ser., vo. 29, IS S, p. 4.19 Bu. U. 8. Gaol. Surrey No. 4, 1i0, p. 10(. STrans. W Free inst. Bel., vol. 3, pt. 1i08, pp. 115-1157. GEOLOGY OF NORTHERN AND CENTRAL PLORIDA. manufacture of lme. Some eposursre e seen in the wallsof sinks, and its presence may be inferred by the appearance of numerous bowlders containing Nummlites. These scattered fragments are frequently found resting upon surface sands and are mostly rather firmly cemented, probably by an accumulation of silica and iron. A thin deposit of sand, commonly found resting upon the uneven sure of the limestone, appears to be largely the result of disnte- ration of the country rock, and is there residual. The residual sands constitute the impurities of the original rock and may have formed only a small percentage of the whole. Since the publication of Dal's report quarrying at Ocala has bee carried to a somewhat greater depth. The quarry of the Ocala Lime Co., situated near the southwest corner of the city, now shows the following section: Sector in quarry of Ocala Lime Co., Ocala. Feat. L-a-n, sandy, with more or le organic matter (Pleistocene or Pliocene) ....................... ........................ 1 and, ple yellow, reidul................................... 1-4 Lisne, light gray to white, nummlitic (Ocala)............. 25- In this quarr the fossils occur throughout the greater portion of the limestone but are especially numerous near the top, where the removal of the calcium carbonate has loosened the casts of the organic remains. Chert nodules occur in various parts of the section, and in places two sets of vertical siliified bands were noted. These cherty bands are locally approximately at right angles to each other and probably represent planes of silicification along vertical joints. A good section of this limestone is exposed in another quarry sit- uated on the north side of the road to Silver Spring, about one-half mile east of the town. At this locality the rock, which is considerably decomposed, has been quarried to a depth of 40 feet and contains an abmudance of Nummulites. About 20 feet of Ocala limestone is exposed in a third quarry situated one-fourth mile north of Ocala, and about 15 feet of the same rock was seen in a quarry 24 miles southwest of the city. One of the most important sections may be seen about 3 miles southwest of Ocala in a sink hole approximately 40 feet deep, which affords entrance to a small cavern which may be penetrated for a short dis- tance. Clapp reports that Nummulites occur down to the base of this exposure but are not so numerous a at some of the other local ities Lithologically this rock is essentially the same as that exposed at the quarry of the Ocala Lime Co., and the section shows the maxi- Imum observed thickness of the formation. S thi mansript was p Ipred it has ben learned tIat the vertebrate 1os from the Ocola entsod on p. 1i3 were obtaind from thit tndy loom. GEOLOGY AND GROUND WATERS OF FLORDA. A section at the old "Philip" qury, a mile southeast of O , shows about 25 feet of soft, porous, lightgray limestone, which con- tains an abundance of chert dieminated throughout the seon. As this rock contains many Nummulites, its identification as the Oeal limestone can searely be questioned. Solution cavi~t are common, and along certain vertical crevices the rock has been removed, for- ing passages 2 to 3 feet in width, which have been file by the settlig of the overlying sady clay. On Anclote River, about a ile from Taron Springs, n expcsuo extending some distance up the stream shows from 2 to 3 feet of Ocala limestone. The rock here lies near the surface over a consid erable area, and bolder containing Nummulites are common A similar exposure of Ocala limestone wa noted near Port Richey on Pithlachascotee River, where the rock is said to outcrop over a con- siderable area. At the mine of the Fort White Rock Phosphate Co., one-half mile southwest of the railroad station, the Ocala limestone is well exposed In the north pit belonging to this company the following section was observed: section in quarry of Fort White R CPhop o., cer FPort Wfite. Lo n, light gray, sandy (Plestocene)........................... 4- 8 d, ne, evn grned, yellow (redual)....................... 20 Limetone and phophat rock (Ocal).......................... 2 In this pit the Ocal lestone occur i irregular ledges sepaatng the phosphate rock, which appears to be in part the result of replace~ ment of the Oeala. The limestone ledges commonly form two di- ontinuouh series at approximately right angles to eac other, the intervening space being occupied by the irregular bodies of phos phate rock. In general, the limestone bands thcken toward the base of the pit and the phosphate deposits become smaller. Both th limestone and phosphate are more or less cherty, but the silicifica- tion appears to be in the form of nodules and small bowlders rather than to constitute an extensive replacement. Fossils are very abun dant in the mestone, prominent among them being the charter istic Nummulites of this formation. At the mine of the Cuiner Lumber Co, 4 miles west of Iigh Sprins, the Oela lies much nearer the surface, the total thickness of overlyng sand being in few places greater than 10 feet There i the same characteristic an ment of the limestone and phosphate rock as at Fort White. Similar relations between the Oeala limestone and the phosphate were observed at the mine of the Union PhosphatO Co., 7 miles east of Newberry. The Alachua sink was visited by Clapp, who reports an exposure of about 10 feet of soft white limestone containing many tfint nodules. From the collections made at this locality it is evi- dent that the Ocala limestone forms part of the walls of the sink, GEOLOGY OF NOIRTHERI AND CENTER FLOBIA and it also appears probable that the overlying Hawthorn foratin is present. On the island opposite Melbourne, Sellards reports the occurrence of the Oeala limestone at a depth of 222 feet, baking ti determination on a large fragment containing Nummulites, which was obtained in drilling a well; although the specimens were not sp~ ifically determined, the occurrence of the genus appears to warrant the correlation of the rock with the Oeala limestone. ThI is a point of special interest, because it shows the Ocala limestone to be n the surface in that part of the State than would have been inferred from previous publications. The Ocala limestone is known to be well exposed at various point in the region where rock phosphate is being mined. Nummulites have been collected from various mines in the vicinity of Hernando, Citrus Countyo In a pit in aec. 10, T. 18 S., R. 19 E., a section wa observed consisting of 2 to 3 feet of yellow sand, wit phosphatic gravel anond brown and yellow elays, and phosphatic white and gray cnd, in pla gree the whole unde li by osphatic bl gray days, containing some hard sandstone with bowldere of hard rock phosphate containing Numulites. The ent section prob- ably represents altered and weathered phosphatic Ocala limestone. Nummulis were also obtained by Edrdge from a stone quar on the Burns place, 1i miles southwest of Owensboro, Citrus Ounty, and from Mr. Clement's mine No. 8, on the east side of Blue Sprns, T. 16 S., R. 19 E. "Miliolite imeton.'In 1887 Heiiprin noted at Wheeler, on Homosassa River, the occurrence of a porous and cavernous lime- stone whWih he called "Mlolite limestone" because of the preence of many Forainifera belonging to the iliolid. Dall' reports sii- lr rock 6 miles southwest of Lake City; he think the "Miliolite imestone" belongs wit the other foraminferal liesones but does not express an opinion as to whether it belons with the "Peninsular" or the Ocala limestone. The "Miliolite limestone" is here placed with the Vicksburg group and is tentatively referred to the OCal limestone, to which it probably belongs. lNOMENCLATURE. Prior to 1887 the rocks belonging to the subdivision of the Ol r cae, here designated the Apalachicola group, from its exposures along Apalachicola River in western Florida, were inclu< ed with the ocene and were regarded as part of the Vicksburg. In 1887, however, 'Hp Arino, ABo xplotkraon on th t of Fioida: Trns. Wanr Fre aist. aL, rol. I, 1K, p. S7. ,s W. L, B.L U iB. o. la. ry No. 84, m10 pmp. I0iOL GEOLOGY AND GROUND WATES OF FLOA Langdon described beds occurring on Apalachicola River, referring them tenttivly t tthe lower Mioene and desinating t the Chattahoochee group. With the Miocene beds, DalU, in 1892, in eluded not only the Chattahoochee group of Lngdon but the Hlaw thorn formation, the "Waldo formation," the "Tampa limestone, the "Tampa silex bed," the Chipola marl, the Alum Bluff formation, and certain sands, gravels, and ays which he did not specfiecly The use of the name Miocene to designate the group here called Apalachicola continued for a number of years, the Oligacene beds being often called "old Miocene" or "subtropical Miocene," to distinguish them from the "new Mioene" or "cold-water Miocene." In 1896 Dall' discussed the faunal reasons for regarding the "old Miocene" as Ol ne, and in his publications e that date he has restrict the term Miocene to later beds (here called Jacksonvile formation and Choctwhatchee marl). However, the Chattahoochee formation still included in the Miocene by both Smith* and McCalie in their latest publications. The Apalachicola group was formerly designated "upper Oligocese or Chipolan stage"* and "Chipola group," but these names are abandoned because the name Chipola has been used to designate a marl belongings t the upper formation of the group The Apalachieola group includes a number of b which diffe widely in lithologic character but which are recognized by thei fossils as integral parts of a single group. Limestones and marls predominate, but the group also includes beds of nearly pure sand and clay. The enti period of deposition appears to have been chara tried by the accumultion of more or less tcrrigenous m~terls, rendering most of the limestones impure by admixture of clay and sand. At certain times the conditions appear to have been especially favorable for the development of organic life, and some member, such as the Chipola marl member of the Alum Bluff formation and the "silex bed of the Tampa formation, contain very large faunas. Owing to the ithologic variations and daely separated exposures, the exact correlation of the formations of the group is dependent on the organic remains they contain; and, although the paleontologic studies, specially those of Dai, have shed much liht on the strat- I D I~ D. W., fr., Some a ioe Am. Jour. SB d sr., vol. 8, 1, pp. 8 SBull U. 8. Gel. SurveyNo. 84, 1, pp. 106 Dtcri~ton of Tertiary l the ntl Pro. U. INt. Muf, vol 19, 1o.i1, Ipp. Bmith, E. A., The undergrond water resouro of Aln: Geol. Survey Alabama, 1907, p. 81. *McCellte, I. W, Preilminary report on the iumndeund wate of Georgia Ge eol. B Geoy Girah IB, pp. SIal nd a. 'Dali, W. H., A table of North Ameiomn Tertiery haorone: Eighteenth Ann. Rept. U. 8. Geol. 8or. vey, pt. 2, 188, p. 834. I Foerste, A. H., Stdles on the Chipola t Mien of Bar G., and of Alum Bluff, Pla.: Am. Jor. Sd, 3d ear., vol. 46, 9s3, p. 244. GEOLOGY OF NORTHEN AND CENTRAL FLOBnDA graphic relations of the different beds, many pointare as yet unde cided. For this reason it seems best to retain the old names of certain formations and to indicate as far as possible their relationships. The Apalachicola group, therefore, is described as consisting of four formal~ tions, the Chattahoochee, the Hawthorn, the Tampa, and the Alum Bluff. There i some reason for bdieving thatthe mt three are, inpart at least, synhronous, but exact equivalence is difficult to determine formation, upon which it rests. The name Chattahoohee group was ft applied by Langdon* to the beds occurring at a series of outcrops along Chattahoochee and Apalachicola rivers The localities examined by Langdon extend from the final outcrops of the Vicksburgian, 9 miles by water above River Junction (Chattahoochee), to where the Oligocne outcrops give place to the overlying sands and mar of younger formations. The outcrops amined are at Alum Bluff, Rock Bluff, Ocheese and River Junction. In 1893 the section along Apalachicola River was examined by Foerste," who recognized the presence of three dissmlar groups, to which he gave the name Chattaoohee, Chipol, and Chesapeake His paper gives considerable attention to the character of the materials comprising his Chipol and Cheapeake groups, with a view to corrt lating them with the nonmarine deposits grouped under the name of "Grand Gulf and Lafayette formation" The major portion of the discussion, however, deals with the conditions of sedimentation during the deposition of the rocks belonging to the various groups. In 1892 Da*ll divided the formations here included in the Apa- lachicola group into two groups, retaining the name Chattahoochee group for the limestones and marsa, which are extensively developed in the northern part of the State, and applying the name Tampa group to the beds which he called Chipola marl, Alum Bluff sands, Sopchoppy limetone, Tampa limestone, and Tampa silx bed. In his later paper on the Tertiary faunas of Florida, Dall place the "silex bed" at Tampa in his Chttahooche group. The discovery of the character tic species of the genus Orthaulax in the basal portion of the Chat tahoochee formation led to this change in the correlation HAWTHOIRN FORMATION. Gene chara1ter-In 1892 DBall* described, under the name Hawthorne beds, some limestones, sands, and clays extensively erposed in the interior of Florida. These beds are here designated SL gd D. W, r., or lorid e Am or.S r., vol. 8, 8p. 22. orate, A. H., op. dt, pp. 241-254. Bll. U. B. ol. re No. 84, 182M, pp. I0-128. BL U. B. Go. S oy No. 84, lNs, pp. 107 et seq. OGOLOGY AND GROUND WATERS OF PLORIDA. the Hawthorn formation. At the tie of the publicaon of Dall's report, the Hawthorn formation was being quaried and had aroused considerable interest because of the presence of phosphoric acid in the rock. The formation consists of clays, sands, and pho- phatic limeetones and lies stratigraphically between the limestouI of the Vickhburg group and the Alum Bluff formation. I is appsur ently the stratigraphic equivalent of the Chattahoochee formation but diffe from it theologically and is therefore given a separate name. tratigr~P ic pouiion.---The stratigraphie relation of the Hawthorn formation to the underlying Vicksburg group has been obseved at several localities in the interior of th peninsu It is b ved that the deposition of the Vicksburg group was followed by widespread eme ence, which permitted expense erosion and the formation of hills and valleys. There is no doubt t ha such emergence and consequent erosion affected the central part of the peninsula, when the Hawthorn formation s wel pod, for thin formation rst unconformably upon either the Ocala or the "Peninsular" limestone. This relation is emphasized by the lithologic character of the beds there being an abrupt change from the sof figrained limestone of the Vicksburg group to the days, sands, and phosphatic e stones of the Hawthorn formation. At numerous point in the peninsula of Florida the Hawthorn formation is found resting unconformably upon limestone of Vicif burg age, and in the vicinity of Hawthorn thin beds of conglomer- ate occur in the bas of the group. At many of the phophat mnj min central Florida the lii tone of the Hawthorn formation are found overlg either the Ocala limestone or the "Peninsular" limestone with an apparent unconformity which has permitted the deposition of sands and some limestone beds along channel developed in the upper surface of the Vicksburg formation. It should be said, however, that in many of these places the materials belonging to th Hawhorn formation appear to have been more or less disturbed sine their deposition, and it is possible tha at some localities the apparent unconformity may be due to the falling of the roof of caverns developed near the contact of the two forma- tions. The relation of the Hawthorn formation to the Alum Bluff formation has not yet ben accurately determed, though, at De Leon Springs, ChiGpola fossils have been found in a marl overlying phosphate rock which belonged to this formation. The relation of the Hawthorn to the other formations of the Apalacicola group is somewhat uncertain, but there is no doubt that its deposition was in part contemporaneous with the Tampa and Chatahoochee formations. In fact, although the absence of GEOLOGY OF NORTHERN AND O(fTRAL FLORDA. aleontoloc information makes it possible to relate thee formations on biologic grounds, there is no doubt tat they were deposited during an extensive submergence which succeeded the nergeenc of the rocks belongig to the Vicksburg group. On physical grounds therefore, there is good reason for regarding theee formations as synchronous. Li c charge At the request of Mr. aughan te typ locality of the Haworn formation was recently visited by Sellards, who reports that the rock is no longer quarried According to Sellards, the rock is a lightcolored, soft, porous limestone. The original building-stone quarry near Grove Park station, about 3 miles west of Hawthorn, is badly overgrown, so tat the thickn of the limestone can not be determined. At the old phosphate mine, which is at least a mile southwest of the stone quarry, the rock is a phosphatic conglomerte At many localities the limestones of the Hawthorn formation are ilicifed, forming bowlders and beds of he. (S P. IX, p. 80.) This is a very common condition in the rock-phosphate region, where these Jlmestones rst directly on those belonging to the Vicsburg group. (See P. X, p. 94.) Beneth the phosphatic liestons of the Hawtor formation t some localits are beds of sand, sandstone, or gravel, which are underlain by several feet of clay. The snd beds contain iron oide, which forms a coating on the grains of siliea. The ays are gre h and local are sucienty calreou to be caled mar.t Thie.~The thickness of the Hawthorn formation varied greatly, in places aggregating approximately 95 feet. The three members of this formation with their maximum observed thick- nesme, according to Dall,1 consist of greenish clay 70 feet, ferrugi- nous yellow sandstone 4 feet, and phosphate rock 20 feet. The maxImum thickness of the Hawthorn formation, as given by the same author, is 125 feet. However, over a large part of the penin- sula, where the sole representative of the Hawthorn formation is the phosphatic or ailiceus rock, the thicknes is but a few feet. Py6igraphwi expression. The Hawthorn formation in few places has much influence on the configuration of the region which it underlies. Locally, however, the cherty beds protect the underlying rock from erosion and thus give rise to ridges, and where the days lie near the surface they are characterized by an erosion surface of moderate relief. Most of the cherGt capped ridges are inconspicuous, but in some parts of the sposphate region they form distinct topograplhic features. Pal eon~tloic clharacter.-The fauna of the Hawthorn formation has received but little attention and is practically unknown. The SBuB . .GeoLBurv No. 84, 1i, p. 1M0. 2 Ia, p. 8. |
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