STATE OF FLORIDA
DEPARTMENT OF CONSERVATION
FLORIDA GEOLOGICAL SURVEY
S. E. RICE, Supervisor of Conservation
HERMAN GUNTER, Director, Geological Survey
GEOLOGICAL BULLETIN No. 27
LATE CENOZOIC GEOLOGY OF SOUTHERN FLORIDA,
WITH A DISCUSSION OF TIlE GROUND WATER
GARALD G. PARKER AND C. WYTHE COOKE
UNITED STATES GEOLOGICAL SURVEY
Prepared by the United States Geological Survey in cooperation with the Florida Geological Survey, Dade County,
and the Cities of Miami, Miami Beach and Coral Gables
rn rN n
Manuscript received March 4, 1944
Published, September 1, 1944
LETTER OF TRANSMITTAL
Honorable S. EU. Rice, Supervisor,
Florida State Board of Conservation.
I have the honor to transmit a report entitled the "Late Cenozoic Geology of Southern Florida, With a Discussion of the Ground Water" by Garald G. Parker and C. Wythe Cooke of the United States Geological Survey, to be published as Geological Bulletin No. 27.
In connection with a detailed investigation of the water resources of southeastern Florida by the United States Geological Survey in cooperation with Dade County and the Cities of Miami, Miami Beach, and Coral Gables an excellent opportunity presented itself to study the geology of that region. This was done by Garald G. Parker during the progress of the water supply studies. Dr. Cooke, who has studied die geology of Florida for many years, accompanied Mr. Parker in the field for three weeks. This report is an outstanding contribution to our knowledge of the geology of southern Florida. It is replete with photographss graphs, and cross sections illustrating the succession and thickness of the formations of the region. This report will do niuch to unravel the complicated and difficult geology of that area. Corning as it does at this time when there is much interest in the geology of Florida I feel certain that it will receive an enthusiastic reception.
The Florida Geological Survey is indebted to the United States Geological Survey for the opportunity of publishing this report. It comes to the Florida Survey without cost other than that of publishing.
HERMAN GUNTER, Director
I ntroduczioix . . . . . . . . a . * a a * a a * * . a a a a * * * a a * a a a a a 15
l~rev'ious investigations . * * a a a * * a * * . . . . . . . . . . . . 15
Present investigation . . . . * * a a a * * . . . . . . . . . . . . . . 16
ickno~vledgineiits . . . * . . * * * * a * * * * * * * * * * * 17
1'loridiai I'lateau . . . . . . . . . . . . . . . . . . * * * * * * * 18
L.ate ~2enozoic history . . . . . . . . . . . . * * a * * . . . * * * 2]
lleistoceiie * * a a * * * * a * * * * * * * . . . . . . * . . . 21
J.let3ent a 0 0 S 5 5 S 0 a * * * * * * * * * . . . . . . . . . . 26
~ general features . a a * * . . . . . . . . . * * a * * . . . . . . 27
III~rainage . . . . . . . . a * a * * * * * * * * C 5 3 5 5 5 0 5 5 0 3 5 0
i rch 4Zreek . . . . . . . . a * * . . a * * . . . . . . a . . . . . . 36
11' opographic.ecologic (livisiolls * a a * a . a a a * a * . . . . . . . . . 38
'if' lie Sandy 13'Iatlaiids ........* a a. a a a a a * a a * a a a aa a a a a a a a a a a a a a a 38
Okaloacoochee Slough and Devil's Garden.......a......a........... 40
AlIapattaI~ and Loxahatchee Marshes. ............ ................... 41
Sandy flatlands south of Loxahatchee Marsb....a......a..a......a. 41
hake Irafford a a a a a a a a a a a a a a a a a a a a a a a . a a a a a a a a a a a a a a a a a a a a a a a a 41
'.I'he Big ~1yj~ress Sivaiip ..........a.... a a a a a a a a a * a a a a a a a a a 0 0 C 3 3 44
General features * a a a * a a a a a a a a a a a a a * a a a a a a a a a a a a a * a a a a a a *
Pjj7~0 1~i'erg1ades *aa**a*aa*a a a a a a a a a a a * a a * a a a a * a a a a a a a a a a a a a a a 46
4encral features . . *.*. 053003** ** OOt* 0000a ** *0 a a asa ar a.. 50
The ALtIantie Coa8tal Ridge . . . . . . . . . . . . . . . . . . . . . . 53
General features . . . . . . . . . a . a * . . . . . . * . a *
Origin of the Coastal Ridge and the Transverse Glades .............. 54
"Bottomless boles" in New River ................................. 55
Coastal marshes and niangrove swamps ,.............................. 56
Plioeeiie rocks . . . . . . . . . . a a * * a * * * * * * * * 56
'~Vater.bearing characteristics . . . . . . . . . . . . . . . . . . . 59
~Tater-bearing characteristics. . . . . . . . . . . . . . . . . . . 62
1~' aniiamiii forniatioxi . . . . * * * * * * * a a (i2
Water.bearing characteristics ..".............".... .............. 65
Pleistocene rocks . . . . * * * * * * * * a * *. a * * a . a * * . a a a a 65
S~?ater.bearing characteristics . . . . . . . . . . . . . . . . * 67
Icie)r Largo liniestomie . . . . . . . . . a * * . . . . . . . . . . . . 67
Historical suniniary . . . . . . . . . a * . . . . . . . . . . . . 67
III~ e'veloJzraent . . . * * a a a * . . . . * a . . . . . . . . . 67
Water-bearing characteristics ...................................... 68
Historical suiiiiiiar)T ******** ** **. * *. ** *. .* .. .. . .. . . a. 68
1?anilico forinatioii a a * * * a * . . . . . . . . . . . . . . . . . . 74
Historical suniniary . . . . . . . . * . a a * . . . . a . . . . . . 74
II~evelopniexit .. ..*. 445S5**** *~....** a. * * . . **aa.*.. a a a..... 75
Water-bearing characteristics ~ 75
Talbot and Penholoway formations ...........................~...... 75
[IistoricaL sunuiriary * a a a a a * * * * * a a * . * * a . . a a 4 * . * 75 L~eireloiiiiieiit a * a a a a . * a * . . . . . . * a a a a a a a . . a * * 77
4J oiielation studies . . . . . . a a a a a * a a a a a a a * a a a a a * a a a a a a 4 a
G eiieral 8tLltCIlIeIlt a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a 79 Sections on and near Caloosahatclxee River *t.fla*a**~*fl*...*..*...... 81
Correlation of Fort Thompson fornication aaa.a.....aa.aaaa.a.aa....aa 94
Correlation of formations by means of exploratory test well (hita ........ 96
41exieral statenieiit a . a a a a a a a a a a a a a a a a a a a a a a a a a a a . a a a a a a a a a a a a a a 96 S ectioi~ 2~~j ~i a.aaaa a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a 96 Sectioii B.B' . . . . * a a * . . a * * . . . * a a . * a a a a a 106
Sunitnary a a a . a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a . a a 112
II efereiices at a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a . . a a a a a a 113
Iiid ex ... a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a 1116
1. Generalized NNW-SSE geologic cross section from vicinity of
Ocala to Florida City, Florida ................................ 19
2. Mapshowingcontours onthefloor of Deep Lake ~ 31
3. Map showing contours on the floor of Lake Okeecliobee ............ 52
4. Geologic cross section at Station 325, type locality of die
1. Map of Floridian Plateau showing contours on ocean 1)000111
and area covere(l by this report ................................ 13
2. Tentative correlation chart of formations in southern Florida. . . . 20
3. Hypsometric map of southern Florida showing approxiiiiate
distribution of Pleistocene terraces and shore .............. In Pocket
4. Recent and late Pleistocene wave*cut 1)dnebes [111(1 notches
iii soutlieri 1~'lorid1a . . . . . . . . . . . . . . . . . * * * 23
5. Solution effects in limestone in southern Florida . . . . . . . .... 28
6. Deep Lake and Still Lake, Pleistocene sink holes . . .e. .0 **S*~~0 30
7. Arch Creek natural bridge and Hillsborougli Lakes Marsh of
8. Topographic.Ecologic map of southern Florida. . . . . . . . In Pocket
9. Views of the Sandy Flurlaiids and in the Devil's Garden. . . . . . 39
110. Views in the Big Cypress Swainp................................... 42
11. '~jeivs iii the J~'vergla(les . . *000s*** . . . . . . **.....* . *... *1*e
12. Map showing contours 011 the rock floor of tile Everglades. .. ..... .. 47
13. Map of the Everglades Drainage District showing directions
114. Surficial deposits of southern Florida exclusive of
orga;uic soils * * * * * . . . . . . . . . . . . . . . . Iii Pocket
15. Geologic map of southern Florida exclusive of
116. Sections of Pleistocene and Pliocene rocks exposed along the
22. Map of stations along the Culooszdiatcliec River used in geologic
s ectioli ~..f' a * * * * * * * * . * . . . . . . . . . 80
23. Geologic section along the Caloosubatchee River, C-C'... ....... *8* 82
24. Map of southerii Florida showing location of geologic cross
sections and certain test ivells ~ in Pocket
25. Geologic section from Luke Okeechobee to Miami Springs, .VA'...... 96
26. Geologic section along Tamiami Trail from Monroe-Dade County
Southern Florida gives evidence of repeated oscillations of sea level but of little structural deformation. The oldest outcropping formations arc the Caloosahatchee marl, the Buckingham marl, and the Tamiami formation. The Caloosahatchee consists predominantly of 5(111(1 011(1 shell marl; the Buckingham of calcareous clay with phosphate grains; and the Tarniami of calcareous sandstone and sandy limestone with beds and pockets of quartz sand. Well records show that the Caloosabatchee marl and the Tamiarni formation interfinger and are essentially contemporaneous, though the outcropping tongue of the Tarnianii overlies the fades represented by the Caloosahatchee. The Buckinghani marl merges into the Caloesaliatchee. These Pliocene formations are separated from the overlying Pleistocene formations by an erosional unconformity which indicates that they were above sea level during middle and late Pliocene time and earliest (Nebraskan stage) Pleistocene time. They may have been very slightly tilted toward the west at the time of their emergence.
The Fort Thompson formation (including the Coffee Mill Hananiock marl member at the top) consists of three thin marine shell beds separated from one another by two fresh-water limestones or mans, each of the younger beds filling solution holes in the older. The total thickness at tile type locality is about 8 feet. The marine beds are interpreted as deposits formed during Aftonian, Yarmouth, and Sangamon interglacial stages, when the region was flooded by the sea to depths apparently as great as 270, 215, and 100 feet. The solution holes and the fresh-water limestones and marls apparently were formed during the Kansaii and Illinoian glacial stages, when tile sea temporarily withdrew to con* siderable distances below its present level.
The Anastasia formation (predominantly 8011(1 and shells), the Key Largo limestone (an extinct coral reef), and tile Miami oolite are contemporaneous Pleistocene formations which apparently accumulated on and along the southeastern coast mainly during the Sangamon interglacial stage and therefore are equivalent to oniy part of the Fort Thompson formation developed in the Everglades and the Caloosahatcliee River area. The Penholoway mid Talbot formations, whicli are coastal terrace deposits, consist of sand swept down from the north by longshore currents during the middle and late parts of the same interglacial stage.
A thin sheet of sand, the Pamlico formation, was spread over part of the shallow sea floor during a mid-Wisconsin invasion by the sea.
rpj a n nn..mfllfl#nfl nt tI.nrn ~ rlnnnctc tn ,rnr;nu.a ti. 4nL-nnococ nru th0
ivest. The northern and lowest part of this basiii is ~now occupied by Lake Okeechobee, wbicb, before drainage and diking operations changed it, overflowed southward across the opei Everglades more or less as a sheet flow that imposed an aligned drainage pattern on die organic deposits of tile Everglades.
Tests made in ground water investigations of the Miami area indicate that tile Tainiami formation is among the most productive water bearing formations ever investigated by the U. S. Geological Survey. Its coefficient of permeability is about 35,000, which indientes that through a section of tile formation n mile wide and a foot thick 35,000 gallons of water a day, at 600F, would ~fl8S through tinder a hydraulic gradient of one foot.
Large areas of salty ground water in the northern part of the Everglades are eonsi(Iere(I to be remnants of sea water left during Pleistocene sea invasions and now altered by dilution with fresh water and by chemical reactions, mainly of the base-exchange variety, with the enclosing rocks.
- - - - - ---- - - -- /
%4 PENSACOLA /
p - - -
TALLAHASSE U: *JAC SO VILLE
- en r 26
SCALE IN MILES F" LAKE
C ib 20 40 40 so Thoc 0 EECHOB C
W. PALM S / BEACH
SHADED PORTION REPRESENTS AREA COVERED MIAM
PLATEAU. PUB CARNEGIE INST OF WASH. NO ~ (
LATE CENOZOIC GEOLOGY OF SOUTHERN FLORIDA
DISCUSSION OF THE GROUND WATER
GARALD G. PARKER AND C. WYTHE COOKE*
Previous investigations-Interest iii the geology of southern Florida began in the first half of the nineteenth century, but iiiformation aI)OUt the region was confined for many years to what could be learned by making boat traverses along the coastal waters. The interior remained inaccessible. The first notable speculation as to its origin and geologic history was that of Louis Agassiz (1852), later modified and given wider circulation in Joseph LeConte~s (1878) "Elements of Geology." These writers supposed that peninsular Florida, south of latitude 280, had been built up by successive growths of coral reefs on a sea bottom 12 to 20 fathoms deep, and that the waves and winds had heaped up the detritus upon the reefs to a height of a few feet above sea level. They assumed that Florida has now ceased to grow southward because the depth limit at which corals can grow and flourish has been reached by the advancing reefs. Later information about the composition of the interior amply disproves this theory.
Angelo Heilprrn (1887) was the first geologist to describe the interior of southern Florida. He explored the Caloosahatchee River in 1886 and recognized the Pliocene age of the shell beds in its banks. These beds are the richest collecting ground of Pliocene fossils in the United States. His "observations failed to bring forward a single fact confirmatory of a coral-reef theory of the formation of the peninsula such a.i had been advocated by Louis Agassiz and Prof. LeConte" (Heilprin, 1887, p. 31). Dali (1887) visited the region about the sanie time and confirmed the Pliocene age of the "Caloosa-
16 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Alexander Agassiz (1895, 1896) exauiined coastal outcrops of tile formation now known as the Miami polite aid decided that the de. 1)osit is of aeolian origin. Griswold (1896) examined the polite not only at the shore but also at inland outcrops and rejected Alexander Agassiz 's theory.
The keen observations of Samuel Sanford, while acting as geologist for the Key West extension of tile Florida East Coast Railway in 1907 and 1908, brought to light many new facts contradicting Louis Agassiz 's speculation. His paper on "The Topography and Geology of Southern Florida" (Sanford, 1909) presents an excellent summary of the physical features of that region. iii the same volume Matson and Clapp (1909, pp. 123-128') wrote the first formal description of tile Caloosahatchee marl.
The cutting of draiiiage canals across the Everglades gave Sellards 1919) the first opportuJlity to compile a geologic section from the Gulf of Mexico to the Atlantic Ocean. He described several new Pleistocene and Recent formations.
Descriptions of the geologic formations of southern Florida were included iii Cooke and Mossom's (1929) "Geology of Florida." They were the first geologists to cross tile state along the Tainiami Trail (U. S. Highway 94). The map accompanying their report exteiids the mapped area of Pliocene rocks far south of its formerly known limit.
Richards (1938) made a study of tile Pleistocene stratigraphy of Florida and suggested a correlation of certain formations and terraces. Mansfield (1939), aided by F. S. MacNeil, made a correlation of deposits along the Caloosahatchee River. However, MacNeil (1942) (lid not concur with Mansfield on the published description. MacNeil's correlation, especially of the lower argillaceous beds, is very similar to that of the present writers. Cooke (1939) interpreted the "Scenery of Florida" in the light of the long-known Pleistocene oscillations of sea level, and Parker (1942) first noted the possible correlation of individual beds in the Fort Thompson formation with Pleistocene glacial and interglacial stages.
Pr~sozt innogflgnflnn-.-Thp ~ron onu~roA tIlc r~nnrt
LATE CENOZOIC GEOLOGY 17
to the Gulf of Mexico. The extensive studies in tile Everglades have a~ direct bearing on the water resources problem of Dade County and the municipalities within it; thus tile study was extended northward as far as the north end of Lake Okeechobee.
Acknowledgments-This paper results from the investigation of' the water-resources of southeastern Florida made by the U. S. Geological Survey in cooperation with the Florida Geological Survey, Dade County, and the Cities of Miami, Miami Beach and Coral Gables. To the officials of these cooperating agencies we are grateful for services, help, and data contributed. We have profited by the advice and encouragement of 0. E. Meinzer, Geologist in Charge of the Ground Water Division of the U. S. Geological Survey, and V. T. Stringfield,
of that Survey, under whose supervision the 1)roject was carried on; both have critically reviewed this 1)aper. To A. G. Unklesbay of the U. S. Geological Survey, Hernian Gunter, Director of the Florida Geological Survey, and John H. Davis, Jr., of that Survey, we are especially grateful for helpful advice and for critically reviewing both the manuscript and the interpretations of the geology in the field. In addition, the Florida Geological Survey contriI)uted laboratory, library, and museum facilities at Tallahassee. We are grateful to Harold T. Stearns for his review of the Pleistocene historical section and helpful ideas and criticism.
Julia Gardner and H. G. Richards identified the fossil mollusks, I. A. Cushman, L. G. Henbest and XV. Storrs Cole i(lentified the foraminifers, and Remington Kellogg ideiitified tile cetaceans. Water
samples were analyzed under the supervision of S. K. Love. Acknowle(lgrneIlts are due Nevin D. Hoy for painstaking assistance ni field and laboratory and to Russell H. Brown, uiider whose (lirectioll a line of test wells was drilled through the Everglades and who, with G. C. Goddard, aided in contouring Deep Lake. Carlton W. Lingham sounded both Still Lake and Salt Spring. The (Irawings were made by Ross A. Ellwood and Robert W. Hardin.
We are particularly indebted to C. Kay Davis and John C. Stepheiis, both of the Soil Conservation Service, who made possible and helped in the drilling of 15 exploratory test ;veiis in remote and heretofore
18 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
was acconipanied in the field for three weeks by Cooke, who has worked for many years on the geology of the Coastal Plain and who has long been a student of the Pleistocene oscillations of sea level.
The peninsula of Florida is tile emerged part of a much wider projection from the continental mass of North America named by Vaughan (1910:1 the Floridian Plateau (Plate 1). The Plateau separates the deep water of the Atlantic Ocean from the deeper parts of the Gulf of Mexico. Its core is probably composed of metamorphic and igneous rocks like those underlying the Piedmont region of the Eastern States (Mossoni, 1926; Campbell, 1939a), of which it seems to be the southern extension. The steep submarimie slopes that bound it On the east, south, and west presumably represent fault scarps or inonochinal folds in the original basement complex, though their outlines may have been modified by the accumulation of sediments upon them.
The core of the Floridian Plateau is overlain by a cover of sedimentary formations that ranges in thickness from about 4,000 feet in north-central Florida (Marion County) to more than 11,000 feet in southern Florida, where no well has yet reached the basement complex. A deep well, drilled to a depth of 10,006 feet in the northeastern part of Monroe County about 50 miles west of Miami, began
in Pliocene calcareous sandstone (Taimami formation) and ended in liniestone and anhydrite supposed to be Lower Cretaceous (Campbell, 1939b; Cole, 1941). Since that time two more wells have been drilled to more than 11,000' in Collier Co., near Sunniland, Florida. The first of these sells, drilled near the Sumijiand railroad station was 11,626' deep (See Fla. Geol. Sury. Bull. 26, pp. 162-163, 1943) an(l has produced oil in commercial quantities. The second well, about a mile west of the Sumijiand railroad station is below 12,000 feet but has not been a producing ivell. The rocks penetrated were dominantly limestone. No sand or clay is reported below the Miocene Hawthorn formation-an indication that southern Florida was long remote from sources of elastic sediments.
LATE CENOZOIC GEOLOGY 19
dip is less than tile slope of many sea bottoms, it doubtless involves some deformation.
A further hint at deformation is found in the asymmetrical profile of the Floridian Plateau and in the pattern of the geologic map of Florida (Sellards, 1919, pp. 105-131; Cooke and Mossom, 1929). Only the eastern part of the Plateau stands above sea level; the western half slopes geiitly out beneath the waters of the Gulf of Mexico before it plunges to greater depths. This suggests that the Plateau
,LU CD ~w
4 a 010, 4~J
o ~ o.a ci r fl~ I-I- Ito
~/A1 (MIQcS -60
UNDIFFERENTIATED EQOENE, (b~ -900
PALEOCENE, AND 'QOCSNS)
UPPER CRETACEOUS -1200
300 MILES ~1
FIGURE 1-Generalized NNW-SSE Geologic cross section from vicinity of
Ocala to florida City, flu. Greatly foreshortened.
has been canted westward. Moreover, the trend of the boundaries between successive geologic formations is out beneath the Gulf. This, however, might indicate merely that the western side of the Plateau was eroded deeper than the eastern while the sea stood lower on the land than now. The sloping surface of the Plateau
- 1 --- a -- - - 1.. -- - - ~ - -- -
FLORIDA GEOLOGICAL SURVEY BULLETIN 27. PLATE 2
~ TENTATIVE CORRELATION OF FORMATIONS IN SOUTHERN FLORIDA
(PLIOCENE TO RECENT)
GARALD G PARKER 8 C WYTHE COOKE
COASTAL SOUTHWESTERN CALOOSAHATCI4EE EVERGLADES SOUTHEASTERN
EPOCHI AGE TAMIAMI TRAIL
TERRACES COAST RIVER AREA AREA COAST
NOTE TERkACES A9OVE SOLUTION AND EROSION SOLUTION AND EROSION. SOLUTION AND EROSiON.
THE PENHOLOWAY ARE SOLUTION AND EROSION. SAND BARS AND OLD LAKE FLIRT MARL. FORMATION OF BEACH
Z NOT PRESENT IN THE FORMATION OF BEACH CHANNEL FILLS CON- FORMATION or ORGANIC RIDGES, LAKE FLIRT MARL.
Lii AREA COVERCO By THIS RIDGES, OYSTER BARS1 TINUED DEPOSITION or SOILS: MUCK, GROWTH OF OUT
0 REPORT BUT OCCUR TO MARL, MUCK, AND SAND LAKE FLIRT MARL AND PEAT AND MUCK. ER CORAL REEF.
THE NORTH AS FAR AS SOILS ORGANIC SOILS.
SOLUTION AND EROSION SOLUTION AND EROSION SOLUTION AND EROSION. SOLUTION AND EROSION DUNES RIVER CUTS AND FILL LAKE FLIRT MARL LAKE FLIRT MARL
LAKE FLIRT MARL DUNES
SEO 8, STA 325
tPAMLICO PAMLICO FORMATION PAMLICO FORMATION PAMLICO FORMATION
U SEA LEVEL + 25 FEET BED 7, 5Th 325 (LOCALLY PRESENT) PAMLICO FORMATION
z SOLUTION AND EROSION. SOLUTION AND EROSION SOLUTION AND EROSION SOLUTION AND EROSION
DUNES BLACK CARBONACEOUS DEEP CUTS IN MIAMI
_________ (IN PART
SAND ). OOLI'E
TALBOT MIAMI OCJTE
SEA LEVEL + 42 FEET
PENHOLOWAY z COFFEE MILL HAM- MIAMI POLITE
4 ANASTASIA FORMATION 0 MOCK MARL AND
O SEA LEVEL t 70 FEET AND TERRACE SAND (MARINE SHELLS) LOCAL PATCHES or ANASTASL VIA :~ --az __________4 4 BED 6, STA 325 MARINE SHELLS KEY LLRGC LS
jSEALEVEL +100 FEET
HIGHEST FRESH -I
LEDGE MERGING INSOLUTION AND EROSION TO SOFT FRESH- SOLUTION AND EROSION SOLUT:CN AND EROSION Q.z
-' WATER MARL BELOW
BEDS 5A a sg. STA
SEA LEVEL t 170 FEET ~ MARINE SHELL MARL
ANASTASIA PECTEN HORiZON" MISSING UNDIFFERENTIATED
COHARIE FORMATION 0
I BEG 4, STA 325.
SEA LEVEL t 2'S FEET
WATEF1 MARL LOCALI SOLUTION AND EROSION a INDURATED MAK- SOLUTION AND EROSION I SOLUTION AND EROSION
4 ING A SHELF
~- BED 3, STA. 325
z BRANOYWINE 0 MARINE SHELLS
SEA LEVEL + 270 FEET MISSING LOCAL. MISSING ~UNOIFFERENTIATEO
2 BED 2, STA 325.
SOLUTION AND EROSION
m Li z
w TAMIAMI 'TAMIAMI
LATE CENOZOIC GEOLOGY 21
LATE CENOZOIC HISTORY
Inasmuch as the development of the surface and subsurface features of southern Florida was profoundly influenced by the relations of land and sea during late Cenozoic time, it seems desirable to sketch the history of the Floridian Plateau during that epoch before cxamining iii more detail the topography and geology of southern Florida. Such a general resume should make more intelligible the interpretation of specific features. See P1. 2, tentative correlation chart.
Plioceize-During early Pliocene time, southern and eastern Florida were submerged, but west-central Florida remained dry land. The shore line probably extended southward through Lake County to Sebring, thence circled westward through Arcadia and Sarasota and northwestward across the Gulf to Tallahassee. The Alachua formation (Sellards, 1914, pp. 161.162) and the Boiie Valley gravel (Sellards, 1915, pp. 41-44), both of which enclose early Pliocene land animals (Simpson, 1928, p. 257), accumulated on the land and in deltas while the shell marl beds, sandy limestone, and calcareous clay of the Caloosahatchee and Buckingham marls and the Tamiaini formation were being depositedd in the sea.
The late Pliocene was a time of widespread crustal instability. The Atlantic seaboard and other large areas in North America were variously warped and tilted. It was probably then that the Coastal Plain north of Cape Hatteras was strongly (lowuwarped towards the cast. The northern and eastern extremities of tile Coastal Plain, 1)reflously a plateau about six thousand feet high crossed by deep gorges, was completely submerged, and its gorges became submarine canyons (Cooke, 1930a, p. 589; 1930b, pp. 392-393). During this time more of tile Floridian Plateau emerged, was probably tilted toward the west, and was actively eroded.
Pleistocene-During the Pleistocene epoch the Atlantic seaboard south of the glaciated areas remained relatively stationary, but the level of the sea repeatedly fell and rose upon it responsive to the
C ill~~ 1 1 1 1.1 1 4%
22 FLORIDA GEOLOGICAL SURVEY--BULLETIN 27
and marshes occupied the Lake Okeechobec-Evergiades depression. rrIlese five states ilI)I)C8~ to corrcsl)o11(1 to the Ncbraskan~ Kansan,
and Illinojan glacial stages, and to two sub-stages of the Wisconsin
the Iowan (earls- Wisconsin) and tile Post Iowan (late Wisconsin the daciated regions
Cooke. 1935, p. 333'~ hi r they arc represented
by glacial drift, mortunes, and other iec-bor'ie 811(1 water-borne (1eI)ris. In Florida they are iiidicated by erosion surfaces, solution holes.
soil zones. and fresh-water liniestones and marl (Parker, 1942; Parker
dIl(l Hoy, 1943).
Between each of these major low-water stages came a 1I1&ijOr Sta'~c ot r which the sea 8100(1 111)011 the 1)VCSCIlt 1811(1 (sec
hiah water, during
Plate 3) These four major high-water stages fl1)1)Cfl~ to COrreSl)OIid to
the Aftoniaii, Yarniouth, and Sananmon illter(rlaci&d stages and to a
Post-Iowan retreat of the Wisconsin ice referred to by Cooke (1935. p. 333: 1943,
p. 1714) as the "Peorian interglacial sub-stage". EviS
deuce for these times of deglaciation is yielded by (lCCplV weathere(1
~.oil zones aIl(l I)~' erosion within the alaciated regions and hr sedi*
mentarv deposits and shore-line features within the areas invaded
1w the sea. The location of' the Cornier shore lines is indicated bYS
beach ridges diiiies. the nip of the sea or wave-cut benches iii seacliffs, or by a change in slope. (See Plates 4 and 18)
Although onE' four intervals of deglaciation iii the northern States
are here cite(l at least seven hiah-lcvel shore lines iii southeastern
United States had been detectc(l (Cooke, 1931) prior to the preselit invcsti~ation. Since then one more has been fouiid. The extra three or
more appear to record iIiterille(liate levels between the highest flood
of the interglacial sea and the lowest of tile succeeding glacial stage.
They mar represent pauses in the growing of the ice sheets or, possiblv. inactive periods in the intermittent enlargement of the oceanic
The eight shore lines, which still remain horizontal in tile southeastern states, stand at altitudes of approximately 270, 215, 170. 100,
70. 25, and 5 feet above tile present sea level. They form the
inland boundaries of marine terraces (emerged sea bottoms) named,
Ikri'i: CENOZOIC GEOLOGY 23
RECENT ANI) LATE PLEISTOCENE WAVE.CIJT BENChES
AN I) NOTCHES IN SOUTHERN hl~OII I HA
l'IGUIIE a-.--'\Vave.eut bench 1111(1 noteh (lCVdOped in the Key Largo lime-
24 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
boundaries of tile terrace as shown Oil the hypsoinetric map (P1. 3, iii pocket) except as they have been modified by subsequent erosion and solution.
Stearns (1942), in the Hawaiian Islands, records 10 high-level Pleistocene shore lines, of which his Waimanalo (+25), the Laic 4 70), and the Kaena (+100) correspond exactly to the Panulico,
Penholoway and Wicomico shorelines. Stearns also records the Kapapa, a wave-cut bench at +5 feet.
A bench at 5 feet above sea level, here iiamed the Miami, is likewise present at Silver Bluff in Miami, and thcrc is also a wavecut notch at +8 feet (Plate 4). The Miami bench is traceable northward from Miami toward Fort Lauderdale where the highway (U. S. No. 1) follows closely along it for several miles. The notch at +8 feet and the head of the wave-cut bench at +5 feet may have been cut as the sea withdrew during latest Paiulico time. Both may have been developed simultaneously, the 8-foot notch by storm waves and tile ivave-cut bench by tide and normal wave action; or both may record separate halting stands of the sea.
These features are preserved in southeastern Florida because of beS
ing developedd in consolidated rocks. Such features are not preserve(I along a sandy shore; however, it is entirely 1)ossible that the beach ridges surmounted by dunes in Palm Beach, Martin and St. Luck Counties were successively built up as the sea withdrew from its 8-foot and later 5-foot stands, but the difficulty of establishing Cornier mean sea level at the base of these 01(1 ridges, since filled by windblown sand or obliterated by slump, is too great to prove this iiiter-pretation.
In Nebraskan time the sea withdrew from the land area and a long interval of solution and erosion ensued. There are no recognized terrestrial deposits in southern Florida that mark this interval, but the unconformity between the Pliocene and the later Pleistocene
(leposits is quite marked.
In Brandywine time (Aftonian interglacial stage) nearly all of Florida was beneath the sea (Cooke, 1939, fig. 112), amid much of
coiu iborn Pin.4 A0 tint nn~inrnwnrl Lw warn4aa a ~. c~rn r...
LATE CENOZOIC GEOLOGY 25
Florida was Occupie(i by lakes and marshes, iii which thin sheets of
marl and limestone containing fresh-water shells were (1e1)osite(1. Much of this deposit was probably removed duriiig tile next invasion of the sea (Yarmouth interglacial stage) which stopped first at a height of 215 feet (during the Coharic epoch) and later (Sunderland epoch) receded to 170 feet above the present sea level. Sources
of' sediment were again remote, and only a thin marine shell niari and calcareous saiidstone in tile Fort Thompson formation are referred to these epochs. If they were once thicker, erosion and sointion 1)artly reiiioved them before the next deposit was lai(1 down.
Another bed of fresh-water marl and limestone, in 1)laeCS 4 feet thick, was probalily deposited during the succeeding Illinojan glacial stage. These fresh-water beds are very conspicuous along the Caloosahatchee River from 01(1 Fort Thompson eastward to Lake Flirt.
When tile sea next invaded southern Florida during the Sangainon interglacial stage (Wicomico time) it reached wily 100 feet above its preseilt level, aiid a long narrow peninsula, here named the Highlands Peninsula, rclllaine(1 aI)ove water in the adjoining Highlands County. This peninsula was attached to the mainland at the north near Avon Park, and when the water fell to 70 feet above sea level in Penhioloway time Highlands Peninsula was only sightly eiilarged. However, a broad area south of the mainland became dry 11111(1 separated from the Highlands Peninsula by a narrow gulf now CH1)ied by the licadwaters of Fislicating Creek. The further lowering of' sea level to 42 feet in Talbot time expanded the land surface into Glades and Charlotte Counties (Cooke 1939, figs. 13-15).
During this Wicomico-Penholoway-Talbot time (Sanganion interglacial stage) the Miami polite was deposited in the southeastern I)art of southern Florida while the sandy limestone and shell beds constituting tile Anastasia formation were accumulating all along the East Coast north of Broward County. At the same time, multiS
tudes of the little clam C hi one cancellata and nrnnerous other marine mollusks. whose shells compose the Coffee Mill Hammock marl mciii-
26 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
the polite became deeply pitted by solution holes. Sand worked southward along the shores, and bars and dunes were built in many places.
Rise of the sea to the 25-foot level in Painlico time flooded much
of southern Florida again (Cooke, 1939, fig. 16). Most of the region north of Caloosahatchee River was land, and south of the river an island, here called Immokalee Island, extended beyond Inimokalec. A peninsula terminating south of Indiantown partly eiiclosed the site of Lake Okeechobee, which was open to die sea on the south. During Pamlico time (probably of relatively short duration'I longshore currents brought sand from the north aiid distributed it over the Anastasia formation and the uneven surface of the Miami oolite as far south as Miami. The channels across the polite were choked with sand. Here and there the sand bar reached the surface of this post-Iowan sea and was built up into dunes. In the interior, sand covers some of the northern part of the Big Cypress Swamp, but it has only a slight extent into the Everglades.
Late Wisconsin time was of comparatively short duration. The
sea receded slowly 25 feet or more below present sea level (Stea.cneCOO 119 3), and as it did so left a series of parallel beach ridges and bars i'i parts of southern Florida (Plate 13).
On tile east coast, beach ridges now surmounted by dunes were built prominently in Martin, St. Luck and Palm Beach Counties. On the ivest coast sand was carried southward beyond tile town of Everglades, and dunes were built there and at Marco. The (fillies near Everglades now are wholly or partly submerged and make the foundation for some of the Ten Thousand Islands, but at least one of the Marco dunes stands as high as 52 feet above present sea level, and another is almost as high.
During this interval solution of limestone was resunied, the Lake Flirt marl began to be deposited, some of the sand-filled channels were partly re-excavated, and several short streams on the east coast were formed. On the west coast the Caloosahatchee River and Peace Creek cleared channels that had probably been cut long before, and many shorter streams canie into being. -
LATE CENOZOIC GEOLOGY 27
lakes, the largest being Lake Okeechobee. Saw-grass took root where tile water was not too deep, aiid its compacted remains make up much of the peat and muck of the Everglades. Widespread deposits of fresh-water marl (Lake Flirt marl) eontiimed to accumulate where conditions were suitable. Part of the higher lainis ivest of the Everglades proved congenial to cypress trees and became the Big Cypress Swamp. Mangroves invaded die tidal zone where the Everglades merged into the Gulf. Along the east and ivest coasts sail(l and broken shells were shifted southward by the currents and built the present beaches, and a new coral reef began to fringe the keys.
General--A large Part of southern Florida i5 underlain by limestone and oilier calcareous depositss, and, as the surface waters are highly charged with organic acids, solution days a eOIlS1)ieuOuS role in the development of its features aiid is dominant over abrasion. The same was true iii previous epochs. At times iii the past when the Floridian Plateau stood high above the sea, no deep gorges were carved in it by running water, which carried little sand to act as an abrasive. Rallier, the surface was etched by waters carrying corrosive acids, and much of the run-off passed downward through solution holes into caverns.
An excellent illustration of the corrosive effect of acid-charged water was noted near the Big Cypress Swamp 40 miles west of' Miami, where the Miami polite has been etched to a depth of almost a foot, leaving a lacy surface network supported by jagged and uneven pilliars that crumble under foot. The surface of the rock, which usually projects above water level, is better preserved than the subsurface. Solution passages several feet deep are COIUIlIOIl in this area, and some extend deeper (Plate 5a).
Apparently no original cavity is needed to start a solution hole, though the existence of a ready-made hole hastens the process. It has been suggested that many vertical solution holes began to be dissolved along tap roots, and possibly some originate in this fashion,
it 4 a Lq~ n n - a 4 .i-1 n ~ n 4 n ~ ---- n -- *. n - - 1 .1 1 : -. a nA. a - a a e a a Cl
28 FLORIDA GEOLOGICAL SURVEY--BULLETIN 27
SOLUTION EFFECTS IN LIMESTONE IN SOUTHERN FLORIDA
FIGURE a-Effect of acidic ground waters on limestone (Miami oolite) in
a place where the water table is generally a few iiicbes below
LATE CENOZOIC GEOLOGY 29
large areas of southern Florida it is evident that at least one-fourth of the total volume of limestone, once iiiore or less solid rock, is now occupied by solution holes, generally filled with sand. Trees blown over by hurricanes rip up rock with their roots, thus leaving a new and localized depression for coneentratioii of surface water and the start of more active solution holes. Adjacent holes enlarge,
coalesce, and become increasingly effective iii draining surface water under ground. Many solution depressions of this kind, some as much as 150 feet in diameter, may be seen in the pineland and wet prairies south of Miami.
In certain areas, 8uch as near S. W. 12th Avenue and the Tamiami Trail iii Miami, some apparently solid foundations occasionally uive
way beneath buildings. The area is one of very active solution and erosion. In such a place water may be heard trickling in caverns iindcrgrouiid, and rain water vanishes quickly (lown to these sill)a a
terranean courses, often taking along with it the soil and larger rock particles from tile surface. Test ivells have shown some of these un(lergrouild solution channels to be as much as 11 feet from roof to floor; their horizontal extent, however, is uiiknown. These channels occur, in son~e places, within a few feet of the surface; the Jar aest one noted at shallow depths occurs bctweeii 10 and 21 feet below the land surface and was peiietrated by an exploratory test well (G-189) in the Silver Bluff area of Miami. The effects of solution are. at tunes an aid and at other times a hindrance in working out the stratigraphy in a hiniestone area. For exanII)le, along the Caloosahatchee River in the Fort Thompson area many of the older Pleistocene (leposits have been almost entirely removed, but remnants still fill solution holes in a lower bed. In thi8 way the former presence of' these deposits is proved. Further, a younger filled solution hole maY l)elietr&Ite aJI earlier filled within l)a11t1v
one, thus defining three separate deposits aiid two unconf'orinities a very small area. Locally an overlying bed not onk fills
vertical solution holes but also spreads out, filling a cavern below. Close scrutiny is needed to (liscern the actual relationship. Such
-A-- --------- a a a
-- C .L -- k------------------
30 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
DEEP LAKE AND STILL LAKE, PLEISTOCENE SINK HOLES
ir. r. n .. T fl I - C 1 ft fl In r. 4
LATE CENOZOIC GEOLOGY 31
C ADNOS 114 FEET SELOW LAKE LEVEL
84 ~-25-4Z SCALE IN FEET
:. E LEVEL 2'- 0 eEtOw LAND SuRFACE
20 0 20 43 tO DEEP LAKE, COLLIER COUNTY, FLORIDA
Fic. 2-Map showing contours on floor of Deep Lake.
are Deep Lake in Collier County, Rocky Lake in Liendry County, and Still Lake in Lee County. The other two, just outside the boundary of this report, are Salt Spring and Little Salt Spring in Sarasota County.
Most accessible of these is Deep Lake (Plate 6a), iii the Big Cypress
r%. -- n rr. m n -rr.
32 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Still Lake lies about 16 miles cast and slightly south of Fort Myers. Soundings made in May 1943 show that its general form is that of a funnel, and that the greatest depth is 208 feet below tile water stirface, which, at that time, stood about five feet below the land surface. This depth occurs in a sort of elliptical drain or "chimney" filled to about 170 feet with soft organic ooze. The diameters of the drain arc about 20 and 40 feet. The floor of tile lake deepens rather uniformly with a gradually increasing slope to about 125
feet, then drops abruptly in the drain or 'chiniiiey The average diameter of this Jake is about 600 feet, and the area is approximately
Rocky Lake lies in the Big Cypress Swamp about. 17% miles east of Imniokalee. It is nearly circular and has an average diameter oi about 840 feet; its area is about 12.7 acres. The (leptil is unknown.
All three of these sinks contain PotaI)le water, normal for the area iii which each is found.
Salt Spring, iii Sarasota County, is about 7% miles northwest of Murdock, and Little Salt Spring is 1.9 miles northeast of Salt Spring. Both springs yield saline waters. The greatest depth in Salt Spring, when sounded in October 1942, was 167 feet. Its surface then stood about 3 feet below tile level of tile land. The spring is almost cirS
eular; its average diameter i8 about 250 feet; and its area is approximately 1.1 acres. Its floor 8101)08 gently out to about 40 feet from shore, then drops abruptly to about 40 feet, where a shoulder 6 to 30 feet in width slopes to a depth of 50 or 60 feet, then falls precipitously to tile bottom. Apparently tile deepest I)art of the sink is along and near the southeastern wall. A rel)ort by Stringfield (1933b) includes a brief description of Salt Spring and a chemical analysis
of a sample of the water. The chloride content was 9550 ppm at the time the sample was collected. However, Stringfield states flint COfll1)OSitioil of the water may vary with the rainfall iii view of the fact that relatively large quantities of surface water may flow through the s~)riflg iii rainy seasons.
Little Salt Spring has not been sounded. It is almost circular,
...,'l ; natn, ntn~l *n b0 ~ *1, a a arm, a n. '~fl 04- V nl 4- V ncr rri.~
LATE CENOZOIC GEOLOGY 33
It may be that the differeijee in salinity of their waters accounts for their flames, or it may 1)0 (1110 to the difference in their flows. Areal size has nothing to (10 with it since they are essentially of the same diameter.
Few chemical analyses of their waters have been IIIa(1e; however, iii January 1943, Capt. A. B. DeWoif, U. S. Arniy Engineer Corps, collecte(1 saml)1es which were allLdyze(1 by K. J. Brehm of the City of Miami laboratory. This analysis follows; for others see pitg~ 34.
Big Salt Spring little Stilt Spring
No.1 No. 2
Chloride (CI)...... . . . . . ........ 9,300 1,450
lTar(Ifless (Soap). . . . . . . . . . . 3,020 854
Sulfate SO4 (Gravimetric) . . . . . . I ,61 5 515
Alkalinity ((mnCO3). * * * * * . 011 CO3 11C03 oii (Nh nco3 0-0-125 0-0-134
1~11. . .4 ~4~***t C * S * S S * S S C S S S 54 7.9 7.6
rrhlese salty springs flow because their bottoms penetrate an ai> tesian aquifer (Hawthorn formation) which has a piezonietric hea(l higher than the rim of the spring. Salty zones above the artesian aquifer, probably remnants of' sea water trapped during Pleistocene
invasions of the sea, contaminate the artesian water as it rises to the surface. The water iii the artesian aquifer is probably not much difS 4
ferent from that supplied by the various shallow artesian wells in the vicinity. This artesian water is hard, sulfurous, and only slightly saline; wily near the Gulf shore is it high in chloride (Stringfield, 1933b, p. 222-7, and Table 2).
The occurrence of dee1) sink holes iii southern Florida gives 1)resumptive evidence of' former stands of the sea much lower than the present, for it is not likely that such sinks could develop ) much below
ANALYSES OF WATERS FROM BIG AND LITTLE SALT SPRINGS
Mag- Sodium Total TernNo.c Date of Total Silica Iron Cal- nes- and Bicar- Sul- Chlo- Ni- hard- pH pera- (
Collection Dissolved (SiO2) (Fe) cium jum Potassium donate phate ride trate ness as ture
Solids (Ca) (Mg) (Na&K)a (HCO3) (SO4) (Cl) (NO3) CaCOaa 0F.
1 Feb.10,1927.. 17,812 18 1.12 766 471 5,124 167 1,704 9,350 .. 3,846
2 Aug. 4,1930.. 17,770 .... 508 630 5,288 173 1,676 9,550 3,853
3 Aug. 11, 1943. 17,670 0.08 639 541 5,250 164 1,705 9,450 .. 3,820 7.0 86
4 Aug. 11, 1943. 3,220 0.07 212 137 779 278 533 1,420 .. 1.092 7.2 84
b F, Margaret D. Foster, 17. S. Geological Survey L, S. Kenneth Love, U. S. Geological Survey P. Garald G. Parker, U. S. Geological Survey
S, George W. Simons, Jr., Flit. State Board of Health
No. 1 Big Salt Spring No. 2 Big Salt Spring No. 3 Big Salt Spring
No. 4 Little Salt Spring
LATE CENOZOIC GEOLOGY 35
time that probably corresponds to tile Illinojan glacial stage, and some of the other four stands may have been as low as 1800 feet below sea level (Stearns, 1942). If the holes were formed at an early stage, subsequent submergence did not destroy them, for the supply of sediment was too scanty to fill the sinks.
There are dry sinks of comparable depth in the lime-sink district of Florida. Falling Water in Washington County and the Devil a Mill Hopper in Alachua County are both deeper than 100 feet, and both are drained by underground channels at the bottom. The Devil's Mill Hopper apparently extends about to the water table, for the bottom is sometimes dry, sometimes wet. The ultimate depth of such a sink is largely dependent upon the depth to the horizontal channels that carry away the flow below the bottoms of the sinks.
Southern Florida is so low and flat that the drainage of most of' it. is very sluggish. The largest river is the Kissimmee, which flows southeastward into Lake Okeechobee carrying a large volume of water from the central highlands beyond the northern boundary. Fisheating Creek, a much smaller stream, also rises in the central highlands and enters Lake Okeechobee from the west.
The outflow from Lake Okeechobec passes eastward through the St. Luck Canal, westward through the Caloosahatchee Canal and River, and, during part of the year, southeastward through several other canals that terminate between West Palm Beach and Miami. The St. Lucie Canal, Lake Okeechobee, and the Caloosahatchee Canal and River form links in the Intracoastal Waterway. Before the canals were cut and the high dike around thQ lake was built, water from Lake Okeechobee overflowed into the Everglades and drained southward and southeastward more or less as a sheet through interconnected, nearly parallel courses. On land adjacent to the lake, ditches, dikes, and pumps have been installed, and a lowered controlled water level is maintained in the lake. This has resulted in a greatly reduced outflow to the south from the lake; in fact, during some parts of the
36 FLORIDA GEOLOGI CAL SURVEY-BULLETIN 27
tidal part of the river from its hca(lwatcrs (Hejiprin, 1887. p. 22') alit1 has lCSSCIiC(l tile (la1na'~C from 1100(15. 'hit' Caloosahatchee River now is ti(lzd to Ortona Lock.
The estuaries of Peace Creek and IM iakka River. both lda(liIlg i Ida (liarlotte Harbor. cross the northwestern part of souilwrn Florida.
Ti (lEVITt ions ott surhcial draiiiage are shown 011 the map of tim
It~-ergIadcs Drainawc District, Plate 13, which is based on many field
data and careful studies of tile alirl)laIle 1)IlotoUi'ilphs niade for 1114'
Soil Conservation Service in 1940. ilw arrows ill(liCute normal drainaiw direct ions iii the area before tile installation of the canals. in most iiiStLiilCCS the canals have affected this pattern very little and over lie !zreatcr I)aI't of' I 1w area it reniaiiis lIIICIIUI1! C(l. HOwcW'i'. local
1 11115 hiLlY tClnl)Orarilv 'UCVC17SC t1it~ dii'cctioii of flow in these Natdniiii&i~c 1%Alys. In the wet scaso~. .liiiic through (1)ctolu'ix lviii" r
when the lands are flooded anti canals are overtaxe(1. tile flow 1)Litteril lIl(liCatc(I is especially applicable.
Arch Crcck-Arch Creek (Plate hi crosst'(1 hr tile Dixie Withwar iii Dade County ~outh of the Broward County line, flows in southern lilorida. nh streani
I)CIlCLitll tIit only IILlIlJI'UhI l)ri(lgc
IltNItlS III LI lOW lfl~Ii'SIiV &I1'C&l (tOIIIICCIC(l with the Everglades. Cl'0$~e S a i'idge of iXliaiiii oolite through a ~'cr1 ical-walled cut (*o~rtbIeQil at.
Otie idace 1)V a narrow iiatiirall bridge, uh1(l thence WUH(lCVS 11117011 rh
Hal marshes to Biscavuc Bay. '1'he stream is ti(lal throughout most
ot its 2-mile course. The rock cut and the bridge probably orisziiiated as follows:
Ihe oolitc in the vicinity of Arch Crcek is 1)('l'1O1'Ut~1 hr ninny
yen iuii tubular solution boles leading" (lowil to the Wiltef t a1)> dull i there with a maze
~reuinabIr COIIIlCCtC(l of horizontal i~assa~es.
Fnlaritcment and coalescence of such horizojital ~~gt'~ itsuilted
iii the formation ot a colitimious tunnel through the oolite ridgc, which 1)erluuttc(l surf aec water and ground water 1)ack of the rid"c to wiss throu!zh it as through a culvert 11110 the ti(1211 lilLirshes heVOllIl.
lh~- SI% dliii) water. I)CiIlg highlY chiartrctl with Or"aIlic acids. dee1dv r r
LATE CENOZOIC GEOLOGY 3:
ARCH CREEK NATURAL BRIDGE AND HILLSBOROUCLI
LAKES MARSH 01? THE EVERGLADES
FIGURE a-The itatural bridge of Arch Creek over which the 01(1 Dixie
HiizI~vav PflSSCS. The swampy ac1(lie waters undercut the banks.
38 FLORIDA GEOLOGICAL SURVEY BULLETIN 27
TOPOGRAPHIC-ECOLOGIC DIVISIONS THE SANDY FLATLANDS
General features-Within the area of this report the sandy flatlands (P1. 8) range in altitude from somewhat less than 10 feet above sea level to nearly 80 feet. The (~reaIer Part 15 lower than 25 feet and fornis 1)art of tile lowest Pleistocene marine terrace, the Pamlico, whose shore line is now about 25 feet above sea level. The areas above 25 feet are not quite so flat. They are called by Sanford (1909, pp. 185-186) the "Rolling Sand Plains." These higher areas are within the Talbot terrace (shore line about 42 feet ) aii~l the Penholoway terrace (shore line about 70 [cci )
The sandy flatlands surround Lake Okecehobee except on the soul iiem 1111(1 southeastern sides) where tile wi(1e CXI)HIISC of the Everglades meets die lake. On tile ivest the san(lv flatlands CXtCIl(l 1)raCtiCLtllV without interruption to the Gulf of Mexico. They continue south ill this western area beyond Naples, where coastal marshes begin. Inlahl(1 they extend from this coastal strip to the irregular niarwiiis
of the Big Cypress Swamp aiid, passing north of the Big Cypress, meet the western boundary of the Everglades. East ot Lake Okeechobee they extend as a broad l)elt almost to the ocean, limited on the east by the narrow coastal ridge with its Pleistocene (hilles, d11(l on the southwest aIl(l west by tile eastern border o1 the Everglades This strip continues southward between the Everglades and the coastal ridge to Coral Gables, in the Miami area, with all occasional break through the ridge north of Miami. where they form tile floor ol old (lraiIla(rel%'avs &I11(l ti(lal channels.
These sandy flatlands are poorly (lraiIle(l. Rainfall either sinks
directly ilito the surficial saIl(l or is store(l ill shallow r~j whole flatlands area is (lotted with these shallow circular I)oII(Is~ ire~er&jl1y only a foot or so deep and rarely over 4 feet (led). Dianicters of' the poiids range ill) to several hun(lrcd feet. The pOIl(lS api~car over areas of (leeji saud as ivell as over areas where only a thin sand mantle covers underlying Ilimestones and shell mark. The ma
1 - 1 - ... 1 - - i ~- - I -. 1 - - r~ -~ 1 n -. - -. a 1 .1 : 1 -
LATE CENOZOIC GEOLOGY 39
VIEWS OF THE SANDY FLATLANI)S ANI) IN THE DEVIL'S GARDEN
PLATE 9 i'1(;I.~IIE; a -T3 pica1 ~'icw of tint Sandy Flatlands ~vesL of Lake Hiepoclice
with the Caloosahatelice River ineaidering to the ivest.
49 FLORIDA GEOLOGICAL SURVEY-BULLETiN 27
Clayton, Neller and Allison (1942) have shown that transpiration
and evaporation may exceed rainfall, the deficiency being accounted for by seepage and run-off from contiguous areas.
Drainage is sluggish and, except in the rainy season when lower
parts are inundated, there is generally little or no surface run-off. Though the surficial sands are quite permeable, the movement of around water is very slow because the land is flat and the iminer
diately underlying shell mans, calcareous niaris, and clayey mans are relatively impermeable.
In some more or less well-marked areas on the sandy flatlands (Iraillageways inherited from the past and modified by present
conditions are still used by surface waters. Most unportant 0f these are the Okaloacoochee Slough and Devil's Garden, tile Loxahateliec Marsh, and the Allapattah Marsh.
Okaloacoochee Slough and Devil's Garden -The Okaloacoochee Slough and Devil's Garden (Plate 8) form a marshy drainageway 011 tile sandy flatlands south of the Caloosahatchee River, west of the Everglades, and, ill general, north of the Big Cypress Swanip. The Okaloacoochee Slough extends southward about 50 miles from the vicinity of LaBelle into die Big Cypress Swamp. Its average width is little more than 2 miles, but a wide prong, called the Devil's Garden, extends northeast of Inimokalee.
The northern end of the Okaloacoochee Slough has a number of branches mostly discharging into little creeks flowing into the Caloosahatchee River. The southern end branches out likewise but is lost in the maze of intertwining courses iii the Big Cypress Swamp. Fahkahatchee Slough is the southwestern branch of the Okaloacoochee.
The Okaloacoochee Slough drains both northward and southward from about the latitude of the Devil's Garden. The Devil's Garden itself largely drains westward to the Okaloacoochee, but in tiniest of high water it may overflow in all directions-into the flatlands oii the north, the Everalades on the east, and into tile Big Cypress on
the south. See Plates 8 and 13 on which arrows indicate directions of surficial flow.
LATE CENOZOIC GEOLOGY 41
Drainage from the Okaloacooeliee Slough and Devil's Garden and from tile Allapattah and Loxahatchee Marshes is retarde(1 by a rank growth of vegetation and by an accumulation of organic peat and muck that clogs the channels; therefore, tile movement of water is, at times, difficult to discern. Direction of flow in the channels may be changed, too, by local rains. "Spot 'showers," which typify tile rainfall iii southerii Florida, may cover only a fraction of a square mile or several square miles, but they may be so intense that surface-water gradients are temporarily reversed in tile sluggish drainageways.
Allapattak and Loxahatchee Marshes-The Allapattah Marsh splits into two southern prongs, one that discharges its waters to Lake Okeechobee north and ivest of Indiantown, and another that formerly (irailled almost due south of that city into the Everglades, but is now cut by tile St. Lucie Canal.
The Loxahatchee Marsh is shaped like a wishbone with the apex pointed toward Jupiter Inlet and with prongs leading to the Everglades. Drainage usually flows in both directions from a low divide in the middle of the northern prong, and also usually flows in both directions from another divide in the southern p~~g not far west of Kelsey City. The southern prong drains directly into the Hillsborough Lakes Marsh at a point a few miles southeast of Loxahatchee (Plate 8).
Sandy flatlands south of Loxahatchee Marsh-Southward from the Loxahatchee Marsh the sandy flatlands extend a short distance past Coral Gables, where they abut against the coastal ridge of oolitic limestone and are overlapl)ed by Everglades soils. Apparently the sand never did extend farther south because the currents that SWeI)t the sand southward lost their efficiency there.
Between Fort Lauderdale and Miami are several low, shallow valleys, floored with sand of the Painlico formation, that reach to the PreseIlt shore. These are called transverse glades because of their orientation and their characteristic vegetation. They occupy
42 FLORIDA GEOLOGICAL SURVEY-IIULIJETIN 27
LATE CENOZOIC G~EOI,)GY 13
VIEWS IN THE BIG CYPRESS SWAMP
FIGURE a-Turner River, ini the southwestern part of the Big Cypress
Swamp. Picture taken from a bridge of the Tamniami Trail
(U. S. Highway 94). Trees are bay, willow and cyre.
FIGURE b-A hammock in tihe Big Cypress Swamp showing typical vegetation, and a "glades-buggy" used to get around in the area.
FIGURE c--Typical view of the stunted cypress growth in the Big Cypress
Swamp. A cypress "head" appears to the right side with small peripheral trees fringing larger ones until the center is reached where the tallest trees are found. Pickerel weed lines the canal batik and saw-grass covers the intervening area. This is On the margin where the Everglades and Big Cypress Swanip
U I'LORII)A CEOI4OG WA!4 SURVEY 1W LIET1N 27
pt)1tt'tl to he not deeper than 2() feet. It covers aI)Ollt 5 S(jHUI'C nides.
area varvillir '~reudv with the stage of the water.
TI I)dSiII. which lies near tlit' HhI1C~ inar~~iii of tin' Panihico icrmar rcI)rcscIlt an original hollow in die Illi(l-WiSCOIlSIIi SCU i)Ot 10111. iloirerer. as it iS uIl(lerlaiIl I)V soluble calcareous marl Buckinghain marl its bottom ina~' have been loWCrc(1 I)y solution. Ihie ~~rt'st~it't' of numerous smMi circular lakes nearby that apiwar to be solution features lend cre(1eiice to this 1)OSSlbilitV.
THE BIG CYPRESS SWAMP
Gciaeral features-The Big Cypress Swamp Plate 8') is a yent itidefinitelr (let iiied area. In general, it is bouiided on the cast and
southeast hr the Evcr'r1ade~
La which is distinguished by its organic
soils. sedges. and lower-lvjna area. The sandy flatlands adjoin it Oil
die north. where tiler arc higher, and oti the west, where they are lower. On the southwest and south the Big Cy press grades into tile l~1Vejyj~ja coastal marshes 811(1 mangrove swanii~s. in marked coii- r
trast to the surrouiidina areas of mucky, SaildY, aini maNy soils with
110 outcrop~)1ng rocks. the Bia Cypress r areas at
the surface. or where thin mark soil lies in shallow pockets in the
rock. In old (Irailla(rewavs this many soil is suitable for truck farmr
intr if the water table is a(lequatelv controlled 1w ditches, dikes,
dams and piiiiips.
Drainage is very effectivee, and in tile rainy season the larger part
of the Big Cypress is more or less flooded; hut eveii then the only niovement of water (liscernible is ill SIl~llOW, I)oor]Y (IefiIle(1 drainage courses locally called slougbs, rivers, or creeks. Near the Gulf of \ lexico these courses are 1)etter defined though so intricate that tile : erviec of' a ctui(le is rc(luired by a stranger.
The Big Cypress j5 not a vast morass of r fllOss-sIlrOuded cypress
trees as is sup~)ose(1 hr many pCOpk unfamiliar with the area. Rather,
it is an area of alterilating swampY and higher lall(l (hammocks) with the former the 1)rewileIlt type. Davis (1943 ) (ICsc1'il)CS these relationships and lists the prmewM members of tile flora. The dif-- -~ r ~ -I------1 .1 -
LATE CENOZOIC GEOLOGY 15
VIEWS IN TIlE EVERGLADES
Fi~i ~ni~ ;i--Ceawral view of the central Iwergiades looking northwest a! nag
the Miami tuna I from 1(11) of hit' airplane beacon '100 feet ~ at the ('OhlflIICIWC w jilt South New River (Latin!. Saw-ixrass carpets
46 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
General features-The Everglades, a region of organic soils (Plate 8), occupies an irregularly defined area of over 4,000 square miles surrounded by slightly higher areas on all sides but the south and southwest.
An arm of the Everglades borders the western side of Lake Okeechobee, and a narrow tapering arm extends northward along the eastern side about to Canal Point, where it nierges with the Allapattali Marsh and cypress swamps. The Everglades extend southward and southwestward from the lake in a vast sweep about 40 miles wide and 100 miles long, merging near the Bay of Florida and the Gulf of Mexicointo salt-water marshes and mangrove swamps. The boundary between the Everglades and surrounding areas is very indefinite. It may be regarded as the place where the sedges of the Everglades give way to true grasses and pines or cypress or to salt-marsh plants and mangroves.
Large areas in the northern and eastern parts of the Everglades are almost treeless expanses of saw-gras8 (Mariscus jamaicensis), a sedge, growing as tall as 10 or 12 feet. Low shrubs of wax-myrtle, willow, bay, and custard apple appear on slightly higher areas, generally in isolated clumps called tree-islands, all more or less aimed in accordance with the general drainage pattern (Fig. 4). Trees grow in the Everglades where there is enough height above the perennial water table to allow for aeration of the soil; along spoil banks conditions are very favorable, and trees and shrubs grow there in rank profusion (Plate 41).
Floor of the Everglades-Sanford (1909, pp. 192-193) thought that the rock floor in the northern part of the Everglades slopes off to the westward more steeply than in the southern part; that depth to bed rock 5 miles west of the eastern rim back of Fort Lauderdale is probably not less than 20 feet; and that the Everglades probably occupies a series of coniparatively shallow rock hollows. He states,' 'Whether
these hollows were as deep when the Everglades first occupied them as they now are, that is, whether they have been deepened by solu-
FLORIDA GEOLOGICAL SURVEY BULLETIN 27. PLATE 12
SI 32 33 34 35 36 3? 38 39 40 41
37 St LUCIE 38 39 40
0 W. PALM BEACH 43
44 45 46 47 48 g POMPANO 49 LAUDERDALE 50 SI 52 53 54
-7- CONTOURS ON TOP OF ROCK ALL CONTOURS ARE DRAWN TO OXEECHOBCE 58 SUBTRACT 1.44 FEET FROM FIGURES GIVEN HERE TO CONVERT TO 3d S. L.
48 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
limestone believed to be nearly level. Rarely, if ever, does it fall
below sea level, and nowhere, in the Everglades proper, (foes it reach the surface. The fact that it reaches the surface on all margins, except along the shore to the southwest, suggests that the Everglades may owe their existence to an original rock basin. The rock floor is slightly more uneven in the north than iii the south, and various explanations have been offered, based on erosion, solution, and deformation."
Data gathered by the U. S. Geological Survey while drilling mxiiierous exploratory test wells, and by the Soil Conservation Service while making soil surveys in the Everglades, shows that Sanford's observations were very good. Beginning along the eastern rim of the Everglades, from Lake Okeechobee to the latitude of Boca Raton, there is a rapid descent from the Atlantic coastal ridge to the shallow basin which contains the Hilisborough Lakes Marsh in its southern end (see Fig. 3 and Plate 8). Elevations drol) off from +10 to +3 feet (M.S.L. U.S.C. & G.S. datum) within a distance of about a mile; a slope which, in southern Florida, is distinctly scarp-like. Leading
into the shallow basin of the Hulisborough Lakes Mardi there is a shallow trough from the southeastern side of' Lake Okeechobee. Southward froni the Hilisborough Lakes Marsh this trough continues to old spillways and tidal channels emptying into the Atlantic Ocean between Fort Lauderdale and Miami. Some of these old channels have been deeply eroded in the rock and were later filled with saud; and it was to these sand-filled channels that Sanford ahIu(le(l when he said that depth to bed rock west of Fort Lauderdale is not less than 20 feet. Sanford, however, did not know that these (1c1)ths exist only in channels because sufficient (lata were not available to him.
West of Pus trough, which lies along the eastern margin of the Everglades, the rock floor forms a domelike surface with its 101) about 10 feet above mean sea level. This "high" centers on tile Palm Beach-Broward County east-west line about 6 or 7 miles east of the Palm Beach-Hendry County north-south line, and due south
of Lake Okeechiobee. Froni the top of this low dome the floor slopes
LATE CENOZOIC GEOLOGY 49
Cypress on the ivest and the Atlantic coastal ridge on the east, tile floor of the Everglades slopes gently from the sides toward tile CCIIter where a low, broad, flat valley swings gently to the southwest.
These major features of the floor of' the Everglades arc locally marked by smaller basins and higher areas. iii general, the floor sags from the sides into the Lake Okeechobee-Evergiades depression, within which there are local ridges and basins, none higher than the lands surrounding the Everglades, and few deeper than sea level.
Solution is actively engaged in etching out the floor of the Everglades at the present tune, deepening tile hollows and roughening
the ridges. Deposition, too, is taking place in some parts, especially iii the soils of the hammocks where calcium carbonate is being deposited, making a carbonaceous marl that locally hardens to friable, impure limestone.
The floor is composed of Fort Thompson formation fresh-water and marine marls and limestones in the north, Miami polite in tile south, and Tamiami formation in the central, western, and southwestern I)arts. A blanket of thin gray calcareous Lake Flirt marl covers large areas of the rocky floor, and along the eastern and western margins of the Everglades a thin mantle of' Pamlico saud occurs. Over these are several kinds of' peat and muck (Evaiis and Allison, 1942).
Origin of the Ever glades-This gently sloping basin was originally the Pliocene sea bottom, which was not perfectly flat but had slight inequalities. During the earlier Pleistocene glacial stages of the northem states this floor was subject to erosion, solution, then deposition of the first four beds of' the Fort Thompson formation, azid possibly slight folding. Then, probably during Sangamon interglacial time, the Miami polite, Anastasia formation, aiid Coffee Mill Hammock marl member of the Fort Thompson formation were depositedd over much of it. Later, these younger deposits were subjected to ero3ion and solutioii and still later were partly covered by sand of Pamlico age. During latest Wisconsin time the sea withdrew, leaving a large area that became occupied by fresh-water marshes and lakes in
50 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
growth of plants dies and sinks below the surface of the shallow water and is incorporated in the organic mass below. And it would continue on a much steeper gradient than that existent in the Everglades were it not for man's interference through drainage and farming. Fennemgn (1938, p. 63) in discussing the origin of the Everglades says: "The tendency of accumulating vegetation to build up and that of moving water to cut down are necessarily in opposilion. In Dismal Swamp, moving water is helpless on a gradient much steeper than that in the Everglades. Vegetation has not yet shown what it can do in southern Florida. If given a free field and no interference it would build much higher in tile interior before the steepening Mope would serve as a check. Meantime the vegetation would change, though slowly. The tree-clad hammocks would become steadily larger and more numerous and should ultimately be dominant."
Drainage pattern in the Everglades-In the Everglades there are many elongated tree-islands, arranged more or less in parallel, rows and separated from one another by shallow saleses" "runs," "slouglis," or "lakes," as they are variously called locally. These treeislands and sales trend northwest-southeast in the upper part of the Everglades as far south as the old spillways' through the Coastal Ridge between Miami and Fort Lauderdale (see p. 48), then they
begin to bend to the south, and finally about 18 miles south of Miami, they swing abruptly to the southwest.
The linear arrangement of this pattern is most noticeable from the air, from which, as Dickerson (1942) says, "They reveal a decided "grain" to a broad sweep of country . as if a great coarse broom had been rudely brushed over the low-lying Everglades region." This arrangement is noticeable to one crossing the Everglades along the Tamiazni Trail where, toward its western side, the development is best and one crosses alternate strips of tree-islands and saw-grass.
Dickerson postulates that this "grain~~ may be the result of Pleistocene ocean currents during Pamlico time when this whole area was a shallow sea bottom. He notes that off the east coast of Florida a
-w - - -
LATE CENOZOIC GEOLOGY 51
currents, is (ICVCIOI)C(l entirely on fresh-water ~)(~&It 811(1 muck, and (loes not reflect an underlying l)LltterIl of marine bars. It represents merely a drainage I)atterll produced on a very gently sloping plaiti. rrhe is composed of tree-islands and swales that trend at right angles to tile regional slope, just as one wou1(1 cx1)ect of consequent drainage. Streams flowing across the Sunderland terrace into Oket'enokee Swamp in Clinch and Warren Counties, Georgia, show a similar pattern of parallel lines. On certain parts of the Pamlico terrace, e81)eci&dly in St. Lucie 811(1 Martin Counties, a patrailki airrangemeut of old (miles, beach 1'i(lgCs, bars, and lagoons is noticeable. This pattern is (lireetly a 1)rodIIet of lowering sea level in a shore-line environment but is not the same as that of the organic Everglades soils.
11w drainage pat tern in the Everglades is gradually i~eiiig chaIlge(1 by man 's oI)erat ions there. "Subsidence valleys" (Evans and Allison, 1942, p. 38) have develo1)e(1 along the principal (Iraillage canals, and direction of flow iii the northern end of the Everglades at certain limes of the year is iiorthward into 11w Lake, exactly o~)posIte to the original coiidit ion ( Stephens, 1942)
Lake Okeechobee-Lake Okeechobee OCCLIl)ICS the northernmost and largest of the iIltercoIInCcte(l series of l)asiIls aid shallow troughs which makes up the Lake Okeechobee-Evergiades d01)reSSiOIl (Fig. 3 and l~late 12) It is an original hollow iii the Pliocene sea floor, pOSSllily 1lIo(lifie(1 by solution, erosion, an(1 (1cI)osItion of sedjinemits duriiig tile Pleistocene and Recent epochs.
The lake is a little less than 30 miles in average (liamneter. At a sLa~e of' 20 feet above sea level, Okeechobee datum (Okeechobec
(latUill is 1.44 feet below U.S.C. & G.S. 1\'LS.L. ) it. has an area of 73() square miles; at a stage of 16 feet the area is about 710 square hues. As the lake ranges in stage from about 13.5 to 2() feet its area chiawrcs accordingly.
rElic lake is very shallow ; its deepcsL 1)ttrts are approxiiiiately ait sea level (Fig. 3) It is saUcer-sIlape(1, 811(1 because of its physical characteristics is subject to violent wind tiles and W&IVC action (liii>
1* Tr n it-n I. 1.
52 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
rceor(ls show that hurricanes with much greater wind velocity than that of' 1928 have occurred, notably that of the Florida Keys in 1935, Which IlLI(l 1111 estimated Wifl(1 velocity of a~)~)roximately 200 m.p.h. and a i axinuun hurricane tide of 16 to 18 feet."
Froni these (tutu it is easily uhldCrStOO(l that the I)OttOfll is rallier thoroughly scoiire~i l)y tile action of' storm WUYCS, ttiid, SiflC(' tlwse 4'UC('tiveIv ('List out detrital material, loose sand is scarce on the hot 10311. Arouiid portiolis of t lie lake, especially on the iioi'tliwesterii,
TION 610 c'?.'
LATE CENOZOIC GEOLOGY 53
northern, eastern, all(1 southeastern borders, a definite "sand ridge" ha~ been built up. rrliig is a beach ridge, probably built by storm waves, and lies outside the hurricane levee. It is the dwelling P1~'~ of most of the rural families who live arouIl(1 the eastern margin of the lake. Shallow 81111(1-point ivells, (Iriveil into this deposit, furnish I'anuily sul)plies.
rhe accompanying map, Fig. 3, shows contours on a 5-foot interval on the 1)ottom of the lake.
Hilisborougli Lakes Marsh-Hill8horougll Lakes Marsh (Plates 8 and 71)) is a I)oggy area occupying approximately 55 square miles in Palm Beach County. It lies north of the Hilisborough Canal, south of the West. Palm Beach Canal, west of the 8th1) of Sail(iy flatlands that borders the Atlantic coastal ridge, and, iii general, east of' a north-south line (Irawil through the coiiflueiiee of the Cross Canal anul West Palm Beach Canal.
it 0CdU1)iCS one of the larger aIl(l (Iceper basins in the floor of the Everglades; a basin that is now nearly filled with j)eat an(1 muck. ihese organic soils are being constantly I)uilt up over the greater 1)art of this area by aquatic an(1 semiaquatic vegetation. Large cx1~~I1S~ of Oj)CII water are (lotte(1 with small tree-islands of peat [111(1 muck, and here and there are flotant masses or "floating iSlaIl(1s." in shallower portions sawgrass grows thickly; in dee1)er water pOIl(l lilies an(l 1)iekel'e1 wee(1 are the most common 1)htnts.
rElic excavation of the Hilisborough Canal along the southern margin of tile Hilisborough Lakes Marsh lowered the water table considerably 1111(1 rejuvenated the better established (1I'aiIlage courses, some of which alrea(ly have become streams that have strip~)e(1 off tile organic depositss from their channels and exposed the bed rock. ill(liali Run (P1. 8) is a goo(l example. The Soil Conservation Service is (lamnhIliiIg the outlets of these streams, raising the water table, and attempting to restore conditions once more to approximately their original status. An area such as the Hilisborough Lakes Marsh is valuable as a water 1111(1 Wil(l-lifC I)reserve.
TT-TF ATTA1'JTTC ('C~AQTAT
54 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Ju1)iter. Silver Bluff is notched by wave action that occurred in former higher stands of the sea; one notch is at 8 feet and the oilier at 5 feet above present mean sea level (P1. 4b).
The highest parts of tile coastal ridge (50+ feet above sea level) are the summits of Pleistocene sanri duties, which lie in a series of' more or less I)arallel and discontinuous rows hack from the present shore. The southern end of the dune area lies in northern Broward County, where the dunes are much lower and broader than ill the vicinity of West Palm Beach, Jupiter and Hobe Sound. Northward front Hobe Sound, and extending into St. Lucie County, the belt Of (lunes surmounts old beach ridges, and is still better (levelope(1. These dunes are now quiescent and are largely overgrown with 1)UflCIl grasses, low sllrul)s, plies and palmettos.
South of tile (mile area saIl(1 extends as far south as Coral Gables. This veneer of sand (Panilico formation) was spread out over the limestone bedrock by ocean currents during iiiid-Wisconsin time.
rulit. coastal ridge almost everywhere has a rock foundation. North of Boca Raton it consists of' sandy limestoiie 4111(1 ealcareous sandstone of the Anastasia formation; south of Boca Raton it is the Miami polite. The oolite lies at or near the surface almost everywhere from Miami southward to tile point where tile ridge finally dies out on the lllainlall(l southwest of Florida City. The height of tile Coastal Ridge south of Fort Lauderdale averages probably 8 feet above sea level with maximum altitudes of about 25 feet oil the western shore of Biscayne Bay near Coconut Grove in Miami.
The Coastal Ridge (IisaI)I)ears southwest of Florida City in a series of low "islands," often culled "Everglades Keys," surrounded
Everglades soils. The Coastal Ridge reappears once again iii the lower Florida Keys, Big Pine Key to Key West, where Miami polite is again the bedrock. The, highest altitude observed on Big Pine Key is less than 7 feet; that of Key West about 13 feet.
Cutting~ across the coastal ridge in several places are many or
iiiucky strips called by Harper (1927, p. 176) "tr&msv6rse glades,"
~ flora on 00001~b1~110 nf udonic iuviB1r~~ s4 ni nC din ittrhor r;dIgr~,
LATE CENOZOIC GEOLOGY 55
It took the form of an irregular limy bar, oolitic south of Boca Raton and sandy and shelly farther north. This bar, which probably reached slightly above the ocean surface, lay between tile broad shoal of the Lake Okeechobee-Everglades (lepressioll and the deep sea, along the edge of the Floridian Plateau. The whole area of southeastern Florida was then much like the present Bay of Florida-Florida Keys area, but on a larger scale.
The surface of the bar never was level and it 1)robably wa8 made more uneven by the accumulation of low dunes of oolitic material hea1)ed upon it above sea level, and by tidal scour and wave erosion. While the sea was falling at the end of Talbot time, tidal currents scoured in and out of gaps across low spots iii the bar, notably
I)etwedll Miami and Fort Lauderdale. [he gaps 1)ersisted as tidal inlets until sea level fell below them, then they became fresh-water outlets during the early Wisconsin (Iowan) glacial substage. During the I)08t-IOWafl deglaciatioii the sea level rose and the Pazulico sea 81)read sand over the coastal ridge as far south as Coral Gables and choked the tidal channels. When, in late Wisconsin time, the sea
dgaill withdrew and the Lake Okeechobee-Everghtdes (1eI)ressioll filled with fresh water, the lower of the 01(1 tidal channels 011CC more became discharge outlets to the sea for excess water froni the northern 1)art of the basin, and this coiidition has contiuue(l ever since. Occasional hurricanes have shifted sand about as tile sea invaded these low areas, but, during Recent times, the main changes in the configuration ~of the coastal ridge and the tran8verse glades has been brought about by solution.
South of' Coral Gables are the transverse glades that are floored with polite. They represent modern (Iraullageways that are fllo(Iifie(1 Pleistocene tidal channels, iiiost of which (10 not reach across tile coastal ridge. They were short tidal runways in the waning stages of the Talbot sea, 811(1 again were likewise used by tile mid-Wisconsin (Panulico) sea.
"Bottomless holes" in New River-New River is a short, twoforked stream that occupies one of tile old spillways and tidal channels connecting the Lake Okeechobee (leDrcssioIl with the ocean.
56 FLORIDA GEOLOGICAL SURVEY-BULLETIN 2?
distantt past, whence the name "New River." Many of the deeper holes are situated at the outer edge of bends, and were scoured out by the river, but. others appear to be partly filled solution holes, more or less modified by scour. They may have had their beginning (luring the early Wisconsin time when sea level was lower than it is now, were largely filled with sand during Pamlico time, and partly re-excavated and i11o(lified iii late 'Wisconsin and Recent time.
There are numerous sand-filled solution holes in the Miami oolitc ridge that may have had a similar history.
COASTAL MARSHES AND MANGROVE SWAMPS
The coastal marshes extend around the southern end of the Peninsula from Naples to South Miami and continue northward to Fort Lau(Icr(lalc as a narrow bail(l bebifl(l tile preseilt gaudy 1)CaCIl
ridge. They are separated from the sea by the mangrove swamps which fringe tile coast and ti(lal lagoons and inlets throughout southem Florida (Plate 8) 811(1 are best developed in the Ten Thousand Islands and along the northern shore of Florida Bay.
The coastal marshes are characterized by many soils i~jxed locally with muck 811(1 tile strip bordering salt water the vereta~
tion consists of the usual salt-marsh subtropical assemblage, which ~rives way to fresh-water marsh plants at the outer edge of tNt Saul(IV flatlands, the Everglades, aiid the coastal ri(lgc. rrlie general relarioiishl1v of all these plants and assemblages is discussed in a recent
Lv Davis (1940) Where a properly controlled water table fiali I)C uiiaiiitained the coastal marshes are excellent for truck-f arming.
Rocks of Pliocene age lie at or near the surface in the southern 1)arts of the Big Cypress Swamp aiul the Everglades; elsewhere in Southern Florida they are overlain by Pleistocene and Recent materials (see Plate 14). From the Big Cypress Swamp Pliocene rocks s101)e aendy out under the Everglades to tile Atlantic coastal ridge,
I I 1. 1 1 it 1 U
LATE CENOZOIC GEOLOGY 57
neously; the Caloosahatchee as a sandy, many faces, a favorable habitat for mollusks, the Buekin~ham as a claycy facies, and the
Tarniami where liiny ooze mingled with the sand. Apparently the locus of lime deposition migrated several times back and forth over a distance of possibly 30 or 40 miles so that the Caloosahatchee marl and the Tamiami formation interfinger at depth. iii its final 1)llase, however, tile Tammami overlaps the Caloosahatchee marl in tile latitiide of Fort Lauderdale and to the north as far as the Tanijami formation extends (Plate 25, cross section A-A').
Historical summary-Shell beds ex1)ose(1 011 the upper reaches of the Caloosahatchee River (then spelled Caloosaliatehie) were first recognized as Pliocene by Hejiprin (1887, pp. 26-33), who ProPosed to call them Floridian. This was the first recognition of Pliocene beds in the United States east of the Pacific S1OL)C. Shortly thereafter, Dali (1887, PP. 161-170) confirmed the Pliocene age and referred to the deposits as Caloosahatchie beds and Caloosahatchic mans. The fonnatioii name Caloosahatchee marl was a(lopte(l by Matson and Clapp (1909, p. 123) and has since been genera11~ used.
An extension of the marl along tributaries of Charlotte Harbor was noted by Dali in 1892 (pp. 140-149), aIl(l later (1903, pp. 16031605) he listed species from Shell Creek, Alligator Creek, and Myakka River. The map accompanying Matson 811(1 Clapp 's (1909, pl. 1) report shows C&doosahatchee marl on these creeks and along Caloosahatchee River for about 15 nijies below LaBelic. A map iw Sellards and Gunter published in 1922 by tile Florida Geological Survey connected these areas aii~i extended the forniation somewhat beyond them.
The opening of the Tamiami Trail in 1928 1)erlnitte(l Cooke and Mossom (1929, p. 156) to examine Pie rocks that underlie the Ever('jades and the Big Cypress Swamp in Collier and Monroe Counties.
These rocks proved to consist of sandy limestone or limy SaIldStOllC
('ontaininif some characteristic Caloosahatchee fossils thouszh the
58 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
SECTIONS OF PLEISTOCENE AND PLIOCENE ROCKS
EXPOSED ALONG THE CALOOSAHATCHEE RIVER
Fw.uRE a-Banana Creek cuts down through almost 4 feet of Pleistocene
sand (Pamlico formation) to the basal conglomerate that here
1 ;~ nit tnn n# tim Pllnnnna Colnnanhlotnlmna nnrl 'I'I-ma 'ohla ;a
LATE CENOZOIC GEOLOGY 59
Development-The sandy Caloosahatchee marl underlies most of southern Florida. It interfingers with or grades into the Tainiami formation at depth in a zone possibly 40 miles wide centered in the latitude of Fort Lauderdale. The Caloosahatchee underlies most of the Everglades and is present in the subsurface between Lake Okeechobee and the Atlantic coastal ridge. It is probable that it jIlterfingers with or grades into the Tamiami formation under the coastal
ridge in the vicinity of West Palm Beach. See section A-A', Plate 25.
The Caloosahatchee marl is a littoral and neritic deposit eoulpose(l of sand, silt, clay, shells, and often enough calcareous material to make it a true marl. It contains many local beds or lenses of pure sand or clay, but the usual condition is just what one would expect of a deposit where constantly shifting currents acted upon a shallow sea bottom and shores adjacent to a low land mass that contributed only fine sediments.
Many exploratory test wells have been drilled through the Caloosahatchee in southern Florida. Preliminary study of cuttings from these wells indicates that it thickens to the east, southeast, and south. It ranges from about 30 to 50 feet in thickness in the zone where it interfingers with the Tarniami formation.
Water-bearing characteristics-The permeability in the Caloosahatchee marl varies with its lithologic characteristics, but as a whole the formation is of relatively low permeability, and some xvells ending in it yield no water. Where the formation is more permeable, and near the coast, the water is apt to be potable but hard; inland, around Lake Okeechobee and the upper part of the Everglades, the water is always hard and often so highly mineralized
as to be unfit for human consumption. These vanously mineralized bodies of water near the lake are probably the result of Pleistocene invasions by the sea during interglacial stages and of subsequent partial flushings or dilutions by fresh percolating ground water during glacial stages, and the various chemical reactions, especially of the base-exchange variety, that have taken place and are still going on.
~ n r ~. - -
60 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Caloosahatchee River underlain by soft elaycy marl that hardens into limestone on exposure. Ten years later, Mansfield (1939, pp. 111-116) proposed the name Buekingliam limestone for the deposits so mapped, which he retained iii the upper Miocene and described as "chalky limestone that contains a little saud and many small grains of brown phosphorite."
Age and development-Mans field's identification of the Buckingham as Miocene was based niore on affinities than on definitely
identified species. in his list of mollusks (Mansfield, 1939, p. 11) the only definitely identified species that was suI)posed to lie restricted to the Miocene is Chione zdocyma. All the oilier previously (lescribe(l species range froni Miocene to Receiit. Comparison of Foraminifera from the Buckingliain with Calloosahateliec faunas leads J. A. Cushman to report that the Buckinwhain fauna includes species that are common to 1)0th Miocene and Pliocene, but none that are (let initely restricted to the Miocene. W. Storrs Cole, who examined forantiniferal faunas from Buekingham and from the Caloosahatchee River at stations 24 and 390 (see pp. 84 and 83), reports that lie WOIII(I have little hesitation in placing the Buckiugham marl in the Pliocene, as lie found no species restricted to the Miocene. He identified Rotalia beccari tepida Cusinnan, Diocibicides biserialis (Cushniaii and Valentine) Discorbis subaraucanus (Cushman) Cibicidos lobat us ( Cushman) Elphidiiim fimbriamlzim. (Cuslinian) Angidogerina occidentalis (Cushman) Buliuzinella elegantissima (d'Orbignv ) and Elphidium incertum (Williamson)
A wel1-I)reserved jaw bone of a whallebone whale collected at station 24 was examined by Remington Kellogg, who finds that it represents an inidescribed SI)CCICS whose affinities are closer to known Miocene than to Pliocene whales. This same relationship, however, exists 1wtween tim pelagic mammals of the early Pliocene Bone Valley gravel of Florida ajid the Miocene of Europe (Kellogg, 1924, p. 765), though as Kelloaw cites no European Pliocene faunas containing pelagic mammals, the basis for his statement that those in the Bone Valley are ol(ler than Pliocene is not apl)arellt.
LATE CENOZOIC GEOLOGY 61
Uneven weathering in the transition zone has locally given a false appearance of unconformity to the contact between the Buckiugham and the overlying tongue of the Caloosahatchee marl. On Caloosahatchee River east of the mouth of Banana Creek (pl. 16h I and elsewhere rain water and waves from passing boats have washed away tile less cohesive sand and shells from above tile sticky, more resistant Buckiugham marl, which projects as an uiidulaiit shelf just above water level. At first glance this uneven surf ace suggests unconformity, but more careful examination shows that the clayey Buckiughani merges gradually upward into the saiidy Caloosahatchee.
Well records show that tile Buckiugham commonly lies on saH(Iy Miocene limestone similar to that on which tile Bone Valley gravel lies unconformably. (Cooke and Mossom, 1929, p. 166). The Buckingham is overlain nearly everywhere by thin (lepOSits of Pleistocene saud.
The Buekingham marl extends southward from the type locality through Lee and Hendry Counties into Collier County, where it is cut into by shallow ditches along Florida Highway 164 as far as a point 17 miles north of the Tamiami Trail, south of which point it is succeeded by the Tamiami formation into which it presuiiiably merges. Its northward limits have not been accurately traced because of the cover of Pleistocene sand.
Nearly everywhere tile Buckiugham marl is a creamy white to green ealcarcous clay. Where exposed to the weather it has 1)een case-hardened and stained into light-brown solution-riddled linicstone. This faces was more conspicuous at Buckiugham before tile l)it there had been deepened and widened to its present extent and accounts for the name Buckinghain limestone originally given to
A notable feature of the Buckiiiaham is the abundance of 1)hos1)llatiC grains within it. These are noticeable in the pit at Buckina-0 ham and increase iii quantity and size with depth. The abundance of pliospliatic grains allies the Buckimigham with the Bone Valley
trrn'.rnl ~ 0 nnoA CflI' nilnoibil 'ito InVtlI Oh' nnrl-lt (111,1 ~ fll' 0
FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
l~amlico I orination
Absent froni this iveli but consisting of as much a~ 5 feet of gr&t
to creamy gray sand in other nearI)v wells. Bizrkinuhamn marl
grains at a depth of fl) feet, larger grails and nodules at 20 feet, and niore abundant phosphatie I)erhaps
30 percent of total saniple, at 1)ottoIll........................ 0-30
(:re&tin.eoIore~I, pliosI)hatie clay marl plus greenish
(.1a~? at... t0 e S C S S S S *O 0*ae S S S Ce C g a a a S A S S * S S S S C g S S S S
(:reahlI-eolore(1, shell. phosphatie marl, 110 greeti -, at... e.g.. 40 IKIaii-thorii format ion
Greenish-gray Iiniestoiw iIIixf3(J 1%-lilt creain.colored,
phosphatie marl I probably fallen from above) ; lighter
coIorC(l 'tear Ijottoni. *...*... . . gac...... . . . . . . . . .45-111
Water-bearing cli aracteristics-The Buckingliani marl is a very ~ aquifer. It is so inlpernleal)le that it acts as a seal to the underlieds. ill Which
Iviiw more permeable an artesian head has
1)IIiIt Lii). A few of the shellier and san(licr 1)LIrts of the Buckingham yield relatively small quantities of water to wells C(~iiipped with J)OIIltS or screens. but most of tile residents of the Buckin~ham area collect rain water iii cisterns or use the artesian sulphur water from tile (Ieel)er formations.
TAM lAMI FORMATION
Historical sum m(lry--Fhe rr~uiili&Iiili formation Mansfield, 193% p. B was first noted by Sanford I~ 1909, pp. 222-224) who naiiied it
the Lostmaiis River limestone from exposures near tile head of that iuitcr course. He Ilote(1 that the formation uiiderlies the gray sands I 110W CLdIC(1 the Pamlico formation) that mantle the margins of the inainlaiid. and that it also underlies tile mans of the coastal swamps, the keys of the southern border of the Ten Thousand Islands, [111(1 that it extends aIom~ the southwestern border of the Everglades.
He did not ascertain the relationship with the Miami polite (Pleisto4~j~Jj(1 I i)Ht correctly thought that the oolite was younger.
1 -- I ~i- j -lana flfl~7\ S 1 -rb
LATE CENOZOiC GEOLOGY 63
CONTACT OF THE MIAMI POLITE AND THE TAMIAMI FORMATION
11(;UIIE a-~--X. drcdged rock fragiucia along the South New River Canal sIio~
wita nt r ;r~ht n to d10 wzit ~r :1 ~ret iou of tim iiit-
64 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
the road bed of the Tainianii Trail over a distance of about 34 miles iii Collier and Monroe Counties, Florida." This was the same limestone that Cooke and Mossom (1928, p. 207) had correlated with tile Caloosahatchee marL Mansfield (1939, pp. 8-10) assigned it to the Pliocene and placed it tentatively below the Caloosahateixee marl and above the Buckingham marl. He had never observed this relationship but correlated it thus on the basis of fossils from a spoil bank.
The Taininini place name is preferred to Lostmans River because the exposures on the Tamiami Trail are much more accessible than those of the Lostmans River area, and further, the rocks along the Trail are exposed above water in spoil banks and canals whereas in the Lostmans River area they are submerged. The term limestone is not appropriate because the formation generally contains too much sand.
Parker (1942, pp. 64-66) correlated the Tamiami formation with the highly permeable rocks underlying the Miami oolite on the Atlantic coastal ridge that had previously been variously assigned to tile Pleistocene or to the Pliocene. He noted that in the western Everglades and Big Cypress Swamp the Tamiarni forniation overlies the Caloosahatchee marl and on this basis arrived at the conclusion that the Tamiami is younger than the Caloosahatchee. Subseqilelit study of well cuttings and the drilling of additional exploratory test wells showed that there is also an interfingering or grading toaethier at depth of these two formations.
Dc velopnz en t-The Tamniami formation is conipo~ed principally of white to cream-colored calcareous sandstone, sandy limestone, and l)eds and pockets of quartz sand. Where it is exposed on and near the surface in Monroe and Collier Counties it is grayish-white to tan and is riddled by solution holes, which are usually filled with many soil. To the east of its outcrop area the Tamiami formation sloI)Cs gradually under the IN'Iiaini polite, and for several miles the contact of tile two formations is visible in big pieces of rock dredged from the Tamiami Canal. At times of extreme low water this con1 1 1 1 1 1 0 1 Cl 1 itT fl
-- a ~ A. ~ - A. - - ~ -.
LATE CENOZOIC GEOLOGY 65
west it is about 45 feet 8 miles west it is about 80 feet thick: and near the shore of Biscayne Bay at Silver Bluff it is about 100 feet thick. On a line due south from tile 19-mile point (Krome Road, 19 miles west of IN'Jliaiui) the Tamiaiui holds its thickness of' 45 feet, neither thinning nor thickening as far south as Florida City, at least. Due south of the outcrop area of the Tainiami very little is known of its attitude or hthology because of lack of reliable well cuttings.
Water-bearing characteristics-In tile vicinity of Miami tile Tainialili is one of the most highly permeable formations ever illvesligate(1 bY the U. S. Geological Survey, and ranks with clean, ivell-sorted r('ravel ni its property of transmitting water. Tests made by two (Idferent methods indicate that for each foot per mile of hydraulic gra(lieflt, water will P~'~ through a section of the formation a mile wi(le and a foot thick at the rate of about 20,000 to 40,000 gallons a (lay, or more. Thus, about 1,500,000 to 3,000,000 gallons a day would pass through a section 75 feet thick. Many 6-inch diameter wells along the coastal ri(lge from Miami to Florida City yieid 1,00(1 gallons per minute without measurable drawdown.
In the Everglades and north of Fort Lauderdale the Taniianii formation contains more sand than to the south of Fort Lauderdale, an(l therefore yields are generally lower and drawdown greater. In the Fort Lauderdale area wells are often finished with screens, whereas in southern and eastern Dade County most wells are "open hole" wells, i. e., uncased an(l unscreened in the last 5 to 20 feet of the hole.
The quality of the water is very good except where it has been contaminated by sea water in a zone about 2 miles wide along the shore, in Miami, and in narrow tongues that follow up the uncontrolled drainage canals (Cross and Love, 1942; Parker and others, 1940; Parker and others, 1944). Undoubtedly contamination has occurred elsewhere along the southeast Florida coast as a result of drainbig the Everglades and lowering the fresh-water head, but detailed studies have not been made north of Dade County. It has been necessary to abandon many wells in these areas of contamination.
66 FLORiDA GEOLOGICAL SURVEY~BULLETIN 27
grew along the southern edge of the Floridian Plateau from Miami to Big Pine Key. These formations have been most difficult to correlate. Many geologists have worked with them in the past, but the lack of sufficient data heretofore has been the principal handicap in arriving at the conclusions reached by the preseilt writers.
Historical summary-The Anastasia forniatioii was named by Sellards (1912) from its typical development on Anastasia Island, near St. Augustine, Florida. He applied the name to "the extensive deposit of coquina rock found along the East Coast." Cooke and Mossorn (1929, p. 199) expanded this to include "all the marine deposits of Pleistocene age that underlie the lowest plain bordering the east coast of Florida north of the southern part of Palm Beach County." In the geologic map accompanying their text they showed a strip of Anastasia formation along the west coast of Florida as far north as Tampa Bay. The Anastasia formation as here defined includes the coquina, sand, sandy limestone and shelly marl of prePamlico Pleistocene age that lies along both die Florida east and west coasts. This excludes the surficial sand, of Pamlico age. The upper part of the Anastasia is contemporaneous with the Miami polite, the upper part of the Key Largo limestone, and the Coffee Mill Hammock marl member of the Fort Thompson formation, all of which might be considered as faces of the Anastasia formation. The lower part probably is contemporaneous with the lower pan of the Key Largo limestone and with the older marine nicinbers of the Fort Thompson formation.*
Development-On the eastern coast of southern Florida the Anastasia composes the backbone of the Atlantic coastal ridge north of Boca Raton and extends westward to the Lake Okeechobee-Everglades depression, where it merges with marine nieinbers of die Fort Thompson formation. It is wedge-shaped, thin toward the interior and thick toward the coast, where it may be as much as 60 feet thick. On the west coast it is a very thin irregular deposit cx,nA;n~ fran, Murnn IalanA RQ ('sir north n~ Tsmiiinn flniv ~ itQ (rrPrutPQt
LATE CENOZOIC GEOLOGY 67
cites Vaughan's (1910, p. 169) study of a fauna from a depth of 113 feet at Deiray, and concludes that it "indicates a considerable thickness of the Pleistocene and may well represent an earlier stage than the Miami-Anastasia."
Study of cores and sand cuttings from S-394, a test well drilled in 1940 near the Deiray Beach city water tower, at an altitude of about 20 feet above mean sea level, gives the following log:
Quartz sand 0- 10'
Quartz sand 10 -42
Calcareous sandstone 42 42-5
Coarse coquina 42.5- 43
Gale. sandstone and coquina 43 67 Gale. sandstone 67 -69
Gale. sandstone and shell 69 -79
Caic. sandstone 79 -80
Gale. sandstone aiid shell 80 -82
Caic. sandstone 82 .83
Gale. sandstone ana shell 83 -84
Gale. sandstone 84-87
Gale. sandstone and shell 87 92
Gale. sandstone 92 -93
Coquina 93 .108
Cbalky limestone 108 -108.5
Gale. sandstone 108.5-109
Shells and sand 109 -115
Quartz sand and shell 115 -135
Soft rock, shell, saud 135 -140
Sand and shell 140 -165
Soft rock, shell, sand 165 -216
This log agrees with Vaughan's log except that his "quicksand"
between 43 and 108 feet is represented here by calcareous sandstone, shell and sand. The well Vaughan reports may have been drilled in an old solution hole filled with sand.
Water-bearing characteristics-The Anastasia formation is a good aquifer, especially in its consolidated portions, where open-hole (unscreened) wells may 'be developed. In the sandier portions wells must be finished with well points or screen and gravel packs. The yield is usually larae and the drawdown small. The aualitv of the
68 FLORIDA GEOLOGICAL SURVEY--BULLETIN 27
long aiid has a maxinnun surficial width of about 3 miles; however, its base is much wider am1 interfingers at depth with the Miami oolite. It rests on tile Tanijaini formation amid may lie 50 feet or more thick. Its upper part is definitely contemporaneous with the Anastasia formation and the Miami polite, but its lower part is older amid underlies part of the polite.
The liniestonc contains a large amount of coral, afl(l the spaces between aIl(l around the coral Ilea(ls are filled with amorphous limestone or detritus from wastage of the reef (Plate 18a). These fraginents ap~)areI1t1y fell or were washed into holes, and were then incorporated in the rock as a limestone breecia.
[[flier-bearing characterisncs-Solution holes and caverns, which are common in the rocks, allow sea water to move freely in and out 811(1 perillit the rain water to escape rapidly to the Sea. The Key
Lar~ro innestone vwlds water freely, but it is salty. About the oily use made of tile water is for fire-fighting or flushing.
Hasiorwal summary-I he limestone deposits of southern Florida
were first noted by IT. S. Army officers (lurilig the Seminole Indian
Wars. Later, Buckiugham Smith (1848) noted marine shells in the limestone, aiid 011 the basis of a study of these shells dated the (IC0
1)osit as 1)ost-Pliocdne. Tuomey (1851) descriliefI outerolis of the rock along Miami River, ahl(l Louis Agassiz (1852) gave an account of them in describing the Florida reefs. Shaler (1890) accepted
time VICWS of' Louis Agassiz and reffar(le(1 the oolitc as having been fornied on a coral reef. 11e iIlclu(led tile oolite with other rock, possiblv coquina, iii his Miami Reef.
Alexander Agassiz (1895) was next to describe the oolite. From his oI)servatIolls of outcrops aloiv~ Biscayne Bay and Miami River lie came to believe that tile polite was formed by acolian processes, aIl(1 in a later 1)&l1)Cr (1896 ) he presciited hjs reasons fully. Griswold
(1896) examined these outcrops of the polite, but he also examined them as ninth as 20 miles inland, amid froni his observations
LATE CENOZOIC GEOLOGY 69
ViEWS OF CUTS IN THE KEY LARCO LIMESTONE AND MIAMI POLITE
FIGURE a-A quarry in the Key Largo limesione shows tile porous, solutionpitte(1 characteristics of this coral reef rock. Windley's Key,
70 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Development-The Miami oolite underlies tile Atlantic coastal ridge from a transition zone near Boca Raton to Florida City; it floors tile Bay of Florida and re&ippears above water level once again in the lower keys from Big Pine Key to and beyond Key West. It is thickest along the coast, possibly reaching a maximum thickness of 40 feet in places, and thins out in the Everglades to a feather edge.
To the north and northwest tile Miami polite thinly overlaps the Fort Thompson formation and in some places is itself overlaiii by a thin fresh-water marl and limestone. This latter relationship led Parker (1942) and possibly Richards (1938, p. 1280) to suppose that at least part of the Fort Thompson formation is younger than the Miami polite. However, the youngest fresh-water marl aiid liniestone is now classified as Lake Flirt marl, very late Pleistocene or Recent in age.
The contact between the Miami oolite and the underlying Tanijami formation is visible in many places in the Everglades and in the southeastern part of the Big Cypress. The contact (Plate 17) is often on a clean, solution-pocked surface of calcerous sandstone, but in many places a limestone breccia or conglomerate separates the two. This breccia is probably a result of erosion, solution and redeposition that took place in some of the Pleistocene glacial or interglacial stages precediiig the deposition of the Miami oolite.
The Miami oolite is soft, cross-bedded to massive, and grades from ahiiost pure calcium carbonate to sandy limestone, becoming sandier northward. The gradation to the sandy Anastasia formation is
visible along the ilulisborough Canal a few miles ivest of Deerfield.
The occurrence of large, well-developed cone-in-cone structures in tile cross-bedded portion is notable. Tarr reports (Twenhofel, 1932) that heights of cones in limestone range from 1 to 200 millimeters; that those from 10 to 100 millimeters are most conunon, and that basal diameters depend upon the heights and angles of slope of die cones. The cone-in-cone structures in the Miami oolite are all
LATE CENOZOIC GEOLOGY 71
Study of the structure of the polite throughout its areal distribution indicates that both Alexander Agassiz and Griswold were partly right. Apparently the steeply dipping (up to 450) cross-bedded portiolis are remnants of old ealeareous dunes or beach ridge (le1)osits, and the parts that are massive or have low-pitched dips and contain numerous marine fossils are marine. Stearns (1943) observed that the cross-bedded parts of the oolite are counterparts of Pleistocene calcareous dunes as found on Maui, T. H., and elsewhere in the Pacific.
In some places the steeply dipping cross-bedded portions are truncated by horizontal beds including numerous marine shells. The occurrence suggests fluctuating sea level at the time of deposition so that the ocean rose above previously deposited dune or beach ridge material on the low oolitic bar, and new deposits of the same nature but containing marine animals were laid down.
Near the western shore of' Biscayne Bay at Silver Bluff several large pieces of' cross-bedded oolite are embedded in structureless oolite, a proof that previously formed oolite was broken away, washed into the sea, and incorporated into the latter portions of the deposit.
This might indicate that conditions were right for the forznatioii of polite in this area during parts of two or more interglacial stages, or it may simply indicate that caleareous dunes formed in an early part of a stage were later attacked (after consolidation) and incorporated in the later-formed portion, all occurring within one stage.
The polite is tile product of deposition in a marine environment on a shoal or bar just about at sea level, so that at times and in certam places calcareous dune8 or beach-ridge deposits may have been built up above sea level. Most of the building of this bar probably
took place in the Sangamon interglacial stage either at tile beginning of the stage (early Wicomico time) or at the end (near tile close of the Talbot), or both. However, the basal parts of the oohite may
represent low-sea-level deposits of the older Pleistocene interglacial sta oes.
I 1 11* 1 1' *.. - 1 I
72 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
VIEWS SHOWING DEVELOPMENT OF THE FORT THOMPSON FORMATION
C ~ ;J\~~.
-~ I ~'~'
4 1~ *
*-A -. tJ&ii~
FIGURE a-View showing general development of the Fort Thompson formadon across tbe Caloosabatchee River from the type locality.
LATE CENOZOIC GEOLOGY 73
FORT THOMPSON FORMATION
Historical sumnzary-Sellards (1919, pp. 71-72) proposed tile name Fort Thonipson Beds for the alternating fresh- and brackish-water and marine 8hell mark and lirnestones typically exposed at old Fort Thompson, about 1 miles east of LaBelle. He noted that these beds underlie a persistent marine shell bed, which he called the Coffee Mill Hammock marl from its typical development at Coffee Mliii Hammock about one-fourth mile ivest of the Atlantic Coast Line railroad bridge at Goodno. Cooke and Mossom (1929, pp. 211-215) changed the name Fort Thompson beds to Fort Thompson formation, and included the Coffee Mill Hammock marl in it. Tile)' indicated that the Fort Thompson lies uneonformably on the Caloosahatchee marl Pliocene) and is overlain by tile Lake Flirt marl, of probably Recent age. This definition is followed iii the present P~1)~.
Development--The Fort Thompson formation is thin, probably not over 20 feet in its greatest thickness, and it. averages less than 10 feet. It has its typical development at the site of 01(1 Fort Thompsoil, between LaBelle and Lake Flirt, where a thickness of about 6 feet of alternating fresh-water and marine 1)CdS is exposed (Plate 19,) rihe beds differ in thickness from place to ~iace within a very short flhiSSiIW Ojily
(listaIlce, and some may be altogether or preserved in
solution holes in a lower lied. Sections at Station 325 and at Station 327 (pp. 89 and 90') indicate the lithologic composition along that stretch of the river where the Fort Thompson formation has its best exposed development, and they are typical of the format ion where all or most of its membgrs are present. The inequalities of the surface of the underlying Caloosahatchec marl give unequal thickness to tile Fort Thompson, since it usually is thicker iii the low parts an(1 thinner on the high parts.
The Fort Thompson formation extends eastward 1111(1 westward from the type locality but has oiilv a limited (10VC101)IllCflt to the ivest where, beyoiid Denaud, it merges with the Anastasia formation; it floors the Lake Okeechobee-Everglades depression as far south as the latitude of Fort Lauderdale and as far east as the Atlantic
74 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
However, the present writers favor the view that they represent almost uniform deposition over the inequalities in the Pliocene floor
which they were deposited, possibly modified by sagging where ground water has removed soft calcareous marl that gave support to the overlying less-soluble beds. In some areas the Fort Thompson beds lie almost perfectly flat for miles; however, since iii most of the area of its development the Fort Thompson formation is covered with water, peat and muck, or sand, the structure of the beds can not be ascertained definitely.
Water-bearing characteristics-Stringfield (1933) first reported oii the water-bearing characteristics of the Fort Thompson formation. It is a poor aquifer; its Ijinestones are dense and hard, and the calcareous muds or mans have very low permeability. The freest movement of water is iii the sand and shell beds, but these commonly have a low coefficient of permeability because of the admixture of fiiie sand, silt and clay. Water is apt to be of poor quality because of residual mineralization from various invasions by the sea of the area underlain by the Fort Thompson during the several interglacial stages. Chloride ranging from 16 to 3150 ppm. has been found in some of the exploratory test wells (Parker and Hoy, 1943). U. S. Treasury standards allow maximum chloride of 250 ppm in public supplies, and most people can definitely taste 400-500 ppm. The fact that sonie wells drawing from the Fort Thompson formation find usable water is due to the circumstance of having been drilled in more permeable beds that were flushed of their highly mineralized waters. Heavy pumping on certain of these wells, however, has caused iniiieralized water to be drawn in froni adjacent mineralized zones, and some of the wells had to be abandoned.
Historical sum mary-The Panilico formation was named by Steplieiison (1912, pp. 286-290), and described as consisting, in North Carolina, of fine sandy barns, sands and clays, and, to a limited extent, gravels. The surface of these deposits forms a nearly level
nini *b 'nyit ann ni##~~ s-in n k~..,-. nan inn1 ~ -. ,.. .~1 .1 .. 1 ..iI. -- nr r -
LATE CENOZOIC GEOLOGY 75
the Pamlico formation into Florida and include in it all marine Pleistocene deposits younger than the Anastasia formation. The Pamlico generally lies at altitudes of less than 25 feet above sea level on the east, south, and west coasts of Florida, and consists chiefly of sand (Plate 3). Where dunes or beach ridges were formed above the Pamlico share line the deposits are higher than 25 feet.
Development-The Pamlico formation in southern Florida grades from almost pure quartz sand to sandy shell deposits, which are locally consolidated. The sand grains range in size from very fine to coarse with medium-sized grains predominating. Most of it is white, though in some places, especially in old spillways from the Lake OkeechobeeEverglades depression, the sand is commonly stained black by an organic material on the surface of the grains.
The Pamlico deposits extend down the east coast to Coral Gables, mantling the Atlantic coastal ridge, and are in places overlapped by Recent muck, marl, or sand beds. Pamlico sand is present on the western fringe of the Everglades almost to the latitude of Fort Lauderdale and mantles a large part of the surface of the western part of southern Florida, including the northern part of the Big Cypress. The formation usually does not extend above the 25-foot contour, which was the approximate location of its shore line. The Pamlico extends from the Gulf coast eastward up the Caloosahatchee River Valley, where it is present except in abandoned cuts or fills of the Caloosahatchee River. It is generally covered by muck, marl and organic material in the swampy area near Lake Okeechobee. Along the coasts it is in places preserved in dune form. The thickness ranges from a feather edge to possibly 50 feet; the greatest thickness being in the old beach ridges now surmounted by quiescent dunes.
Water-bearing characteristics-The Pamlico formation is the source of many small domestic water supplies along the coasts of southern Florida. 'They are usually obtained by driving sand-point wells of small diameter. The quality of the water varies in different localities depending upon whether it has flowed through organic soils or sand. Usually the water is good when derived from the sand distant from swamp deposits.
TALBOT AND PENHOLOWAY FORMATIONS
Historical summary-The Talbot formation was named by Shattuck (1901, pp. 73-75) after Talbot County, Maryland. The formation is now recognized as extending from 'Delaware into Florida.
The name Penholoway was first applied to a terrace by Cooke (1925, pp. 24-26; 1931, pp. 509-510) who later (1932, pp. 5, 8) ex-
76 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
VIEWS OF TALBOT TERRACE AND OF SCARP LINE WHERE
IT ABUTS UPON THE PENHOLOWAY TERRACE
'- .- ;
FictUIE a-Sandy flatlands developed on the Talbot terrace near the inner
boundary with the Penholoway terrace. Looking south from Florida Highway 18, the Okeechobee-Arcadia road, about 4
miles west of the Kissimmee River.
FuUHE 1)-Inner boundary of the Talbot terrace where it adjoins the
Penholoway terrace. The scarp here is plainly visible. Along the scarp line a woody-peat deposit is developed in the old lagoon that once occupied this zone. This old shore line with most of its features is plainly visible from the air, and still looks like many modern sandy shore lines. Looking west along
Florida Highway 18, 3 miles east of Childs.
LATE CENOZOIC GEOLOGY 77
tended the name to the deposits formed when the Pleistocene sea stood 70 feet above the present level. The name is derived from Penholoway Creek in Georgia.
Development-The Talbot, Penholoway, and Wiconico formations comprise a conformable sequence of deposits whose differentiation is based mainly on the location of their respective shore lines, namely, 42, 70, and 100 feet above present sea level (Plates 2 and 3). Presumably the Penholoway everywhere merges downward into deposits of Wicomico age, and the Talbot into Penholoway and Wicomico, successively. The surficial deposits consist mainly of. poorly sorted gray to white quartz sand of various degrees of fineness and angularity. Below the surface, the sands are gray to orange, tan, and brown. In some places iron oxide has stained and cemented the grains to make a hard reddish-brown to black sandstone.
The sequence unconformably overlies the Caloosahatchee marl. It is likewise separated by a stratigraphic break from the Pamulico formation, which fringes around it. Because the terraced surface was very slightly dissected in this region before the invasion of the Pamlico sea upon it, the boundary between the Pamnlico formation and the Talbot formation is very inconspicuous. The scarp at the shore line of the Talbot terrace is very noticeable in many places, and is seen to good advantage where one crosses it on Florida Highway 18, the Childs-Okeechobee road (Plate 20b). The Talbot forniation occupies Immokalee Island (Plate 31.
North of Caloosahatchee River there is a wide lobe of the Talbot and Penholoway formations west of Lake Okeechobee. Another lobe northeast of the lake extends almost to the latitude of Canal Point. The boundary between the Talbot and the Pamlico formations is more conspicuous west of Stuart and Salerno, where it was probably steepened by wave erosion. Streams, such as Fisheating Creek, Taylor Creek, and Kissimmee River cut into these lobes and occupy wide indentations in their borders. Old bars and inner lagoons exert primary control on the direction of flow of surface runoff. and are responsible for the existence of certain of the sloughs or sales now filled with organic soils.
Water-bearing characteristics-Little is known of the water-bearing properties of these formations, inasmuch as the present groundwater investigation has not been concerned with the area in which they occur. The area is sparsely inhabited, and most supplies are obtained by driving wells of small diameter equipped with well points.
78 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
VEHICLES OF TRANSPORTATION USED IN THE EVERGLADES
FIGuRL a-A "glades buggy" used to transport mien and equipment over
the swampy soils covered with marsh plants, especially sawgrass (a sedge, Mariscus jamaicensis). These vehicles have a wide bearing surface of many tires. Designed and built by
the Soil Conservation Service.
FIGURE b-An "air-boat" used in those parts of the Everglades too wet to
support a "glades-buggy" or a tractor with wide-cleated treads.
A pusher-type propeller scoots them over Weedy water at speeds up to about 35 miles per hour. Designed and built by the Soil
LATE CENOZOIC GEOLOGY 79
General statement-Good exposures of rock are scarce in southern Florida except during short periods of extreme low water. Continuous exposures are rare; the land is so flat and the water table so high that only a few feet of rock is exposed anywhere; indeed, most of the exposures are in canal and spoil banks. Correlation of stratigraphic units must therefore depend largely upon studies of data gathered by drilling exploratory test wells. Both surficial outcrop and exploratory test-well data have been fully utilized in these studies, but neither is wholly reliable.
Changes in lithology often take place rapidly both horizontally and vertically. The area has long been one of shallow-water deposition with shifting shore lines and currents. Bays, lagoons, and estuaries with silty, clayey or marly bottoms and mangrove-covered shores alternated with open sandy shore lines. On the very gently sloping surface of the Floridian Plateau slight shiftings of sea level caused the shore to migrate many miles and thus brought about the re-establishment of shore line features many miles away. Under these conditions areas that had lately been under a marine environment became, with a drop in sea level, a part of the fresh-water province in which marls or sands of fresh-water origin were laid down. With even a slight rise in sea level great areas of land and fresh-water marshes once again came under marine influences. Furthermore, the swinging of the shore line back and forth over southern Florida not only brought about a deposition of sediments in any given place peculiar to the conditions prevalent there, but caused a mixing of previously deposited materials with those being deposited.
The changes of shore line have tremendously influenced the faunal distribution. Ecologic conditions resulted in a number of dissimilar faunas living not far apart; the fauna of an open sandy beach was considerably different from that along a marshy mangrove shore; that of a shallow ocean bottom was different from that of a shallow brackish bay bottom; that of a tidal lagoon was different from that of a coral reef. In addition to these original differences in faunas a considerable amount of mixing of faunas has resulted from the several advances and retreats of the sea, and from the action of hurricanes, which whip up huge storm waves that thoroughly scour the shallow sea bottom, and which, by shifting bars and sediments about, as well as the faunas thereof, may actually change ecologic conditions. Too, hurricanes often cause the flatlands to be inundated temporarily by salty water, thus bring about the death of countless fresh-water
FLORIDA GEOLOGICAL SURVEY BULLETIN 27. PLATE 22
*PALM ALE E
3 330 3 8 341 .OCK
20 3 2 343A NO.
318 MOORE HAVE
322 334 NA 14
e 5 0 32.7 C-. FC E MILL E
350 / 00E TONA -Z. CK 0-4OHE
C LOCK No 2
A BELL T. T OMPSON 343 S 365 5 325 -1
CALOOSA RIVE N 20
69 ? BU36 A8
26 390 24
SCALE IN M SEDS ADAPTED FROM
lllr U. S.E. 0. MAP Of
CALOOSAHATCHEE RIVER DRAINAGE AREA 91LDA House Doc El 5; TOTH CONG.
LOCATION OF STATIONS USED IN CORRELATION STUDIES ALONG CALOOSAHATCHEE RIVER
LATE CENOZOIC GEOLOGY 81
mollusks and sweep their shells into the ocean or bay, where they mingle with those of marine animals. Floods caused by heavy rains may likewise sweep fresh-water animals into marine or brackish water and bring about their death.
Fossils in southern Florida are generally so perfectly preserved that it is not unconnon to find them in better condition than many shells picked up on existing beaches. Some Caloosahatchee fossils (Pliocene) still retain their color. At the present time fossils are being washed out of Pleistocene and Pliocene sediments and are being incorporated in modern deposits. Doubtless such mixing of faunas took place in each succeeding deposit, at least since the Eocene. Cole (1941, pp. 12-16) cites evidence of reworking of foraminiferal faunas from mid-Eocene deposits by the Oligocene sea. Another method of mixing is by the intrusion of later shells into solution holes or caverns (see p. 89, fig. 4, and Pl. 19b).
These conditions may be recognized and due allowance made for them in the study of outcrops, but where it is necessary to rely upon well cuttings and their fossils the task is more difficult. Cuttings from many wells contain only long-range fossils; the well cuttings are such a small part of the total formation that chances of getting representative fossil sampling are slight. Micro-faunas offer much better sampling coverage, but owing to the conditions enumerated above they are none too reliable in southern Florida.
SECTIONS ON AND NEAR CALOOSAHATCHEE RIVER
Exposures are almost continuous along the Caloosahatchee River and Canal from Ortona Lock to Caloosa, below which the banks are very low. To study them adequately a boat traverse must be made because of the rapid lithologic transitions. All of the following sections are in the river or canal banks except the first two, which are in rock pits not far from the river.
Station 26-Buckingham pit, a borrow pit on south side of Florida Highway 26 about half a mile west of Orange River near Buckingham. This is the type locality of the Buckiughan marl. Estimated height of the land surface about 9 feet above low tide level in Caloosahatchee River.
2b. Gray quartz sand 'A
2a. Brown quartz sand 1
82 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
lb. Tan-brown limestone, hard, irregular 1
la. Soft white to creamy fossiliferous calcareous clay marl, contains brown grains of phosphate; practically imipermeable. To water level in pit 21 Most of the fossils at Buckingham are preserved as casts or molds. The ones commonly retaining their shells are species of Ostrea, Anonia, and Pecten. Most of the Turritellas are strongly compressed. The species are listed by Mansfield (1939, p. 11).
Station 365-Caloosa pit, an old borrow pit 0.2 mile south of Florida Highway 292 on the river road to Heitman Groves No. 3. This road is 2.3 miles west of the bridge at Alva. Land surface about 7% feet above low tide level in Caloosahatchee River.
2b. Gray quartz sand /
2a. Brown to black carbonaceous sand %
1. Creamy clayey marl with a few chunks of nodular limestone and many phosphatic grains. The same fossils as at Station 26. To water level in pit 5% Station 363A-Alva, Florida, on left bank near southwestern corner of southern bridge abutment.
2. Grayish-white quartz sand 1%
lb. Tan-brown hard limestone
la. Creamy-white soft calcareous clay marl or marly clay, as at Station 26. To low tide level 114
It was near Alva that Dall (1892, p. 146) first noted that "The uppermost strata of the Pliocene begins to appear above the level of the river at low water . .
Station 25-Right bank, across the river from the main grove
buildings at Floweree Grove. This is the place about which Mansfield wrote (1939, p. 15) "The information so far obtained indicates that the Buckingham limestone forms an arch that crosses the Caloosahatchee River, the highest point of the arch being near Floweree Grove." Top of bank about 6% feet above low tide level.
RIDA GEOLOGICAL SURVEY
26 365 363A 25 3
------------- TOP OF LAKE FLIRT MARL *qt
12 ---.. TOP OF PAML/CO FQRMATION (AND RECWT SANOSJ "Qp
TOP OF FORT tHOMPsON FORMATION 0Qf"
TOP OF CALOOSAHATQNEE MARL 0Pcs
z - rOP OF SUCKING AN MARL P b'
2 3 4
0- LOW TIDE LEVEL _-GEOLOGIC SECTION Al
390 358 24 385 384 20 350 345 318 320 322 325 327 14 330
w w 2 0
JB 0 z wn 0
49* ) w x.
<2 w a z w I- U
0 4 W.0 w 4 LL J 40
00 4 02
- ..IN THIS AREA THE LAKE
-A/ -FLIRT MARL IS MIXED WITH
SAND OF THE PAMLICO FORMATION
-O Q ... -Q
SHELLS IN '.- 0
POCKETS :.- /
,,~~ 4 VERNIC c0
-c -. rPV
ETACEAN --. Of
-BONES FRESH WATER PC STRATI p
r: ,AND LAND SHELL$ : iE
: r CETACEAi P2--- -- OSTREA ZONE Pb
BONES .', 'A YE Pb -Pb / C ZONE
LONG THE CALOOSAHATCHEE RIVER FROM BUCKINGHAM TO ORTONA LOCK, FLORIDA, C- C'
BULLETIN 27. Plate 23
320 322 325 32? 14 330 333 348 341 343 343A LEGEND
2 0V) 32 34LGN
a. z3- SAND
om uJ IL -0 -q go LIMESTONE
IN THIS AREA THE LAKE 12 MUCK
FLIRT MARL IS MIXED WITH /
SAND OF THE PAMLICO FORMATION WATER SHELL BED
to.10 I4 SHELL MARL
-Yd SHELLY SAND w. SANDY LIMESTONE
/If: SANDY CLAY MARL
-6I MARLY CLAY
Of at l Ii MUCKY SAND
E -MARLY SAND
E~ ULARIA U SHELLY LIMESTONE
-- ULARIA ZONE r4 I-7
~N Of -SANDY CLAY
Op it- COVERED
PC -BASAL CONGLOMERATE Zf BLACK CARBONACEOUS
~ ~ -?QPSAND
NA LOCK, FLORIDA, c- C'
LATE CENOZOIC GEOLOGY 83
3c. Gray quartz sand I
3b. Black carbonaceous mucky sand 11%'
3a. White marly sand %
Caloosahatchee marl transitional to Buckingham marl:
2. Grayish-green to brown quartz sand, white oti surface due to wash from marly sand above 11'A
1 Creamy-white sandy clayey marl, like that at Station 26. To low tide level 2 Speaking of this sane station, Mansfield (1939, p. 14) says: '"Tie top of the Buckingham limestone is about five feet above water level at Floweree Grove . ." The writers visited this station at extreme low tide during the dIry season and found only 21%2 feet exposed at the crest of the "arch." It appears likely, therefore, that Mansfield included the overlying beds, No. 2 and No. 3a (section above) in his Buckin gham. This "arch" is apparently not constructional but is produced by differential erosion in beds, the lower one of which is clayier than the upper.
Station. 390-Goober Farm (also known locally its the "Turkey
Farm"). Station is at west end of an old cut-off at a point where it joins the dredged section of the Caloosahatchee. Two small drainage ditches from the groves empty into the river at this point. A fairly complete whale skeleton was discovered at the base of this section. Top of bank about 10 feet above low tide level.
41). Gray quartz sand 1%
4a. Cream to brown to white sugary quartz sand with lenses of black carbonaceous to mucky sand 2
Fort Thompson formation:
3. Basal conglomerate containing mixed fresh water and_ marine _shells in pockets to %
Caloosahatchee marl transitional to Buckingham marl:
2. Gray-cream sandy marl as at Station 24.
Weathers out at base to give appearance of being deposited on an uneven= ly eroded surface. This is only superfi. cial, however, for there is very little difference between sediments above and below this line except that there is more clay in the lower part 3% to 4%
1. Creamy-white clayey marl, as at Station 26 and 24. To low tide level 2% to 2%
84 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Station 358-Loft bank of Caloosahatchee River about 1 mile upstream from mouth of Ft. Simmons Branch. Top of bank about 8 feet above low-tide level.
5d. Gray quartz sand /-1/
5c. Black carbonaceous sand %
5b. Gray to tan quartz sand 2
5a. Black carbonaceous sand %
Fort Thompson formation:
4. Gray sand and broken marine shells 0-%
3. Basal conglomerate or remnants of former thin hard limestone bed. Thin layer of Rangia cuneata shells above and mixed in with the rounded lime. stone cobbles
Caloosahatchee marl transitional to Buckingham marl:
2. Grayish-cream sandy clay marl 2%1/3%
1. Gray-tan-cream marly clay that disappears below water level a few feet west. To low tide level 0-1%
Station 24-Left bank of the Caloosahatchee River about 120 yards upstream from the mouth of Banana Creek. Top of batik about 13 feet above low-tide level.
5b. Gray quartz sand 2
5a. Black carbonaceous sand %
Fort Thoimtpson formation:
4. White, gray to orange sand, marly in
3. Basal conglomerate
Caloosahatcheee marl transitional to Buckinghain marl:
2b. Gray-cream sand 4
2a. Gray-cream sandy clayey marl; con.
tains cetacean bones 3%
1. Greenish-gray marly clay, very finely sandy, contains cetacean bones. To low tide level 1%
As at Station 390 there is a differential weathering process which proceeds at uneven rates between beds 1 and 2 due to differing amount of clay in the sediments. A fresh cut right across this false "erosional unconformity" shows no change in lithology, nor are the fossils different; they are the same here as at Buckingham (Station 26) and at other stations to the west. Samples taken 1% feet, 4 feet, and 8 feet above low-tide line at Station 24 contain Foraminifera that have been identified by J. A. Cushman as species that are common to both
LATE CENOZOIC GEOLOGY 85
Pliocene and Miocene but none that are definitely restricted to the Miocene. Foraminiferal faunas from samples taken at 0, 2.5, 4, and 5.5 feet above water level were later examined by W. Storrs Cole. His findings corroborate those of Cushman.
Station 385-Denaud, Florida, right bank near northwest corner of northern bridge pier. Top of bank about 81/2 feet above low-tide level.
5. Black carbonaceous sand 1
Fort Thompson formation:
4. Gray fresh-water calcareous marl 1
3. Marine shells and fine sand, locally mixed with bed 4 1
Caloosahatchee marl transitional to Buckingham iarl:
2. Hard gray nodular sandy limestone and shells; indurated, weathered, and perforated by solution holes. Uppermost portion makes a ledge, and younger material from above fills solution holes in it 4
1. Soft sandy marl, appears to grade upward into Bed 2. To low tide level 1 Station 384-Walker farm, 0.7 miles east of Denaud store by way of old road to LaBelle. Station is on left bank of. Caloosahatchee River about 50 yards east of Walker house. Top of bank about 10% feet
above low-tide level.
6b. Gray quartz sand 14-2
6a. Black carbonaceous sand 1.1%
Fort Thompson formation:
5. Marine shells 0.%
4. Grayish-white sandy marl 2-21
3. Hard, tan, fresh-water limestone ledge; may be equivalent of basal conglomerate at other stations. Some parts entirely separated from others and rounded by solution %
Caloosahatchee marl transitional to Buckingham marl:
2. Shell marl, hardened in places to a calcareous sandstone with nodular structure. Many coral heads. Toward base many fresh-water and land shells. At contact with bed 1 an oyster bed overlies a Barnea zone 5
1. Whitish marly clay. Fossils as at Buckingham outcrops. To low-tide level 1
86 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
It is worthy of note that here, as elsewhere, the beds vary greatly in a short distance, and rise and fall with respect to water level. For instance, ill less than 50 yards to the west bed 1 dips completely out of sight below water level, and all the rest of the beds lose altitude likewise; bed 3 is discontinuous; bed 5, about 15 or 20 yards west, contains a few cobbles of rounded, fresh-water limestone, probably remnants of a former thin overlying bed.
Station 20-LaBelle Chamber of Commerce Picnic Grounds. Two miles southwest of Court House by Florida Highway 25, thence 0.6 mile by Denaud Road to entrance to grounds. Top of bank about
9 feet above low-tide level.
S5. Gray quartz sand /2
5n. Black carbonaceous sand -1/24 /2
Fort Thompson formation:
4. Marine shells (more or less mixed
vith overlying sand in many places) 12.1 3. Hard Ian-to-gray limestone ledge 1/2-1
2. Hard nodular sandy, shelly limestone; probably a consolidated shell marl altered by solution and redeposition 2
1. Creamy-tan shell marl, weathers out very rough on exposed surfaces. An excellent area for collecting Caloosahatchee fossils. To low-tide level 4
This station is located in an area where wide variations ill lithologv are conmont. In some places nearby the entire Pliocene section consists of sort unconsolidated shell marl; in other places the top layer of ledge rock is entirely missing, or is represented merely by scattered cobbles. The Caloosabatehee contains many coral heads at this station and nearby.
Station 350-Right bank of Caloosahatebee River at a point a few yards west of the mouth of Bee Branch, about 1% miles west of
Lalelle. Top of bank about 81/4 feet above low-tide level.
7. Gray quartz sand and marine shells 21/2 6. Black plastic muck 11
LATE CENOZOIC GEOLOGY 87
Fort Thompson formation:
5. Gray calcareous fresh-water marl ill places stained black from overlying muck 3/
4. Black carbonaccous sand %
3. Marine shell hed mainly preserved in
solution holes ill underlying rock 0.1
2. Fresh-water limestone layer riddled by solution holes generally filled with marine shells i
1. Grayish-cream shell marl with oyster zone at top and bottom. A good fossil collecting station. To low-tide level 2%
Station 345--Right bank of' the Caloosahatchie' River about % mile west of the bridge at LaBelle. Top of bank about 12% feet above lowtide level.
3d. Gray quartz sti l 111( 3c. Black carbonaceous sand /
31l. Tat sand grading down into grayishwhite sand 21/2
3a. Black carbonaceous sand %
Fort Thom)son formation:
2. Marine shells, somewhat mixed at base with sand from bed below 1
1. Grayish-green or light greenish-gray sand containing considerable calcare. ous material and a fine assemblage of Caloosahiatchee fossils. A Vermicularia zone is prominent here 2%
Covered by talus. To low-tide level 2
Station 318-Right bank of Caloosahatehee River about 75 yards east of the bridge at LaBelle. T11 of hatk about 13% feet above
5c. Gray quartz sand 5b. Black carbonaceous sand, unevenly distributed laterally '
5a. Gray quartz sand mingled with black carbonaceous material 2.3
4. Black carbonaceous sand that follows the old erosion surface on top of the underlying Fort Thompson
88 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Fort Thompson formation:
3. Broken marine shells underlying and in places mixed in with carbonaceous sand above 0.1
2. Greenish-gray clayey sand or marl. Very
few fossils 61/2
1. Stratified greenish sandy clay; no fossils. To low-tide level 2%
Station 320-Right batik of the Caloosahatehec River 0.7 mile east of bridge at LaBelle. Top of batik about 9 feet above low tide level.
5c. Gray quartz sand %-%
5b. Black carbonaceous sand 0-%
5a. Gray quartz sand 2.2%
Fort Thompson formation:
4. Fresh-water shell bed 0.%
3. Marine shell bed. In places the freshwater shells from bed 4 are mixed in with the marine shells 0-1A
2. Gray-cream calcareous shelly marl, with a few lenses of claycy marl; a hard, irregular, calcareous sandstone layer near the base 2-2%
1. Greenish-gray marly clay; no fossils
noted to low-tide level 3%1 .
Station 322-Right batik of the Caloosahatchee River about 11/ miles east of the bridge at LaBelle. At this point the first hard limestone ledges of the Fort Thompson fortmation appear. Top of bank about 9 feet above low-tide level.
Lake Flirt marl and Pamlico formation:
7. Black carbonaceous sand
6. Gray quartz sand with admixed fresh.
water shells. Apparently this resulted from a mixture of materials by waves of a fresh-water lake working ott a floor of Pamlico sand 1%
Fort Thompson formation:
5. Marine shell bed 2
4b. Fresh-water hard limestone ledge % 4a. Fresh-water soft calcareous marl % 3. Marine shell bed %
LATE CENOZOIC GEOLOGY 89
2. Consolidated shell marl of linearly aligned concretionary structure containing an excellent fauna of Caloosa. hatchee fossils %
1. Creamy-gray shell marl, to low-tide
Station. 325-Type locality of the Fort Thompson formation. Left bank of the Caloosahatchee River near site of the old fort, 1% miles
T 7. 1 W.-'ATER LINE
-,-.--- C, LOW TIDE
r -T -r -5 i-- -- -EXPLANATION
SPOIL, DREDGED OUT IN DEEPENING f T MARINE SHELL BED WITH MIXTURE
9 AND STRAIGHTENING CALOOSAHAT- '"',, O ESWARSHELLS AT
CHEELZZZER..a j BASE. YARMOUTH INTERGLACIAL STAGE.
BLACK CARBONACEOUS SAND,
--8 OF THE I,AKE FLIRT MARL. f7r j FRE SH WATER GRAY CALCAREOUS
3MARL, LOCALLY NA RDENED IN UP-vPER POR TION TO A HARD GRAY
-- GRAY CALCAREOUS QUARTZ SAND LIMESTONE. IIELISOMA AND AMERTm ~lWITH A FEW FRESH WATER SHELLS, IA SPS. KANSAN GLAClAL STAGE.
Lir.tJ HELISOMA AND AMERlA SPS., WASHED
IN PROM NEARBY LAND AREAS. Fc7TT 7W MARINE SHELLS, FOUND ONLY LOPAML1CO. kcC 2dI CALLY IN SOLUTION HOLES OR DEC9 PRESSIONS IN BED NO. I, OR LYfCZ. MARINE SHELL BED, THE COFFEE HNG ON OR MIXED IN WITH A THIN
6 .t MILL HAMMOCK MARL. SANGAMON BASAL CONGLoMERATE, AFTONlAN
L %z.lNTERGLACIAL STAGE. INTERGLACIAL STAGE.
5b FRESH WATER GRAY MARL (5,i ) j. L x MARINE SHELL MARL. CALOOSA5 CONSOLIDATED IN UPPER PORTION f ijTej HATC HEE MARL. PLIOCENE.
-- TO MAKE A HARD FRESH WATER Ii.'"I
LIME STONE ( S b 1. HELISOMA AND
AMERIA SPS. ILLINOIAN GLACIAL
STAGE. NOTE: CORRELATIONS TENTATIVE.
GEOLOGIC CROSS SECTION at Sto.325- Type IloaIty of the Fort Thompson formotlon
FIGURE 4-Idealized geologic section at Station 325, old Fort Thompson,
Florida, showing relations of formation and various members.
(See also PLATE 19 for photographs of this station.)
90 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
east of the court house at LaBelle. Section is about 30 yards east of the big gap through the high spoil bank. Top of bank is about 81/4 feet above low-tide level. See Fig. 4.
Lake Flirt marl:
8. Black carbonaceous sand 1A-1
7. Gray quartz sand with fresh-water and
land shells mixed in 1A-1
Fort Thompson formation:
6. (Coffee Mill Hammock marl meimber): Marine shell bed usually pre. served only in solution holes or caves in lower beds but in places is a few inches thick over the top of the underlying rock 0-3
5b. Hard fresh-water limestone riddled with solution holes usually filled with overlying marine shells 2-3
5a. Soft fresh-water calcareous marl cut through by solution holes and usually filled with overlying marine shells 1.2 4. Marine shell bed 0-1
3. Fresh-water shell marl locally hardened in top 6 inches to a hard limestone 1/2-2
2. Marine shells, present only in low and protected areas in the underlying bed. Probably remnants of a once much thicker bed. Associated with the shells is a thin basal conglomerate 0Caloosahatchee marl:
1. Creamy-gray shell marl with an oyster
zone at top. To low-tide level 0-1
This section is further dismissed on page 73.
Station 327-Right bank of the Caloosahatchee River. This station is at the western end of the Lake Flirt basin; it is about % mile east of Fort Thompson. Top of bank is about 10 feet above low-tide level.
Lake Flirt marl and Pamlico formation:
7. Black carbonaceous sand 1
6. Gray quartz sand with admixed freshwater shells %
Fort Thompson formation:
5. (Coffee Mill Hammock marl member): Marine shell bed that fills solution holes in underlying limestone and has a thickness of about 3.31/2 feet above it 3.5
LATE CENOZOIC GEOLOGY 91
4. Fresh-water hard limestone ledge with many solution holes usually filled with overlying shells. Partially ad. mixed at base with underlying marine shell bed 1%.2
3. Marine shell bed 0.1
2. Fresh-water marl 1%.3
1. Creamy-gray soft shell marl. To low.
Station 14-On left bank of the Caloosahatehee River at a point reached by driving 3.0 miles east of court house at LaBelle on Florida Highway 25, then through fields to the river at right angles to road. Top of bank about 6% feet above low-tide level.
Lake Flirt marl and Pamlico formation:
5. Gray non-carbonaceous to black carbonaceous sand 0-/4
4. Creamy-gray fresh-water calcareous
3. Black carbonaceous sand 1.1%
Fort Thompson formation:
2. (Coffee Mill Hammock marl mem.
ber): Marine shell bed .I
1. Grayish fresh-water marl consolidated in place to a hard limestone. To lowtide level 1.2
300 yards upstream bed 1 disappears below water level by dipping east and bed 2 is partially hidden.
Station 330-About 25 yards east of Station 14 and on opposite (right) bank. Top of bank about 51 feet above low-tide level.
Lake Flirt marl and Panilico formation:
6. Black carbonaceous sand 0.%
5. Gray quartz sand with admixed freshwater shells 1'A-2
4. Black carbonaceous sand 1
3. Fresh-water marl or calcareous mud 0.%
Fort Thompson formation:
2. (Coffee Mill Hammock marl member): Marine shell bed 1-2
1. Fresh-water marl. To low-tide level %
Station 332-Right bank of Caloosahatchee River about 1 mile
east of old Lock No. 3. Top of bank about 7% feet above low-tide
92 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Lake Flirt marl:
7. Black, compact, sticky muck '
6. Fresh-water, gray, calcareous marl 11'A 5. Black sandy muck 'A
4. Fresh-water gray calcareous marl 1
3. Black carbonaceous sand with considerable humus 'A-1'A
2. Fresh-water gray calcareous marl 1-2
Panlico formation (?):
1. Black carbonaceous sand. To low-tide
Station 334-Right bank of Caloosahatchee River about 11/2 miles east of old Lock No. 3. This point lies at the east end of a big bend in the Caloosahatchee River. Between it and Station 332 the sequence of alternating mucky, carbonaceous, and marly beds is fairly constant, but the beds thicken and thin irregularly, and in places the section is almost entirely narl. Top of bank about 8 feet above low-tide level.
Lake Flirt marl:
8. Black compact sticky muck A
7. Grayish quartz sand %
6. Black compact sticky muck -/
5. Fresh-water gray calcareous marl %
4. Black muck %.%
3. Fresh-water gray calcareous marl 1
2b. Brown to black carbonaceous sand 1%
2a. Brown to gray quaitz sand 2
Fort Thompson formation:
1. Gray sand with a nodular, calcareous sandstone layer about three inches thick at top. To low-tide level 1%
Station 338-Right bank of Caloosahatchee River at a point about 3 1/3 miles east of old Lock No. 3. Top of bank about 61/2 feet above low-tide level.
Lake Flirt marl:
3. Gray fresh-water marl 4.4%
2. Black muck and carbonaceous sand 3-I 1. Gray to brown quartz sand 1-1%
Upstream, 200-300 yards, the section is the same except that the upper foot is occupied by a black compact muck layer.
LATE CENOZOIC GEOLOGY 93
Station 341-Right bank of Caloosahatchee River about 25 yards west of Atlantic Coast Line railroad bridge. Top of bank about 11 feet above low-tide level.
Be. Black carbonaceous sand 0.1
8d. White sugary quartz sand 1/8c. Black carbonaceous sand %-%
8b. Light-brown quartz sand 12-1
8a. Dark-brown quartz sand %-1
Fort Thompson formation:
7. (Coffee Mill Hammock marl menher): Marine shell bed 2-21/2
6. Fresh-water gray calcareous marl 14-1
S. Marine shell marl, fills solution holes that cut through all the lower beds. Panope zone at base 2.6
4. Gray sandy limestone containing mixture of fresh-water, brackish, and marine fossils 1.11
3. Marine shell marl 01
2. Hard marine sandy shelly limestone 1%-2
1. Creamy calcareous shell marl. To
low-tide level 1.2
Station 343-Left bank of Caloosahatchee River in and adjacent to the cut at the end of the road from Florida Highway 25 at Goodno store. Top of bank very irregular due to spoil heap but averages about 11% feet above low-tide line. The spoil covers top portion of section so that it can not be determined here.
Covered by dredgings (spoil) composed of mixed sand, shells, and lime. stone, Pliocene and Pleistocene 4.5%
Fort Thompson formation:
7. (Coffee Mill Hammock marl member): Marine shells generally partially or completely hidden by spoil I (?)
6. Hard gray marine limestone ledge 1-1%
5. Creamy-gray shell marl, a mixture of
both marine and fresh-water shells 34.1 14 4. Hard gray sandy limestone %-11
3. Verrnicularia bed %.1
2. Hard gray sandy limestone %'114
1. Creamy-gray shell marl. To low-tide level 11/4-2
94 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
Station 343A-East end of U.S.E.D. Reservation above Ortona Lock.
Black carbonaceous sand. To water level %-1 CORRELATION OF THE FORT THOMPSON FORMATION
Figure 4, which is drawn to scale with ito vertical exaggeration, is a graphic section of the left bank of Caloosahatchee River at the site of Fort Thompson, 1% miles east of LaBelle. This section at the type locality of the Fort Thompson formation (Station 325, p. 89), is especially instructive because it gives indisputable evidence of the repeated oscillation of sea level during the Pleistocene epoch. Four separate Pleistocene marine invasions of this region are attested by beds 2, 4, 6, and 7; and five withdrawals of the sea are shown by erosion surfaces and fresh-water deposits below, between, and above them. These alternations agree in number with and presumably correspond to the oscillations of sea level recorded by the marine terraces along the Atlantic coast.
Tlie first withdrawal of the sea is indicated by the erosional unconformity that separates the marine Caloosahatchee marl (bed 1) from the overlying Pleistocene deposits. This unconformity probably represents late Pliocene time and the Nebraskan glacial stage.
The earliest Pleistocene marine invasion deposited a bed of marine shells (bed 2) that is now represented only by patches filling hollows in the surface of the Caloosahatchee marl and often mixed with the overlying fresh-water shells of bed 3. This bed presumably was deposited during Brandywine time (Aftonian interglacial stage?).
Bed 2 was eroded and then covered by fresh-water marl (bed 3) containing numerous fresh-water shells. Still later the bed became perforated by solution holes and the water drained off. Bed 3 indicates an epoch of low sea level that may correspond to the Kansan glacial stage.
The second Pleistocene invasion by the sea filled the solution holes in bed 3 with marine shells (bed 4) and also spread them over the top of bed 3, which has been locally hardened into limestone. The lower part of this marine shell bed includes some fresh-water shells, which doubtless were reworked from the bed below it. Bed 4 probably accumulated during Coharie and Sunderland time (Yarmouth interglacial stage).
Bed 4 is covered by fresh-water marl (bed 5) the upper part of which is consolidated into hard limestone. This fresh-water deposit
LATE CENOZOIC GEOLOGY 95
is perforated by solution chimneys, some of which extend only through the hard upper limestone, others extend to tile porous shell bed (4) below it, and still others reach all the way down to the Caloosahatchee marl. This indicates that when the Yarmouth sea withdrew the region became at first occupied by a fresh-water lake or marsh, which later drained away, then the area was subjected to the solvent activity of downward percolating ground water. This may have happened duxring the Illinoian glacial stage.
The solution holes in the fresh-water marl and limestone (bed 5a and 5b) are filled with an accumulation of Chione cancellata an1d other marine shells (Coffee Mill Hammock marl member of tile Fort Thompson formation, bed 6), which also overlies bed 5 in disconnected patches. This third marine invasion probably corresplonds to Wicomico, Penholoway, and Talbot time (Sangamon interglacial stage).
Evidence for a fourth withdrawal of the sea (early Wisconsin glacial substage) is found in the uneven surfaces of beds 5 and 6, from which part of the Coffee Mill Hammock marl has been stripped off, leaving it in disconnected patches.
Return of the sea in post-Iowan (Pamlico) time brought with it chiefly barren sand (bed 7) and a few fresh-water shells washed in from the land, which was only a mile or two away on the north and 3 or 4 miles on the south. The scarcity of marine shells during this epoch may indicate that the water was too cold for the warmwater mollusks that had inhabited the region during the earlier interglacial epochs, or that the currents and food supply may have been unfavorable. This was the only Pleistocene epoch during which sand accumulated in notable quantities at this locality, which, during Pamlico time, lay in a strait between Immokalee Island and the mainland. The depth of the water in this strait was only 15 to 20 feet, and sea level stood about 25 feet higher than now.
Sand of the Pamlico formation is overlain by a layer of black carbonaceous sand, which probably is a swamp deposit of late Wisconsin or Recent age and corresponds to the Lake Flirt marl and the peat and muck of the Everglades.
The typical Fort Thompson formation, as here interpreted, coinprises all of the Pleistocene deposits older than the Pamlico forination. These include marine and brackish-water shell beds that may represent the Aftonian, the Yarmouth, and the Sangamon interglacial stages and marls and limestones deposited in fresh-water lakes and marshes during the intervening glacial stages. Most of these beds are of very local occurrence because they were subjected to solution and
96 FLORIDA GEOLOGICAL SURVEY-BULLETIN 27
erosion whenever the water table was low enough to permit the active circulation of ground water-or whenever the overflow from the interior through ancestral Caloosahatchee River became of great enough volume.
CORRELATION OF FORMATIONS BY MEANS OF
EXPLORATORY TEST WELL DATA
General statement-In the course of this investigation more than 60 exploratory test wells have been sunk for the purpose of obtaining data on the occurrence of water, which, of course, is dependent upon the geology; therefore considerable effort was made to collect and identify fossils and to gather complete data on lithology.
These test wells are scattered over southeastern Florida. Reference to other papers (Parker, 1942; Parker and Hoy, 1943; Parker and others, 1941) will give data on many of these. The present paper is concerned with two lines of wells, a northwest-southeast line A-A' and an cast-west line B-B' (Plate 24 shows these lines and gives the location of the wells).
The formations involved have already been discussed in their respective sections. Following is a description of the well logs:
SECTION A-A' (front northwest to southeast) WELL GS-3 (4" DIAM.)
Site is near the south corner of the water tower at the U. S. Sugar Corporation, South Shore Camp, Bean City, Florida, sec. 8, T. 44 S., R. 36 E., Palm Beach County. Land surface about 15 feet above mean sea level.
feet to M.S.L.
Recent organic soils:
Black muck (may include a thin layer of Lake Flirt
marl at base but cuttings did not definitely
prove this) ................................. 7.4 +7.6
Fort Thompson formation:
Hard limestone layer ............................. 0.8 +6.8
Shell marl ........................................ 2.1 +4.7
Hard limestone layer .............................. 0.9 +3.8
Shell marl, sand, and shell beds .................... 12.3 -8.5
Dark-gray shell marl and sand with a few strata of
hard rock in layers an inch or two thick ...... 11.8 -20.3
Hard sandy limestone layer ........................ 1.4 -21.7
Very fine shelly sand to bottom of hole ............ 14.0 -35.7