STATE OF FLORIDA
STATE BOARD OF CONSERVATION
GEORGE VATHIS, Supervisor
FLORIDA GEOLOGICAL SURVEY
HERMAN GUNTER, Director
GEOLOGICAL BULLETIN NO. 33
GEOLOGY OF CITRUS AND LEVY
ROBERT 0. VERNON
Associate State Geologist
FLORIDA GEOLOGICAL SURVEY
THE FLORIDA GEOLOGICAL SURVEY
Frontispiece: Fault breccia exposed along the northeast edge of Crystal River Rock
on1 . -
LETTER OF TRANSMITTAL
HONORABLE GEORGE VATHIS, Supervisor of Conservation.
I am transmitting a report entitled "THE GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA", prepared by Dr. Robert 0. Vernon, Associate State Geologist, with the recommendation that it be published as Florida Geological Survey Bulletin 83. The study is very comprehensive and contributes considerable new data to the knowledge of the geology of the two counties and the geologic history of the State.
It is believed that the report will assist materially in the development of the mineral resources of the counties and the State and some of the data will help in the search for oil and gas.
The Geological Survey sincerely appreciates your cooperation and continued interest in its work.
HERMAN GUNTER, Director Geological Survey
Tallahassee, Florida June 15, 1951
The writer has attempted to present the high points of the geologic history of Citrus and Levy counties and adjacent areas so that they can be understood readily by both the citizens of the State and by the geologist. All of the geologic information available on these two counties, the large part of which has been collected by the writer and others in the field, has been assembled and detailed descriptions of the physiography, economic resources, and geology are printed in a form intended for the convenience of those interested for scientific study or economic development.
Special attention is invited to the structural map drawn on top of the Inglis member of the Moodys Branch formation, to the map of the fracture patterns and to the geologic sections. These may provide some additional data for interpreting geologic history having a bearing on oil and gas explorations. Certainly the preparation of a map based on a specific top will be more significant than the map of the eroded surface of the Ocala limestone, formerly used as a reference datum for studying Tertiary structure in Florida.
The chapters on the detailed geologic history provide information about the formations penetrated by deep oil test wells and about younger beds of Eocene to Recent age that crop out at the surface. This information can be used to compare these beds with beds of similar ages in other states, and makes it possible to subdivide some of them in Florida. Information on beds that are exposed at the surface in Levy and Citrus counties, is presented as an areal map on Plate 1.
The final chapter gives descriptions of the dolomites, limestones, limonite ore, sand, clay and phosphate with recommendations for further exploration and exploitation. Some attempt is made to estimate the probable tonnage of material available in these counties and to evaluate the economic possibilities of development.
Messers W. A. Jenkins, Walton Jones, Clarence Simpson, Robert Neill, Robert Hart, Lester Chastant, Alfred Fischer and Ralph Heath, all members or former members of the State and U. S. Geological Surveys at Tallahassee, have assisted in the field work. Geologists and paleontologists of the oil profession located in Tallahassee have been most helpful in discussions of problems. In particular, the members of the Exploration Department of the Humble Oil and Refining Company have contributed freely and unselfishly their time and experience in the study. Members of the Southeastern Geological Society have been interested in the study and contributed much information in informal discussions, particularly during the Fifth Field Trip of the Society in these counties on December 5-6, 1947. Mr. H. H. Cooper, Jr., District Engineer of the Water Resources Branch of the U. S. Geological Survey, Tallahassee, Florida, has been most helpful in the development of some of the discussion pertaining to hydrology, dolomitization and structure.
Considerable incidental assistance has been given by many others, and the writer is particularly grateful to these workers: Dr. H. B. Stenzel, Geologist, Bureau of Economic Geology, Austin, Texas, identified some of the mollusks and prepared a preliminary check list of these. Dr. Horace G. Richards, Assistant Curator, The Academy of Natural Sciences, Philadelphia, Pennsylvania, also has identified and is preparing a paper on the molluskan fauna of the area. Dr. A. G. Fischer, while with the Survey, prepared a paper on the echinoids of the Eocene beds and on the destructive analysis of carbonates of the area. The first paper is published in Florida Geological Bulletin 34, and the second is to be published as a Report of Investigation. Dr. H. V. Howe, Director, School of Geology, Louisiana State University, Baton Rouge, Louisiana, studied the fauna of an Avon Park limestone locality and prepared a paper on the ostracodes, published as a part of Bulletin 34. Dr. K. P. Oakley, British Museum, London, England, has kindly studied certain concretions. As members of the Florida Survey, Mr. Charles Hendry contributed many hours in preparing maps and illustrations from rough sketches, Mr. Carlton Gray and Mr. William Henry assisted by picking foraminifers and ostracodes for identification and Mr. Hal Chittum, Jr., ran precise levels on many outcrops and all of the wells in the area. Drs. James L. Calver and Herman Gunter and other members of the Survey have offered many suggestions for factual presentation and clear
statement in editing. Mrs. Mary Blount prepared the manuscript from difficult copy and also helped in editing.
Paul and Esther Applin of the U. S. Geological Survey, Tallahassee, Florida, edited portions of the paper, particularly that of the Mesozoic and older rocks. Dr. John Charles Rabbitt of the U. S. Geological Survey analyzed four samples of phosphate used in correlation of the Miocene and Dr. Earl Ingerson of the U. S. Geological Survey, Washington, D. C., identified some clay minerals. Dr. A. F. Greaves-Walker, R. S. Hagerman and other members of the clay laboratory of the Florida Engineering and Industrial Experiment Station, Gainesville, Florida, fired several samples of clay and evaluated the possibility of developing these. Mr. Donald W. Gravell, Cabon Gref Oil Company, Havana, Cuba; Mrs. Marie de Cizancourt, Paleontologist, Paris, France, and Dr. Louise Jordan, Independent Paleontologist, Tallahassee, Florida, have all identified some of the foraminifers of the Eocene.
The study could not have been completed without the help and courteous attention of the citizens of these counties. In particular, I wish to express my thanks to R. W. Saults, Sr., R. W. Saults, Jr., L. K. Runnels and Ben Robinson who directed me to many localities and helped in completion of the work over difficult terrain.
TABLE OF CONTENTS
Letter of transmittal ---------------------------------------------------------------- -- IlI
Preface ------------------------------------------------------------------------------------------------- IV
Acknowledgements -------------------------------------------------------------------------------- V
Geology of Citrus and Levy counties, Florida ----------- --------------------------------- 1
Introduction --------------------------------------------------------------------------------------------- 1
S c o p e o f stu d y ........... ............. . .. ................. ... .. .............--- - - 1
Location of area ---------------------------------------------------------------- 1
M a p s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .- 2
T o w n s . . . . . . . . . . . . . . .. . . . . .... ..-- -. . . .. . . .- 4
T r a n s p o r ta tio n ........ ........... .. ............... . .............. . .- 6
C lim ate an d v e g etation .............. ..................... .. ..... 9
C u ltu re an d lan d u tilization .......... ............... .. ..................... 11
C o u n ty n a m e s .. ......... ......... ....... ......... 1 1
P o p u l a t i o n .. - --.. .. .. .... .. .. .. .... .. .. .. ..... . . ..... .......- 1 1
Land utilization ....... .......------------------------ 12
Physiography ---------------------------------------------------------------- 14
Introduction 14 G en eral lan d form s of F lorid a ........... ............ . ............... 14
Geologic controls 16 Physiography of Citrus and Levy counties ............. ..................... 17
I n t r o d u c t i o n ...... ......... ............. ........... ............ .. ..- 1 7
Tertiary Highlands --------------------------------------------- 18
Delta Plain Highlands ----------------------------------------------------------- 18
(Terraced Coastal Lowlands --------------------------------- 19
Modern submarine plain ------------------------------------- 20
Coastal terraces ---------------------------------------------------------------- 21
Pamlico terrace ------------------------------------------ 22
Wicomico terrace ---------------------------------------- 25
Chiefland Limestone Plain ----------------------------- 25
Coharie-Okefenokee Sand Ridge 25 River Valley Lowlands ----------------------------------------- 27
Stream valleys ---------------------------------------------- 27
Stream terrace sediments --------- ------------------------------------- 28
Suwannee River Valley Lowland 29 Withlacoochee River Valley Lowland -------------------------- 29
Tsala Apopka Lake----------------------------------- s0
Waccasassa River Valley Lowland --------------------------- 1
Williston Limestone Plain -------------------- -----------32
Stream capture------------------------------------------- 33
Pleistocene history in Florida ------------------------------------36
Terraced Coastal Lowlands -----------------------------------36
Stream valleys in western Florida 41 Stream valleys in Citrus and Levy counties ------------------ 41
Introduction --------------------------------------------------------------------- 42
Sinks ------------------------------------------------------ 44
Lakes ------------------------------------------------------ 44
Long Pond -------------- -------------------------------- 46
Fracturing ----------------------------------------------------- 47
Structure and sections ------------------------------------------------53
Ocala uplift---------------------------------------------------- 54
The Kissimmee faulted flexure ----------------------------------- 56
The Sanford high --------------------------------------------------------------------- 57
The Osceola low ----------------------------------------------- 57
Structures within Citrus and Levy counties -------------------------------------------- 58
Domes ------------------------------------------------------------------------------- 58
Homosassa Springs dome ------------------------------------59
The West Levy dome ---------------------------------------60
Bronson graben --------------------------------------------- 60
Inverness fault ---------------------------------------------- 60
Long Pond fault -------------------------------------------- 61
Dates of structural movements ------------------------------------- 61
Stratigraphy --------------------------------------------------------------------------------- 63
Previous work ----------------------------------------------------63
Florida general stratigraphy and structure --------------------------- 64
General stratigraphy of Citrus and Levy counties --------------------- 66
Paleozoic era ----------------------------------------------------- 68
Preliminary notes on the Paleozoic strata beneath Citrus and Levy
counties, Florida, by Jean Berdan and Josiah Bridge ---------------- 68
Mesozoic era -----------------------------------------------------71
Triassic system --------------------------------------------------------------------- 71
Cretaceous system -------------------------------------------------------------------- 74
Introduction ----------------------------------------------------------------------- 74
Lower Cretaceous (?) (Comanche series) --------------------- 76
Upper Cretaceous (Gulf series) ------------------------------ 77
Atkinson formation ------------------------------------------------------ 78
"A zone" .-----------------...-------------------------------------------- 79
"B zone" .-----------------...-------------------------------------------- 79
Beds of Austin age -------------------------------------- 80
Beds of Taylor age -------------------------------------- 81
Lawson limestone (Navarro equivalent) -- 82
Cenozoic era -------------------------------------------------------------------- 84
Tertiary system --------------------------------------------------------- -------------- 84
Paleocene series ---------------------------------------------84
Cedar Keys formation --------------------------------- 84
Eocene series ----------------------------------------------- 86
Oldsmar limestone ------------------------------------ 86
Claiborne group -------------------------------------------------------- 88
General nomenclature ----------------------------------88
Regional correlation ------------------------------------------- 89
Lake City limestone ----------------------------------------- 90
Avon Park limestone --------------------------------------- 95
Jackson group ------------------------------------------------------------------111
History -------------------------------------------------------------------- 111
Jackson-Claiborne contact -------------------------------------- 113
Moodys Branch formation ----------------------------- 115
Introduction and definition ---------------------------- 115
Inglis member ----------------------------------------------------- 115
Williston member ------------------------------------------------------ 141
Ocala limestone (restricted) ---.......---------------------------- 156
Oligocene series ----------------------------------------------------------------- 172
Introduction ----------------------------------------------------------------- 172
Suwannee limestone ----------------------------------- 173
Miocene series -------------------------------------------------------------- 178
Introduction ---------------------------------------------------------------------- 178
Miocene problem ------------------------------------- 181
Pre-Miocene surface ------------------------------------------ 183
Geologic history of the Miocene ------------------------ 183
Hawthorn formation ------------------------------------------------------- 186
Alachua formation ------------------------------------ 189
Origin of phosphate ---------------------------------------------------- 195
Mineralogy of the phosphate deposits -----------------200
Quaternary system ------------------------------------------------- -------------------------- 208
Pleistocene series ------------------------- -------------------------------------------- 208
Introduction ------------------------- -8----------------------------------208
Pre-Pleistocene surface ------------------------ --------------- 209
S t r a t i g r a p h y .. ......... ....... ............ .............. 2 1 0
R e c e n t s e r ie s .......... ...... -- -- -- -- ---- -- -- -.......... ......... 2 1 5
F r e sh -w a te r m a rls 2.......... .. ........ ........... ........ .. 2 1 6
P e a t a n d m u c k 2.. . . . . . . . . . . . . . . .. . .. . .... . 2 1 6
Economic Geology ------------------------------------------------------------- 217
Introduction ........ .......... .......... ........ ..............................-217
L i m e s t o n e ... . . . . . . . . . . . . . . . . . . . . .. . . .- 2 1 7
D o l o m i t e r o c k . . . . . . .... . . . . . . . . . . . . . . . . . .. .. . . .- 2 2 1
P h o s p h a t e r o c k ... ..... ..... .. ... .. ... .... .......... .. ... -- 2 2 4
I n t r o d u c t i o n . . . . . . . . . . . .. . . . . . . . . . . ... . . . ..- 2 2 4
H ard -ro ck p h o sp h ate .... .......... .............. ........ ....... 2 2 4
C o llo id a l p h o sp h a te -c la y .. ......... .. .. ...... ............. ......... 2 2 8
C l a y d e p o s it s .. .... ...... .. ....... ....... ... ...... ... ..... .. ..... ....... .. 2 3 0
C e m e n t . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. . .- 2 3 3
Chert ........ .......... ......................... .... .......... ....-234
Sand ............ .......... .......... ............... ....... .......-234
L i m o n i t e . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .- 2 3 5
Possibilities of oil and gas production ......... .......... ....... .- 237
P ossib le oil b earin g h orizon s ............ ......... .......... ............ 23 7
F avorable structural features ... ......... .......... .......... 238
P r e v i o u s o i l t e s t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- 2 4 0
Surface water .....................-------------------------------------- 240
Ground water ------------- 90-------------------------------------------------240
D a te o f a r te s ia n sy ste m .. . ........... ........... ......... .......... 2 4 3
M in e r a l p r o d u c tio n .... ............. ........ ...... ......... ........ 2 4 4
Bibliography --------------------------------------------------------------------------- 247
Index ..... .....................-----....................................................................-253
Frontispiece-Fault breccia at Crystal River Rock Company quarry ------------I
Plate I Geologic map of Citrus and Levy counties,
2 Structure map of the northern peninsular
Table 1 Climatological data ------------------------------------------------------------------ 10
2 Land utilization ------------------------------------------------------------------------ 12
3 Forest pioduction -------------------------- 12-------------------------------------------- 12
4 Agricultural products ---------------------------------------------------------- 13
5 Correlations of Pleistocene terraces ------------- ----------------- 40
6 Geologic formations in Citrus and Levy counties, Florida --------- 67 7 Paleozoic rocks in Citrus and Levy counties -------------------- 72
8 Wells that penetrate the Lake City limestone -------------------94
9 Comparison of Alabama and Florida sections of upper and late
m id d le E o c e n e d e p o sits ........ ............. ..... ............. ................. 1 12
10 Checklist of foraminifers of the
Moodys Branch formation ------------------------- Between 140 and 141
11 Wells that penetrate the Avon Park limestone
and younger beds ------------------------------------------------------ 153 to 155
12 Well data at the type locality of the Ocala limestone ------------156
13 Ocala limestone exposure in the vicinity of Williston ------------163
14 Miocene rocks in peninsular Florida ---------------------------------- 183
15 Complete analyses of phosphate-rock samples ------------202 to 203
16 Age and elevation of the Pleistocene formations in Citrus and
Levy counties ------------------------------------------------------------------------- 209
17 Tests of clays ------------------------------------------------------------------------------- 232
18 Oil and gas tests in Citrus and Levy counties ------------------239
19 Mineral producers in Citrus and Levy counties, 1944-49 --------- 244 20 Mineral production in Citrus and Levy counties, Florida, 1944-49 -_ 246 Figure 1 Location map ------------------------------------------------------------------------------3
2 Physiographic map ----------------------------Between 18 and 19
3 Terraced Coastal Lowlands as seen from the Tertiary Highlands ---- 19 4 Drowning of coastal margins ------------------------------------- 21
5 Mosaic of aerial photographs illustrating physiography and the
trace of the Long Pond fault ---------------------------------------------- 22
6 Limestone of Inglis member, Moodys Branch formation paving
the coastal hammocks ------------------------------- ------------------------- 24
7 The Chiefland Limestone Plain --------------------------------------- 26
8 Broad ancestral valley of the Waccasassa River -----------------32
9 Aerial photograph of the ancestral valley of the Waccasassa River 34 10 Solution pipe in the Ocala limestone -.---------------------------- 45
11 Fracture pattern of the northern part of the
Florida Peninsula ----------------------------------- ---- Between 48 and 49
12 Differential weathering of the limestone of the Moodys Branch
formation ---------------------------------------------------------------------------- 51
13 Geologic sections ------------------------.---------------- Between 54 and 55
14 Geologic section along the proposed "ship canal" ___ Between 56 and 57 15 The principal structures in Citrus and Levy counties -------------59
16 Cretaceous sections and structural map -----------Between 76 and 77
17 Lake City limestone sections and structural map ---- Between 94 and 95
18 Exposure of the Avon Park limestone and Moodys Branch formation at the Florida Power Corporation dam ..--------------------- 100
19 Avon Park limestone in sink at locality L-119 ------------------------ 108
20 Type locality of the Inglis member, Moodys Branch formation --- 123
21 Contact of Williston and Inglis members, Moodys Branch formation, south of Chiefland --------------------------.-------------------- 128
22 Contact of Williston and Inglis members, Moodys Branch formation, east of Chiefland ----------------------------------------------- 129
23 The Inglis member near dam of Florida Power Corporation -.. 131
24 Contact of Williston and Inglis members, Moodys Branch formation, north of Crystal River ---------------------------------133
25 Cross-bedded limestone of Inglis member ----------------------16
26 Type locality of Williston member of the Moodys Branch
formation -------------------------------------------------- 145
27 Williston member at locality L-17 ----------------------------150
28 Pinnacles of the Williston member extending into the Alachua
formation -------------------------------------------------- 152
29 Twenty-three feet of Ocala limestone (restricted) near Williston -_ 168 30 Exposure at Crystal River Rock Company quarry ---------------168
31 Contact of the Suwannee and Ocala limestones at the Crystal
River Rock Company quarry -------------------------------- 169
32 Exposures at the Thomas pit -------------------------------- 172
33 Isopachous and structural map of the Miocene
of Peninsula Florida -------------------------Between 180 and 181
34 Irregular limestone surface, a Karrenfeld, lying beneath the Alachua
35 Pinnacle of limestone extending into the Alachua formation at
the Section 12 Mine, Kibler-Camp Phosphate Enterprise --------- 196 36 Sand and clay of the Alachua formation exposed at Crystal River
Rock Company quarry ------------------------ .. ..---------------- 205
37 Distribution of the economic deposits in Citrus and Levy counties 218 38 Pit of the Connell Schultz Company illustrating mining methods -- 219 39 Flow sheet for the Section 12 Mine, Kibler-Camp Phosphate
40 Piezometric surface of Florida -------------------------------242
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA Robert 0. Vernon
SCOPE OF STUDY
The location of Citrus and Levy counties, Florida, on the crest of the Ocala uplift, and the presence of good exposures, make the area favorable for field study and also make it a critical one in Florida Tertiary stratigraphy.
The study was begun in early 1947, following a field conference of geologists, when it became 'apparent that the area would have to be mapped in detail to obtain a more complete understanding of the stratigraphy. This work was accomplished largely through intermittent trips, no defiinte full time being available. Swamp areas in the counties were accessible only when water levels in the swamps and hammocks were at their lowest. During the latter portion of the field study it became desirable to trace the rock units and correlations recognized in Citrus and Levy counties into adjacent counties. Accordingly a detailed study of samples from approximately 1,350 wells in 35 counties was undertaken and the units mapped at the surface were identified in each of these wells and correlation points were extended into the subsurface. Many of the wells were located in general terms and elevations were not available. It was deemed necessary to establish accurate controls on each well used and the survey was made on all wells in the 35 counties. Only those wells for which accurate controls were available, or were determined, were used in the preparation of the structure and isopach maps.
LOCATION OF AREA
Citrus and Levy, adjoining counties, are located on the west coast approximately in the center of the Peninsula of Florida between latitudes 280 30' and 300 00' North where the coast has a deep indenture, see figure 1. Because of the large number of islands these counties have a long coast line that resembles the coast line further south in Monroe County.
Levy County is bounded to the northwest by Dixie County, the county line being drawn along the Suwannee River; to the north by
2 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Gilchrist and Alachua counties, and to the east by Marion County. To the south Citrus County is separated from Levy County by the Withlacoochee River which circles Citrus to the east and is the county line between Citrus and portions of Marion and Sumter counties. Hernando County lies to the south.
The two counties measure about 46 miles in width and 61 miles in length and the total area, including Gulf and islands is 1,798 square miles. Levy County is about 1,137 square miles, made up of 1,103 square miles of land and 34 square miles of lakes, and Citrus County is 661 square miles in area, composed of 570 square miles of land and 91 square miles of lakes.1
These counties are sub-tropical and have a low relief. The highest point in the counties, slightly above 220 feet, is in Citrus, but most of the area is below 50 feet in elevation. The coastal areas are commonly rocky although marshy, the coastline being indented by many bays and inlets.
The location of Citrus and Levy counties in the warm water embayment of the Gulf causes winters to be warmer and the summers to be cooler than the average seasonal temperature of the interior. The regular sea breezes and afternoon showers reduce the temperature during the summer and the warm currents of the Gulf moderate winter extremes.
When the field work in Citrus and Levy counties was undertaken almost no maps showing accurately either physical features or the culture of the area were available. A complete set of U. S. Department of Agriculture aerial photographs covering both counties were available and field maps were constructed from these photographs. The planimetric maps of the U. S. Coast and Geodetic Survey, based on aerial photographs and covering the Florida Gulf Coast, were most helpful during the latter part of the field work. Topographic maps covering the eastern portions of both counties were published in 1890 and 1893 by the U. S. Geological Survey, but the culture and topographic controls were so inaccurate and out-dated as to render these maps practically useless. State Road Department county maps and the official surveyed sectional land grid, filed with the land office of the State Department of Agriculture, were used in plotting sections, townships and ranges. The
'Sixteenth Census of the United States, 1940.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 3
- -- ----- ---\ I I wo,,
... ..... _ !
LOCATION 0'' OF
CITRUS AND LEVY
COUNTIES, FLORIDA .-.,. I
0 50 100 200
250N Scale in miles
Figure 1. Location of Citrus and Levy counties, Florida
base map published as Plate 1 was compiled largely from aerial photographs and U. S. Coast and Geodetic Survey hydrographic and planimetric maps upon which the sectional grid was superimposed. A list of maps covering the two counties, some of which were used in the field work, follows:
U. S. Department of Interior, U. S. Geological Survey, Topographic Quadrangles on a scale of 1:62,500 with a 10-foot
Dunnellon Sheet, 1890
Panasoffkee Sheet, 1893
4 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
Tsala Apopka Sheet, 1893
Williston Sheet, 1893
Florida State Road Department, Division of Research and Records,
Maps on scales of 1:63,360 and 1:126,730:
Citrus County, 1936, Revised 1945 Levy County, 1936, Revised 1946
U. S. Department of the Army, Corps of Engineers, Series of planimetric maps along the proposed Cross-Florida Barge (Ship) Canal on a scale of 1:10,000 with partial topography on a contour interval of five feet, 1933:
U. S. Department of Commerce, U. S. Coast and Geodetic Survey, Planimetric maps on a scale of 1:20,000, compiled from
aerial photographs, 1940:
Chart T-5791 Suwannee River and Vicinity
T-5792 Cedar Keys and Vicinity
T-5793 Sumner and Vicinity
T-5794 Gulf Hammock and Vicinity T-5795 Waccasassa Bay and Vicinity
T-5796 Withlacoochee River and Vicinity
T-5797 Crystal River and Vicinity
T-5798 Homosassa Bay and Vicinity
U. S. Department of Commerce, U. S. Coast and Geodetic Survey,
Nautical charts on a scale of 1:80,000:
Harbor Chart 480, Cedar Keys, 1930
Coast Chart 1258, Anclote Keys to Crystal River, 1944
Coast Chart 1259, Crystal River to Horseshoe Point, 1943
Bronson is the county seat of Levy County, and Inverness of Citrus County. Both were founded in the prosperous days of hard-rock phosphate mining, but their importance is now due largely to their being the seats of county governments. Numerous pits of former phosphate mines exist about each, although income is now derived largely from agriculture and tourist trade, attracted by the excellent hunting in the hammock areas and fishing along the coast, Suwannee and Withlacoochee rivers and numerous lakes in the counties. Some citrus is grown in the vicinity of Inverness and many small lumber mills operate in the backwoods of Bronson. Additional income is derived from grazing native herds of cattle and hogs, although the trend in the area now is toward
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 5
better bred stock. The county seat of Levy County was formerly at the small settlement of Levyville, now abandoned except for one or two houses. The shift to Bronson was occasioned by the building of the Atlantic, Gulf and West Indies Tourist Company Railroad, popularly called "The Yulee Railroad", which passed through Bronson and by-passed Levyville.
Chiefland, in the northwest part of Levy County, is in a prosperous farming, turkey and stock raising section. Watermelon, peanuts and corn are the chief crops and large shipments of watermelons are made over the Atlantic Coast Line Railroad which serves this area. Both of the main highways along the western coast of Florida pass through Chiefland, and it is developing into a rather prominent tourist, fishing and hunting center. Doublesink, Newton and Meredith are all small farming settlements. Meredith is a remnant of the hard-rock mining activity and was a stop on a railroad, now abandoned, that formerly connected Key West with Gainesville in Alachua County and serviced the phosphate industry.
Williston is the center of the second largest limestone mining area in the State. The soft limestone of Eocene age is mined here by six companies which have operated intermittently. Eve, Raleigh, Runnels, Montbrook and Morriston are all small settlements deriving their income from farming, stock grazing and minor limestone industries. Considerable chert, residual from the erosion of limestone, occurs in this area, particularly about Montbrook and Morriston, and the farmers obtain some income from selling these boulders, picked out of their fields, to rock crushers that are operated intermittently. These settlements were all established during the hard-rock phosphate mining activity.
Cedar Keys, located in the southwest part of Levy County on a white sand key in the Gulf of Mexico, is a small fishing village, the remnant of a formerly much more prosperous town. It was once an active port and railroad terminal that supported several hotels, a customs house and weather station. Its prosperity was due to the building of "The Yulee Railroad" connecting Fernandina with Cedar Keys and to the former freight traffic on the Suwannee River. Some of the best cedar in the nation grows in Gulf Hammock and a thriving industry was created in cutting and shipping this timber for use by pencil manufacturers. Cedar is no longer cut for this purpose. The abandonment of "The Yulee Railroad" during the War Between the States and the completion of a railroad into Tampa made Cedar Keys less important as a port and decreased the usefulness of the Suwannee River freight ships.
6 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
The town population and prosperity decreased rapidly. Fishing, oysters, sponges, and a small company manufacturing brushes from the fibers of the palmetto and palmetto palm are its chief industries now.
Sumner, Rosewood, Ellzey, Otter Creek, Gulf Hammock, Lebanon and Tidewater are all small saw-mill towns which were developed about the rim of Gulf Hammock, a source of large quantities of hardwood, now largely depleted. Timber mills are operated at all of the towns at present with the exception of Sumner and Tidewater where turpentining is the principal industry. Otter Creek manufactures slats for use in crates. The town of Gulf Hammock is owned largely by Patterson MacInnis Lumber Company whose headquarters and lumber mill, the largest in the area, are located here. Additional income is obtained through hunting, fishing and trapping. Wild game, both salt- and freshwater fish and valuable fur animals, including mink, otter, and fox, are found in the extensive swamps and coastal marsh lands of the western Peninsula.
The small farming and cattle raising settlements of Lebanon in Levy County and Red Level in Citrus County are the sites of dolomite pits; Citronelle is the center of a small turpentine industry; Crystal River, Homosassa Springs, Homosassa and Chassahowitzka are centers of hunting, fishing and recreation for tourists and commercial fishing. Crystal River is also a small port for pleasure boats and is the terminal of a branch line of the Atlantic Coast Line Railroad. Some limestone is produced near Crystal River, and in former years large tonnages of road base materials were mined and shipped.
Holder, Felicia, Hernando, and Floral City are small settlements that were founded during the former activity of the hard-rock phosphate mining industry. Income is now obtained from stock raising, tourist recreation, fishing, hunting, the clay-phosphate industry, the hard-rock phosphate industry near Holder and a small clay pit near Floral City. Lecanto is a prosperous small farming and stock raising center.
Before 1943, when U. S. Highway 19 (State Road 55 on Plate 1) was constructed as the coastal route to St. Petersburg and several connecting roads were paved, the few highways that crossed Levy and Citrus counties were poorly connected by unpaved roads. Many of the small hamlets of the counties grew rapidly after these roads were com-
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 7
pleted, expanding to the demands of the large tourist travel along U. S. Highway 19. The area now is a desirable and available hunting, fishing, and recreation center.
The two principal highways along the western part of peninsular Florida, U. S. Highway Nos. 19 and 41, cross Levy and Citrus counties. U. S. Highway 19 traverses the center of Levy County and the western side of Citrus County, connecting Chiefland, Otter Creek, Inglis, Crystal River, and Homosassa Springs with points north and south. This higt,way passes through very beautiful, flat land and skirts a jungle of highland swamps, called hammocks, that teem with bear, turkey, wild hogs, mink, otter and other game. The trees are majestic hardwoods and the hammocks are truly tropical and preserve much of the wild beauty typical of Florida. Several large springs are easily reached from U. S. 19. The springs of Crystal River well up from deep canyons and fissures to make Crystal River and may be seen from glass-bottomed boats. Homasassa Springs and Chassahowitzka Springs rise in the lower hammocks of southern Citrus County and their blue waters are exceptionally clear. Homosassa Springs is inhabited by a variety of both salt- and fresh-water fish, which congregate in great numbers in crevices of the spring and are easily visible from platforms constructed out over the spring and from underwater caissons. The springs are well-developed commercially and are a well-known tourist attraction. One of the prettiest small springs in Florida, visible in its natural setting, also can be reached from U. S. 19. This spring, Wekiva Springs, is set in the sand hills east of the town of Gulf Hammock, where it rises from a fissure and makes a small creek that flows along a valley made of steep limestone walls, apparently a former cavern with the top now collapsed or removed by solution.
The other important highway crossing these counties is U. S. 41, which in part is also U. S. 27. It enters Levy County along the eastern projection of the county and connects Williston and Morriston with Dunnellon in Marion County and then continues along the eastern part of Citrus County, paralleling the beautiful Tsala Apopka Lake, a recognized fishing area, and connecting Hernando, Inverness, and Floral City with Tampa, Sarasota, Fort Myers, and Miami to the south and Lake City, Jasper and eastern coastal states to the north.
There are numerous paved and unpaved but improved connecting roads of which State Road 500, connecting Chiefland, Williston and Ocala; State Road 24, connecting Cedar Keys, Bronson and Gainesville; State Road 44, connecting Crystal River, Inverness and Leesburg; and
8 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
State Road 55, connecting Chassahowitzka with Floral City, are important.
The area is served by the Atlantic Coast Line and Seaboard Air Line railroads. The Atlantic Coast Line Railroad connects Wilcox, Gilchrist County, with Chiefland, Otter Creek, Gulf Hammock, Lebanon Station, Levy County, and Dunnellon in Marion County, where it joins a branch of the line crossing Levy and Marion counties. Shipments made on this line include watermelons, peanuts and corn from the Chiefland and Wilcox areas, timber from the Otter Creek and Gulf Hammock areas, limestone from the Williston area, dolomite from the Lebanon Station area, and soft phosphate from the Dunnellon area.
Both the Seaboard Air Line and the Atlantic Coast Line have branches that cross Levy and Citrus counties along the eastern edges. The Atlantic Coast Line serves Crystal River and formerly handled considerable timber from the large hammocks of southern Citrus County, but now handles minor shipments of limestone, some timber and naval stores and some stock. The main lines of both railroads serve the Williston limestone industry and the hard-rock phosphate industry south of Dunnellon in Citrus County. The only phosphate plant in operation at present is served by the Seaboard Air Line, but in the past when more pits were operated both railroads served the industry. Some clay for use in the Portland Cement Plant in Tampa is shipped from near Floral City over the Seaboard Air Line.
Excellent passenger service is maintained by both railroads over the principal routes connecting Tampa and St. Petersburg with the north.
No flights are scheduled into any town of Citrus and Levy Counties and no commercial airports are maintained.
Inglis is a port of entry and is the western terminal of the proposed Florida Barge Canal. The town lies on the Withlacoochee River which is navigable approximately to Dunnellon by small cabin boats, which must pass the power dam at Inglis through locks. The river is navigable to Inglis by sea-going tugs and shallow-draft boats, a channel of nine feet being maintained from the Gulf to Inglis.
The lower portions of all other streams on coastal water of the area
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 9
are navigable by small cabin boats, but all head waters are rocky and shallow and log jams are common.
Following the construction of "The Yulee Railroad" and subsequently that of the major railroads operating in Florida today, waterways in the counties have gradually decreased in importance as transportation ways. Some oil is barged up the Withlacoochee River to the Florida Power Corporation Plant at Inglis and rarely some timber is barged. Prior to tbe development of railroads, and later the highways, the Suwannee River was an important water way, supplying freight to stores and towns scattered along its banks up as far as what is now Branford, although some shallow-draft boats may have reached the shoals at Ellaville during high water.2 The usefulness of these freight ships has ended and the former river prosperity has dwindled accordingly.
CLIMATE AND VEGETATION
Citrus and Levy counties are low-lying, sub-tropical, coastal land areas, bordered on the west by the warm Gulf waters. Citrus is more tropical than Levy which is rather temperate. Sharp changes in climate occur at about the latitude of the Citrus-Levy county line. Citrus County averages about seven inches more annual rainfall and 20 to 80 days additional each year without a killing frost, although the climate of coastal areas of Levy County approaches that of Citrus County.
Numerous spring-fed sluggish streams drain into the Gulf of Mexico from a poorly defined divide of sand hills extending along the eastern margins of both counties. The coastal margins are low, flat and rocky, and the coast line is broken by many marsh and bay inlets. Islands are numerous. Many inland lakes, particularly Tsala Apopka Lake which is the largest in the counties, temperate the climate.
Citrus and Levy counties have an annual rainfall about three inches less than the average for Florida, the three permanently maintained weather stations in the counties recording an average rainfall of 49.99 inches during the years 1841 to 1949.3 Most of the rainfall comes during the months of June through October, usually falling as heavy rains during thunder-storms in the afternoons. Cooling winds with high velocities commonly accompany these local storms.
The area is in the hurricane belt and these tropical disturbances produce winds of very high velocity and destructiveness, but damage is
2Personal communication, J. C. Simpson, 1950.
3U. S. Weather Bureau, "Climatological Data", published monthly.
10 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
commonly restricted to paths up to 80 miles wide and the area has gone many years between visits of hurricane winds. The latest hurricane to cause extensive damage was in 1950 when the lowlands were flooded by high seas and high winds caused some damage along exposed coasts.
Temperatures over the counties range from an average of 81.4 degrees Fahrenheit in the summer to an average of 58.4 degrees Fahrenheit in the winter. Daily fluctuations vary from about 18 degrees in the summer to 25 degrees in the winter, although extremes in the winter months may approach 50 degrees. The days are commonly comfortable, but the nights are cool. The relative humidity may be as high as 90 per cent, and when combined with a high temperature and little air circulation the physiological effect may be close and muggy. Fortunately, the afternoon rains, associated winds and moderating effects of Gulf waters prevent extreme temperatures in the summer and make such physiological discomfiture rather rare.
The "Climatological Data" published monthly by the Weather Bureau, U. S. Department of Commerce, recorded the following data for the permanently maintained stations, over the period of 1841 to 1949:
CEDAR KEYS INVFRNESS INGLIS (1942-1949) Climatological Data
Year Data Year Data Year Data
Highest Rain ........ 1912 83.40 inches 1937 70.98 inches ..................
Lowest Rain ........ 1931 27.41 inches 1931 36.4 inches..................
Average Rain ........ 1841- 1901- 19421949 47.25 inches 1949 54.53 inches 1949 45.68 inches Min. Temperature .......... 15'F ............. 14'F ........................
Max. Temperatures ......... 101'F ............. 102'F ........................
Av. Jan. Temperature ...... 58.4F ........... 58.5'F ......................
Av. July Temperature ...... 81.8F ........... 80.9F ......................
Growing Season............ 314 days ........... 300 days .....................
The counties are heavily covered with vegetation, although much of the high sand hill area has been stripped of the large pine forests that originally covered it and is now covered by a thick screen of scrub oak and young slash pine. Plains also have been largely stripped of vegetation and are farmed. These sand hills and some farm land have recently been reconverted to slash pine planting, a source of income as pulp wood. The coastal areas are choked with hardwoods, although most of the large trees have been cut for timber. These swamps contain pine,
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 11
pond cypress, bald cypress, white cedar and red cedar of the conifers; and tupelo, sweet gum, soft maple, sweet bay, cottonwood, willow, basswood, southern magnolia, and yellow poplar, all of which are classified as soft textured hardwoods. The hard textured hardwoods include oaks, hickories, walnut, ash, river birch, elm, hackberry and sycamore.
CULTURE AND LAND UTILIZATION
County Names: Citrus County was created by the Legislature on June 2, 1887, and Levy on March 10, 1845 (Utley, 1908). Citrus was named for the fruit and to indicate the abundance of these groves in the county at the most northern latitude along the coast. Levy County was named to honor David Levy Yulee who built "The Yulee Railroad", crossing the county and connecting Cedar Keys with Fernandina, Nassau County. Mr. Yulee was territorial delegate to Congress from Florida, and U. S. Senator during 1841-61.
Population: Citrus and Levy counties are sparsely populated, the area being largely utilized as cropland, pasture and woodland, but the total population varied considerably from census to census, Levy more than Citrus. The average population for the period 1900 to 1950 for Citrus County is 5,811, and for Levy County 10,846. The peak year for Citrus was in 1905 at 7,543 and for Levy it was in 1935 at 12,973. The low for Citrus was in 1920 at 5,220, and for Levy in 1900 at 8,603. The 1950 population total for Citrus was 6,111 and for Levy it was 10,637.4
During the period 1900 to 1950, the Florida population increased 417.3 per cent, but that of Citrus County increased only 12.9 per cent, and Levy County 23.5 per cent. The State population increased 44.1 per cent during 1940-50, but Levy decreased 15.3 per cent and Citrus gained only 4.8 per cent. These figures indicate that the counties are not being settled or developed as rapidly as the remainder of the State, and consequently the price of land is less than that in areas that are being developed more rapidly.
The limited population centers are controlled by the industry supporting the population, many being founded during the former greater activity of the hard-rock phosphate mining industry. Towns are developed only along the valley of the Withlacoochee River, along bays and fresh-water springs on the coast and on the plains that are developed on top of Eocene limestones. Scattered timber growths, small farms and
4Al figures on population are based on figures published by the Bureau of the Census, U. S. Department of Commerce, and include news releases of the 1950 census.
12 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
cattle grazing occupy most of the high sand hills. Lumbering, hunting and fishing occupy the coastal lowlands and hammocks, and farming the high limestone plains.
Land Utilization: The United States Census of Agriculture of 19455 indicated the following land uses in Citrus and Levy counties:
Use Citrus Levy
Private Lands (acres) ................................. 280,454.5 686,702.2
Farm s (num ber) ................................. 361.0 640.0
Croplands (acres) ................................ 19,543.0 81,277.0
W oodlands (acres) ........................... 110,928.0 131,447.0
Other (acres) ................................ 20,536.0 30,646.0
Public Service CorporationsR ailroads (acres) ............................. 1,654.0 1,825.0
Electric Light and Power Company (acres) ...... 2,172.5 1,504.4
Unclassified (pasture, woodland?) (acres) ............ 125,621.0 440,002.8
U rban (acres) ....................................... 18,850.0 3,370.0
State and Federal (acres) ............................ 65,495.5 15,847.8
Total All Lands (acres) ............................... 364,800.0 705,920.0
In a series of news releases by the Division of Forest Economics of the Southeastern Forest Experiment Station in cooperation with the Florida Forest Service (June 1949, p. 26, November 1949, p. 26, September 1950, p. 8) the production of forest products in Citrus and Levy counties were tabulated as follows:
Item Citrus Levy
Pulpwood production (standard cords) .................. 5,870 17,641
Lumber (thousands of board feet)Conifers (soft woods) ............................ 195,800 617,700
Soft textured hardwoods .......................... 76,200 86,400
Hard textured hardwoods ......................... 21,400 96,000
Total all species ................................. 293,400 800,100
5U. S. Census of Agriculture, 1945, vol. 1, part 18, Florida. U. S. Department of Commerce, Bureau of the Census, 1946, 162 pp.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 13
The U. S. Census of Agriculture of 19456 listed the following crops, fruits, nuts, vegetables and stock as having been produced as primary sources of income in these counties during the period of the Census:
Total value of all crops harvested (dollars) .............. 411,570 1,104,621
Corn (bushels) ....................................... 20,493 152,377
Cowpeas (bushels) ................................... 1,265 3,161
Peanuts (nuts) (pounds) ............................... 6,110 1,662,043
Peanuts (hay) (tons)................................. 340 1,107
Irish potatoes (bushels) ............................... 1,921 1,876
Sweet potatoes (bushels) .............................. 6,635 15,727
Sugarcane syrup (gallons) ............................. 9,365 40,059
T obacco (pounds) .................................... ........... 22,675
Chufas (nuts) (bushels) ........................................... 6,832
Tree Fruits, Nuts, Grapes
Value of all fruits and nuts harvested (dollars) ........... 246,015 92,617
Peaches (bushels) .................................... 439 893
G rapes (pounds) .................................... 724 4,125
Pecans (pounds) .................................... 3,288 118,711
Tung nuts (pounds) .................................. 47,332 1,201,195
Oranges (field boxes) ................................ 102,241 305
Tangerines and Mandarins (field boxes) ................ 11,492............
Grapefruit (field boxes) ............................... 14,921 ............
L im es (pounds) ..................................... 261 ............
Value of all vegetables sold (dollars) .................... 14,816 267,407
Value of livestock and products (dollars) ................ 247,820 694,146
Cattle (num ber) ...................................... 11,593 27,790
H ogs (num ber) ..................................... 513 31,646
Goats and kids (number) ............................. 421 1,057
Chickens (num ber) .................................. 13,029 31,018
Turkeys (num ber) ................................... 649 7,664
From this tabulation it is apparent that the chief sources of farm income in Levy County are peanuts, turkeys, cattle and hogs, sugar cane syrup, tobacco, tung nuts and pecans, whereas Citrus derives its farm income largely from citrus and stock raising. Watermelons were not tabulated but they are an important cash crop in 'Levy County, ranking next to peanuts, and a minor crop in Citrus County.
6Op. cit., 1946.
14 FLORIDA GEOLOGICAL SURVEY -BULLETIN 38
Florida as it exists today is the land area of a much greater projection of the Continent of North America which extends south to separate the Atlantic Ocean from the Gulf of Mexico. This continental mass is the east rim of the Gulf Basin, part of the west rim of the Atlantic basin and about 60 per cent of it is covered by shallow marine water. The portion covered is wider on the Gulf side than that on the Atlantic, the land area and the submarine portion almost joining along the southern andsoutheastern tip of Florida.
That portion of the continent covered by marine waters ranging out from the shore line to a depth of about 300 feet of water is called the Continental Shelf, and the range of elevations on it probably represents the degree of change in sea level during the Pleistocene epoch, the shelf being alternatingly above and below sea level during this time. Evidence is rather conclusive that sea level during the Pleistocene occupied levels considerably higher and lower than that of today.
This extension of the continent of North America, including both the land area of Florida and the adjacent continental shelf was described by Shaler (1890) and was named "The Floridian Plateau" by Vaughan (1910). It projects out towards Cuba and almost joins a similar projection extending northeast from Central America, being separated from it by deep water of the Yucatan Channel and from Cuba by the Florida Strait.
GENERAL LAND FORMS OF FLORIDA
Fenneman- (1932) placed the Floridian Plateau in the Coastal Plain Province and land forms recognized within this province constitute subdivisions of it. Cooke (1939, p. 14, 1945, p. 8) in reports on the geology of the State recognized a "Western Highlands", "Marianna Lowlands", "Tallahassee Hills", "Central Highlands" and "Coastal Lowlands" to cover significant land forms of Florida. Vernon (1942, p. 5) in an attempt to make the names of the topographic divisions in Holmes and Washington counties descriptive of their origin used "River Valley Province" for Cooke's "Marianna Lowlands"; "Coastal Plains Province" for Cooke's "Western Highlands" and his "Coastal Lowlands". Wayne E. Moore, who is preparing a report on the geology of Jackson County, has pointed out the duplication of Fenneman's more comprehensive term and the unde-
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 15
sirability of continuing the use of the term "Coastal Plains Province" for subdivisions of the physiography of the State.
Throughout most of western Florida, central Florida, southern Georgia and southern Alabama a large delta plain (Vernon, 1942, p. 8), made up of smaller coalescing subdelta plains (MacNeil, 1946, p. 60) was formed during the interval extending from late Miocene to early Pleistocene time. This plain is underlain by deposits placed in the "Citronelle formation" by Cooke (1939) and in Plio-Pleistocene beds by Vernon (1942).
During the Pleistocene these deltaic deposits were eroded and redeposited throughout several stages when sea level was alternately lowered and raised by the development and subsequent melting of glacial ice in high latitudes. A period of lowered sea level followed by a period of raised sea level constituted a cycle composed of a period of stream excavation and sub-aerial erosion followed by a period of stream alluviation and marine planation and deposition.
Periods of raised sea level were of sufficient duration to cut low seaward-facing embayed escaipments and to cut and construct broad plains, the most recently formed still displaying bars and beach ridges, and each being composed of a distinct depositional unit. Each marine plain has a flu viatile equivalent that extends up the streams of Florida as terraces that exhibit many characteristics of the Recent flood plains. Assuming a net gain of land with the completion of each cycle, brought about by one or more factors, including a progressive decreased deglaciation from early to late Pleistocene stages and the eustatic adjustments in land-sea relationships, a series of marine plains with seaward facing escarpments would result, each plain extending up stream valleys as flood plains and river terraces. 'This combination of marine and fluviatile agencies formed the greater part of the topography of Florida.
Five such cycles have been recognized in Florida by means of the sediments and the terrace-surfaces that were formed (Vernon, 1942, p. 26), the dcposits and surfaces of each cycle being preserved possibly through uplift of Florida and by progressive smaller deglaciations throughout the stages of the ileistocene. Five marine plains, including the present sea bottom, have been formed which merge with five stream surfaces, including the present flood plains, that are associated with the streams that occupy Florida today.
Some areas of Florida were apparently sufficiently high in elevation to extend through the blanket of elastic sediments formed by the delta
16 FLORIDA GEOLOGICAL SURVEY BULLETIN 33
plain and by the stream and marine surfaces of Pleistocene age. Thus some local ground surfaces are composed of weathered Tertiary rocks and there is no younger sediment lying upon them.
The physiography of Florida can be grouped logically into four general subdivisions on the basis of origin. Highlands are composed of either sediments formed as a part of a high-level, widespread, aggradational delta plain or of Tertiary land masses rising above this plain. Lowlands have been formed either by deposition and erosion along coast lines by marine agencies or by alluviation and stream erosion along stream valleys. These obvious land forms can be grouped under four subdivisions of the Coastal Plain Province, namely The Delta Plain Highlands, The Tertiary Highlands, The Terraced Coastal Lowlands7 and The River Valley Lowlands. These terms, applying to major subdivisions of the physiography of the State, can be subdivided to any degree and local names can be applied.
The Delta Plain Highlands, as thus proposed, would include Cooke's "Western Highlands" and "Central Highlands" and the 250-320 foot surface of Vernon's "Coastal Plains Province". The Tertiary Highlands would include Cooke's "Tallahassee Hills" as a general term although Tallahassee Tertiary Highlands would be appropriate as a local name. The Terraced Coastal Lowlands would include Cooke's "Coastal Lowlands" and part of Vernon's "Coastal Plains Province". The River Valley Lowlands is equivalent to Vernon's "River Plains Province", and Cooke's "Marianna Lowlands". The term "River Plains Province" (Vernon, 1942) has been changed to River Valley Lowlands because "lowlands" is more descriptive than "province", and some streams in Florida have not formed alluvial plains although all occupy valley lowlands.
The development of land forms in Citrus and Levy counties is controlled by a warm, humid climate; high annual rainfall; a bedrock composed essentially of carbonates that are easily soluble in fresh water but highly resistant to marine erosion; low surface elevations; flat to gently dipping porous rock, covered by limited porous sand and phosphatic beds; heavily charged phosphoric, humic and carbonic acid waters; fracturing along the crest of the Ocala uplift and certain groundwater conditions.
-7Term proposed by W. E. Moore, manuscript of the Geology of Jackson County, Florida.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 17
Ground water is by far the most important agent altering the ground surface and rocks of Citrus and Levy counties today, although in the geologic past marine and fluviatile agencies were more important. In spite of an average rainfall of fifty inches, surface streams and runoff are ineffective in creating land forms in the counties. Thick sand cover on all high hills, karst topography on plains, and swamps in lowlands trap the large percentage of rainfall and result in heavy recharge to ground water. This is true in spite of the two counties being part of a discharge area for ground water contained in the system of artesian water of Florida generally. Springs are abundant and each stream in the area receives water from springs that empty from vents in the limestone valley walls. This is true of all stream valleys except along "the upper reaches of the Waccasassa and Withlacoochee rivers where deep fills of alluvium form a system of interconnected swamps that are fed by ground-water seepage.
PHYSIOGRAPHY OF CITRUS AND LEVY COUNTIES
Citrus and Levy counties compose a part of the Coastal Plain Province, and the physiography is roughly subdivided into three major units (see figure 2): 1) Tertiary Highlands; 2) Terraced Coastal Lowlands; 3) River Valley Lowlands.
The Tertiary Highlands consist of limestone and clay hills formed by the Suwannee and Ocala limestones and by the Hawthorn formation, which extend above younger sediments and create a rugged topography.
The Terraced Coastal Lowlands in other parts of Florida consist of four surfaces or plains that parallel the present coast. These plains are bounded by erosional escarpments and each is underlain by a distinct depositional unit. Marine deposits, such as bars, beach ridges, beach escarpments and fossils in the lowest, characterize the surfaces and place their origin within a marine environment. Vernon (1942, p. 18) recognized in western Florida four surfaces having shore lines at 220, 150; 105, and 30 feet above the present sea level. In peninsular Florida the two lowest surfaces are present but the bases of the bounding escarpments appear to be lower than they are in western Florida and the shore lines are near 100 feet and 25 feet. The two higher surfaces, with shore lines at 220 and 150 feet, have been so eroded in these counties that they cannot be separated into distinct units, although deposits associated with these surfaces are present.
18 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Each of the two lower coastal surfaces includes a sandy beach developed along the coast line, and a limestone shelf cut by marine planation, upon the youngest of which marine shells and late Pleistocene sandy limestones were deposited.
The River Valley Lowlands include the limited narrow flood plains developed at the mouth of each of the streams crossing the counties, sand bars and alluvium deposited along the valley walls of the Suwannee and Withlacoochee rivers during the late Pleistocene, and Tertiary limestones exposed along the channels and valleys. The lower course 'of each valley has been recently entrenched into the limestone bedrock, probably since the last rise in sea level. This entrenchment has formed steep limestone-walled channels that end abruptly at the surface of each coastal terrace.
Within these two counties, the Tertiary Highlands are present only in central Citrus County and because of limited exposures and a lack of details their distribution is greatly generalized on the physiographic map, figure 2. These highlands are erosional-remnant hills and ridges, composed of the Suwannee and Ocala limestones, sand and clays of the Alachua formation, and marine clays of the Hawthorn formation. Northward they merge with a high, rolling sand ridge that has been named the Coharie-Okefenokee Sand Ridge, page 25. In addition to the generalized mapping of the Tertiary Highlands in figure 2, they are also shown more specifically on Plate I as outcrops of the Suwannee limestone and the Hawthorn formation.
The highlands rise steeply above the surrounding plains, figure 3, to give an impression of relief considerably greater than the moderate relief of 150 feet, which is present. The highest limestone hill on the highlands is 192 feet. Because this hill has no younger beds covering it and early Pleistocene deposits are known to be present in the counties at elevations up to 220 feet, it is presumed that the Tertiary Highlands stood higher during the early Pleistocene and have since been reduced.
DELTA PLAIN HIGHLANDS
Although Cooke (1945, p. 9) mapped the "Central Highlands", equivalent to the Delta Plain Highlands of this report, in Levy and Citrus counties, no sediments similar to those found toward the east in the Delta Plain Highlands of Lake and Polk counties or northward in western Florida, were found. Also no elevation in the counties extends
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 19
Figure 3. The Terraced Coastal Lowlands as seen from the Tertiary Highlands at
the Crystal River Rock Company quarry, five miles southeast of Crystal
River, Citrus County.
above 220 feet, which is the highest level of a definite Pleistocene shore line in the State. Since the Pleistocene terrace surfaces, formed seaward of the various shore lines, are aggradational (Vernon, 1942) and are composed of formational units confined to each surface, it is apparent that if the delta plain sediments ever extended across these counties they have been reworked and deposited as early Pleistocene sediments.
TERRACED COASTAL LOWLANDS
These lowlands cover approximately 90 per cent of both counties, and extend inland from the present shore to near the eastern extremities of the counties, and may have extended over the whole area at one time. Their continuity is broken only by lowlands developed along river valleys.
In other parts of Florida the Terraced Coastal Lowlands include four coastwise surfaces, and deposits found beneath each of these are probably present in these counties, but because of erosion the two higher surfaces could not be separated. Only the two lowest and youngest surfaces are well-developed and preserved. Deposits of the two oldest surfaces make, in part, a high sand ridge which is named the "CoharieOkefenokee Sand Ridge". Tertiary rocks may compose a portion of this ridge in Citrus and are the base of the ridge in Levy County.
The names of three coastal terraces as used by Cooke (1945) and the term Okefenokee as used by McNeil (1949) have been applied to the Pleistocene sediments in Citrus and Levy counties as follows: The oldest and highest terrace is the Coharie with a shore line at 220
20 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
feet, the Okefenokee at 150 feet, the Wicomico at 100 feet, and the Pamlico at 25 feet. These have characteristics in common with the modern submarine plain at sea level. In the discussion that follows the modern plain and the youngest of the terraces are discussed first, the ,,details preserved upon these aiding in understanding older and more
--l -ed terraces.
Modern Submarine Plain
One attack on the problems in geology is to study the effects of geologic agencies that are active today. Marine deposition and erosion have controlled the formation of the coastal terraces that compose much of the land surface of the State. In an attempt to understand the marine plains of the Terraced Coastal Lowlands of these counties a study of the modern submarine plain was made. This study was limited to the evaluation of the submarine surface from hydrographic charts of the area, from a series of core holes placed at one-half mile intervals, 13 miles into Gulf waters by the U. S. Army Engineers along the route of the proposed ship canal, and from three days of collecting submarine rock exposures by diving and by sounding the bottom.
The sea bottom is a rolling plain sloping gently seaward and containing irregularities caused by sand bars, oyster bars, limestone shelves and reefs, and shell deposits. The submarine plain is composed of several parts, these varying in width depending on the location of streams, bay indentations and oceanic currents. Extending along a line drawn perpendicular to the shore, this plain is made up of narrow bands of sediment that parallel the modern coast line. Land along the entire coast is rocky except in the vicinity of the Suwannee River, where it is sandy. The rock is a fractured limestone and bays, inlets, islands and rock pinnacles are common. Sandy mud marshes have penetrated along the low places of the shore line, and the limestone stands above the sediment in these marshes five to eight feet, making an abrupt escarpment, see figure 4. This marsh averages two to three miles in width except for southern Citrus County where it approaches six miles, see figure 2. Extending out from shore and from the marshes there is a submerged plain, varying considerably in width, that is composed of two parts or belts. The coastal belt is covered by water that is very shallow, only rarely exceeding four feet; sand bars are common and make shoal areas. It is present from the shore out to where it ends, often abruptly, in deeper water that covers the seaward belt of Tertiary limestones: that have been eroded to a rolling flat shelf. Depressions in the limestorlb belt have been filled by deposits of modern shells of marine
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 21
mollusks and foraminifers, some of which have been loosely cemented to form thin limestone beds. An occasional sand bar is present on the shelf and some high areas of the limestone rise 10 to 20 feet above "the bottom as pinnacles.
Figure 4. Drowning of coastal margins by salt-water marsh. Photograph taken
facing due west at old Stevens Homestead, three miles northwest of Yankeetown, Levy County. Islands in the marsh in the background are composed of limestone of the Inglis member of the Moodys Branch
The physiographic map, figure 2, and the aerial map, figure 5, reveal two well-developed erosional escarpments across Citrus and Levy counties. These escarpments trend almost north and south and have been developed along the western foot of the Coharie-Okefenokee Sand Ridge. They are the landward boundaries of two Pleistocene seas, the Pamlico and Wicomico surfaces, with shore lines at 25 and 100 feet respectively.
Each shore line is marked by the development of a narrow belt of sand along the coastal margins and further seaward by a broader belt of limestone that has been planed by marine erosion to an irregular rolling shelf. In these respects the Pleistocene surfaces correspond to the modern submarine surface. The Pamlico surface has another characteristic in common with the modern submarine plain which is the development of fossiliferous marine sediments upon the limestone shelves. Fossils have not been noted in the sediments of the Wicomico surface.
A high sand ridge, the Coharie-Okefenokee Sand Ridge, developed to the east of the two definite Pleistocene surfaces covers most of eastern Citrus and Levy counties. Remnants of this sand over the Williston
22 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
Limestone Plain and in the Withlacoochee Valley indicate that the ridge was once present over these areas and has been removed. This ridge is underlain by the Alachua formation of Miocene (?) age and by unfossiliferous sand and clay deposits of early Pleistocene age. In other parts of Florida the Pleistocene deposits occur beneath two high surfaces occurring at definite levels, but evidences of the original surfaces have been destroyed along this ridge.
Figure 5. Mosaic of aerial photographs of northern Levy County illustrating the
physiography and trace of the Long Pond Fault. Note the well-developed terrace escarpments along the right side of the figure, and the offsetting
of the two blocks in the upper-left portion of the photograph.
Pamlico Terrace: This surface is well-developed in both counties and is underlain by sediments that characterize the surface and compose the Pamlico formation. The Pamlico formation is considered to be contemporaneous with sand bars developed along the Suwannee River at comparable elevations.
The present coast of Citrus and Levy counties is obviously submerged, as evidenced by the extensive coastal marsh, see figure 4, and the many drowned valleys and inlets, Plate 1. This indicates a rising sea level that
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 23
is out of adjustment to the land mass. As a result, the Tertiary limestones and younger beds that underlie coastal flat lands are being eroded along coastal margins to form a fairly continuous limestone escarpment, standing three to five feet above sea level. In the vicinity of the Suwannee River, sand bars deposited by the river obscure the limestone escarpment and modern dunes, developed along the coast from Cedar Keys to the Suwannee River, cover the Pamlico surface and create an irregular ridge-like topography of Recent origin on a flat plain of Pleistocene origin. This ridge, not separated on the physiographic map, figure 2, is included with the Pamlico surface.
The Pamlico marine plain, the lowest of the coastal terraces, extends inland from the coast to approximately the 25-foot contour which marks the foot of a 10 to 20-foot escarpment. The surface of the plain is about eight to ten miles wide in Citrus County but covers most of central Levy County, making a deep embayment along the Waccasassa River, where it merges with a fluviatile equivalent developed as a small delta plain at the mouth of a large stream that once occupied the valley, see pages 88 to 36.
The Pamlico surface is similar to the modern submarine plain in that it is composed of long, narrow belts of sediment that parallel the Pamlico coast line. A narrow band, up to three miles wide, extends seaward of the Pamlico coast line and makes a distinct pattern on aerial photographs, figure 5. This belt is composed of sand that makes a poorly drained flat surface, covered by slash pine and palmetto. Elevations range between 15 and 25 feet although ridges that were apparently sand bars in the Pamlico seas rise to slightly above 40 feet.
Toward the modern coast and seaward of the Pamlico coast line a broad limestone shelf, up to 12 miles wide, composes the Pamlico surface. This shelf lies near sea level at the modern shore line and rises inland to an elevation of 20 feet. The Tertiary limestones, Avon Park limestone, Moodys Branch formation, and Ocala limestone, have been eroded by fresh-water and marine erosion to rolling flat limestone plains. Irregularities produced by solution have been obliterated by a thin covering of Pleistocene sediments of Pamlico age. These sediments include beach coquina deposits, brackish-water sediments, sandy unfo.siliferous pasty limestones, fresh-water marls, and sand. Prior to this coating of Pleistocene sediments the limestone surface was doubtless made rugged with considerable relief, but the effect of the deposition of these sediments has been to level this surface. In the vicinity of the Suwannee River, sand bars have been deposited over the limestone by the river.
24 FLORIDA GEOLOGICAL SURVEY- BULLETIN 3-3
1 he lower coastal margins of the limestone shelf have been drowned by salt-water marshes. Here the limestone extends as peninsulas and islands into these marshes rising three to eight feet above the sediment in the marsh. Along the Pamlico coast line the limestone shelf is covered by the sand belt described above. The contact of sand on limestone is distinct, being marked by a small definite depositional escarpment which connects the gentle slopes developed upon the two belts.
Because the limestone shelf (see figure 6) is connected with the artesian water system, the water levels in the ponds and lakes of the coastal areas fluctuate greatly. During high seasonal rainfall the area is flooded, ponds, lakes and streams coalescing to form a shallow swamp. In periods of droughts most of the surface is dry and paved with rock but the discharge from the aquifer maintains swamps in shallow basins. This shelf is greatly fractured which, combined with the heavy discharge from ground water, gives rise to numerous clear water springs scattered throughout the hammocks. These are beautifully set in a tropical vegetation and are so located as to combine fresh water along the upper parts and brackish water along the lower parts of the channels, and both fresh- and salt-water species of fish inhabit some of the springs.
Virtually the entire belt of the Pamlico terrace, shown on figure 2 as limestone flatwoods and hammocks, is a continuous hammock, various portions of which have been designated by the principal streams that
Figure 6. Limestone of the Inglis member forming the floor of the coastal hammocks along State Road 55, U. S. 19, six miles north of Crystal River,
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 25
traverse them, such as Homosassa Hammock, Chassahowitzka Hammock and Gulf Hammock developed about Waccasassa Bay. These hammocks teem with game and fish and are valued as tourist attractions. Much of the timber of Florida, cypress, cedar, pine, tupelo, gum, maple, bay, cottonwood, willow, basswood, magnolia, poplar, oaks, hickories, walnut, ash, birch, elm, sycamore, palm and tropical vegetation, grows in such great abundance that the entire area is choked and virtually a cancpy of vegetation is developed.
Wicomico Terrace: Like the Pamlico terrace and the modern submarine plain, the Wicomico terrace is composed of a belt of sand developed along the Wicomico shore line, and a submarine limestone shelf, named the Chiefland Limestone Plain. The sand belt is developed along the western foot of the Tertiary Highland and Coharie-Okefenokee Sand Ridge. It enters Citrus County along its eastern central margin and trends northerly to the vicinity of Bronson, Levy County, where it merges with fluviatile sediments deposited along the valley of the Waccasassa River. The belt is about two miles wide for the most part, but broadens in southern Citrus County and up the valley of the Withlacoochee River. The terrace is bounded on the east by an escarpment rising onto the Coharie-Okefenokee Sand Ridge and to the west by the escarpment of the Pamlico terrace. These escarpments and the terrace surface are clearly evident on the aerial photograph of figure 5. Chiefland Limestone Plain: The limestone shelf that is associated with the Wicomico terrace is believed to have been preserved partly as -he Chiefland Limestone Plain. In the vicinity of Chiefland a flat rolling surface, figure 7, has been eroded upon Eocene limestones. The irregular erosional surface has been leveled by the deposition of fine argillaceous sand in the low places. Surface elevations range from about 40 feet at Chiefland to about 80 feet near the Waccasassa Valley. The relations of the elevations of the Wicomico limestone plain to its contemporaneous sand belt is comparable to the distribution of elevations upon the sand belt and limestone shelf of the Pamlico terrace and the modern submarine p!ain.
Coharie-Okefenokee Sand Ridge: A high ridge of unfossiliferous sand, having considerable relief, extends almost north and south across the eastern portions of Citrus and Levy counties. The sand ridge merges with and partly covers the high hills of Citrus County, which are composed of Tertiary sediments. No consistent elevations or definite terraces were apparent, although elevations were generally higher on the eastern side of the ridge. A maximum elevation of 220 feet was noted
26 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
Figure 7. The Chiefland Limestone Plain northeast of Chiefland. Levy County, in
the center of Township 11 South, Range 15 East. Photograph taken
on one hill in northern Citrus County. Here the sand covered the Suwannee limestone of Oligocene age.
The ridge is bounded to the west by the Wicomico terrace and its fluviatile equivalent and to the east by the Wiliston Limestone Plain in Levy County, and the Tsala Apopka Lake in Citrus County. The eastern boundary is much more irregular, and remnants of the sediments com'posing the ridge preserved on the lowlands along this boundary indicates that the ridge probably extended over these lowlands and has been removed.
The ridge is composed of Miocene (?) sediments of the Alachua formation, covered by thick deposits of late Pleistocene sand. The sediments and fauna of the Alachua formation indicate that they were formed under terrestrial conditions upon a very irregular limestone surface eroded prior to their deposition and subsequently greatly altered by the very erosive process of phosphate fixation, see pages 195 to 202. Erosion by phosphoric and carbonic acids formed numerous sinks that were partially filled by sediments of the Alachua formation.
Sands covering the irregular surface at elevations above 105 and below 220 feet and the presence of Pleistocene surfaces with shore lines at 150 and 220 feet throughout the State indicate that early Pleistocene seas deposited a thick cover of elastics over a broad area throughout the State. The greater portion of the sediments has been removed in these counties leaving a high ridge, the ground surface of which is sand.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 27
Phosphate fixation and the solution of limestone bedrock is continuing today and the entire ridge is marked by slumps and sink holes, the sediments forming the ridge being greatly distorted and the ground surface made irregular.
RIVER VALLEY LOWLANDS
The River Valley Lowlands covers all stream valleys in the two counties being found only along stream courses, and are very narrow except for the specialized broad valley of the Withlacoochee River in Citrus County and the Williston Limestone Plain in Levy County, a part of the Waccasassa River Valley Lowland. These two valleys are developed along the eastern portions of both counties, and lie east of the Tertiary Highlands and the Coharie-Okefenokee Sand Ridge.
A number of sluggish clear water streams cross Citrus and Levy counties, most of them flowing from high sand hill divides in a westerly and southwesterly direction to the Gulf of Mexico. Only two originate from outside the counties, the Suwannee River that borders the northwestern portion of Levy County and the Withlacoochee River that circles Citrus County along the southeastern, eastern and northern boundaries.
The Waccasassa River, Otter Creek, Cow Creek, Ten Mile Creek, Turtle Creek and Wekiva River in Levy County; Crystal River, Halls River, Homosassa River, and Chassahowitzka River in Citrus County, are the larger streams of those originating within the counties. These streams, as are the Suwannee and Withlacoochee rivers, are almost entirely spring fed (see Vernon, 1947, p. 18), and all but three originate in springheads. The Waccasassa River, Otter Creek, and Ten Mile Creek flow in their upper courses over sandy soils and rise from swamps and sinks as poorly defined and poorly connected channels that gradually develop into definite stream courses. Their waters are heavily charged with dissolved solids of surface origin, largely humic acids and organic muds, and differ from the clear spring water of the other streams. In the lower courses, their valleys are formed in limestone, the same as other streams of the area.
Each of the streams originating in a springhead rises from caverns that extend back into the limestone bedrock, and the upper portions of many of the stream channels appear to be collapsed caverns. From the springhead to the mouth each stream channel is formed in bedrock. These streams, together with the larger Suwannee and Withlacoochee rivers,
28 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
flow throughout much of their length in limestone channels that are broken by a maze of fractures and caverns, from which large flows of ground water issue. Levy and Citrus counties are located in a discharge area of the Florida artesian ground-water system.
Both counties have poor surface drainage, sand covered plains and hills and karst topography capturing the large part of the surface waters. Good surface drainage is present only along the coast, in central Levy County, and along the valleys of the two major streams that cross the area. Elsewhere ground-water drainage is predominate.
Stream Terrace Sediments
Stream terraces have been described in Florida by Vernon (1942) and their origin discussed. In Citrus and Levy counties patches of alluvium lie along the valley walls of the Suwannee River and the Waccasassa River well above the flood plains. These sediments occur at two definite levels and stream cut escarpments are present where the deposits are in contact. Each of the levels represent a period of alluviation at a time when the streams were adjusted or were adjusting to sea levels, higher than the present level.
The deposits that occur as sand bars along the Suwannee River Valley are narrow and extend up the valley somewhat parallel to the present flood plain. The bars have been well-preserved since their deposition because of their great porosity and resistance to erosion by surface wash. The deposits along the Waccasassa River are apparently unrelated to the modern river system. The lowest of these deposits is a large valley fill and delta that covers central Levy County at elevations from 20 to 50 feet above sea level. The valley is flat and gently sloping from its upper portion to the center of the county where the stream deposits merge with marine deposits of Pamlico age. The lower part of the valley was probably a bay and sandy limestones of possible bay origin are found interbedded with the alluvium. Alluvium is also preserved at altitudes of 100 to 120 feet above the sea level, along the west side of this valley, figure 2, covering a broad limestone plain in the vicinity of Newton, Florida. These sediments are believed to be remnants of a flood plain developed along a stream, larger than the Waccasassa River, that once occupied and developed the valley the Waccasassa now occupies. This flood plain occurs at levels comparable to the coastal terrace that is a part of the Wicomico marine plain developed when sea level stood at 100 feet above modern sea levels.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 29
Suwannee River Valley Lowland
The Suwannee River Valley, a narrow band of alluvium, thinly veneering limestone bedrock except at the mouth where the fill of alluvium is greater, extends along the northwestern boundary of Levy County. The river empties into the Gulf of Mexico at Suwannee Bay where the lower section of the valley is drowned and the flood plain is covered by saltwater marsh. The river carries almost no sediment other than fine muds and dissolved solids. During floods, fine to medium sand is reworked along the river banks and dropped as sand bars along the valley walls. Muds and dissolved solids are deposited along the lower reaches of the valley at its mouth and in Suwannee Bay.
The valley of the Suwannee River is a solution valley and -outcrops of limestone are almost continuous throughout its length. Thin sand bar ridges veneer the limestone bedrock away from the channel. This sand occurs at two definite levels above the flood plain and the river is presumed to have occupied its present course since the late Pleistocene. If sand bars of the Suwannee River were deposited during the early Pleistocene they have either been removed by marine planation, or they have been incorporated with other sediments from which they could not be separated.
Withlacoochee River Valley Lowland
The Withlacoochee River rises in Polk County and for the most part, throughout its course to the Gulf of Mexico, at Inglis, it flows on limestone and through a limestone-walled channel. A flood plain is developed only along its course in Citrus County, above Dunnellon, Marion County. From Dunnellon to the coast the channel is cut in limestone and only a thin veneer of highly organic mud has been deposited along its banks. Along this portion of the river the flats of the Terraced Coastal Lowlands continue without a break to the edge of the channel walls, the river having cut .a deep trench to the coast, modified by almost no alluviation. The mouth is drowned by Gulf waters and is mar' hy.
The river crosses the crest of the Ocala uplift in the vicinity of Dunnellon, and has had difficulty maintaining a course across it. The river is clearly antecedent and the fold of the Ocala uplift has ponded the river above Dunnellon to form the Tsala Apopka Lake. The valley below Dunnellon is a limestone solution valley and where it crosses the Coharie-Okefenokee Sand Ridge the banks are steep and the Alachua formation and early Pleistocene sands make a deep V-shaped valley, con-
s0 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
taining a deep alluvial fill composed of sediments re-worked from the Alachua formation and Pleistocene sand. Tsala Apopka Lake: Tsala Apopka Lake is part of a rolling plain area, up to 14 miles wide and 25 miles long, extending along both sides of the Withlacoochee River and gradually merging up stream in Hernando County with normal flood-plain topography. T his plain is part of a broad valley that is bounded by high sand hills to the southwest and northeast. The northeastern (right) side of the valley is a broad swamp broken by a few lakes, of which Lake Panasoffkee in Sumter County is the largest. The southwestern (left) side of the valley is a system of connected lakes, Tsala Apopka Lake, partially separated by rolling flat peninsulas and islands.
The land surfaces are composed of Eocene limestones, over which there is present a thin residuum of the Alachua formation, which apparently was once of much greater extent, and largely has been removed to form the valley. The land surface of the valley is one of considerable relief, the low places being filled with water and the high places being land, paved with limestone, predominantly the Inglis member of the Moodys Branch formation. Phosphorite, clay and sand of the Alachua formation thinly veneer the limestone and has filled fractures and sinks to considerable depths. Near the river and along abandoned river courses alluvium has been deposited, filling deep cut channels.
The water levels in lakes and swamps stand at elevations of 35 feet in the lower, and 45 feet in the upper part of the valley. Land elevations are commonly less than 60 feet but may rise to about 80 feet. The river is a few feet lower than adjacent swamp and lake levels in the lower part of the valley, but in the upper part the channel of the river is not clearly distinguishable from swamp and lake. The river meanders torturously through the upper Tsala Apopka Lake, the channel often being recognized only by relatively unobstructed water passing through dense cypress and other water growths. Where the channel is obstructed by hyacinths it is exceptionally difficult to locate and it is almost impossible to traverse the river. Numerous tributaries, the Panasoffkee River, Juniper Creek, Dead River and smaller streams contribute to the complicated pattern of channel crossings through the lake.
From a study of the stream patterns and the geology along the Withlacoochee River, it is evident that the river is antecedent, at least in part, to movements forming the Ocala uplift. The course of the Withlacoochee River, for the most part, is along the top of the Ocala uplift. It apparently has adjusted to the fractures developed along the crest
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 31
of the uplift, the course of the river paralleling the fracture pattern of the area, see figure 11. In the vicinity of Dunnellon the river departs from this pattern and heads westerly toward the Gulf of Mexico. This course is across the crest of the Ocala uplift and the river has cut a deep limestone-walled channel to the coast. The most striking feature of the upper Withlacoochee River is that the stream channel is not formed continuously in bedrock as it is toward the coast, instead deep alluvial fills more than 100 feet thick, reaching depths to 88 feet below sea level are present, see well W-1198 of figure 14.
This information indicates that the river was established along its present course by erosion of a deep valley cut into the Alachua formation and Eocene limestones. The river has meandered across its valley along the east flank of the Ocala uplift and has eroded a broad valley and filled it with alluvium. This ponded water has accelerated groundwater recharge to the underlying limestone bedrock. Solution of the limestone has created depressions throughout the valley, and these, together with flood plain lowlands, form the basins of the many lakes that occupy the valley.
There is no evidence of either erosion or deposition that indicates the river has occupied its position for any great time. Its valley is steep and V-shaped where it crosses the Coharie-Okefenokee Sand Ridge and no high level river terrace deposits are found along its valley walls, which suggests that the river was established during the late Pleistocene. If this is true, periodic structural movements along the Ocala uplift must have continued into the Pleistocene, although there is evidence that the major movement was during the Miocene.
Matson (1918, pp. 38, 84) used the name Tsala Apopka Terrace for a marine terrace surface lying between elevations of 40 and 60 feet, in the vicinity of Tsala Apopka Lake. In view of the evidence developed during the study of Citrus and Levy counties this surface is clearly fluviatile in origin and the abandonment of the name as a physiographic term by other writers is substantiated.
Waccasassa River Valley Lowland
The Waccasassa River rises as a poorly defined channel connecting swamps and tyty ponds in Gilchrist County. Along its upper course in Levy County the stream is a sluggish, poorly connected series of swamps, lakes and ponds that have formed in a valley up to three and one-half miles wide, see figures 8 and 9. Approximately two miles south of Newton, Levy County, this valley fans out, and one side extends westerly
32 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
toward Long Pond and breaches the Chiefland Limestone Plain at this point. The other continues southerly along the foot of the Coharie-Okefenokee Sand Ridge. The pattern of this widened valley and the sediments that underlie the flat surface exhibit characteristics of an alluvial plain, see figure 2. The limestone bedrock is buried 14 to 18 feet beneath cross-bedded sands and clays throughout the area.
Figure 8. Broad lake-filled valley now occupied and only partially drained by the
Waccasassa River. Photograph taken facing south in Section 13, Township
11 South, Range 16 East.
From the poiiut where State Road No. 34 crosses the river to the coast the river flows through a limestone-walled channel that is a trench cut by the river into the flat surfaces of the Terraced Coastal Lowlands and of the alluvial valley described above. Throughout its lower course the river is spring fed and has all the characteristics of other streams of the area. A modern narrow flood plain of organic muds and sand is present only in the lower portion where the river merges with the marshes formed by drowning of the mouth of the river.
In northern Levy County, northeast of Newton, the Eocene limestones are covered by a thin deposit of alluvium containing Pleistocene sands and sediment reworked from the Alachua formation, see figure 2, and limestone exposures are rare. This alluvium lies at an average elevation of 110 feet and is believed to have been deposited by a stream larger than the Waccasassa, see pages 33 and 36, that occupied the valley during Wicomico time when sea level stood at 100 feet, and the Chiefland Limestone Plain was a marine shelf.
Williston Limestone Plain: Over most of eastern Levy County, particularly in the vicinity of Williston where it is well-developed, there is a gently rolling limestone plain. Exposures of Eocene limestones are common and only a thin veneer of sand and residuum of the Alachua forma-
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 33
tion covers the bedrock. Pockets of phosphate of the Alachua formation, preserved upon this plain, were the sites of the early hard-rock phosphate mines in the area. The plain ranges in elevations from 60 to 80 feet with an occasional knoll rising to 100 feet. Shallow prairies, sinks and lakes mark its surface irregularly.
The plain has very irregular boundaries, being bound to the west by the Coharie-Okefenokee Sand Ridge and to the east by high sand hills composed of sediments similar to those of the Coharie-Okefenokee Sand Ridge. The plain is about 10 miles across at its widest and extends east and south into Marion County, narrowing and branching to the south. Toward the north in Alachua County the plain widens and branches to include Payne Prairie, other large prairies, lakes and much of the Arredondo quadrangle. The plain can be traced across the western portion of Alachua County into Gilchrist County where it joins the broad valley now occupied by Cow Creek and Waccasassa River.
In its pattern, sediments and physiography, this broad plain resembles the Tsala Apopka Lake region and is believed to have had a similar origin, to have been occupied once by a well-developed stream or stream system. This stream emptied westward into the Waccasassa River Valley Lowland prior to stream capture in that valley. Prairie Creek now emptying into Payne Prairie may have been this stream, which was captured by underground drainage. Its tributaries meandering down the eastern slope of the Ocala uplift could have removed in early Pleistocene time the unconsolidated sediments that covered the Tertiary limestone.
The broad and shallow valley present in northern and central Levy County that is occupied now by the Waccasassa River contains no definite and significant streams for the most part, and the width of the valley does not correspond to the size of the streams that occupy it, see figure 8. On the aerial photograph, figure 9, this valley can be traced from central Levy County across Gilchrist County to the Santa Fe River where it ends. The valley trends almost due north and south being slightly concave toward the east; and is bounded to the west by good farm land developed upon the undulating Ocala limestone plains and to the east by high sand hills composed of the Alachua formation and Pleistocene terrace sands.
The valley is flat and sandy and contains a maze of small prairies, tyty ponds, and small open lakes. Much of the valley is now drained underground by sinks and during heavy rainfall many of the swamps,
34 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
. .... .~ ~.......
Figure 9. Aerial photograph of a broad, poorly drained valley crossing Gilehrist
County into northern Levy County.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 35
prairies and lakes are connected. Some of the prairies and swamps are arcuate and enclosed and resemble old meander scars in pattern and distribution. This is particularly true in the vicinity of Franklin Sink, Gilchrist County.
The valley is drained in the north by Cow Creek and in the south by Waccasassa River and, for the most part, is not occupied by any definite continuous drainage. The two streams that drain the extremities of the valley are sluggish and swampy and are too small to have formed such a broad valley. It is presumed that the valley was once occupied by a large stream which has been beheaded by stream capture in the vicinity of its juncture with the Santa Fe River Valley, or that the stream may have been captured by underground drainage.
Stream capture and water diversion is not uncommon to the north in Columbia County, several dry stream valleys, such as Long Arm Hammock, being present." Likewise numerous collapsed-cavern water courses which connect between natural bridges are present in the county. These are prominent on aerial photographs of Columbia County, the Itchtucknee River and Olustee Creek with their subterranean connections being good examples.
The presence of confirmed dry stream courses in Columbia County suggests the possibility of stream capture in adjacent counties. Cow Creek is separated by an almost imperceptible divide from the swamps forming the headwaters of Waccasassa River, and its course is more clearly defined than that of the river indicating a higher gradient in Cow Creek, presumably the reversed portion of a larger stream with the Waccasassa River being the beheaded remnant. Cow Creek is also most peculiar in that it has a northerly course, whereas most streams of the area run south and southwest toward the coast. Each of these facts considered together indicate stream capture, but the valley may have resulted from the modification of a Pleistocene marine terrace and escarpment, since such a terrace and escarpment is known to be present along the east side of the valley. It is believed, however, from a study of the character and distribution of sediments of northern Levy County that once a large stream formed a delta (shown in figure 2) that extended over much of central Levy County forming a thin veneer of clastics on limestone bedrock. These sediments are cross-bedded sands and clays containing elements of the Alachua formation, presumably eroded from the eastern side of the valley along the base of the escarpment rising onto the Coharie-Okefenokee Sand Ridge of eastern Gil8personal communication from J. C. Simpson, February 7, 1951.
36 FLORIDA GEOLOGICAL SURVEY -BULLETIN .33
christ and Levy counties. This stream was probably the ancestor of the Waccasassa River, which remains as a sluggish stream, occupying a portion of a broad valley, largely abandoned.
The stream capture is dated by the Pleistocene history and sediments. The alluvium along the Waccasassa River merges with marine deposits of the Pamlico and Wicomico formations. A major stream obviously occupied the valley during Pamlico time when sea level stood at 25 feet. This is the youngest coast line in the area and is believed to be late Pleistocene in age. The stream capture probably occurred during entrenchment of streams into the limestone bedrock following the uplift of the land during the late Pleistocene and the last rise in sea level. If this premise is true, the date of capture would be early Recent.
PLEISTOCENE HISTORY IN FLORIDA
TERRACED COASTAL LOWLANDS
Many studies have been made and numerous publications covering terraces in Florida have been printed. The major contributions on terrace studies were summarized by Vernon (1942, pp. 15-18). From these studies two basic theories of terrace origin within the State have been developed. One theory proposes that these terxaces ~a entially marine planation surfaces cut during cyclic eustatic and permanent loweri sea levels throughoutthe Pleistocene epoch. These surfaces were cut 'oeinto lerertiary beds and a widely developed bed of clastic sediments, named the Citronelle formation of Pliocene age. In part these cut surfaces are thinly veneered by as much as 50 feet of reworked elastic and other sediments. In the mouths of streams that emptied along the coast of each marine surface, limited deltaic deposits were formed.
According to this theory the terraces are preserved because sea levels rising during interglacial stages never reached the position of an older stand of the sea and younger surfaces were cut at lower elevations. The progressive decrease in the elevations of sea levels throughout the stages of the Pleistocene resulted from greater deglaciation during early Pleistocene than during late. Additional stands of sea level were produced by the development of large oceanic deeps at various irregular intervals during the Pleistocene. 'i he formation of these deeps enlarged the oceanic basins and decreased sea levels throughout the world.
Cooke (1989, 1945, pp. 12, 13) is the principal proponent of this theory and has described up to nine surfaces, including the modern
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 37
submarine plain, that occur throughout the Atlantic and Gulf Coast States.
Four similar terrace surfaces occurring along the central Gulf Coast States have been described by Fisk (1938, 1940). These are stream terraces, the coastal ends of which are widely-developed deltaic plains. Each terrace. surface is aggradational and underlain by sediments that are characteristic of the terrace, being a depositional sequence of coarse elastics at the base and finer clastics at the top. This theory of terrace origin presents evidence that the surfaces are deposited as deltas and as alluvium in erosional valleys, each terrace being comparable to the present delta plains and flood plains of Louisiana today. Terraces were formed by adjustments of streams and coasts to eustatic changes in sea level resulting from cyclic withdrawals from and filling of oceanic basins during stages of the Pleistocene. Glacial stages were periods of lowered sea level, valley cutting and broader land areas. Interglacial stages were periods of elevated sea level, valley alluviation and flooding of land areas. Each terrace has been segregated by the tilting and uplift of the land adjusting to the extensive sedimentation of the Gulf of Mexico.
Evidence presented by Vernon (1942) and developed during the study of the physiography of Citrus and Levy counties does not allow the complete application of either theory in Florida. The topography of Florida is dominated by a series of uplifted broad flat surfaces that rise in step-like patterns from the coast inland to highlands composed of Tertiary and younger deltaic sediments. These flat surfaces or plains occur in four belts that extend completely around the State parallel io the modern coast. Each plain has a fluviatile 'terrace extension up the major streams of western Florida and sand bar deposits occur at comparable elevations along the streams of the Peninsula. Each uplifted plain contains upon it features of the modern submarine plain, and its fluviatile extension has features that characterize the modern stream flood plain and deposits, all in varying degrees of preservation.
The marine plains and fluviatile equivalents are separated by erosional escarpments and are considered to be terraces.
In Florida, auger holes and wells penetrating the Pleistocene deposits that underlie the terraces, indicate that the base of each rests upon an erosional surface, which lies at a lower elevation than similar cut surfaces, older in age. Each terrace surface is aggradational, except where Tertiary limestones have resisted erosion and have been planed off to the level corresponding to the elevation that the sea stood during the creation of the terrace. In western and most of peninsular Florida, where
38 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
abundant sediments were available and where the Tertiary formations were easily eroded, each surface is underlain by its unit formation. In Citrus, Levy and adjacent counties, however, the Tertiary limestones were not eroded and each surface is made up of belts of beach sediments and limestone planation shelves that contain in irregularities in the limestone, thin deposits of Pleistocene sediments. Along the most southern portion of Florida these Pleistocene terraces are represented by marine limestones and the erosional escarpments that bound each terrace are represented by fresh-water marls.
The terraces are thought to have been segregated by uplift of the State caused by adjustments to the filling of the Gulf by sediment, and through the progressive decrease in deglaciation from early to late Pleistocene.
The creation of the fluviatile terraces of Florida can be explained most easily by Fisk's valley cutting and subsequent alluviation theory, with the exception that there is present a high level delta plain, entirely disassociated with the streams that traverse the State, and there is present a very low alluvial terrace (Vernon, 1942, pp. 13, 14) which is not recognized by Fisk9. He recognizes, however, a low escarpment-bound, alluvial surface which has been referred to in Louisiana as "second bottoms" or "high level flood plains". It would seem logical that the same geologic controls and conditions creating Fisk's higher terraces would also most easily explain the formation of this low terrace.
Cooke, in a series of papers, has recognized nine terraces, one of which is covered by the modern sea, and one which he has not named1 and which corresponds to the Okefenokee Terrace of this report. Only four of these terraces are widely developed in Florida, and this writer has seen no evidence of a general development of terraces with shore lines at 270, 170, 70, and 42 feet. If these terraces of Florida were formed through the cyclic eustatic adjustments in sea level throughout the Pleistocene, a period of stream and sub-aerial erosion followed by a period of fluviatile and marine deposition, each marine terrace should have a fluviatile extension up the streams of Florida. Only four stream terraces are present and these merge with coastal terraces associated with former coast lines at 220, 150, 100 to 105, and 25 to 30 feet above the present sea level.
According to Cooke" additional terraces were formed over the states
9Personal communication, 1939.
'0Personal communication, 1942.
11Personal communication, 1942.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 39
of the southeast where sea level was lowered by irregular increases in the size of oceanic basins through the formation of deeps. There is no evidence of deep valley erosion along the streams of the Gulf Coast that would indicate stream adjustment to a permanently lowered sea level. Five erosional sub-valleys compose each of the modern stream valleys in the State, each of these sub-valleys in succession having been cut and then filled to form four terraces and a flood plain along the modern valley.
By definition, a terrace is a flat surface, either deposited upon or cut into bedrock, that is limited by definite escarpments. These surfaces and escarpments, because of destruction by erosion and of the development of slopes instead of escarpments along some bays, can not be uniformly and continuously present. However, they must be present throughout the State at intervals sufficiently frequent to establish their identity. For each coastal terrace there would be developed in the valleys of principal streams of the State a fluviatile terrace equivalent. Theoretically, the sea as it withdrew from off the land during a glacial stage stood for brief periods at all elevations from the position of its highest shore line to the position of its lowest shore line, located somewhere out on the continental shelf. The withdrawal of any of the Pleistocene seas was controlled by climatic conditions and brief periods of warmer climate during any glacial period may have stabilized sea withdrawals momentarily and allowed some reworking of sediments and deposition of sand bars sufficient to create some minor features which may have been interpreted as terraces. These features have no fluviatile depositional equivalents and are not universally developed as are the four terraces generally recognized by most workers.
Minor terraces such as Cooke's Sunderland, Talbot and Penholoway, which are not present in any area worked in detail by the writer, possibly represent temporary pauses by the sea in withdrawing from the land mass. The writer does not consider these to be representative of a cyclic period of erosion and fill, and therefore not terraces as used in this report.
The four Pleistocene terraces, composed of a marine plain and a fluviatile equivalent, together with a highlands delta plain as recognized by Vernon (1942) are shown in Table 5, with possible correlations of seven of Cooke's (1945) terraces and his Citronelle formation and of Fisk's four delta plains and his "high level flood plain and second bottoms". The terms Pamlico, Wicomico and Coharie have been used in this report for levels and deposits present in Citrus and Levy counties
TABLE 5.-Correlations of Pleistocene Terraces
Western Florida Citrus and
Fisk, 1940 Cooke, 1945 Vernon, 1942 Levy Counties, Florida Tentative Age Assignment (Elevations of shore lines in feet) (Elevations of shore lines in feet) Vernon, 1951 of Terraces in Florida Williana Citronelle fin. Delta plain Not present Early Nebraskan and posBrandywine, 270 sibly pre-Nebraskan
Valley erosion Valley and sub-aerial erosion Valley and sub-aerial erosion Nebraskan (glacial)
Bentley Coharie, 215 220 Deposits of Coharie, 220 Aftonian (interglacial)
Valley erosion Valley and sub-aerial erosion Valley and sub-aerial erosion Kansan (glacial)
Montgomery Sunderland, 170 150 Deposits of Okefenokee, 150 Yarmouth (interglacial) ;.
Valley erosion Valley and sub-aerial erosion Valley and sub-aerial erosion Illinoian (glacial) Wicomico, 100 Prairie Penholoway, 70 105 Wicomico, 100 Sangamon (interglacial) Talbot, 42 t I d Valley erosion Valley and sub-aerial erosion Valley and sub-aerial erosion Glacial stage
Second bottoms and high Pamlico, 25 30 Pamlico, 25 Interglacial stage level flood plains CID
Valley erosion Valley and sub-aerial erosion Valley and sub-aerial erosion Glacial stage
Modern delta Modern submarine plain Sea level Modern submarine plain Recent (interglacial) and stream food plains
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 41
at elevations comparable to those of Cooke. However, since Cooke recognizes no terrace at 150 feet, the term Okefenokee is preferred as used by MacNeil (1949) as a name for the terrace in Florida with levels below 150 feet.
STREAM VALLEYS IN WESTERN FLORIDA
In western Florida each of the stream valleys is composed of a series of uplifted flat surfaces that border the present flood plain and extend up stream valleys in step-like discontinuous patterns. These surfaces have been interpreted as the former flood-plain alluviation of valleys cut into older alluvium and Tertiary rock by the stream now occupying the valley (Vernon, 1942). Detailed work has proved that each of these surfaces is underlain by a definite depositional sequence, from coarse sand and gravel at the base to silts and clays at the top, and that each has present upon it features of modern flood-plain deposition such as natural levees and rim swamps.
The origin of such alluvial surfaces as a combination of cyclic Pleistocene eustatic changes in sea level and uplift was proposed by Fisk (1938) for Louisiana and was extended to Florida by Vernon (1942) with the application of the theory of progressive decreased deglaciation throughout the Pleistocene. Thus valleys cut during low sea level glacial stages were filled with alluvium as sea level rose with the melting of glacial ice during the interglacial stages. The continuous uplift of Florida throughout the Pleistocene that has progressively raised and separated these terraces, is presumed to be associated with the thick alluviation of the Gulf of Mexico, principally by the Mississippi River, and adjustment to this alluviation. Uplift does not account for the separation of the lower terraces, however, because these surfaces would be covered by alluviation if all the ice on polar caps should melt. It is presumed that more ice melted during the stages of the early Pleistocene than during the stages of late Pleistocene.
The modern flood plain and four depositional surfaces are associated with each major stream in western Florida. Each alluvial surface ends on a broad flat plain that extends all around Florida, the modern flood plain ending on th modern submarine plain and each alluvial terrace ending on a coastwise surface exhibiting marine characteristics.
STREAM VALLEYS IN CITRUS AND LEVY COUNTIES
Marine coastwise surfaces are present across Citrus and Levy counties, but alluvial surfaces are not present. At the elevations that alluvial
42 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
terraces are found in western Florida, only sand bar ridges have been deposited in the Citrus-Levy County area.
The bedrock of the area is essentially carbonates, greatly fractured and cut by caverns. The amount of dissolved solids in ground water indicates that the limestone is being continuously reduced by solution in surface and subsurface waters. During stages of the Pleistocene when sea level dropped, and streams in western Florida were excavating their valleys, the streams of these counties found it easier to drain through fractures and caverns into the underlying bedrock and did not excavate deep valleys. Subsequently as sea level rose during the interglacial stages, the limited sediment available to these streams was deposited in Levy and Citrus counties as sand bars, and the streams adjusted their channels to the uplift of the area through accelerated solution to form limestonewalled channels. In effect no valleys were cut during glacial stages to be filled by sediment during interglacial stages of the Pleistocene so that terraces have not been formed.
The word Key is a modification of the West Indian word cayo, meaning small low island, and is used in southern Florida for an island of any rock composition in marine waters. In Citrus and Levy counties these keys are composed of limestone thinly coated with sand or they may be essentially sand. Most of the keys of Cedar Keys and north to the Suwannee River are sand islands, the sand probably being reworked into bars and spits from deposition made by the river along its lower course.
The keys of the coast south of Cedar Keys are limestone islands, the entire coast being rocky. Islands are remnants and pinnacles of limestone, left after solution, which have been drowned by salt-water marshes. None of these are coral reefs, as found along the Florida coast to the south.
Tidal passes up to 15 miles long, and deep enough to traverse in shallow draft boats wind past the islands and connect the Gulf with spring fed streams emptying along the coast line.
Citrus and Levy counties are underlain by limestone and other calcareous deposits. Except for the portion covered by the Coharie-
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 43
Okefenokee Sand Ridge these deposits lie at or near the ground surface. The bedrock is greatly fractured and very porous and almost all the rain that falls in the area is absorbed by loose sand or is captured by solution holes and the fractured porous bedrock. These waters are highly charged with organic and carbonic acids and solution plays a conspicuous r6le in the development of the physiography of the area. The ground water that passes through these carbonates to emerge as springs or seeps carries in solution great quantities of mineral solids, since limestone is readily dissolved in organic and mineral acids contained in water.
Limestone is as a rule jointed vertically and bedded horizontally and openings along these joints and beds provide easy avenues of travel for water. The ultimate source of all of Florida's ground water is from the rain and precipitates from the atmosphere. As the rain water falls through the air it becomes charged with carbon dioxide gas that combines with water to form carbonic acid. On the ground humic acids from rotting vegetation is added. These are the common natural solvents of limestone. A good portion of this acid charged water soaks into the ground, and as it descends small portions of the rock are dissolved, but where the rock is saturated and bathed continuously in these weak acids, solution is most active. Because of the pressure of water entering the rock, ground water tends to move horizontally along bedding planes which offer the easiest exit. As it moves through pores and open spaces in the limestone it acts as a slow solvent to increase the size of the openings and to connect them to form a continuous system of channels. As these channels are expanded by solution, cave systems are developed horizontally and one system may lie over another and may be connected by vertical tubes and rooms.
These solution holes are formed principally while the limestone is saturated by ground water. Since many large caves and vertical tubes, now completely dry, are present west of Long Pond, south of Newton in Levy County and in the vicinity of LeCanto in Citrus County, it is obvious that the levels of ground water have been lowered over most of the area. The remains of land vertebrates of Pleistocene, Pliocene and Miocene ages (see pages 184, 192 and 212) that are found in deposits in the caves indicate that many were dry during at least some stages of these epochs. These caves are now being modified through the deposition of calcite along the walls and floors, to form icicle-shaped masses called stalactites that hang from the ceilings and more columnar masses called
41 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
stalagmites that extend upward from the floor, and pavement coatings along many of the walls.
As solution progresses, cavities of irregular shape are gradually cut out and enlarged. Some of these may expand to a point near the ground surface where surface deposits, largely sand in Florida, will collapse into the cavern and a sink hole is formed. The larger part of Florida's natural lakes, sinks, depressions and ponds are the result of the solution of limestone. The features range from small pits a few feet in diameter to large depressions several miles broad. Many are perfectly round, others highly irregular. Some are cone-shaped with rocky bottoms and walls, some have broadly-developed, sediment-filled flat bottoms and are known as prairies. Still others are vertical tubes, only a few inches in diameter in some cases, that extend as much as 100 feet down into the limestones. These are "natural wells", or solution pipes.
As Vernon (1947) has indicated, the generally accepted theses of the solution of limestone rarely include a conception of the effect of artesian water upon soluble aquifers such as limestone. Citrus and Levy counties are a part of a large artesian ground-water system, in which water gains entrance into a thick limestone aquifer in areas centered at Polk and at Pasco counties. The water is confined in these limestones under hydrostatic head and discharges in Citrus, Levy and other coastal counties. This water is heavily charged with natural acids and the active circulation through the aquifer removes large tonnages of rock. The solution holes thus formed are filled with water and where they emerge at the ground surface springs and seeps of water issue from them. Since artesian water is under pressure it tends to expand upward along joints and more soluble rock because of greater porosity toward the ground surface. The localization of this movement vertically may explain the formation of solution pipes and "natural wells", see figure 10. Where solution by artesian water removes a large section of limestone the overlying beds may collapse and create a sink hole, or the solution of the limestone may be more gradual and a spring opening may be expanded to the proportions of a sink.
Lakes in Citrus and Levy counties are largely water-filled solution depressions except for Tsala Apopka Lake and Long Pond, the basins of which originated as structural and fluviatile irregularities and were modified by solution. Water to fill the lake basins comes from local
GEOLOGY OF CITRUS AND LEVY COUNTIES, 2'LORIDA 45
Figure 10. Solution pipe formed in the Ocala limestone (restrLcted) and bisected
by the Levy Lime Rock Company quarry located at the Atlantic Coast Line Railroad in the southeast corner of Section 19, Township 12 South, Range 19 East. The clay filling has been washed out and deposited as
a cone at the base of the quarry face.
rainfall, local ground water, artesian ground water or a combination of these sources. Where the basin intersects the artesian aquifer, water will fill the basin to the elevation of the static water levels, and will flow if the rim of the basin is below the piezometric surface. Where the surface of the ground and the ground-water levels are approximately the same elevation, swamps are present along the low areas, and if this relationship is present in a basin, a prairie is formed.
46 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Many of the lake basins are located at the foot of Pleistocene escarpments along which irregularities localize the ground-water recharge and accelerate solution. Others are close to and are developed along welldeveloped fractures in the underlying limestone that provide channels for ground-water movement. In addition to physiographic irregularities, those created by structural movement also localize ground-water recharge.
Long Pond: The basin of Long Pond is of particular interest since it was formed by a combination of solution, structural movements, and Pleistocene erosion and deposition. The lake is located one mile south of Chiefland, Florida, in sections 7, 16 and 19, Township 12 South, Range 13 East, and is a slightly arcuate lake, two and one-third miles long and one-quarter mile wide. It lies along the western margin of the Waccasassa River delta plain that composes a portion of the Pamlico Terrace. The lake is bound to the west by limestones of the Moodys Branch formation exposed along the upthrown side of a fault that passes through the lake and makes a high escarpment along the western margin.
The lake basin extends along the foot of the escarpment to near the north end of the lake where a well-developed valley branches off and runs westerly toward the Suwannee River widening as it nears the river. This valley is walled with limestone but the floor is composed of a fill of sand and reworked Alachua sediments similar in lithology to that contained in the delta plains to the east. The sediments in the valley and brackish water deposits along the lake basin of Long Pond indicate that the area about the lake was a bay during Pamlico time, and that this bay was filled by alluvium deposited from the east by a large stream once occupying the Waccasassa River valley. The valley draining westerly from Long Pond and breaching the Chiefland Limestone Plain probably was occupied by a distributary of this stream. During extreme flooding today, the excess water from Long Pond drains through this valley.
The basin of Long Pond may have developed initially along the foot of the fault escarpment in irregularities of the ground surface, solution of the limestone bedrock possibly being accelerated by fracturing along the fault zone. The downthrown side of the fault would develop a wide and irregular basin, which apparently has been narrowed by alluviation and deposition of brackish-water sediments during the Pamlico stage.
Springs are of two types. In one the water is derived from local rainfall under ground-water table conditions, in which the water enters at a high
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 47
elevation and emerges along lower elevations in stream valleys and lake basins. In the other the water rises from depth under artesian head, the water having moved from some distance through the aquifer to emerge in these counties. The first type are generally small springs or seeps, but artesian water may issue as small springs, seeps and also as copious flows of water. Several large artesian springs are present in these counties and the water is beautifully clear and colored blue to green, the color depending on the depth of water and the degree to which light transmitted by the water is scattered by the water molecules.
Wekiva Springs, Fanning Springs and Manatee Springs, in Levy County, Homosassa Springs, Chassahowitzka Springs and springs in the head of Crystal River in Citrus County are the larger and more beautiful springs in the counties. Numerous seeps and springs in the coastal hammocks are sources of water for sportsmen, and hunter's camps are developed commonly at these sources. The channels of streams are a maze of springs and seeps issuing from out of the limestone bedrock. The springs are utilized in stock raising and as recreational areas, Manatee being a proposed State Park. Many are commercialized. Excellent descriptions of the large springs in the State were published in Florida Geological Survey Bulletin 81 in 1947.
Faulting has not been previously recognized in Florida and is mapped in figure 11, and on Plate 1, for the first time. The fracture patterns, shown as figure 11, were mapped from their physiographic expressions as shown on mosaics and contact prints of aerial photographs, available for each county except Orange, Taylor and a portion of Marion. They have been checked geologically in the core hole section along the proposed ship canal that crosses the western Peninsula at the Citrus-Levy County line, by surface geology, and by preparation of detailed geologic sections, figures 18 and 14 and a structure map, Plate 2.
In Citrus and Levy counties regional fractures parallel the axis of the Ocala uplift and locate the crest of the fold exactly. These fractures trend generally northwest-southeast. A secondary system trending northeast-southwest intersects this system at large angles and are irregularly spaced along the flanks of the uplift. Geologic sections crossing the Ocala uplift show that many of the fractures paralleling the axis of the fold are faults, but insufficient data are available on geologic sections crossing transverse joints to determine the displacement along these.
48 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Figure 11 illustrates a fundamental regional pattern made by the regular development of two systems of fractures trending northwestsoutheast and northeast-southwest. These are grouped irregularly at wide intervals of 20 to 30 miles to form a rough rectangular pattern where they intersect. Cross joints are only poorly developed along the crest of the Ocala uplift, but are strongly developed and numerous along the northwest plunge of the uplift in Jefferson, Madison, Hamilton and Suwannee counties and sharply delineate the northwestern limit of the crest of the fold. The southeast plunge of the fold is not as sharply marked. The zero contour of the Inglis structure, Plate 2, has been drawn on the map of the fracture pattern to illustrate the relationship of these fractures to the Ocala uplift.
The systems of fractures can be traced from county to county throughout the State and the northwest-southeast fractures appear to be the major system. However, two well-developed patterns of fractures are present that deviate from either of the systems described above. A particularly well-developed set of fractures, radiating in all directions from Union County, resemble in their pattern the fracturing that is present over salt domes of the Gulf Coast. Another system located in the southeast corner of figure 11 has fractures that trend more westerly and are somewhat more irregular in pattern. The geologic-control data in these areas are widely scattered and sufficient only to generalize on possible causes of these fractures. Applin (1951a) has recently published a critical analysis of the subsurface geology of the State. When the data he has developed are superimposed upon the fracture pattern (see figure 11) they indicate some possible causes. The dome-like patterns in Union County are located almost exactly over the area where Applin's peneplaned pre-Mesozoic surface has been folded into an anticline, named the Peninsular arch.
The distribution of possible pre-Cambrian crystalline rocks as mapped by Applin (1951a), corresponds remarkably well with the more westerly trending fractures shown in the southeastern corner of figure 11. It is probably more than coincidental also that Applin's boundary, believed to be a fault, separating Paleozoic sediments to the northwest from rhyolite, tuff and agglomerate to the southeast corresponds closely to the most strongly developed and distinctive northeast-southwest fractures mapped on figure 11.
If the fracture pattern can be assumed to reflect these ancient land ,masses, they must do so through several thousand feet of Cretaceous, Tertiary and, younger sediments. The thickness may in fact provide the
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 49
mechanism for such expression, in the adjustment of relatively unconsolidated sediments over structurally stable and fundamental land masses. 'ithe writer does not attempt to explain the association of these fractures with deeply buried structures, but the remarkably close relationship suggests such a possibility.
The regional fracturing associated with the Ocala uplift is believed to reflect structural movement during the late Tertiary. Stream patterns and sink alignment commonly parallel both the northwest and the northeast systems of fractures. Particularly well-developed expression of these joints or faults are shown by the control of portions of the valleys of the Ocklawaha, Withlacoochee and Kissimmee rivers, all of which show strongly developed, rectangular trends northeast-southwest and northwest-southeast with large angle turns. Some of the bay entries occur where fractures intersect the coast, the high sand areas of Polk and Hillsborough counties are bounded by strongly developed patterns, and most of the larger springs of Florida lie in or along these fractures. The fundamental pattern of joints and faults appears to be differential crustal shifts along straight line fractures. Judging from their distribution and alignment with the Ocala uplift the fractures are associated with land movements of a regional nature and the stresses forming the folds of the Ocala uplift created these joints and faults.
Considering the physical properties, low rigidity, high porosity, brittleness and inherent weaknesses of the poorly consolidated Tertiary limestones in which this fracture has occurred it seems impossible that the Ocala uplift could have been formed in any other way than by compressive stresses acting from the west against the Peninsular arch. When thus analyzed there exists an arch about 230 miles long by 70 miles broad which was gently folded and arched by compressive orogenic forces. During the time these forces were elevating this heavy mass of rock into an elongate anticline they were opposed by the weight of the rock and there were two vertical compressive shearing stresses that created horizontal tensional stresses at right angles to the compressive forces and to each other. The fractures mapped in figure 11, are believed to have formed under a combination of tensional stresses over the anticlinal flexure. The presence of tensional forces and stresses over folds is almost universally accepted although they are not recognized to be a local phenomenon. The compressive stresses effective all along the arch would tend to concentrate shearing parallel to the axis of the fold, although bulging along the flanks would have a similar effect. Most of the traces on the crest, parallel to the axis, appear to be shear faults of normal type. Primary tensile stresses would be developed parallel to the
50 FLORIDA GEOLOGICAL SURVEY BULLETIN 33
compressive forces. Because of inequalities in these forces secondary tensile stresses are developed at right angles to the primary tensile stresses. Thus tensile fractures would be most strongly developed along the axis of any folding and along the axes of flank bulges. This combination of stresses is capable of producing the regional fractures mapped in figure 11. The poorly consolidated sediments composing Tertiary rocks of Florida favor adjustments to strain by step fracturing rather than by bending.
Because the tensional and shearing stresses would be greatest over the up arched area of the Ocala uplift fracturing developed by them would tend to occur in groups along the axis of the fold and to indicate the direction of greatest stress and of the elongation of the arch. If these joints are tensional they would tend to die out with depth because stretching is greatest toward the outside and least toward the inside. Available geologic data indicate that only tensional fractures are present in the area and that these are shallow.
At least seven well-developed faults have been recognized in the geological section drawn along the proposed Florida Ship Canal crossing the State along the Levy-Citrus County line into Marion County, see Plate 1, and figure 14. Each of these faults can be readily traced on aerial photographs, on which they appear as continuous trough-like depressions and ridges marked by significant vegetation changes and soil colorations. These straight and continuous lines correspond exactly with the map positions of vertical displacements of twenty to one hundred and sixty feet along the section of figure 14. These vertical throws are distributed along many closely spaced parallel faults, the planes of which probably are inclined into the crest of the Ocala uplift. It was impossible to make measurements on the limited exposures of the fault traces, but the straight course of the faults across a very uneven topography suggest that the planes of the faults are inclined very steeply.
The broad flat crest of the Ocala uplift, the straight-line traces and presumable high dips of the fault planes, the inclinations of the fault planes into the crest of the fold, the grouping of several essentially parallel faults along the crest of the fold indicate that these faults are normal dip-slip shear faults that have formed graben depressions and horst ridges and flattened the crest of the Ocala uplift. The displacement in the faults is apparently essentially vertical since the traverse fractures are not interrupted where they cross known faults. The only indication of horizontal movement is an abrupt change in the trend of the strongly developed fractures running southwest from the Ocklawaha River Valley to the point where the southern line of Hernando County intersects the
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 51
coast. At the point where these fractures cross a fault near the southern boundary of Citrus County the trend changes abruptly to a more southerly direction and splits into three parallel joints. This change in trend makes an angle too small to show in figure 11 on the scale at which the map is reproduced but is evident on aerial photographs.
Following the development of the graben and horst structure, waste would be expected to accumulate on the low-standing blocks, and the fault traces would be concealed by sand and a residuum cover that masks the structure. A definite fault zone, however, is exposed on the northeast side of the Crystal River Rock Company quarry where the red sands and clays of the Alachua formation have been deposited up against and over large slump blocks, a fault breccia developed along one of these faults. Well-developed fractures are also rarely exposed at the surface because younger sediments cover them and mask the identifying features, but some evidence can be seen in joints exposed along the highway to Cedar Keys; along the old highway near Inglis in the center of the northeast quarter of Section 35, Township 16 South, Range 16 East, figure 12; and at Red Level where dolomitization has apparently extended along one of these fractures. It is not surprising that in a thick limestone section containing little close zonation and covered by conyf,,
Figure 12. Differential weathering along a fracture in the limestone of the Inglis
member, Moodys Branch formation, trending northwest-southeast as
exposed in Section 35, Township 16 South, Range 16 East.
52 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
siderable Pleistocene and Recent alluvium and marine deposits that these small faults have gone so long without being recognized. Under these conditions only a large fault would be obvious and it has been necessary to piece together small bits of evidence and to make careful observations and correlations to obtain a reasonably accurate structural pattern and history. There will undoubtedly be added by future explorations much data that may completely change the interpretation of the structure as described herein. Perhaps this description will serve as a basis for discussion from which the complete structural history of the area may be, developed.
In mapping the joint pattern an attempt was made to include all irregular trends whether poorly marked or well-developed, and to include only the well-developed trends running northwest-southeast or at right angles to this set.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 53
STRUCTURE AND SECTIONS
A well-developed regional anticline developed in surface rocks was described in a U. S. Geological Survey press release of 1920. The fold was exposed in eastern Levy County and was named the Ocala uplift. With the increased activity in prospecting for oil beginning about 1943, it was discovered that the structure of older and deeply buried sediments did not conform to the structure developed in Tertiary beds. The highest structure on Cretaceous and older beds was found to be centered under Union County, with the crest of the structure trending northwest and southeast from this area, paralleling the crest of the Ocala uplift. Largely because the crests of the two structures were parallel and perhaps for want of a better name, the Ocala tiplift was thought to be assymmetrical toward the east with depth and the term "Ocala uplift" was extended to include the structure of older beds.
The study of the geology of Citrus and Levy counties shows that the Ocala uplift crests in these counties and Applin (1951a, pp. 3-5) illustrated that the axis of the surface structure does not coincide with that of the subsurface structure and that no close structural relations exist between the two features. He has contoured the subsurface structure and named it the Peninsular arch. According to Applin (1951a, p. 3) the arch
"... is the dominant subsurface structural feature of eastern Florida and an adjacent part of southeastern Georgia. The anticlinal fold, or arch, which is approximately 275 miles long, trends south-southeastward and forms the axis of the Florida peninsula as far south as the latitude of Lake Okeechobee."
Applin showed conclusively that the deeper structure was formed during the Mesozoic and was covered by transgressing beds ranging in age from Lower Cretaceous through the Upper Cretaceous. Data are presented in the present study which definitely indicate that the area over the Peninsular arch was high through the Oligocene epoch and that the Ocala uplift was probably initiated during the lower Miocene epoch.
The term Ocala uplift is therefore restricted to its original usage to apply to the dominant structures formed in Tertiary beds, with the highest point of its crest located in eastern Citrus and Levy counties. Well data indicate that the two structures, the Ocala uplift and the Peninsular arch are not superimposed. Wells drilled on the crest of the Ocala uplift penetrate the Peninsular arch well down on its flanks, so that Tertiary beds which are structurally high overlie Mesozoic beds which are structurally low, and conversely wells drilled along the crest
54 FLORIDA GEOLOGICAL SURVEY- BULLETIN 33
of the Peninsular arch begin in Tertiary beds that are structurally low and end in older beds that are structurally high.
The structure map, Plate 2, has been drawn on the top of the Inglis member of the Moodys Branch formation. Controls are based on outcrops in Citrus and Levy counties and on well penetrations throughout the north and central portions of peninsular Florida. The map indicates that the Ocala uplift is not a simple, elongate, double-plunging anticline but that it is composed of four separate structures that have deformed Tertiary rocks. These structures include the crest of the Ocala uplift along the western Peninsula and structures named the Kissimmee faulted flexure, the Sanford high and the Osceola low in this report, Plate 2.
The term "Ocala uplift" appears to have been published initially in a press release dated April 19, 1920, issued by the U. S. Geological Survey. The release was a summary of oil possibilities in Florida based on a study of surface geology and cuttings from wells made by 0. B. Hopkins, and was summarized by Gunter in 1921. The term has been used to apply to dominant structural features of Florida since that time.
Hopkins' release clearly delineates that structure to which he applied the name "Ocala uplift". He stated:
".. the anticlinal fold . trends south-southeast, and forms the axis of the Floridian Peninsula. The axis of this uplift passes near Live Oak, 10 to 20 miles west of Gainesville, and an equal distance west of Ocala, and represents the southern continuation of the broadly anticlinal area of south-central Georgia. There are two high areas along this anticline. One, called the Ocala uplift, appears to have its highest part or crest in eastern Levy County, and the other near Live Oak. Of these, the Ocala uplift is the larger and structurally higher."
Hopkins' identification of the Ocala uplift was based on surface outcrops of Eocene limestone in western peninsular Florida and this work has been well substantiated by later studies. However, his identification of the "Live Oak uplift" was based on an inaccurate correlation of the Oligocene-Suwannee limestone exposed along the Suwannee River with the Miocene-Hawthorn formation cropping out at Live Oak, on an assumed and inaccurate estimate of the thickness of beds covering the Ocala limestone at Live Oak, on the apparently directed course of the Suwannee River where it circles Live Oak before continuing its southerly course, and on scattered well data which indicated that the Ocala limestone was high at Live Oak.
In later years detailed work on additional data proved the Ocala limestone had been extensively eroded prior to having been covered
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 55
by lower Miocene sediments and the "Live Oak uplift" was not substantiated by this work. Up until this report on Citrus and Levy counties was nearing completion Tertiary structure maps were drawn on the top of the Ocala limestone. The structures thus represented were merely reflections of highs and lows in Tertiary beds and were not truly representative.
Toward the completion of the work in Citrus and Levy counties it was possible to subdivide the Ocala limestone, and a very characteristic bed at the base provided an uneroded top, the contouring of which provided a more accurate map of Tertiary structures. The map is presented as Plate 2, and it indicates that in fact Hopkins was partially correct in depicting the Live Oak area as structurally high. The fault-flattened crest of the Ocala uplift present in Levy, Citrus, Sumter, Lake and Polk counties divides into two gentle folds, at the north Levy County line, the crest of one trending almost due north from this point and passing east of Live Oak, and the other continuing the northwest trend of the crest of the Ocala uplift. The courses of the Suwannee and the Santa Fe rivers have apparently adjusted to the slopes of the bedrock developed along the flanks of these two folds.
The data on the geologic-history of the Ocala uplift and the structure of surface beds can be illustrated best in cross section. The series of six sections presented as figures 13 and 14 cross the State essentially perpendicular to the axis of the Ocala uplift and of the Peninsula. Sections A-A', B-B', C-C', and E-E' are drawn along U. S. Army Engineers routes 7-A, 8-A, 12 and 13-B, alternate routes for the proposed Florida Ship Canal. The ground surface for these sections is taken from published reports of the U. S. Army Engineers, but the surfaces in sections AA-AA' and D-D', and the eastern end of C-C' are approximate. Excellent corehole records and rock samples are available along each of the proposed ship canal routes. These are generally quite shallow and deeper water wells have been projected into these sections along the strike of the Inglis member of the Moodys Branch formation, used as a structural control bed. Sections D-D' and AA-AA' have been constructed from the records of scattered water wells. Section AA-AA' extends easterly from Tallahassee to Monticello, Florida, and connects into section A-A' at well W-1596. The location of each section is shown on the index maps of figure 13 and figure 14.
These sections and the structure map, Plate 2, indicate that the Ocala uplift developed in Tertiary sediments as a gentle flexure, approximately 230 miles long, and about 70 miles wide where exposed in central peninsular Florida. The anticline is composed of two well-defined shal-
56 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
low folds, the more westerly being higher structurally, see figure 18 and Plate 2. Along the Florida-Georgia State line the east fold is separated from the west fold by a shallow trough, 54 miles wide. The folds converge southward and in Levy and Citrus counties they are separated by only a few miles and their crests are extensively fractured and faulted. The crests trend northwest-southeast through Levy and Citrus counties, but in Sumter, Orange and Polk counties they diverge, the east fold merging with a large fault block, named in this report the Kissimmee faulted flexure, and the west fold continuing in a south-southeasterly direction and gradually merging with the regional dip.
The development of vertical dip-slip faults, the traces of which parallel the crest of the Ocala uplift, tend to flatten the crest and to lengthen its cross-section. From the limited-core hole evidence available for this study the dip of the fault planes could not be determined, nor was it possible to estimate the extent of faulting at depth. There are numerous possibilities, one fault may terminate at depth against another or it may cross to form a graben and horst structure. Figure 14 is one interpretation of the geologic section along the proposed Florida Ship Canal and here a graben and horst structure is clearly indicated. The fault planes are drawn in at angles greater than 60 degrees and may be steeper. They are thought not to dip at angles less than 60 degrees because of the sttaight-line traces of the faults and because the closely spaced core holes do not penetrate any thinning or thickening of the beds.
THE KISSIMMEE FAULTED FLEXURE
Throughout an irregular area in the vicinity of Kissimee in Orange, Osceola and' Lake counties, wells penetrate a variable thickness of Miocene sediments lying upon the Avon Park limestone. The Moodys Branch formation, the Ocala limestone (restricted), and the Suwannee limestone are not present, although they occupy their normal stratigraphic positions in the surrounding areas. This high is the southern extremity of a wedge-shaped block that is approximately 90 miles long along its longest axis, 54 miles across the northwest border which is open, and 17 miles across the southeast margin, which ends at a fault forming the northwest boundary of the Osceola low. The block is tilted with the southeast end being upthrown, and it apparently has been rotated also, the southwest boundary being higher than the northeast and the outcrop pattern of the Avon Park limestone being extended along the southeast boundary. The beds within the fault block are greatly disturbed, many small folds and structural irregularities being present. Numerous irregular fractures, figure 11, are present throughout the block and at
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 57
least one well-developed fault, Plate 2 and section D-D' of figure 13, has been identified. Fractures appear to be concentrated toward the southeastern extremity.
The southern portion of the block appears to be a small anticlinal fold that trends west-northwest-east-southeast and terminates in both directions against a fault. The Inglis member has been thinned over much of the top of the block and removed from over the fold.
THE SANFORD HIGH
A semicircular area bordering the northeast boundary of the Kissimmee faulted flexure in the vicinity of Sanford, Seminole County, is similar to the southeastern extremity of the Kissimmee faulted block in many respects. Wells here penetrate the Avon Park limestone beneath a thin veneer of Miocene sediments. The structure appears to be a closed fold that has been faulted, the Sanford high being located on the upthrown side of the fault. The Inglis member of the Moodys Branch formation has been thinned by erosion along the flanks of the fold and removed from off the crest.
The similarity of the structures forming the Kissimmee faulted flexure and the Sanford high, the presence of a fault separating them, and the reconstruction of the stratigraphic section imply that the structures were once continuous and have been offset by faulting and subsequently eroded and covered by Miocene sediments. The reconstruction of the pre-Ocala land surface and of this anticline indicate that it trended westnorthwest across the Peninsula and possibly connected the outcrop area in Citrus and Levy counties. The presence of a structural high in and near these counties during the early Eocene is indicated by the extensively cross-bedded limestones of the Inglis member that were formed as shallow-water marine deposits that covered a land mass composed of the Avon Park limestone. This land mass is also indicated by elements of the Avon Park limestone reworked into the base of the Inglis member and by an unconformity present at the base of the Moodys Branch formation.
The faults bounding the Kissimmee faulted flexure cut all beds of Eocene age and the irregularities created by erosion have been filled by Miocene sediments. The age of these faults can thus be dated as postEocene and pre-Miocene.
THE OSCEOLA LOW
The Osceola low is a wedged-shaped downthrown k bounded on the northwest and east by normal faults, and open on -1 southwest. Three wells, Florida Geological Survey wells W-1728, W-1749 and
58 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
W-1770, located in the northeast extremity of the low, penerate the Inglis member at depths ranging from minus 412 to minus 482 feet. The Inglis member lies below a normal thickness of the Williston member, 50 feet of Ocala limestone and a very thick section of Miocene sediments, up to 850 feet thick. 'This depth to the Inglis member contrasts with the penetration of the bed at depths less than 200 feet to the east
and the absence of the bed along the fault block to the northwest.
The base of the Miocene contains no identifiable reworked fragments
of Eocene sediments. The absence of these implies that the faulting was probably associated with movements that formed the Ocala uplift but the faulting is younger than that which created the Kissimmee faulted flexure and Sanford hirh
STRUCTURES WITHIN CITRUS AND LEVY COUNTIES
Citrus and Levy counties are situated upon the crest of the Ocala
uplift and the regional dips of the Tertiary beds are southwest and northeast along the flanks and northwest and southeast along the plunge of this broad elongated arch, see Plate 2, figures 18, 14, and 15. The dips are slight, the regional average approaching nine feet per mile on the flanks and three feet per mile along the plunge, but dips greater than
these are present locally along small folds and in faulted blocks.
The Ocala uplift has been breached by erosion in these counties and
the Avon Park limestone of middle Eocene age is exposed in an irregular dendritic pattern in southern and central Levy County and in northeastern Citrus County, see Plate 1. Younger beds of Eocene age crop out in a concentric pattern about the Avon Park limestone. These ribbons of outcrop are interrupted by horst-graben normal faults and outcrops have been extended along the faults irregularly. In western Levy County and west-central Citrus County two small sharply raised domes are indicated by annular outcrop bands. These two domes and three major faults crossing the counties are named and shown in figure 15. Smaller graben and horst faults are well-developed but have not caused significant changes in the regional outcrop pattern and although mapped on Plate
1 and Plate 2 they are not shown on figure 15 and are not named.
There are included under this term two areas in which the outcrop
patterns are annular. These small domes have comparatively narrow diameters and very slight dips. They may in fact be only minor flexures in the folds forming the Ocala uplift. There is a possibility that they may be the expression of deeply buried domes. Almost nothing is known about their subsurface characteristics and until they are prospected in
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 59
detail the features are tentatively called domes because of their outcrop patterns.
Homosassa Springs Dome: This dome is located just north of Homosassa Springs in Citrus County. It exposes the Inglis member of the Moodys Branch formation and is circled by a band of the Williston member of that formation. The dome is about five by three miles, and adjoins a small basin in which the Ocala limestone (restricted) is exposed and the Crystal River springs are located. The northeast margin is bound by a small graben, the southeast fault of which is exposed in the Crystal River
, ~ 7
POND oBRONSON )4 I
SPRINGS DOME A
QHOMOSASSA IVRE~ SPRINGS
5 0 5 10 Miles
Figure 15. The Principal structures in Citrus and Levy Counties.
60 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
-Rock Company quarry, located in Section 6, Township 19 South, Range 18 East.
The West Levy Dome: A small dome in western Levy County is exposed as an island in the broadly developed hammocks along coastal and Suwannee River lowlands. The area occupied by the dome is an outcrop of the Inglis member and it is surrounded by a broad outcrop of the thin Williston member of the Moodys Branch formation. The broadness of the Williston outcrop implies very gentle dips westward, and the dome is of little significance. Little is known of its subsurface characteristics but the attitude of the beds could be determined by shallow prospecting.
The general development and description of fractures and faults is given on pages 47 to 52. In Citrus -and Levy counties sufficient details have been accumulated to identify three major fault zones that are named the Bronson graben, the Inverness fault and the Long Pond fault.
Bronson graben: The graben upon which Bronson is located, is based on studies of outcrops in which the Ocala limestone (restricted) was identified within the graben, although older Eocene beds border it over much of its extent and apparently end abruptly along its borders, indicating faulting. In addition, well W-1870, at Bronson, bottomed in Ocala limestone (restricted) at minus 87 feet without penetrating the Moodys Branch formation, although well W-1633 about six miles southeast penetrated this formation at 40 feet above sea level. The Moodys Branch formation is exposed throughout a broad area west of Williston and over a much broader area west of Bronson at elevations exceeding fifty feet above sea level. The structure map, Plate 2, can be resolved only if a graben or deep fold is placed across Levy County. The graben appears to be the most logical of the possibilities and its bounding faults are drawn along fracture traces as recorded on figure 11. Inverness fault: The fault near Inverness is based on outcrops along the Tsala Apopka Lake. The exposures of bedrock here and those uncovered by phosphate mining in the area east of the fault are all limestone of the Inglis member, Moodys Branch formation. These exposures lie at elevationds of 28 to 50 feet above mean sea level whereas five wells, W-874, W-1'167, W-1791, W-1847 and W-1848, all located on the southwest side and within two miles of the fault, indicate that the Inglis member lies at elevations ranging from minus one in the south to plus 37 feet in the north. Numerous exposures of the Williston member of the Moodys Branch formation, the Ocala limestone (restricted) and the Suwannee
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 61
limestone on the hills southwest of the fault indicate comparable displacements.
The northeast block has been tilted in faulting, the southeastern portion being upthrown with a displacement of as much as 50 feet, whereas the northwest portion is downthrown with displacements as much as 20 feet. The fault could be traced northeast into the Avon Park limestone outcrop where it is either obscured or the structure absorbed by possible incompetent beds.
Long Pond fault: This fault is the major fault in the area, and as much as 160 feet of displacement has been recorded, see section E-E', figure 14. The fault is well exposed at Long Pond. Southwest of the lake on the upthrown block, the Inglis member of the Moodys Branch formation crops out on hills as hicgh as 85 feet above sea level. The outcrop patterns of both members of the Moodys Branch formation are extended northwest along this fault on the upthrown block. One and one-half miles east of Long Pond on the downthrown block a dug well, located in the northwest quarter of the northeast quarter of Section 8, Township 12 South, Range 15 East, penetrated the Williston member at a depth of approximately sea level, indicating a minimum displacement of 50 feet. Near the Levy-Citrus County line the Long Pond fault trace is paralleled by a series of small faults. It is believed that the fault planes of these converge and have formed minor horst-graben structures. In Citrus County the Long Pond fault is either obscured within the outcrop of the Inglis member, the displacements along the fault being too small to breach the formation, or the fault ends abruptly in the area.
DATES OF STRUCTURAL MOVEMENTS DEFORMING TERTIARY BEDS
Several portions of the geologic history and stratigraphy help in dating the structural movements that have formed the Ocala uplift and related structures. Some evidence is contained in the unconformity at the base of the Moodys Branch formation and in the overlap of this formation upon the Avon Park limestone in the outcrop area. The fault zones that bound the Kissimmee faulted flexure cut beds as young as the Ocala limestone (restricted) and are covered by lower Miocene sediments. The adjacent Osceola low contains a very thick fill of Miocene sediments, figure 33, which contain no identifiable residuum derived from the erosion of the limestones exposed over the Kissimmee faulted flexure.
Along the east side of the Florida Peninsula the upper Eocene and Oligocene sediments are thin to absent when compared to the thickness
62 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
of these sediments over the crest and on the southwestern flank of the Ocala uplift, the structural high in Tertiary rocks today, see sections of figures 13 and 14. In Brevard, Orange, Seminole, Volusia and Flagler counties, as shown in sections C-C' and D-D', the Ocala limestone (restricted) and even the Moodys Branch formation are absent and the Miocene rests directly upon the eroded surface. This unconformity continues northward into Georgia along the coast, where the Oligocene is absent and the Hawthorn formation of lower Miocene age rests on the Ocala limestone.
The Eocene and Oligocene beds are thin along the eastern coast line of Florida even though the area is structurally low. The thinning of these beds corresponds roughly with the crest of Applin's (1951a) Peninsular arch, and the thinning and removal of Tertiary beds, apparently from erosion, across the crest of this arch suggests that the eastern part of the Florida Peninsula was high throughout the post-Oligocene, and that the movements forming the Ocala uplift are post-Oligocene and pre-Miocene in age. The inclusion of some basal Miocene beds in faulting along the Ocala uplift, see section E-E', the overlap of a very eroded limestone surface and the wedging out of Miocene sediments against the Ocala uplift, see sections of figures 13 and 14, dates these movements fairly definitely as lower Miocene in age. However, some of these structural movements may have continued irregularly throughout later epochs, see pages 29 to 31.
The Hawthorn formation is a wedge-shaped deposit, excessively thickened toward the northeast and south, overlapping and pinching out onto the structures composing the Ocala uplift. From the evidence presented in the sections and structure map the structural axis in Tertiary beds through at least post-Oligocene time coincided with the axis of the Peninsular arch and was located along the eastern seaboard. A secondary axis may have been present during the late Eocene, extending more westerly across the central Peninsula from Seminole County to Citrus County, see pages 56 to 57.
Following an extensive period of post-Oligocene erosion Florida was flooded by lower Miocene seas. The sequence of beds in the Miocene indicate that these seas transgressed upon the Ocala uplift by a series of overlaps and Miocene deposits pinch out against a well-developed erosional surface. This transgression was apparently accompanied by downwarping of the eastern and southern portions of Florida and the elevation of the Ocala uplift along the western Peninsula. Evidence presented under the discussion of the Alachua formation, pages 195 to 200, indicates that a large area situated upon the Ocala uplift was land throughout the Miocene period, and was never covered by Miocene seas.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 63
The knowledge of Florida stratigraphy and structure was pioneered by J. A. Cushman, W. H. Dall, E. H. Sellards and Herman Gunter. In particular, Dall and Cushman deserve recognition for their identifications of the faunas of the different formations upon which much later stratigraphic work was based. Cushman (1919) recognized the major subdivisions of the Oligocene and Eocene and provided much of the early identifications of foraminifers. Dall (1890-1908, 1892, 1894, 1897, 1915) recognized much the same subdivisions and his identifications of mollusks were most important in the later classification of beds ranging from Eocene to the Recent.
Cooke (1915) determined the Ocala limestone to be Jackson in age. Sellards (1919), based his stratigraphy on fossil identifications of Cushman and Dall, prepared a sketch map of the geology and structure of Florida and recognized the major stratigraphic subdivisions and regional Tertiary structures of the State in a generalized fashion. This work was amplified by Sellards and Gunter in 1922.
Important studies of stratigraphy and structure were presented by Stuart Mossom (1926) in which the first structure map of Florida was issued, the contours being drawn on the top of the Ocala limestone; Herman Gunter (1928) announced the discovery of "basement rocks" in a Marion County oil test well; Cooke and Mossom (1929) described the surface geology of the State; Gravell and Hanna (1988) described and figured several important guide fossils and recognized several zones in the Tertiary, useful for correlation throughout much of the Gulf Coast; Robert Campbell (1939) announced the discovery of Lower Cretaceous beds in a deep oil test drilled in Monroe County, based on the identification of foraminifers by E. R. Applin; Robert Vernon (1942) prepared a report covering surface outcrops in Holmes and Washington counties, Florida; Cole (1938, 1941, 1942, and 1944) in studies of wells drilled in the State described and figured numerous species of Foraminifera, and contributed to the knowledge of the subsurface stratigraphy. His 1942 study was of the Florida Oil Discovery-Sholtz and the Suwannee Petroleum-Sholtz wells in Levy County, during which he subdivided the Eocene section into an upper, middle and lower Eocene. He proposed his Cedar Keys formation for the lower Eocene in his study of 1944. The Applins (1944, 1947) and Applin and Jordan (1945) contributed to the
12Previous studies have been summarized by the Applins (1944, pp. 1674-77). These are briefly listed here, with additions of work completed since 1944.
64 FLORIDA GEOLOGICAL SURVEY -BULLETIN 83
knowledge of the subsurface stratigraphy of the State. They described and figured numerous species of Foraminifera, prepared excellent lists of guide fossils, subdivided early and middle Eocene and the Cretaceous and illustrated their studies by numerous sections and maps; Paul Applin (1951a) recognized and named a deeply buried structure in rocks older than the Mesozoic and subdivided these rocks into three general classifications; crystalline rocks of possible pre-Cambrian age, Paleozoic sediments, and possible Paleozoic volcanics. His study is an important contribution to the knowledge of the early geologic history of Florida, fundamental to the later geologic history.
Early in 1948 the writer found an exposure of dolomite south of Gulf Hammock, Levy County, Florida, in which he found numerous casts and molds of specimens of Coskinolina and Dictyoconus. These he believed at the time represented beds older than the Ocala limestone. Both the writer and Sidney A. Stubbs, formerly with the Survey, prepared in 1943 well logs in which beds of middle Eocene, "The Coskinolina zone", were recognized. David Ericson (1945), working with the geologists of the U. S. Army Engineers, recognized beds which he believed to be equivalent to the Avon Park limestone and named surface outcrops the "Gulf Hammock formation". The study of the geology of Citrus and Levy counties was begun in 1946.
FLORIDA GENERAL STRATIGRAPHY AND STRUCTURE
The rocks that compose Florida are a portion of the Floridian Plateau, which has apparently always been part of continental masses, since the oictest seiments penetrated by deep oil test wells are shallowwater marine deposits formed on continental shelves and no sediments fdrmed in-deep oceanic basins are present. The sedimentary section of peninsular Florida consists essentially of fragmental and pasty marine limestones, sandstones and shales reaching a known cumulative thickness in excess of 18,000 feet. Only three deep wells have penetrated crystalline rocks in Florida, granite was cut by the Humble Oil and Refining Company, Carroll well No. 1 in Osceola County, by the Oil Development Company, Arnold well No. 1 in Lake County and hornblende diorite by the Sun Oil Company, Powell well No. 1 in Volusia County. Because of their stiacigraphic position and crystalline texture, Applin (1951a) believed that the diorite is questionably pre-Cambrian and the others either pre-Cambrian or Paleozoic intrusives. From Mr. Applin's study it can be inferred that the core of the Floridian Plateau is pre-Cambrian and that upon this rather poorly defined area dominantly marine Paleozoic sediments, ranging in age from late Cambrian or early Ordovician to
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 65
Devonian, were formed. Twenty-seven deep wells in the State have cut sandstdnes of the lower and middle Ordovician series, the Stanalind Oil and Gas Company, Perpetual Forests, Inc., well No. 1 in Taylor County penetrating a thickness of 2,250 feet of these sandstones. Three wells cut black shales and sandstones bf Lower Devonian or Upper Silurian age, the Humble Oil and Refining Company, J. P. Cone well No. 1 in Columbia County penetrating a thickness of 906 feet of these sediments. These Paleozoic rocks were subsequently exposed to erosion and were folded, possibly faulted and preserved in structurally low regions throughout an extensive erosional period.
Ths eroded pre-Mesozoic surface, as described by Applin (1951a), is highest in an arch centered at Union County, Florida. This structure trends south-southeastward and was named the Peninsular arch. Folding was accompanied by downwarping in southern Florida, and a thick deposit of marine and deltaic sediments, largely carbonates, ranging in age from possible Triassic to Recent, formed upon this land mass. Applin (1951a), recorded that an extensive submergence began at the south end of the Peninsula during the early Cretaceous and possibly Jurassic. This is indicated in the Gulf Oil Corporation, State of Florida Lease 373, well No. 1 on Plantation Key, Monroe County, which penetrated more than 15,000 feet of limestone, dolomite, and anhydrites of Tertiary, Upper Cretaceous, Lower Cretaceous and possibly Jurassic ages, whereas the Sun Oil Company, Ruth M. Bishop well No. 1 in Columbia County penetrated only beds of Tertiary age and those equivalent to the Austin of the Upper Cretaceous. The submergence apparently advanced northward along the Peninsula because the series of wells north of Sunniland, Collier County, in which the beds of Trinity age are penerated at 13,000 feet show that beds of Trinity, Fredericksburg and Washita age overlap and encroach progressively upon the floor of eroded pre-Mesozoic rocks. These definitely marine beds interfinger northward into a elastic facies of red and green shale, sandstone and siltstone that occupies the south flank of the Peninsular arch and are correlatives of Trinity to Washita sediments (the Comanche series of the Lower Cretaceous), see figure 16, section-, B-B'.
The Peninsula of Florida was covered by shallow marine waters throughout the period extending from the Paleocene to the Recent, except for brief periods when it stood as land and was weathered and eroded. Except for the sediments of Miocene to Recent age these deposits are composed essentially of carbonates, with thin beds of evaporites, sandstone and shale.
In general the Tertiary sediments of the State are composed of two
66 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
depositional facies, an essentially marine and carbonate facies and a more shallow-water elastic facies, a small proportion of which is also marine. The coastal plains of western Florida and states westward to Texas have been in general a region of active deltaic sedimentation. On the other hand peninsular Florida, removed from large streams and continental sedimentation is dominantly marine. The two extremes merge through interfingering phases in the coastal areas of Alabama, western Florida, and northern-central Florida. As the Applins (1944, pp. 1679-80) stated:
On the one hand, west Florida and southern Georgia are occupied by
a elastic facies which is similar in its broader aspects to the sediments of the Western Gulf Coastal Plain and is composed largely of sand and shale with some limestone and chalky marl. On the other hand, over most of the peninsula, the sedimentary section is almost continuous limestone from the top of the Oligocene into the Lower Cretaceous . In northern Florida and in the north quarter or north third of the peninsula, the limestone and elastic facies grade laterally into each other. In general, with the passage of time, the limestone of the peninsula encroaches upon the elastic facies, spreading northward in successive stages . In general also, the foraminiferal microfaunas of the elastic facies resemble those present in formations in the western Gulf Coast, whereas the microfaunas of the limestone facies in the peninsula from the top of the early middle Eocene to the top of beds of Taylor age resemble those of Cuba, the West Indies, Mexico, and Europe, with only few species present that are known in other places in the United States. Species of ostracods and bryozoans show a like dissimilarity with those found in western faunas. Beginning with the top of the beds of Taylor age in the peninsula, the more familiar Gulf Coast microfaunas again appear. Some mingling of faunas of the two facies has been noted in a few wells in north Florida in the early middle and lower Eocene, but none in the Paleocene or late Upper Cretaceous. The fauna of the Lower Cretaceous limestones of southern Florida again resembles that found in certain derived deposits in Cuba and also that of the El Abra limestone of southern Mexico (Cenomanian-Albian) there
designated as Middle Cretaceous."
GENERAL STRATIGRAPHY OF CITRUS AND LEVY COUNTIES, FLORIDA
Oil prosrnect hqve nowhere in Citrus and Levy counties passed through beds older than Paleozoic. In Levy County, the Coastal Petroleum Company's James B. and Julian P. Ragland No. 1 well bottoms in beds believed to be Upper Silurian or Lower Devonian, and the Humble Oil and Refining Company's C. E. Robinson et ux No. 1 well and the Sun Oil Company's J. T. Goethe well No. 1 ended in sandstone of the Middle Ordovician.
The data from these wells indicate that Cretaceous beds lie directly on beds of Paleozoic age, separated by an unconformity representing
TABLE 6.-Geologic Formations in Citrus and Levy Counties, Florida
Era System Series Formation
Recent Sand, peat and clay, unnamed Lake Flirt marl, of late Wisconsin glacial stage
Pamlico formation, of Peorian E age
a Wicomico formation, of Sangamon age
Okefenokee formation, of Yarmouth age
Coharie formation, of Aftonian age
MAlachua formation iTerrestrial Hawthorn formation Marine
Oligocene Suwannee limestone Ocala limestone, of Jackson age Williston member S Inglis member Avon Park limestone, of Claiborne age
Lake City limestone, of Claiborne age
Oldsmar limestone, of Wilcox age
Paleocene Cedar Keys formation, of Midway age
Lawson limestone, of Navarro age
Beds of Taylor age U Beds of Austin age Bd of Eagle Ford age
;4 Beds of Woodbine age Comanche? Undifferentiated shale and sand, "red beds"
Triassic? Quartz diabase, possible sill?
Upper Silurian Possible fault contact
A Lower Ordovician
68 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
several geologic oeriods, see figure 16, section A-A'. This would indicate that the western peninsula of Florida was land for a long period prior to deposition of the Cretaceous beds. This and the geologic history as interpreted from well penetrations imply that these counties have been a part of a structurally stable land mass which was gradually covered by overlap of Cretaceous and younger sediments. The area, essentially a peninsula since the early Cretaceous, was a shoal, surrounded by deeper water, or land that separated the Gulf from Atlantic waters.
The sequence of formations, penetrated by wells, and those exposed at the ground surface of Citrus and Levy counties is given in Table 6.
The deeper oil prospects in Citrus and Levy counties bottomed in beds believed to be Lower Ordovician and Upper Silurian or Lower Devonian in age. However, several wells drilled as oil tests in the State have penetrated additional Paleozoic sediments. Dr. Josiah Bridge and Dr. Jean Berdan have been engaged during the past two years in a study of these beds. They have completed their study and have been kind enough to prepare for inclusion in this paper some notes on the Paleozoic strata of Citrus and Levy counties.
Since no copnlusions can b, drawn on th9 limitd information available from the samples taken from the three wells that penetrate Paleozoic sediments in these counties, and time has not permitted a critical study of wells outside these counties, the paper by Drs. Berdan and Bridge is presented here.
PRELIMINARY NOTES ON THE PALEOZOIC STRATA BENEATH
LEVY AND CITRUS COUNTIES, FLORIDA
By Jean Berdan and Josiah Bridge
Three deep wells drilled in southern Levy County in search of oil encountered early Paleozoic strata lying unconformably beneath Mesozoic rocks. Data on these wells are summarized in Table 7. No other deep wells in either county have reached Paleozoic rocks, but they have been encountered in a number of wells in the counties lying immediately to the north and east of Levy County and in a single well in Hernando County, directly south of Citrus County. From this it is reasonable to assume that both counties are underlain by Paleozoic rocks, and evidence from other areas indicates that they are quite thick. Still farther to the south and southeast several wells pass directly from Mesozoic sediments into crystalline rocks of various types that are believed to be of Pre-Cambrian or early Paleozoic age.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 69
The top of the Paleozoic rocks in southern Levy County lies at depths between 8960 feet (Goethe) and 5792 or 5810 feet (Ragland) below sea level, and this taken in conjunction with the elevations of the top of the Paleozoic in wells in adjacent counties indicates the presence of a well-developed peneplane surface on the Paleozoic rocks. This surface slopes gently southwest from an elevation of about 3500 feet below sea level in the northeastern part of Levy County to around 7000 feet below sea level in the southwestern part of Citrus County; the average slope of the surface being about 100 feet per mile, or slightly more than one degree (see Applin, 1951, p. 4).
The Ragland well cut about 40 feet of soft, laminated, somewhat silty, finely micaceous and pyritic, very dark gray to black shale, of which only the bottom 10 feet was cored. This bottom core contains a poorly preserved fauna consisting of crinoid stems, hyolithoids, cephalopods, pelecypods (probably Actinopteria) and a few other forms. A similar association of fossils in a better state of preservation has been found in the Humble Oil and Refining Company's J. P. Cone No. 1 well, in northern Columbia County, which cut 962 feet of a lithologically similar black shale without passing through it. From this it seems reasonably safe to infer that the Ragland well may have penetrated only the upper part of a considerably thicker shale section. A preliminary study of the better preserved fossils in the Cone well indicates that the probable age of this black shale fauna is Upper Silurian or Lower Devonian.
Overlying the black shale in the Ragland well is about 18 feet of unctuous yellow, gray, lavender and pink variegated well-stratified shale, the age of which is still under discussion. It is comparable in position and lithology to a zone of unctuous variegated shale which occurs over the black shales in the Cone well, and which contains fossils similar to those found in the underlying black shales. In the Ragland well this material is unfossiliferous, but has been considered by some to be analogous to the shales in the Cone well, which are believed to represent a weathered phase of the Paleozoic shales which is still in place and therefore a part of the Paleozoic sequence. However, others believe that the variegated shales are reworked and redeposited material derived from the weathering and subsequent erosion of the Pa]eozoic beds, which has been transported and rearranged and is therefore the basal part of the Mesozoic sequence. As, in the Ragland well, these beds are overlain by a conglomerate of quartzite pebbles which is apparently early Mesozoic in age, and as deeply weathered strata are a normal occurrence just beneath a peneplaned surface and their preservation and subsequent burial beneath the sediments of a younger cycle is not unusual,
70 FLORIDA GEOLOGICAL SURVEY -BULLETIN 83
the first hypothesis is preferred and the variegated shales are considered to represent a weathered part of the underlying black shales.
The Robinson well penetrated one or more sills or flows of diabase, 46 feet thick, presumably of Triassic age and lying just beneath the peneplane surface, and then cored 232 feet of Paleozoic sediments, chiefly light gray, hard, quartzitic sandstone, locally interbedded with films and thin beds of rather hard, dark gray to black, somewhat silty, micaceous shale. A few fossils, chiefly linguloid brachiopods belonging to two or more species, were found in the quartzites in the upper part of this section (between 4390 feet and 4424 feet), and, on this basis, -the strata in this well have been correlated with those in the Union Producing Company's E. P. Kirkland No. 1 well in Houston County, Alabama, just north of the Florida line and 211 miles northwest of the Robinson well. The same types of linguloid brachiopods and the same lithology are found in both wells, and the Kirkland well also carries abundant graptolites associated with the linguloids. The graptolites fix the age of the strata containing them as Lower Ordovician, equivalent to a part of the Deepkill shale of New York. This zone is not known in the southern Appalachian Valley, but is represented by beds carrying the same types of graptolites in Arkansas (shale beds in the Blakely sandstone) and in West Texas (part of the Marathon formation).
Another feature common to the Paleozoic strata of both wells are vertical worm borings of the Scolithus type. These average about 0.25 inch in diameter, and may be as much as 8 inches long. They occur in zones or beds from 4 to 8 feet thick, separated by barren intervals of about the same thickness. The tubes are filled with sand cemented to quartzite, and within them all traces of bedding are destroyed. They contain no visible shale particles, and where they cut through shale layers and films, appear as white, circular spots on the bedding planes. Where the tubes cut across the individual laminae, the latter are commonly disturbed and deflected. Although these tubes are admittedly facies fossils, restricted to a sandy environment, they nevertheless appear to have definite value in local correlation.
The J. T. Goethe No. 1 well, about 10 miles north of the Robinson well, cut 37 feet of gray quartzitic sandstone and micaceous black shale similar to the material just described from the Robinson well. A part of this interval was cored, and these cores contain vertical worm tubes similar to those just described. Although no other fossils were found, a circumstance which is not surprising in view of the limited amount of material available for study, it seems quite reasonable to correlate this material with some part of the section found i-i the .obins-rn wl. Most
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 71
of the deep wells in the adjoining counties also penetrated similar rock, and one of these, the Sun Oil Company's Perpetual Forest No. 1 well in Section 5, Township 11 South, Range 11 East, in Dixie County, cut 2250 feet of similar material without passing through it. It seems certain that the sections encountered in the Robinson and Goethe wells represent some part or parts of the section cut in the Perpetual Forest well, that the Paleozoic section underlying Citrus and Levy counties is of considerable thickness, and that somewhere beneath it at unknown depths crystalline rocks would probably be found.
No other types of Paleozoic sediments have been penetrated in the wells drilled in Levy and adjoining counties, but Paleozoic strata belonging to some of the intervening Ordovician and Silurian horizons have been found in we]Is drilled in northern Florida and southern Georgia. This stratigraphic and structural relations of the Ordovician and Silurian rocks underlying these counties are not known. From the fact that the strata are essentially flat-lying, and because other horizons that would normally lie between them are unknown here, it is believed that they are possibly in fault contact (see figure 16), the age of the faulting being pre-Cretaceous.
Triassic Sediments and Intrusives
As indicated on page 69, a thin section of variegated shales occurring at depths of 5,792 to above 5,810 feet in the Coastal-Ragland well is believed by some workers to have been reworked and redeposited sediment derived from weathering and erosion of Paleozoic rocks. This bed has been tentatively placed in the Lower Cretaceous system by some workers, and it could be Triassic, but is considered a logical part of the Paleozoic system in this paper.
The Humble-Robinson well penetrated a sill (?) of igneous rock at least 46 feet thick at depths of 4,331 to 4,377 feet. The upper portion (4,331 to 4,844 feet) of the rock is considerably altered and the rock is quite calcareous. Serpentine and alteration products are common, and portions of the weathered material appear to have been reworked and included in the overlying light-greenish, soft sandstone of Mesozoic age. The rock is believed to have intruded Paleozoic sediments and its weathered surface to represent a long period of erosion and peneplanation extending through the early Mesozoic. It is a greenish-black diabase made up largely of thin laths of plagioclase feldspars, augite and a rhombic pyroxene, enstatite, with interstitial quartz and needles of apatite. The lower part
TABLE 7.-Paleozoic Rocks in Citrus and Levy Counties.
Depth to Elev.-Top
top of Paleozoic Thickness Lithology
Company Well Date Elev. Paleozoic below zea Paleozoic of Type of Age
Completed and T.D. level penetrated Paleozoic record
Coastal Petroleum Co. JB & JT Oct. 18, 1947 15 5810' or -5795' or 40' or Black, Cuttings, Upper Silurian C Ragland No. 1; 5792' -5777' 58' silty core 5840-50 or Lower M Sec. 16, T. 15 S., shale. Devonian
R. 13 E. 5850'
Sun Oil Co .......... JT Goethe No. 1; June 8, 1946 45 3960' -3915' 37' Gray Cuttings and Lower
Sec. 31, T. 14 S., qtzitic core Ordovician? R. 17 E. 3997' ss. and black, micaceous
Humble Oil and CE Robinson Aug. 20, 1949 58 4377' -4319' 232' Gray Core Lower Refining Co......... No. 1; qtzitic Ordovician Z See. 19, T. 16 S., 460.9' sandstone R. 17 E. and black, micaceous,
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 73
has many inclusions of a black, waxy, clay-like substance and much calcite occurring as veins and as alterations of silicates along the veins.
Because of the known distribution of diabase in Triassic sediments of the eastern United States along the Appalachian Mountains of the Atlantic border, the similarity of diabase penetrated in Florida to that of known Triassic rock, and its placement in Paleozoic and burial by Cretaceous sediments this rock has been referred to the Triassic system. Their hardness and resistance to weathering suggests that these sills stood as ridges forming some relief on the great plain developed on top of the Paleozoic rocks.
The Humble-Robinson well in Central Levy County also penetrated 13 feet of green arkosic sandstone containing brown sideritic shale lenses which was apparently derived from the weathering of the Triassic (?) diabase. This sandstone lies below Lower Cretaceous sediments and because of this association is believed to represent the basal part of these beds developed as mantle rock during the early Cretaceous and covered by Lower Cretaceous beds sometime later. There is the possibility, however, that this development of the weathering profile extended over periods of time prior to the Lower Cretaceous.
If the sediments described from the Coastal-Ragland and HumbleRobinson wells are Triassic in age there would be an unconformity at the base of the Triassic system in Levy and Citrus counties. These sediments rest directly on Lower Devonian or Silurian rock and it is known that in other parts of North America the Paleozoic era is represented by a large interval of time which is missing in the section of Levy and Citrus counties. There would likewise be a missing interval of time separating this apparently deeply weathered Paleozoic shale from the overlying Lower Cretaceous sediments and an erosional unconformity is present.
The evidence of Triassic diabase is limited to discontinuous diamond cores and the relationship of the flow or sill to the underlying rock can only be surmised. Nothing can be detected as to the large structures of the igneous body. A careful study of the sediment under the lava indicates a two-inch black, silicified, dense shale which may be a contact reaction zone.
The fresh rock of the cores is a deep bluish-black color, and the weathered a light-greenish to yellowish gray. Both effervesce with cold diluted hydrochloric acid, the weathered doing so much more freely. In thin-sections8 both rocks show an even granular diabasic texture
l8Petrology determined by Dr. James L. Calver, Geologist, Florida Geological Survey from thin-sections cut from the top and bottom of a six-foot core taken at depths of 4,344 to 4,350 feet.
74 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
and a subordinate aphitic structure. Extreme alteration of the ferromagnesian and feldspar minerals have taken place and the feldspars have in many places been replaced by calcite. This replacement is greater in the weathered specimens of the rock. What is presumed to represent the weathered upper surface also contains pale-green, fibrous aggregates of serpentinous and chloritic substances, and more calcite than the fresh rock. Chlorite is more abundant than the serpentine which is probably the variety bastite, a weathering product of the rhombic pyroxene. In the weathered rock the pyroxene has been altered to ferrous oxides and carbonates, largely siderite and limonite. Fractures in the rock are filled by calcite, siderite, and rarely a serpentinous mineral. The fractures in the weathered diabase are laminated with alternating layers of calcite and siderite, but fractures in the unweathered diabase are rarely filled by secondary minerals. No distinct pattern to the fracture is observable from the limited cores made available to the Survey. In these cores the contact at the base of the diabase is sharp but that at the top is gradational because some of the products of weathering of the diabase are included in the overlying sediments.
The diabase rests on a two-inch bed of black, dense, hard, silicified shale, which lies on unweathered quartzitic sandstone of Paleozoic age. Since it is known that much of the time record represented elsewhere by upper Paleozoics is absent in these counties and that a long erosional period is represented at the top of the Paleozoic section of Citrus and Levy counties, the shale may represent a soil zone developed on the Palcozoic sandstone and baked and silicified by a diabase flow, but more probably it is a metamorphosed contact zone beneath a sill.
The lower part of the diabase is greatly fractured, although the diabase is unweathered, and calcite has filled the fractures. This bottom also contains phenocrysts and inclusions of oily, greenish-black, unctuous greatly altered shale from below. The fracturing at the base may indicate cooling followed by a continued flow during emplacement.
The weathered mantle rock developed over the crest of the Peninsular arch was almost completely removed and relatively unaltered Paleozoic sediments and igneous rocks lying beneath Upper Cretaceous marine sandstone, shale and chalk are penetrated by wells. This mantle rock, deposited along the flanks of the land mass and merging with marine
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 75
sediments, has resulted in a generalized two-fold division, a red-bed clastic facies and a marine and evaporite facies. The red-bed elastic facies is confined largely to the Lower Cretaceous although some of these clastics in western Florida have been called Triassic. The basal Upper Cretaceous is commonly marine sand, sandstone and shale in peninsular Florida but red-bed clastics are present in southern Georgia14 in beds as young as the Austin equivalent.
The distribution and relationship of the Cretaceous beneath Levy and Citrus counties can best be shown in cross section and by structure maps, figure 16. Section A-A' is based on six wells in Levy County and B-B' on five wells, the Coastal-Ragland well in Levy County being common to both sections, and includes four additional wells toward the south in Hernando, Hillsborough, Hardee and Highlands counties. Section B-B' is modified from data published as chart A-A' of the Southeastern Geological Society Mesozoic Committee, 1949.
In the continuous line of wells connecting the Highlands County well with the Coastal-Ragland well, progressive marine overlap of Cretaceous beds is clearly shown and the possibility that some of the Lower Cretaceous red-bed elastics are shallow-water equivalents of these marine beds is also indicated.
Section A-A' illustrates the abrupt thinning of the Lower Cretaceous elastics toward the crest of the Peninsular arch, and both sections show that the Cretaceous is dipping away from the crest of the arch, indicating some movement in the structure following deposition of the Upper Cretaceous beds. The dip and strike of Cretaceous sediments are illustrated further by the structure map of figure 16. The top of the Lower Cretaceous and a characteristic shale break in the basal beds of the Taylor equivalent as penetrated by wells in Levy and adjacent counties have been contoured. The dips of both beds are approximately the same, being about 20 feet per mile south in Levy County and counties to the north and steepening to about 40 feet per mile further south. The approximate eastern limit of the Lower Cretaceous elastic red beds is also shown.
The Atkinson formation, equivalent of the Eagle Ford shale and the Woodbine sand, shown in sections A-A' and B-B' pinches out toward the crest of the Peninsular arch and is overlapped by limestones and chalks of the Austin equivalent.
14Southeastern Geological Mesozoc Committee, Mesczcc cross sections, 1949.
76 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Only four wells have penetrated the Lower Cretaceous in Levy County and none in Citrus and, as typified by cuttings and cores taken from these wells, these sediments are variegated red, green, and brown elastics, largely sands and shales, that apparently are weathered rocks removed from a pre-Mesozoic near-peneplaned surface and redeposited along the flanks of the surface as it was warped throughout the Cretaceous period, or they are the residuum from the weathering of the rocks exposed at the surface of the land mass, remaining as mantle rocks, largely undisturbed.
The thickness of the Lower Cretaceous ranges from 1,435 feet in the Coastal-Ragland well in western Levy County, to 31 feet in the HumbleRobinson and 67 feet in the Sun-Goethe wells in central Levy County. The sections and distribution of the Cretaceous, see figure 16, indicate that the thickness of the Lower Cretaceous beneath Citrus County has increased slightly over the maximum of 1,435 feet as penetrated in Levy County by the Ragland well.
The sediments of the Lower Cretaceous are interbedded shales and sandstones. The shales are red, purple, green, brown and gray variegated, mottled, waxy and fissile and contain pink calcareous nodules, yellow, pink, argillaceous sand lenses and sand grains of rose quartz. The sandstone is variegated, light-greenish to yellowish-gray, brown, and white, calcareous and siliceous, and contain black siliceous nodules, rose quartz sand grains, seams of sandy shale and lenses of quartz conglomerate. The base is coarse sand and contains pebbles of Paleozoic sediments. An arkosic sandstone, believed to be a mantle developed by the weathering of Triassic diabase was penetrated by the Humble-Robinson well at depths of 4,331 to 4,344 feet.
Lower Cretaceous beds were penetrated by the following wells:
W-355: Florida Oil Discovery Company, Sholtz (Cedar Keys) No. 2.
SE'i NWi See. 16, T. 15 S., R. 13 E.
Lower Cretaceous: 4,254 to 5,248 feet.
W-1007: Sun Oil Company, J. T. Goethe No. 1.
NWii SW,1i Sec. 31, T. 14 S., R. 17 E.
Lower Cretaceous: 3,893 to 3,960 feet.
W-1537: Coastal Petroleum Company, Ragland No. 1.
SE,34 SW/i See. 16, T. 15 S., R. 13 E.
Lower Cretaceous: 4,347 to 5,782 feet.
W-2012: Humble Oil and Refining Company, Robinson No. 1.
NE14 NEL Sec. 19, T. 16 S., R. 17 E.
Lower Cretaceous: 4,300 to 4,331 feet.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 77
Studies of the Cretaceous stratigraphy have been published by Applin and Applin (1944, 1947), Cole (1938, 1941, 1942, 1944, 1945), and the Southeastern Geological Society Mesozoic Committee (1949), in which correlations of the Florida Cretaceous with standard sections of Alabama and Texas have been made. The correlations apparently were based on the experience of the workers and on the lithology and paleontology of the several sections. Many early workers' 5 and Cole preferred to use the nomenclature of the Alabama section, whereas the Applins and the Southeastern Geological Society Mesozoic Committee have used the names applied to the Upper Cretaceous of Texas, in which many of the species of foraminifers and mollusks that occur in Florida are found. Most geologists of the oil profession of the southeastern states prefer to use a nomenclature of Beds of Navarro age (Lawson limestone), Beds of Taylor age, Beds of Austin age (which include the Selma equivalent at the top and occasional beds of the upper Eutaw sand at the base) and the Atkinson formation. Some workers prefer not to use Atkinson and divide the interval into the Eagle Ford shale and Woodbine sand. In general all workers recognize a four-fold division of the Upper Cretaceous, based on an age relationship. The Southeastern Geological Society Mesozoic Committee used Navarro equivalent, Taylor equivalent, Austin equivalent and the Atkinson formation, divided into "A" and "B" zones, and this terminology is used in this report with the exception that the Lawson limestone is used for the Navarro equivalent.
The Upper Cretaceous of the peninsular area is composed of creamcolored to orown, pasty and fragmental rarely 6olitic, marine chalky limestone, dolomitized in part and with abundant fossils. Incipient dolomitization and gypsum impregnation are present rarely. The base of the section contains lenses and laminae of brown to black shale, green bentonitic shale and thin beds of glauconitic fine sand containing some gravel.
Beds of the Upper Cretaceous lie unconformably upon older beds, and in Citrus and Levy counties individual beds of the series appear to be conformable with each other. An unconformity is also indicated at the top of the Upper Cretaceous in the Humble Oil and Refining Company, C. E. Robinson well No. 1, where the overlying Paleocene Cedar Keys formation contains gray, chalky, limestone pebbles in the very base.
liGeologic logs in the files of the Florid Geologikal Survey.
78 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Applin and Applin (1944, p. 1703) likewise indicate an unconformity separating Paleocene from Upper Cretaceous in the vicinity of Tallahassee where the Cedar Keys formation rests on beds of Taylor age, with the Navarro equivalent being absent.
During an investigation of the stratigraphy of Cretaceous rocks in Alabama, Georgia and north Florida, the Applins (1947, chart) determined that:
"The subsurface deposits between the base of the beds of Austin age and the top of the Lower Cretaceous should be considered as a unit in order to explain changes in depositional facies which appear in the upper part of the
Beds occupying this horizon in the subsurface could not be correlated exactly by the Applin's with either the surface exposures of Alabama or with the subsurface classification of Mississippi, because of lithologic and faunal differences. The Atkinson formation, including three unnamed members, was proposed for the early Upper Cretaceous and was tentatively correlated with the Tuscaloosa formation and the McShane formation of Alabama. The Applins expressed the desire that the name would be sufficiently flexible to allow the extension of the surface nomenclature at a later date if desirable.
The Atkinson formation has been adequately described by the Applins and this description is not repeated here. The two basal members contain microfossils and mollusk fragments typical of the Woodbine sand of Texas, whereas the upper member contains a fauna characteristic of the Eagle Ford shale of Texas. On the basis of these faunas the Southeastern Geological Society Mesozoic Committee used a two-fold division of the Atkinson formation, an "A" and "B" zone; the "A" zone containing an Eagle Ford fauna, the "B" zone a Woodbine. This division is used in this report.
The Atkinson formation was penetrated in four wells in Levy County. Evidence presented by the Applins (1947, chart) indicates that the Atkinson is possibly absent in eastern Levy County and it is known to be absent over the crest of the Peninsular arch. However, the absence of the formation in Levy County is not substantiated by the section, figure 16, and perhaps the formation thins rapidly in Marion County and is absent over most of it.
The formation is fairly uniform in thickness ranging from 240 feet in the Sun-Goethe well, 244 feet in the Florida Oil Discovery-Sholtz well to
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 79
36S feet in the Humble-Robinson well, the thickening occurring in the upper "4" zone.
"A Zone": This zone commonly contains in marine shale beds a fauna characteristic of the Eagle Ford shale of Texas and includes Planulina eaglefordensis, Valvulineria infrequens, Gumbelina moremani, G. reussi, Trochammina wickendeni, Globigerina cretacea and numerous ostracods. In western Levy County it is composed of medium-gray to greenish-gray, calcareous, micaceous shale containing seams of argillaceous limestone and variegated, micaceous, glauconitic, pyrite and carbon flecked sandstone. Eastward the zone thickens from 190 feet to about 250 feet and is composed of interbedded, light-brownish to inedium-gray, sandy, dense, hard, shaly limestone with thin seams of sandstone and flecks of lignite; greenish-gray, poorly sorted, slightly calcareous sandstone; and purple, blocky, micaceous shale. Poorly preserved mollusk shells and fish scales are fairly common in the shale beds.
B Zone": This zone contaas a microfauna characteristic of the Woodbine sand of Texas, including Ammobaculites braunsteini, A. comprimatus, A. advenus, Ammobaculoides plummerae, and Trochammina rainwateri, which are rare in Levy County. The zone as identified in Levy County consists of gray, micaceous, calcareous sand that overlies a dark gray, fissile, calcareous shale and shaly limestone, containing thin seams oi gray to cream, shaly limestone, flecks of lignite and traces of gypsum. ,leaum-gray, calcareous, quartz sandstone with thin shale partings and a coarse sand and gravel conglomerate are irregularly interbedded with the shale.
The following wells'6 penetrated the Atkinson formation in Levy County:
W-355: Florida Oil Discovery-Sholtz well Atkinson formation
"A Zone" 4,010 to 4,152 feet
"B Zone" 4,152 to 4,254 feet
W-1007. Sun Goethe well
"A Zone" 3,653 to 3,845 feet
"B Zone" 3,845 to 3,893 feet
W-1537: Coastal Ragland well
"A Zone" 4,121 to 4,243 feet
"B Zone" 4,243 to 4,347 feet
16Loeations given on page 76.
80 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
W-2012: Humble Robinson well
"A Zone" 3,932 to 4,178 feet
"B Zone" 4,178 to 4,300 feet
BEDS OF AUSTIN AGE
Applin and Applin (1944, pp. 1715-1716) recognized three poorly defined facies in the beds of Austin age in Florida. These facies are predominately shales and sands in western and northern Florida, shale and marly limestone in central Florida and limestones in southern Florida. These writers reported that the beds of Austin age in northern and western Florida are composed of marly shales, fine-grained, argillaceous sandstone; sandy, micaceous clay; and some limestone. The limestone contains an occasional lens of black to brownish-black "speckled" shale, characteristic of the lower part of the Austin chalk of parts of Texas. In central Florida the unit is characteristically gray to greenishgray, marly shale with streaks of limestone and a few fine-grained sand lenses, and contain lenses of the "speckled" shale. Both of these facies contain an abundant microfauna. Hard white limestone compose the beds of Austin age in the southern Peninsula.
Five wells penetrated beds of Austin age in Levy County. The top of the Austin equivalent in this report is placed at the first shaly chalk below the Taylor equivalent, and has been picked by the electric characteristics and checked by cores and cuttings in all wells except the Florida Oil Discovery and Suwannee Petroleum wells from which only irregular samples were available. The thickness ranges from 480 feet in the Humble-Robinson well, 490 feet in the Sun-Goethe well, to 527 feet in the Coastal-Ragland well.
The Austin equivalent of Citrus and Levy counties can be divided roughly into three parts. The upper 200-300 feet is light-green, cream, tan and gray, rather tight, shaly chalk that contains medium-gray marl and shale seams. The middle 100-200 feet is light-gray, speckled, fairly dense chalk. The basal 100-150 feet is a gray to cream, dense chalk with a flaky fracture and thick beds and seams of calcareous shale; gray, calcareous sand; and lignitic shale. The top of the Austin equivalent is dolomitized in the Humble-Robinson well.
The upper and middle portions are correlated with the Selma chalk and the basal section with the upper part of the restricted Eutaw sands of Alabama, by some workers. The basal beds have very definite and characteristic potentials and resistivities on electric logs.
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 81
The intervals in the following wells are assigned to the beds of Austin age:
W-166: Suwannee Petroleum Corporation, Sholtz well No. 1
NE% NWh Sec. 16, T. 15 S., R. 13 E.
Austin equivalent combined with W-355 Irregular samples
W-355: Florida Oil Discovery Sholtz well'7
Austin equivalent: 3,690 to 4,010 feet
W-1007: Sun Goethe well
Austin equivalent: 3,163 to 3,653 feet
W-1537: Coastal- Ragland well
Austin equivalent: 3,594 to 4,121 feet
W-2012: Humble Robinson well
Austin equivalent: 3,452 to 3,932 feet
BEDS OF TAYLOR AGE
The Taylor equivalent in Citrus and Levy counties is a fairly thick and consistent section composed of white to cream chalk separated by thin beds and seams of tan, crystalline dolomite and characterized by fragments of Inoceramus sp. and Torreina sp.
Three thin beds in the base of these deposits make a very distinctive pattern on the electric logs, the resistivity and potential both being low. These patterns are particularly well-developed at depths of 3,338 feet, 3,348 feet, and 3,357 feet in the Coastal-Ragland well. Because the potential is flat throughout most of the Upper Cretaceous of peninsular Florida, these strong depressions are very prominent in the potential. These beds are widely developed although only 1 to 2 feet thick, and are believed to be a series of clay beds, probably ash falls. The beds are present in almost all of the wells that penetrate the basal Taylor beds in peninsular Florida and make a very good correlation point between these wells and provide a very suitable contouring horizon for the Upper .Cretaceous, see the structural map of figure 16. Because the clay beds are so thin, the sediments are rarely recovered in rock cuttings, but occasional fragments of greenish-gray to light-gray, fissile, waxy shale and of brown calcareous clay in the cuttings at depths corresponding to these electric patterns are believed to represent the beds.
In the thick section of chalk of the lower Lawson limestone and Taylor equivalents, and the gradual change in faunal content of the two sections, the top of the Taylor is placed by some workers at the first occurrence of abundant fragments of Inoceramus sp. This top has proved to be highly variable, even in closely spaced wells, and the Taylor equiva17Locations of wells given on page 76.
82 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
lent has been identified in this report through its rather distinctive electric log characteristics. The top is indicated by a series of strong and evenly spaced resistivities separated by chalk line resistance as observed on the electric logs as follows: 2,892 feet in the Coastal-Ragland, 2,780 feet in the Humble-Robinson, and 2,535 feet in the Sun-Goethe. These distinctive features are referred to rather generally by geologists as "Taylor kicks".
The Taylor equivalent is present from depths of 2,892 to 3,594 feet in the Coastal-Ragland well, a thickness of 702 feet; from depths of 3,092 to 3,690 feet in the Florida Oil Discovery-Sholtz well and the SuwanneeSholtz well, a thickness of 598 feet; from depths of 2,780 to 3,452 feet in the Humble-Robinson well, a thickness of 672 feet; from depths of 2,535 to 3,163 feet in the Sun-Goethe well, a thickness of 628 feet.
LAWSON LIMESTONE (NAVARRO EQUIVALENT)
The Lawson limestone was described and named by the Applins (1944, p. 1708) for the late Upper Cretaceous beds and the name is taken from the J. S. Cosden-Lawson well No. 1, Marion County, Section 25, Township 13 South, Range 20 East. The formation includes two members, an upper and lower. The name was proposed for:
"A limestone facies of the late Upper Cretaceous occurring in northeast Florida and the peninsula . below the Cedar Keys limestone and above beds
of Taylor age."
In Levy County the Lawson limestone is also separable into an upper and a lower member, each with a distinctive fauna. The upper member is a cream-colored, fragmental, marine limestone with gypsum lenses and porosity impregnation. The lower member is commonly cream to white, pasty, marine chalk and fragmental limestone. The Applins (1944, pp. 1708-1709) recorded that an undescribed Rotalid sp., Vaughanina sp., Orbitoides sp. and Pseudorbitoides? sp., are present in the upper member, and that the lower member is characterized by Lepidorbitoides sp., L. (Asterorbis) aquayoi D. K. Palmer, L. (Asterorbis) rooki Vaughan and Cole, and Sulcoperculina lawsoni Applin and Jordan.
The term Lawson limestone has been accepted by most southeastern geologists. The lower member is clearly Cretaceous in age and correlates with the Cretaceous of Cuba, Mexico and Europe, and occupies the same stratigraphic horizon as clastic beds of Navarro age of western Florida, Alabama and Mississippi.
The upper member was defined as late Upper Cretaceous, but in recent oil tests, particularly, the Humble-Hodges well No. 1, in Taylor
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 83
County, the fauna characterizing the member occurs very high in the section in an interval normally considered to be Cedar Keys formation, of Paleocene age. This additional information indicates that the upper Lawson is a transitional bed including fossils characterizing both Paleocene and Cretaceous, but since characteristic Cretaceous fossils, particularly species of Pseudorbitoides sp., Torreina sp., Orbitoides sp., and Vaughanina sp., are present in the bed it is considered to represent th3 top of the Cretaceous in peninsular Florida by most writers.
The Lawson limestone was identified from rock cuttings from seven wells in Levy County. The top of the upper Lawson is marked by a very definite and characteristic cream-colored, porous, granular, sub-6olitic, marine, fragmental dolomite. The upper few feet is extremely fossiliferous being a coquina of Applin's Rotalid sp., Pseudocyclammina sp., and Pseudorbitoides sp., loosely cemented together and greatly altered by dolomitization. This extremely fossiliferous zone is thin and the lower part of the upper Lawson is similar to the upper part lithologically but is less fossiliferous.
The lower Lawson is a pasty to fragmental, marine, chalky limestone, frequently dolomitized. Torreina sp., Sulcoperculina cosdeni Applin and Jordan, several species of Lepidorbitoides and Cibicides harperi (Sandridge) characterize the bed. Speciments of Lepidorbitoides are quite common.
Gypsum is rare to common throughout the upper Lawson, occurring as impregnations of the porosity, but is rare in the lower Lawson. Some carbonaceous partings are present in the lower Lawson, but these are absent in the upper.
The Applins (1944, p. 1789) assigned only 42 feet of the section in the Florida Oil Discovery-Sholtz well to the upper Lawson limestone. This appears thin for the formation because 173 feet of this member was cut by the Coastal-Ragland well, located about a mile south of the Sholtz. The top of the Cretaceous is believed to be obscured in dolomite in the Sholtz well. The formation thins from west to east in Levy County, being 612 feet thick in the Coastal-Ragland well and only 345 feet in the SunGoethe well, see figure 16.
The Lawson limestone was penetrated by the Suwannee PetroleumSholtz well and the Florida Oil Discovery-Sholtz well but poor sampling prevents exact identification. The formation is present in the following wells as tabulated:
84 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
W-1007: Sun Goethe well
Upper: 2,190 to 2,280 feet Lower: 2,280 to 2,535 feet W-1537: Coastal- Ragland well
Upper: 2,280 to 2,453 feet Lower: 2,453 to 2,892 feet W-2010: C. M. Brukenfeld, Assoc.,
Levy-Lennon Syndicate, Inc., well No. 1
NE34 NW3 Sec. 5, T. 14 S., R. 16 E.
Upper: 2,010 to 2,120 feet (T. D.) W-2012: Humble Robinson well
Upper: 2,290 to 2,420 feet Lower: 2,420 to 2,780 feet W-2166: J. A. Abbott, Prudential Lumber Company well No. 1
NW1b SE/i Sec. 34, T. 13 S., R. 16 E.
Upper: 1,935 to 1,945 (T. D.)
CENOZOIC ERA TERTIARY SYSTEM
CEDAR KEYS FORMATION Terminology: The Cedar Keys formation was proposed by Cole (1944, pp. 27-28) for tan-colored, hard limestones which contain Borelis gunteri Cole and Borelis floridanus Cole in their upper portion, and being sparingly fossiliferous or unfossiliferous in the lower. As used by Cole, the formation extended from the uppermost occurrence of the Borelis fauna to the top of the Upper Cretaceous, as identified by him, and included a thin transition zone at the base which is considered by most southeastern geologists to represent the top of the Upper Cretaceous, being the upper member of the Lawson limestone.
The Cedar Keys formation, as used in this report, covers the interval extending from the-top of the Borelis fauna, the first occurrence of small foraminifers associated with Borelis, or the top of a characteristic lith. ology to the top of the Cretaceous, which in Levy County is the upper Lawson limestone. Cole's Cedar Keys formation is thus expanded by the inclusion of an indefinite thickness of beds at the top and contracted by the exclusions of the upper Lawson limestone. The Applins (1944, p. 1704) applied the name Cedar Keys limestone to a similar interval, and
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 85
with this usage the formation is much more uniform in its occurrence and thickness, than as formerly defined. The Florida Geological Survey has accepted the new definition but retains the original name for this formation.
The bed is characterized by the two species of Borelis, Cribrospira? bushnellensis Applin and Jordan, Planispirina? kissengenensis Applin and Jordan, Valvulammina nassauensis Applin and Jordan, and by two ostracods, Cytherella symmetrica Alexander and Cythereis sp. aff. C. sculptilis Alexander which according to the Applins (1944, p. 1704-05) suggest a slight relationship to the Midway beds of the western Gulf Coast.
The formation is widely developed throughout most of peninsular Florida and is considered the marine equivalent of the clastic facies of the southeastern states to which the term Midway group has been applied. It lies below a definite Salt Mountain fauna of lower Eocene, Wilcox age and conformably upon transitional Upper Cretaceous beds. It thus occupies the interval represented elsewhere by the beds of Midway age.
Lithology: The Paleocene of peninsular Florida is white, cream and gray, pasty to fragmental limestones, which have rare lenses of politic limestone. The porosity of the rock is impregnated by gypsum, giving it a speckled appearance.
The top of the Cedar Keys formation is commonly dolomitized and unfossiliferous. The chalky appearance of this dolomite, however, contrasts strongly with the crystalline, flaky dolomite of the basal Oldsmar limestone. Placing this dolomite in the Cedar Keys formation is substantiated by rare molds of Borelis sp. found in this interval in at least one well, the Abbott-Prudential well. Thin clay lenses and pyrite concentrations occur at the top rarely and almost complete porosity filling by gypsum sometimes marks the top of the formation.
The Cedar Keys formation of Levy County is composed of interbedded tan to gray, finely granular, fragmental, often very fossiliferous limestone and tan to brown, finely crystalline to chalky textured dolomite. Gypsum has completely impregnated the porosity of large sections and occurs irregularly as thin lenses. The limestone is rarely fossiliferous near the top and is dolomitized. The lower portion is more fossiliferous and some beds are essentially composed of specimens of microfaunas held in a pasty limestone matrix. Fossils characterizing the bed elsewhere in peninsular Florida are present and are abundant in these unaltered limestones.
86 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
Thickness: The Cedar Keys formation is only slightly thinner in easterncentral than in western Levy County but it can be presumed to thin toward the Peninsular arch in northern and eastern Florida, that part of the State having been structurally high during the Paleocene. The formation is 600 feet thick in the Coastal-Ragland well, in western Levy County, and 540 feet in the Humble-Robinson well, 713 feet in the SunGoethe well, 550 feet in the Brukenfeld-Levy-Lennon well, and 445 feet in the Abbott-Prudential Timber well in eastern central Levy County.
The Cedar Keys formation was identified at the depths tabulated under the following wells:
W-166 and W-355: Florida Oil Discovery-Sholtz and Suwannee PetroleumSholtz wells samples combined.
Cedar Keys formation: 1,636? to ? feet
W-1007: Sun-Goethe well
Cedar Keys formation: 1,658 to 2,190 feet
W-1587: Coastal-Ragland well
Cedar Keys formation: 1,680 to 2,280 feet
W-2010: Brukenfeld-Levy-Lennon well
Cedar Keys formation: 1,460 to 2,010 feet
W-2012: Humble-Robinson well
Cedar Keys formation: 1,750 to 2,290 feet
W-2166: Abbott-Prudential well
Cedar Keys formation: 1,335 to 1,935 feet
The Oldsmar limestone was used by the Applins (1944, p. 1699) to,
"include the interval that is marked at the top by the presence of abundant specimens of Helicostegina gyralis Barker and Grimsdale, and that rests on
the Cedar Keys limestone."
The formation was separated into four faunal zones, which in descending order were as follows:
Zone 1: Helicostegina gyralis
Zone 2: Salt Mountain faunal unit, characterized in the
Peninsula by Pseudophragmina cedarkeysensis Cole.
Zone 3: Coskinolina elongata Cole
Zone 4: Unnamed, characterized over the northern Peninsula
by Miscellanea nassauensis Applin and Jordan and
GEOLOGY OF CITRUS AND LEVY COUNTIES, FLORIDA 87
over the central and southern Peninsula by Lockhartia cushmani Applin and Jordan.
The Oldsmar limestone as erected by the Applins is predominately a series of faunal zones and is not different lithologically from the overlying and underlying formations. It is composed essentially of fragmental marine limestones, partially to completely dolomitized and containing irregular and rare lenses of chert, impregnations of gypsum and thin shale beds. Fossils are common but sometimes dolomitized and poorly preserved.
The limestone and dolomite of lower Eocene age of peninsular Florida, the Oldsmar limestone, grades westerly and northerly into a clastic facies, greenish-gray clay and variegated, micaceous, glauconitic, sandy, carbonaceous clays containing several highly fossiliferous zones, the faunas having been identified as those of Wilcox age. A few species occurring in the Salt Mountain reef limestone of Wilcox age in Clarke County, Alabama, occur in the limestone of the Peninsula, and the correlation is made more exact.
Thickness: The thickness of the Oldsmar limestone is variable, the top of the formation being identified by the first occurrence of Helicostegina gyralis. In a thick section of limestone of fairly uniform lithologic characteristics in which the original texture of the rock and the fauna have been destroyed or altered by partial or complete dolomitization, an irregular thickness is to be expected. This dolomitization, combined with the irregularities of fossil occurrences, introduce additional variations in thickness. The formation, or rather faunal zone, is 380 feet thick in the Coastal-Ragland well, in western Levy County and 500 feet thick in the Humble-Robinson well, 568 feet in the Sun-Goethe well, 550 feet thick in the Brukenfeld-Levy-Lennon well, and 445 feet in the Abbott-Prudential well of central Levy County. No wells penetrated the Oldsmar in Citrus County.
Lithology: The Oldsmar was penetrated by seven oil tests in Levy County, but no wells have been drilled in Citrus County that penetrated sufficiently deep to encounter the formation.
The Oldsmar limestone is marked by the presence of Helicostegina gyralis in brown, very porous, friable, granular limestone composed of calcite grains loosely imbedded in limestone paste. This limestone is interbedded with brown, coarsely crystalline, sugary, porous dolomite containing seams of white chert and anhydrite; thick beds of coffeecolored, dense chert; and finely crystalline, tan to brown dolomite. The
88 FLORIDA GEOLOGICAL SURVEY -BULLETIN 33
base -of the formation is commonly brown, granular, porous, soft limestone, a coquina of small foraminifers in a soft limestone paste. The faunal zones recognized by the Applins (1944) are present in the formation but these are not tabulated in the following record of wells that penetrate the Oldsmar limestone in Levy County.
W-166: Florida Oil Discovery-Sholtz and W-355: Suwannee Petroleurn-Sholtz wells
Oldsmar limestone: 1,340? to 1,636? feet W-1007: Sun-Goethe well
Oldsmar limestone: 945 to 1,658 feet
W-1537: Coastal-Ragland well
Oldsmar limestone: 1,300 to 1,680 feet
W-2010: Brukenfeld-Levy-Lennon well
Oldsmar limestone: 910 to 1,460 feet
W-2012: Humble-Robinson well
Oldsmar limestone: 1,250 to 1,750 feet
W-2166: Abbott-Prudential well
Oldsmar limestone: 890 to 1,335 feet
The rocks assigned to the Claiborne group of peninsular Florida differ both in faunal content and lithology from those recognized throughout the Gulf Coast elsewhere. In general, the Claiborne group of northern and peninsular Florida is composed of carbonates and evaporites and that of the western Gulf Coast is composed of clastics, largely sands and clays. An occasional fossil common to both sections support stageage assignments, but these are insufficient to allow the extension of the Gulf Coast formational nomenclature to the carbonate rocks of Florida. Because of these differences between the geology of the two areas, the Applins (1944) felt justified in erecting three formations in the Claiborne group. Beds of early middle Eocene were named the Lake City limestone and those of late middle Eocene were divided into a lower formation, the Tallahassee limestone, and an upper formation, the Avon Park limestone. The Tallahassee limestone and an equivalent non-fossiliferous limestone is restricted in its occurrence to the vicinity of Tallahassee and counties lying to the east in northern peninsular Florida.
The Applins (1944, p. 1739) assigned 411 feet of dolomite in the Florida Oil Discovery-Sholtz well, Levy County, to the non-fossiliferous