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The artesian water of the Ruskin area of Hillsborough County, Florida ( FGS: Report of investigations 21 )

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Title:
The artesian water of the Ruskin area of Hillsborough County, Florida ( FGS: Report of investigations 21 )
Series Title:
( FGS: Report of investigations 21 )
Creator:
Peek, Harry M ( Harry Miles ), 1923-
Place of Publication:
Tallahassee
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[s.n.]
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English
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96 p. : illus., maps (1 fold.) ; 23 cm.

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Subjects / Keywords:
Artesian wells -- Hillsborough Co., Fla ( lcsh )
City of Tampa ( local )
Town of Suwannee ( local )
Hillsborough County ( local )
City of Ocala ( local )
Tampa Bay ( local )
City of Vernon ( local )
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non-fiction ( marcgt )

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General Note:
At head of title: State of Florida State Board of Conservation.
General Note:
"References": p. 72-74.
Statement of Responsibility:
Prepared by the U. S. Geological Survey in cooperation with the Florida Geological Survey and the Board of County Commissioners of Hillsborough County.

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University of Florida
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University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
000958539 ( aleph )
01745705 ( oclc )
AES1349 ( notis )
a 60009240 ( lccn )

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Full Text
STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest MittsDirector
FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director
REPORT OF INVESTIGATIONS NO. 21
THE ARTESIAN WATER OF THE. RJSKIN AREA
OF HILLSBOROUGH COUNTY, FLORIDA
By
HARRY M. PEEK U. S. Geological Survey
Prepared by the UNITED STATES GEOLOGICAL SURVEY in cooperation with the FLORIDA GEOLOGICAL SURVEY and the
BOARD OF COUNTY COMMISSIONERS OF HILLSBOROUGH COUNTY
TALLAHASSEE, FLORIDA 1959




4UOOz9. /Jdrzf AGRI.
FLORIDA STATE BOA ^tL' OF
CONSERVATION
LeROY COLLINS Governor
R. A. GRAY RICHARD ERVIN
Secretary of State Attorney General
J. EDWIN LARSON RAY E. GREEN
Treasurer Comptroller
THOMAS D. BAILEY NATHAN MAYO
Superintendent of Public Instruction Commissioner of Agriculture
ERNEST MITTS Director of Conservation
ii




LETTER OF TRANSMITTAL
Jlorida geological Survey
ICallakassee
September 9, 1959
MR. ERNEST MITTS, Director FLORIDA STATE BOARD OF CONSERVATION TALLAHASSEE, FLORIDA
DEAR MR. MITTS:
The Florida Geological Survey will publish as their Report of Investigations No. 21 a comprehensive study of THE ARTESIAN WATER OF THE RUSKIN AREA OF HILLSBOROUGH COUNTY. This study was made by Mr. Harry M. Peek, Geologist with the U. S. Geological Survey, in cooperation the Florida Geological Survey and with the Board of County Commissioners of Hillsborough County.
The area in the vicinity of Ruskin is used extensively for truck farming. During drought periods, considerable difficulty has been experienced through the -accumulation of salts in low places, the salts having been derived from water used for irrigation. This study provides data that will be helpful in evaluating the problem of salt accumulation in soils and will provide the necessary help for a wise and conservative utilization of our water resources in that area.
Respectfully yours,
ROBERT 0. VERNON, Director
111




Completed manuscript received
May 18, 1959
Published by the Florida Geological Survey
E. O. Painter Printing Company
DeLand, Florida
September 9, 1959
iv




TABLE OF CONTENTS
Page
Abstract ------------------------------------------------------ -------- - 1-----Introduction . .. . .. ... -..... ......... ...... .. . ... . 2
Purpose and scope of the investigation ------ -------------- 3
Previous investigations 4-------------------------------------------------- 4
Acknowledgm ents ------------------------- 5
W ell-num bering system ... ............ . ................... 5
Geography ....7---------------------------------- ------------------------- 7
Climate 7---------------------------------------------------------------- ------ 7
Physiography -7-------------------------------------------- -- 7
Culture ----------------------------------------------------------- -- ----- 10
Geology ---.........................................------------- 11
Eocene series ----------------------------------------------------------- 13
Avon Park limestone ----------- 13
Ocala group --------------------- ------------- -- --- --- --- ----- 13
Oligocene series .---------- ------------------------------------------ ------ 15
Suwannee limestone ----------------------------------- --------------- 15
Miocene series ------------------ 15
Tampa formation ....-------------------- ------------------------------- 15
Hawthorn formation ..-------------- ---------------- ----- 18
Pliocene and Pleistocene series -------------------------------------- 18
Ground water --------------- 19
Principles of occurrence ---------------------------------------- -- 19
Ground water in Florida ----- - -------------------- ------ 20
Artesian water-------- ------------- 20
Piezometric surface 21
Ground water in the Ruskin area ------------------------------------ 21
Artesian water ........-------- ---- -------------- - ------- ---------- 23
Current-meter exploration ---------23 Fluctuation of artesian pressure head ----------- ----------23
Piezometric surface -------- ------------------------- 36
Depth of water levels below land surface ------ 40 Wells ... ...........--------------------------------------------- 44
Temperature ---------------------------------------...... .- 46
Quantitative studies ----------- 47
Quality of water ------ ------------------- 54
Salt-water contamination ------------------------ ----64
Relative salinity of the artesian water ..................... 65
Sources of contamination ---- ------ -------.. .. .........69
Summary and conclusions --------------- 70
References .....-- -.--------.---------------------.------------- 72
Water-level measurements --------------------------------------- 75
Well logs ____ -- 81
V




ILLUSTRATIONS
Plate Page
1 Map of the Ruskin area showing location of wells ..... ... facing 4 Figure
1 Map of the peninsula of Florida showing location of Hillsborough
County and the Ruskin area 6
2 Precipitation and temperature at Tampa --.......... .. ..... 8
3 Map of the Ruskin area showing the Pleistocene terraces --------- 10
4 Geologic cross sections showing the formations penetrated by water
wells in the Ruskin area ..... ----- --------............. 11
5 Map of the Ruskin area showing the configuration and altitude'
of the top of the Suwannee limestone .. ....... ----- ------ 16
6 Map of the Ruskin area showing the configuration and altitude
of the top of the Tampa formation --.. ---------------......- ---.. 17
7 Map of peninsular Florida showing the piezometric surface of the
Floridan aquifer in 1949 --------.......-----... ............... ..-.----- 22
8 Graph showing well-exploration data for well 40-30-1 -------------25
9 Graph showing well-exploration data for well 43-26-4 -------------26
10 Graph showing well-exploration data for well 43-26-7 ----------------27
11 Graph showing well-exploration data for well 43-26-12 ------------28
12 Graph showing well-exploration data for well 43-26-26 ------------29
13 Graph showing well-exploration data for well 44-24-15 ------------30
14 Graph showing well-exploration data for well 44-25-42 ------------31
15 Graph showing well-exploration data for well 44-26-10 ------ 31 16 Graph showing well-exploration data for well 44-26-31 ------------32
17 Graph showing well-exploration data for well 45-24-13 ------------33
18 Graph showing well-exploration data for well 45-24-17 ----34 19 Graph showing well-exploration data for well 45-24-23 ------------35
20 Graph showing well-exploration data for well 45-25-20 36 21 Graph showing well-exploration data for well 45-26-2 -------------37
22 Graph showing well-exploration data for well 45-26-3 -------------38
23 Graph showing well-exploration data for well 46-24-7 -------------39
24 Graph showing well-exploration data for well 46-24-8 -------------40
25 Graphs showing well-exploration data for wells 46-24-12 and
46-24-17 ............................ --------------------------------------41
26 Graphs showing well-exploration data for wells 47-23-8 and
48-23-15 ------ 42
27 Hydrographs of wells 42-19-1 and 44-25-39 .............. ...------------------ ---43
28 Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9 ---------- 44
29 Hydrographs of wells 43-26-2, 44-25-5, 46-24-7, and 52-20-1 ..-------- 45
30 Hydrographs of and chloride content of water from wells 43-26-12
and 43-26-26 ..__ . .. .. ..... ... ......... .. ............ 46
31 Hydrographs of and chloride content of water from wells 44-25-38
and 44-26-31 -.. ...- ..-.... 47
32 Hydrographs of and chloride content of water from wells 45-25-8
and 46-24-4 48
33 Hydrographs of and chloride content of water from wells 47-23-22 .
and 48-23-19 49
34 Effects of earthquakes and atmospheric pressure changes on the
water levels in wells 42-19-1 and 44-25-39 ..-----------......................... ... 50
vi




35 Map of the Ruskin area showing the piezometric surface of the Floridan aquifer in October 1952------------------ 51
36 Map of the Ruskin area showing the piezometric surface of the Floridan aquifer in May 1953 --------------52
37 Map of the Ruskin area showing the area of artesian flow and depth of water level below land surface ----------------------- 53
38 Logarithmic plot of drawdown in well 40-27-7 versus t/r2 ....... 54 39 Map of the Ruskin area showing wells sampled for chemical analysis -...-.... ................5-------------- 5--------5-----------------55
40 Map of the Ruskin area showing the sulfate content of water from the Florida aquifer -------------- ....... -- -- --............ .... .. .. 59
41 Map of the Ruskin area showing the chloride content of water from the Tampa formation ------- -------------- 60
42 Map of the Ruskin area showing the chloride content of water from the Suwannee limestone and older formations ---------------61
43 Map of the Ruskin area showing the dissolved-solids content of water from the Floridan aquifer .- ........--------- -.. 63
44 Map of the Ruskin area showing the hardness of water from the Floridan aquifer ---------- --------------- ....- -..... .... -- -.... - 64
45 Graph showing well-exploration data for well 44-25-28 ------------67
46 Graph showing well-exploration data for well 47-23-22 ------------68
47 Graph showing well-exploration data for well 48-23-8 -------------68
TABLES
Table Page
1 Pleistocene terraces and shorelines of the Ruskin area------------- 9
2 Geologic formations penetrated by water wells in the Ruskin area 12 3 Stratigraphic nomenclature of the upper Eocene in Florida .....14 4 Summary of results of the current-meter explorations -------- ---- 24
5 Chemical analyses of artesian water from wells in the Ruskin area 57 6 Measurements of water level in wells in the Ruskin area -----------75
7 Logs of selected wells in the Ruskin area ----------------- ----81
vii







THE ARTESIAN WATER OF THE RUSKIN AREA
OF HILLSBOROUGH COUNTY, FLORIDA
By
HARRY M. PEEK
ABSTRACT
The Ruskin area of Florida, as defined in this report, comprises about 200 square miles in southwestern Hillsborough County. The area has a subtropical climate and an average rainfall of more than 50 inches, so that it is well suited to livestock farming and growing of winter vegetables. As in much of the State, however, truck crops and pasture require irrigation during periods of relatively light rainfall; thus, large quantities of water are withdrawn through many hundreds of wells during the growing season.
The surface formations in the Ruskin area consist predominantly of deposits of sand, limestone, and shells, of Pleistocene and Pliocene age, which range in thickness from a few feet to about 60 feet. These deposits are underlain by the Hawthorn formation, of middle Miocene age, which is exposed at a few places. The Hawthorn consists of calcareous clay or marl interbedded with limestone and sand and ranges in thickness from less than 10 feet in the northern part of the area to more than 150 feet in the southern part. The Tampa formation,' of early Miocene age, underlies the Hawthorn formation and ranges in thickness from 50 feet in the northern part of the area to about 200 feet in the southern part. Its upper surface ranges in elevation from about sea level in the northern part of the area to about 250 feet below sea level in the southern part. The Tampa is the youngest of the limestone formations of Tertiary age, which have a total thickness of several thousand feet in southwestern Hillsborough County. The other limestone formations penetrated by water wells in the area are the Suwannee limestone, of Oligocene age, and the Ocala group and Avon Park limestone, of Eocene age.
'The stratigraphic nomenclature used in this report conforms to that of the Florida Geological Survey. It conforms also to that of the U. S. Geological Survey, with the following exceptions: the Tampa limestone is herein referred to as the Tampa formation and the Ocala limestone is referred to as the Ocala group.
1




2 FLORIDA GEOLOGICAL SURVEY
The Hawthorn and younger formations are the source of some domestic and other small water supplies, but the large quantities of water required for irrigation and industrial use are obtained from the underlying limestone formations.
The Suwannee limestone and Tampa formation are the principal sources of artesian water in the area, although the older limestones yield water to a few wells. The water in these formations occurs in permeable zones that are separated by relatively impermeable beds of considerable thickness. The water is replenished by rainfall in western Polk County and eastern Hillsborough County, and it is confined under pressure by the relatively impermeable strata within the formations and by the overlying Hawthorn formation. The artesian aquifer has a transmissibility coefficient of about 115,000 gpd per foot and a storage coefficient of about 0.0006.
Significant fluctuations of artesian-pressure head result from daily and seasonal variations in withdrawal of water from wells. During periods of heaviest withdrawal, the piezometric surface is lowered about four to five feet throughout the area and more than eight feet at some places. The artesian pressure head declined progressively in the coastal area during a period of extensive agricultural development from 1950 to 1952. Since 1952, however, seasonal fluctuations have decreased in magnitude and a slight progressive rise in artesian head has occurred locally, as a result of a decrease in withdrawals. Records of water levels in wells not affected by local variations in discharge indicate that, regionally, the artesian head declined progressively in 1955-56.
INTRODUCTION
Along much of the coast of Florida, salt water is present in part or all of the principal water-bearing formations. Thus, the problem in many coastal areas is to find supplies of fresh water that are adequate to meet increased demands and are economically feasible to develop. The problem in other areas is to protect present supplies from contamination by salt water encroaching from the sea or from formations that lie beneath the fresh-water supply. Encroachment from either source may be induced by excessive lowering of the fresh-water head.
During recent years, expansion of agriculture in the Ruskin area of southwestern Hillsborough County has greatly increased the use of artesian water for irrigation which has lowered the artesian head in the area. The detection of -relatively salty water in some wells has suggested that salt water may be encroaching




REPORT OF INVESTIGATIONS NO. 21 3
from Tampa Bay. Recognizing this possibility, the Board of County Commissioners of Hillsborough County requested the U. S. Geological Survey and the Florida Geological Survey to make a study of the ground-water resources in the Ruskin area. Accordingly, the Federal Geological Survey began an investigation in October 1950, in cooperation with the above agencies.
Most of the fieldwork of the investigation was done by the author prior to June 1953, under the immediate supervision of H. H. Cooper, Jr., then District Engineer of the Federal Survey, in Tallahassee. Completion of the fieldwork and preparation of the report were under the immediate supervision of M. I. Rorabaugh, present District Engineer of the U. S. Geological Survey. The entire investigation was made under the general supervision of A. N. Sayre, Chief of the Ground Water Branch, U. S. Geological Survey.
PURPOSE AND SCOPE OF THE INVESTIGATION
The purpose of the investigation was to make a detailed study of the geology and ground-water resources of southwestern Hillsborough County, with the primary objective of determining whether the artesian water had been contaminated by salt water from Tampa Bay or from other sources. The investigation, therefore, consisted of several phases, as described below:
1. An inventory of about 650 selected wells, to obtain pertinent information related to the occurrence and use of ground water in the area.
2. Collection of data on water levels, to determine trends and magnitude of water-level fluctuations, and for use in constructing maps showing the altitude to which water will rise in artesian wells.
3. Collection of water samples from selected wells, for chemical analysis.
4. Determination of the chloride content of water from wells, to ascertain the location and extent of areas in which the artesian water has been contaminated.
5. Periodic determination of the chloride content of water from selected wells, to understand the relation between the chlorinity of the water and the artesian pressure head.
6. A study of geologic conditions as related to the occurrence and movement of ground water.
7. Exploration of selected wells with a deep-well current meter,




4 FLORIDA GEOLOGICAL SURVEY
to determine the depth, thickness, and relative productivity of the principal water-bearing zones.
8. Resistivity surveys and determination of the chloride content of water samples collected at several different depths in selected wells, to determine the relative chlorinity of the water in the principal water-bearing zones.
9. Studies to determine the water-transmitting and waterstoring capacities of the different formations.
PREVIOUS INVESTIGATIONS
No detailed study of the geology and ground-water resources of southwestern Hillsborough County has been made previously. However, the Florida Geological Survey and the U. S. Geological Survey have published several reports that include brief discussions' of the geology and the occurrence of ground water in Hillsborough County.
One of the earlier reports (Matson and Sanford, 1913, p. 320, 323; pl. 5) contains a generalized map of the Pleistocene terraces, logs of wells, descriptions of formations exposed at the land surface, and a brief discussion of the ground water of Hillsborough County. A report by Sellards and Gunter (1913, p. 258-262, fig. 16) includes a summary of the geology and ground-water resources of the county and contains a map showing the area of artesian flow.
The geology and ground water of Hillsborough County are described in a report by Stringfield (1936, p. 127, 128, 152). This report includes maps of the Florida Peninsula showing the area of artesian flow, the height above sea level to which water will rise in wells that penetrate the principal artesian aquifer, and the areas in which water with a chloride content of more than 100 parts per million (ppm) is present at moderate depths. Waterlevel measurements and other data from several wells in the county also are included.
A report by Parker and Cooke (1944, pl. 3) contains a map showing the general configuration of the Pleistocene terraces in southern Florida, including Hillsborough County. Reports by MacNeil (1949, p. 105, pl. 19), Cooke (1945, p. 11-13, 245-312), and Parker (Parker and others, 1955, p. 89-124, pl. 10) discuss the Pleistocene terraces of Florida and contain maps showing the configuration of the terraces and shorelines in Hillsborough County.




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REPORT OF INVESTIGATIONS NO. 21 5
The formations penetrated by wells and those exposed at the surface are described in some detail in a report on the geology of Florida by Cooke (1945, p. 34, 42, 47, 125, 208, 222, 290, 305). A report by Vernon (1951, figs. 11, 33, pl. 2) contains maps showing the subsurface features of some of the formations underlying Hillsborough County.
Chemical analyses of water from several wells and springs in Hillsborough County are included in a report by Collins and Howard (1928, p. 216-217) and one by Black and Brown (1951, p. 64).
ACKNOWLEDGMENTS
Appreciation is expressed to the many well owners in the Ruskin area who contributed information and otherwise aided the investigation. Special acknowledgment is made to the well drillers who collected rock cuttings and furnished much valuable information. These include H. J. Tucker, Howard Morrill, and E. E. Boyette, of Ruskin; and May Bros. of Tampa.
WELL-NUMBERING SYSTEM
The well-numbering system used in this report is based on latitude and longitude. The Ruskin area, which lies between 270 and 280 north latitude and 82o and 830 west longitude (fig. 1), has been divided into quadrangles by a grid of 1-minute parallels of latitude and 1-minute meridians of longitude, as shown on plate 1. The wells have been assigned numbers according to their location within this grid. Each well number consists of three parts: the first part is the latitude, in minutes, of the south side of the 1-minute quadrangle in which the well is located; the second part is the longitude, in minutes, of the east side of the same 1-minute quadrangle; and the third part is the number of the well within the quadrangle. For example, the number 43-25-4 designates the fourth well in the quadrangle bounded by latitude 43' on the south and longitude 25' on the east. The degree of latitude and longitude are not included as a part of the well number, as they are the same for all wells used in this report. Well locations are shown on the map, plate 1. Complete well descriptions, locations, and other data are published in Florida Geological Survey Information Circular No. 22 and may be obtained for one dollar per copy.




6 FLORIDA GEOLOGICAL SURVEY
G EOR 0G IA
-- NASSAU
'tyriluesse eHAMILTON
LEON / MADISON as e e tevite
I /UVAL SUWAMNEEi BAKER L1 BERTy WAULLA TAYLOR G t FRANKLIN I L Y
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LEVY MARION
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m&otual29LA 2 CITRUS LA E M E SEMINOLE
HERNANDO ORANGE PASCO r I
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EXPLANATION N1 -I
~222 MANATEEI OIEECOSE MANATEE HARDEE OKEH LUCI Hillsborough County HIGHLANDS .Lc
Rs re DESOTO MARTIN
Ruskin area --t- -R aARaI CHARLOTTI GLADES
LEE HENRY PALM BEACH
COLLIER BROWARD
- Miami MONROE
DADE
25 0 25 50 75 10 Miles
Aamierne Scal.
-__25*
Figure 1. Map of the peninsula of Florida showing location of Hillsborough County and the Ruskin area.




REPORT OF INVESTIGATIONS NO. 21 7
GEOGRAPHY
The Ruskin area, as defined for this report, comprises about 200 square miles in southwestern Hillsborough County (fig. 1). It is bounded on the south by Manatee County and extends northward to the 27056' parallel of north latitude. From Tampa Bay, which forms the western boundary, the area extends eastward to the 82017' meridian of west longitude.
CLIMATE
The Ruskin area has a subtropical climate, with a mean temperature of about 720 F, according to the U. S. Weather Bureau. The mean monthly temperatures at Tampa range from 61.50 F in January to 820 F in August, as shown in figure 2. For comparison, the figure shows the average maximum and minimum monthly temperatures during 1956.
The records of the U. S. Weather Bureau show (fig. 2) that the average yearly precipitation at Tampa during the period from 1891 through 1955 was 49.94 inches; the range was from 32.25 inches in 1908 to 67.19 inches in 1912. The average monthly rainfall ranged from 1.04 inches in November to 8.11 inches in July, and more than 70 percent of the annual precipitation occurred between June 1 and September 30.
PHYSIOGRAPHY
The Ruskin area is in the Terraced Coastal Lowlands of Vernon (1951, p. 16), a subdivision of the Coastal Plain province. The topographic forms consist mostly of marine terraces and associated features that were developed during the Pleistocene time, when the sea at several times stood above or below its present level. The topography may be divided generally into units-a relatively fiat coastal area and a hilly upland area. The coastal area is about three to six miles wide and extends inland from Tampa Bay to an escarpment that represents the shoreline of the Pamlico sea of late Pleistocene time. The coastal area slopes gently toward the bay from the base of the escarpment, which is about 25 feet above sea level. Most of the coastal area is between 5 and 15 feet above sea level, but it contains a few low hills and ridges having altitudes of 30 feet or more. The hilly upland area extends eastward from the Pamlico escarpment, gradually increasing in altitude to more than 100 feet in the vicinity of Wimauma. Most




8 FLORIDA GEOLOGICAL SURVEY
70
GC~ 4994 MEAN
T V(1891 -855)
50,
540
9- 20 -ME 0 ,I,A MNMLY810 AEAE(19-95
Ic
22
A18
24
z g So.4ERAGE EN!MUM16 MINIMUM (1891-19
956
Figure 2. Precipitation and temperature at Tampa.
of the upland area consists of low rolling hills having relatively flat summits, at altitudes of 50 to 90 feet. The marine terraces and associated features have been modified to some extent by stream dissection. Numerous ponds, depressions, and swamps occur in the poorly drained parts of the area.
The history of the Pleistocene epoch and the marine terraces and deposits associated with the fluctuations of sea level in Florida are discussed in detail in reports by Cooke (1945, p. 11-13, 245312), Vernon (1951, p. 15-42, 208-215), and Parker (Parker and others, 1955, p. 89-124). The rise and fall of the sea is attributed to the advance and retreat of the great continental ice sheets, the sea level rising during interglacial periods and falling during glacial periods. When the sea remained relatively stationary for long periods, shoreline features and marine plains were developed. The remnants of five marine terraces of Pleistocene age and the general configuration of four shorelines have been mapped in the Ruskin area (Cooke, 1945, figs. 43-47; Parker and others, 1955, pl. 10), as listed in the following table:




REPORT OF INVESTIGATIONS No. 21 9
TABLE 1. Pleistocene Terraces and Shorelines of the Ruskin Area
Terrace Altitude of shoreline (feet above msl)
Sunderland ------------------------------ --- ------------------- 1701
Wicomico .--- ---------------------------------------- ---------100
Penholoway -------------------------------------------------- 70
Talbot .........-------------- --------------- ----------- 42
Pamlico 25
'Sunderland shoreline not present in Ruskin area.
Figure 3 shows the general boundaries of the Pleistocene terraces in the Ruskin area, as determined from aerial photographs, topographic maps, and field observation. The highest and oldest surface lies above the Wicomico shoreline and represents the remnants of the Sunderland terrace (Cooke, 1945, p. 278-279). The sea was about 170 feet above the present level when the Sunderland was formed, and practically all of south Florida was submerged.
During Wicomico time, the sea stood about 100 feet above the present level and all the Ruskin area was submerged except the Sunderland terrace and associated islands. The shoreline of the Wicomico sea is marked by an escarpment that is well preserved in many places.
The Penholoway terrace was formed when the sea stood at an altitude of about 70 feet. The general configuration of the shoreline can be distinguished on aerial photographs, on topographic maps, and in the field (fig. 3).
The shoreline of the Talbot sea, which stood at an altitude of about 42 feet, is poorly defined throughout most of the area, and in many places the shoreline escarpment coincides with the escarpment of the Pamlico terrace.
The Pamlico terrace is the youngest Pleistocene terrace that has been recognized in the Tampa Bay area. It was formed when the sea was about 25 to 30 feet above the present level. The shoreline of the Pamlico sea is marked by an escarpment which is well preserved throughout most of the area. The base of the escarpment is generally about 25 feet above sea level.
Surface drainage in the Ruskin area is principally through the Little Manatee River, the Alafia River, and Bullfrog Creek, all of which flow into Tampa Bay. Much of .the coastal area is drained by small streams that extend inland from Tampa Bay for relatively




10 FLORIDA GEOLOGICAL SURVEY
82Z30
0 .
_6
L S 0
i RIVER VIEW EXPLANATION EAST TAMPA
IS. s NT N L Pamhico terrace
Tcbot errcce 27*
Penhctoway terrace
ADAMSVILLE
w ccmico terrcce 4
Sunderland terrace
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MANATEES COUNTY S'30A82,25'8~~ Figure 3. Map of the Ruskin area showing the Pleistocene terraces.
short distances. Canals have been dug throughout most of the area to supplement the natural drainage.
CULTURE
The principal towns in the Ruskin area are East Tampa, Gibsonton, Riverview, Ruskin, Sun City, and Wimauma (pl. 1). U. S. Highway 41 passes through all towns along the coast




REPORT OF INVESTIGATIONS NO. 21 11
and connects them with Tampa to the north and Bradenton to the south. U. S. Highway 301 provides a north-south route through the eastern part of the area. State Highway 674 and several other paved roads connect the U. S. Highways. The Atlantic Coastline Railroad provides transportation in the coastal area and the Seaboard Air Line Railroad serves Wimauma and the eastern part of the area.
GEOLOGY
The surface formations over most of the Ruskin area consist of undifferentiated deposits of Pleistocene age, although beds as old as Miocene are exposed at some places. The geologic formations penetrated by water wells are listed and briefly described in table 2, and geologic cross sections are shown in figure 4. The subsurface formations are described on the basis of rock cuttings, electric logs, and drillers' logs of wells in and adjacent to the Ruskin area. Those penetrated by water wells in the area are the only formations discussed in this report.
o d OGAL i, o
-- -A H
TM AMPA
-200 FA ORMTON -0
(O(gieocene)
-500 L ellnE th Ruski area. tO
wO- -500
-0 OCALA GROUP ,j., o nt1otii
(Eocene)cne ~ 40
FORMAIO FO00IO
i --0000
_ I S N LMEST ONE5
2 -500
00 "AO
PEnocen e) 1 P
-500 4M05ce-00
WU -200 FOMAIO -200
SSUANEELMSTONE
-400 O iocene -10
-300 5300
Figure 4. Geologic cross sections showing the formations penetrated by water wells in the Ruskin area.




12 FLORIDA GEOLOGICAL SURVEY
TABLE 2. Geologic Formations Penetrated by Water Wells in the Ruskin Area
.Thickness
Age Formation Characteristics (feet)
Pamlico sand Sand, shells, limestone, and calcareous
Older Terrace clay. 0- 60
" deposits Sand, silt, and some clay.
r Undifferentiated Sand and gravel of quartz and phos- 0- 20?
deposits phate, clay, and bone fragments.
Sand, shells, gravel of quartz and 0- 25?
-_ phosphate, and lignite.
Hawthorn Clay and marl, gray, greenish gray to 10-150
formation blue-gray, sandy, phosphatic, interbedded with sandy limestone, sand, silt and shells. Serves as a confining layer for the water in the underlying limestones but is the source of small water supplies.
Tampa Limestone, creamy white, gray, and tan, 50-200
formation fairly hard, porous to dense, sandy, fossiliferous, silicified in part. A very productive source of artesian water.
Suwannee Limestone, creamy white to tan, fairly 200-225
limestone soft, granular, porous, fossiliferous, crystalline and dolomitic in part. Probably a more productive source of water than the Tampa, but water is somewhat more mineralized.
Ocala group Limestone, white, cream and tan, soft, 250: granular, chalky, fossiliferous, coquinoid in part. Penetrated by only a few wells in the Ruskin area but may be a very productive source of artesian water. The water is probably highly mineralized in the coastal area. Avon Park Limestone, white to tan, soft, somewhat 600-700
limestone chalky, granular, foraminiferal; dolomite, tan to dark brown hard crystalline, lignitic in part, very porous. A very productive source of artesian water but tapped by very few wells. Water is salty in the coastal area.




REPORT OF INVESTIGATIONS NO. 21 13
EOCENE SERIES
The Eocene limestones have a combined thickness of about 5,000 feet in the Tampa Bay area, but only the upper part of this limestone section is tapped by water wells.
AVON PARK LIMESTONE
The upper part of the late middle Eocene limestone in Florida was named the Avon Park limestone by Applin and Applin (1944, p. 1680, 1686). It is the oldest formation exposed at the surface (with outcrops in Citrus and Levy counties) and is also the oldest formation penetrated by water wells in southwestern Hillsborough County.
The upper part of the Avon Park consists predominantly of white to tan, soft, chalky, granular limestone containing many foraminifers and other fossils. The lower part is principally a tan to dark brown, hard, crystalline dolomite containing carbonaceous material but very few fossils.
The Avon Park limestone is probably about 600 to 700 feet thick in the Ruskin area. The top of the formation ranges in depth from about 575 feet below sea level in the northern part of the area to about 900 feet in the southern part.
The formation is very permeable, owing to the extensive development of solution channels, and is a productive source of artesian water. However, relatively few wells in the area penetrate the Avon Park, because it contains highly mineralized water in much of the coastal zone and sufficient quantities of water of better quality can be obtained from the younger formations at shallower depths.
OCALA GROUP
Until recent years, all the limestone deposits of late Eocene age in peninsular Florida were considered as a single formation, the Ocala limestone. As shown in table 3, Cooke (1945, p. 53-62) and Applin and Applin (1944, p. 1683) referred all late Eocene limestones to the Ocala; however, Applin and Applin recognized upper and lower members of the formation, on the basis of lithologic and faunal differences. After completion of his studies in Citrus and Levy counties, Vernon (1951, p. 111-171) separated the late Eocene limestones into two formationis---the Ocala limestone, restricted to the upper part, and the Moodys Branch




14 FLORIDA GEOLOGICAL SURVEY
formation. He also divided the Moodys Branch formation into two members-the Williston member, to include the upper part, and the Inglis member, to include the lower part. Puri (1953, p. 130) changed the name of the Ocala limestone (as restricted by Vernon) to the Crystal River formation, and gave formational rank to the Williston, and Inglis members of Vernon's Moodys Branch formation. The Crystal River, Williston and Inglis formations, as described by Puri, are now referred to as the Ocala group by the Florida Geological Survey.
TABLE 3. Stratigraphic Nomenclature of the Upper Eocene in Florida
U. S. Geological Survey Florida Geological Survey
Cooke (1945) Applin (1944) Vernon (1951) Puri (1953)
Upper Ocala limestone Crystal member (restricted) River formation
Ocala
Ocala Ocala
Oalm len Lower Moodys group
limestone limestone member Branch Williston Williston formation member formation
Inglis Inglis
member formation
The Ocala group lies unconformably on the Avon Park limestone in southwestern Hillsborough County and is probably about 250 feet thick. The top of the formation ranges in depth from about 300 feet below sea level in the northern part of the area to about 600 feet in the southern part. The upper part of the Ocala is a creamy white to tan, soft, somewhat granular, chalky, coquinoid limestone, composed of the remains of foraminifers, mollusks, echinoids, and other fossils which are loosely cemented in a fine, granular, chalky matrix. The lower part of the Ocala is more granular and less chalky than the upper part and contains fewer foraminifers.
The Ocala is penetrated by relatively few wells in the Ruskin area, although it may be a productive source of water. In the coastal area, the water in the Ocala has a considerably higher mineral content than the water in the younger limestones.




REPORT OF INVESTIGATIONS NO. 21 15
OLIGOCENE SERIES
SUWANNEE LIMESTONE
The Suwannee limestone, as defined in this report, includes all deposits of Oligocene age in the Ruskin area. The Suwannee is differentiated from the underlying Eocene formations and the overlying Miocene formations on the basis of lithology and fauna and is separated from these formations by unconformities.
The upper part of the Suwannee is generally a creamy white to tan, soft, granular, fossiliferous limestone, but at some places it contains beds that are crystalline, dolomitic, and partly silicified. The lower part of the formation is generally a tan to brown, soft to hard, granular to dense limestone that is harder, more crystalline and dolomitic, and less fossiliferous than the upper part. The formation contains abundant remains of mollusks, echinoids, and foraminifers. Specimens of the foraminifer Rotalia mexicana are fairly abundant throughout the formation. The occurrence of Dictyoconus cookei and Coskinolina floridana is generally restricted to the lower part of the Suwannee.
The top of the Suwannee limestone in the Ruskin area ranges in depth from about 75 feet below sea level in the northern part of the area to about 400 feet in the southwestern part. The formation has a fairly uniform thickness of about 200 to 225 feet. The contours on the map in figure 5 show the configuration and approximate altitude of the top of the formation.
The Suwannee limestone is probably the most productive source of artesian water generally tapped in the Ruskin area. In the coastal area, however, the water in the Suwannee is somewhat more mineralized than the water in the overlying. Tampa formation.
MIOCENE SERIES
The deposits of Miocene age in the Ruskin area are herein referred to the Tampa formation of early Miocene age (Cooke, 1945, p. 1070) and the Hawthorn formation of middle Miocene age. Both formations are of marine origin, but they represent different depositional environments and are separated by unconformities.
TAMPA FORMATION
The Tampa formation lies unconformably on the Suwannee limestone of Oligocene age and consists of white, gray, and tan hard, dense, sandy limestone. It is crystalline and dolomitic in




16 FLORIDA GEOLOGICAL SURVEY
8230 Couseway Blvd
400
G
0 301
SRIVERVIEW L
EXPLANATION EAST TAMPA ALA. RVER
Well (drllerk loq ovaidable) i NT
Well (cttmgs available)
-150 27*5 d
,Z).
Well (electric kog avilable)
Contour hne represents the altitude of the 11-,00
top of the Suwannee limestone, i feet, 4
w,th reference to mean sea level. -5
Conour interval 25 feet
3 4 5 MILES
27*45'4 0
RusK< o -300
0 40
the top of the Suwannee limestone.
part and contains silicified layers. The formation is generally fossiliferous, containing echinoid plates and spines, tests of ostracods and foraminifers, and many molds and casts of mollusks. Specimens of the foraminifers Archaias and Sorites are fairly abundant throughout most of the Tampa.
The top of the Tampa formation ranges in depth from a little below sea level in the northern part of the Ruskin area to about




REPORT OF INVESTIGATIONS No. 21 17
30Couseay Blvd 8220
- 27*55 27*35
0
L 0 3
EXPLANATION EAST TAA r r Aand RIVER
Well (drillers log available) INT t
S Well (cultings available) 275Y
Well ( electric log avoilable)
-00-ADADA -75-"
200 onusva Contour lne represents the olttude of the0
op of the Tampa formation, in feel, 41
with reference to mean sea level.
Contour interval 25 feet0. 0 Q0
0 1 2 3 4 5 MILES
- 27-45 755b
RUS0 0
of. The toper thiformaone1 in the areas 75othe
42 endS oadGH (pU f.1)
Figure 6. Map of the Ruskin area showing the configuration and altitude of
the top of the Tampa formation.
250 f eet below sea level in the southern part. The contours on the map in figure 6 show the con-figuration and -approximate altitude of the top of the fo rmation in the area. The thickness of the Tampa is about 50 feet near the northern boundary of the area and increases southward, in the direction of dip, to about 200 feet (fig. 4). The average thickness is about 175.feet in the- area south of Big Bend Road (pl. 1).




18 FLORIDA GEOLOGICAL SURVEY
The Tampa formation is a productive source-of artesian water in the Ruskin area. Most of the water is obtained from relatively thin zones that have a high permeability, owing to the many interconnecting cavities formed by solution of the limestone.
HAWTHORN FORMATION
The Hawthorn formation, as defined in this report, includes all marine deposits of middle Miocene age. It was deposited in shallow water and consists predominantly of gray, blue-gray and gray-green, sandy, calcareous, phosphoritic clay interbedded with thin layers of gray, white, and tan sandy phosphoritic limestone, and thin beds of sand and shells. The limestone layers are dolomitic, silicified, and fossiliferous in part. The altitude of the top of the Hawthorn ranges from about 25 feet above sea level to about 50 feet below sea level, and the upper part of the formation is exposed at several places in the area. The thickness increases from north to south in the direction of dip, ranging from less than 10 feet in the northern part of the area to more than 150 feet in the southern part (fig. 4).
The thin beds of sand and limestone yield artesian water to some wells in the area, but the Hawthorn is not generally a very productive source of water. Because of the thickness and low permeability of the clay beds, the Hawthorn serves as a confining, layer for the water in the underlying limestones.
PLIOCENE AND PLEISTOCENE SERIES
The Hawthorn formation is overlain at some places by about 5 to 10 feet of sediments that consist of shells, sand, carbonaceous material, and gravel of phosphorite and quartz. At other places it is overlain by several feet of sediments consisting predominantly of sand but containing some clay, gravel of quartz and phosphate, bone fragments, and shark teeth. The age of these sediments has not been determined, but it is probably late Miocene or Pliocene.
Pleistocene sediments of the higher terraces consist mostly of undifferentiated sands that range in thickness from about 10 feet to 60 feet. The surface of the Pamlico terrace is underlain by sand, sandy clay, and shells. The beds of limesto e and shells, which pinch out near the Pamlico shoreline and are generally less than 20 feet above sea level, were apparently deposited during late Pleistocene time. However, these beds were referred by Cooke (1945, p. 222-223) to the Caloosahatchee marl of Pliocene age.




REPORT OF INVESTIGATIONS NO. 21 19
'he Pleistocene deposits beneath the Pamlico surface range in :hickness from about 10 feet to 50 feet, except where they have been completely eroded by streams. The Pleistocene deposits are the source of a few domestic water supplies in the area.
GROUND WATER
PRINCIPLES OF OCCURRENCE
Practically all the water of the earth moves through the vast circulatory system known as the hydrologic cycle. Water condenses from the moisture in the atmosphere and falls as rain or snow, moves over or beneath the land surface to the oceans, and is returned to the atmosphere. Actually, the cycle may be modified or completed at any time after the water condenses from the atmosphere, as evaporation may begin even before the water reaches the earth and continue throughout the entire cycle. Great quantities of water are returned to the atmosphere by evaporation from vegetal surfaces (transpiration).
Much of the water that falls on the land surface as rain or snow runs off into streams, lakes, or other bodies of surface water, and a part eventually reaches the oceans. Some water is returned to the atmosphere by evaporation directly from land and water surfaces, and a part of it is absorbed by the soil or surficial rocks and becomes subsurface water. The amount of water than sinks directly into the ground from each rainfall depends on many factors, such as the slope of the land surface, vegetal cover, intensity of the rainfall, and previous moisture content and character of the surface material.
Subsurface water may be divided into two general classessuspended water and ground water. Suspended water is the water in the zone of aeration-the zone in which the interstices of the soil or rocks are not completely filled with water. Ground water is the water in the zone in which all the interstices are completely filled with water under greater than atmospheric pressure. This saturated zone is the reservoir that yields water to all springs and wells.
The water in the zone of saturation may occur as (1) unconfined ground water (under nonartesian conditions), or (2) confined ground water (under artesian conditions). Where the ground water is not confined-its upper surface is under atmospheric pressure and is free to rise. and fall-it is said to be under nonartesian conditions. Its upper surface is called the water




20 FLORIDA GEOLOGICAL SURVEY
table. Where the water is confined in a permeable bed that is overlain and underlain by relatively impermeable beds, its upper surface is not free to rise and fall and it is said to be under artesian conditions. The term "artesian" is applied to ground water that is confined under sufficient pressure to cause it to rise above the top of the permeable bed that contains it, but not necessarily above the land surface.
An aquifer is a formation, group of formations, or part of a formation, in the zone of saturation, that is permeable enough to transmit usable quantities of water. Recharge is the process of replenishment of the water in an aquifer, and areas in which it occurs are known as recharge areas. Generally, unconfined aquifers may receive direct recharge from precipitation throughout their lateral extent, whereas artesian aquifers may receive such recharge only where their confining beds are absent or relatively permeable.
The piezometric surface of an aquifer is an imaginary surface to which water from an artesian aquifer will rise in tightly cased wells that penetrate the aquifer. Where the piezometric surface is above the land surface, artesian wells will flow under natural pressure.
GROUND WATER IN FLORIDA
Ground water occurs in Florida under both nonartesian and artesian conditions. Nonartesian conditions are generally restricted to the shallow deposits of sand, gravel, shells, and limestone which form many aquifers of relatively small areal extent. These deposits are the source of many domestic water supplies throughout the State and also of public and industrial supplies in areas where the deeper formations contain salty water. The water in the unconfined aquifers is generally replenished by local rainfall.
ARTESIAN WATER
Most of Florida is underlain by a thick section of permeable limestone formations of Eocene, Oligocene, and Miocene age. These formations compose an extensive artesian aquifer from which most of the large ground-water supplies of the State are obtained. Stringfield (1936, p. 125-132, 146) described the aquifer and mapped the piezometric surface in 1933 and 1934. The name "Floridan aquifer" was introduced by Parker (Parker and others,




REPORT OF INVESTIGATIONS NO. 21 21
1955, p. 188-189) to include "parts or all of the middle Eocene (Avon Park and Lake City limestones), upper Eocene (Ocala limestone), Oligocene (Suwannee limestone), and Miocene (Tampa limestone, and permeable parts of the Hawthorn formation that are in hydrologic contact with the rest of the aquifer)," The artesian water is confined by relatively impermeable layers in the limestone formations and by the overlying clay beds of Miocene age which extend over most of the State. The water in the artesian aquifer is replenished chiefly by rainfall in areas where the confining beds are absent, are breached by sinkholes, or are sufficiently permeable to permit the passage of water from the land surface into the limestone.
PIEZOMETRIC SURFACE
The configuration of the piezometric surface in peninsular Florida is shown by the contour lines in figure 7. These lines represent the height, in feet above sea level, to which water will rise in wells that penetrate the Floridan aquifer. They indicate the areas in which recharge occurs; and, through inference, the general direction of water movement in the Floridan aquifer may be deduced. In areas of recharge, the piezometric surface is relatively high. The water moves away from these areas in the direction of steepest gradient, at right angles to the contour lines, toward areas of discharge, where the piezometric surface is relatively low. In central Florida the piezometric surface forms an elongated dome which is centered in northern Polk County. The presence of this dome indicates that the lake region of Polk County is the center of a relatively large area of recharge which probably extends into adjacent counties (Stringfield, 1936, p. 148). The water enters the limestone formations in this area through the numerous sinkholes and at places where the confining bed is either absent or slightly permeable.
GROUND WATER IN THE RUSKIN AREA
In the Ruskin area the water in the Pleistocene sands and other permeable beds that lie above the Hawthorn formation is generally unconfined and is replenished by local rainfall. A few small domestic water supplies are obtained from these formations, but most domestic and larger supplies are obtained from the permeable beds of the Hawthorn formation or the underlying limestones.
I.




22 FLORIDA GEOLOGICAL SURVEY
SW 83" 82" al" 80'
o G JEO0 R G IA
LIBERT -" WAIULLAA TA 4A O r_ _T r t LA
FRANKLIN r. IE o 90 -A1 0b
i I IIL po-='ro I T
E ALACHUA PUTNAM
9 FLAGLERO L "VYloMARION 1aOcala
ITNLACO -OLUSI 29
t' '' - +-'' I_\ o .., _O,,.~
9S SEMINOLE
HERNANDO ARNGE
- 30 0HILLSBORO GN SCEOLA 28' Tma P L K 50 LNIAN RVE
MANATEE HA E 0 OKECOBE LUC AHIGHLAN SARASOA DESOTO MARTIN HI -ARLOTTE GLACES K
LEE HENRY PALM BEACH so
EXPLANATION iami e
Contour lines represent approximately the height, DADE
in feet above mean sea level, to which water will 3
rise in tightly cased wells that penetrate the
principal artesian aquifer in 1949
___ ___ __ ___ ___ __ ___ --10 25 25 0 25 50 75 100 Miles
K. West
Approxmate scaie
Figure 7. Map of peninsular Florida showing the piezometric surface of the Floridan aquifer in 1949.




REPORT OF INVESTIGATIONS NO. 21 23
ARTESIAN WATER
In the Ruskin area, as in most of the State, the Floridan aquifer is the principal artesian aquifer. The water in this aquifer is replenished chiefly by infiltration of rainfall in the recharge area centered in northern Polk County. From there it moves southwestward into the Ruskin area, as suggested by the configuration of the contours in figure 7.
The Avon Park limestone and the Ocala group of Eocene age, which are productive sources of water in much of peninsular Florida, are probably capable of yielding large quantities of water in the Ruskin area. These formations are penetrated by very few wells in the area, however, as the Suwannee limestone and Tampa formation are sufficiently productive to supply most wells.
The water in the Suwannee limestone and Tampa formation occurs in permeable zones separated by relatively impermeable layers which retard vertical movement of the water and serve locally as confining beds.
The Hawthorn formation consists predominantly of clay and serves as a confining bed for the water in the Floridan aquifer. Thin beds of sand and limestone within the formation contain artesian water that is the source of many domestic supplies and some small irrigation supplies. The artesian pressure head in the Hawthorn is considerably less than the head in the Floridan aquifer; thus, the Hawthorn probably receives some recharge by upward percolation of water from the Floridan aquifer.
Current-Meter Exploration: In order to determine the depth, thickness, and relative productivity of the different water-bearing zones in the limestone formations, explorations were made in several selected wells with a deep-well current meter, a device for measuring the velocity of flow of water through a well bore. The results of the current-meter traverses are shown graphically in figures 8 through 26, which also include well-construction data, electric logs, and resistivity and chloride content of the water. The velocity of the water is expressed in revolutions per minute (rpm) of the current meter. Actual flow rates, which are a function of velocity and cross-sectional area, cannot be computed accurately, as the diameter of the uncased part of the wells is not uniform.
A summary of the information obtained from the currentmeter explorations (figs. 8-26) is given in table 4.
Fluctuations of Artesian Pressure Head: Fluctuations of artesian pressure head range from a fraction of a foot to several feet and are caused by one or more of several factors. The larger




24 FLORIDA GEOLOGICAL SURVEY
TABLE 4. Summary of Results of the Current-Meter Explorations
Well Rate of Depth of principal Well Rate of Depth of principal number flow producing zones number flow producing zones
(gpm) (feet below msl) (gpm) (feet below msl)
40-30-1 250 200 to 245 45-24-17 300 220 to 260 245 to 355 295 to 310 355 to 360 340 to 345 420 to 445
45-24-23 125 155 to 170 43-26-4 100 320 to 325 255 to 265 365 to 395 365 to 380 420 to 480
45-25-20 200 90 to 105 170 to 265
43-26-7 300 245 to 285 315 to 325
355 to 365 45-26-2 125 110 to 140 295 to 305
43-26-12 300 125 to 150 45-26-3 250 170 to 195 235 to 250 265 to 275
325 to 350 355 to 385 410 to 420
43-26-26 300 100 to 120 200 to 270 46-24-7 350 195 to 495 310 to 410
46-24-8 _350 85 to 105 44-24-15 50 280 to 290 235 to 275 395 to 415
44-25-42 350 120 to 160 295 to 335 46-24-12 150 70 to 80 355 to 370 195 to 237+44-26-10 200 100 to 285 46-24-17 250 170 to 190 305 to 320 295 to 333 345 to 370
47-23-8 125 150 to 160 255 to 275
44-26-31 350 395 to 420-+ 25o-7 48-23-15 150 175 to 190 45-24-13 350 70 to 190 215 to 240 395 to 404 265 to 280




REPORT OF INVESTIGATIONS NO. 21 25
VELOCITY
AGE FORMA- SELF-POTENTIAL RELATIVE RESISTIVITY (pOF WA ter)
TIN (rpm of current meter)
TION ,Omv -,. 2 5_ ohms 0 50 100
PLEISTOCENE 6 8 PLIOCENE .
0
-100- 0
__o
-IO.
(I)
bi
wi LdI ::
o O z I- 0- Z
0 0
LLI
-3OO
Lii
Ld
W W
I-- _L t J Zu
z
00 Lii
Figure 8. Graph showing well-exploration data for well 40-30-1.
fluctuations generally result from daily and seasonal changes in withdrawal of water from wells or from variations in recharge from rainfall. Minor fluctuations are caused by tides, atmosphericpressure changes, winds,; earthquakes, and passing trains. The minor fluctuations of water levels and their causes are discussed in detail in a paper by Parker and Stringfield (1950).
Records from continuous recording gages on two wells and periodic water-level measurements in about 20 wells provide information on the fluctuations of artesian pressure head in the Ruskin area during a period of about 6 years. Hydrographs prepared from the records of the continuous recording gages on wells 42-19-1 and 44-25-39 are shown in figure 27. Hydrographs of 16 wells in which water levels were measured periodically are shown in figures 28-33. Water-level measurements in other wells are listed in table 6 and in Information Circular No. 22.




26 FLORIDA GEOLOGICAL SURVEY
FORMA- WELL VELOCITY OF WATER CONTE
AGE TION 43-26-4 (rpm of current meter) arts per million) 0 50- 100 0 50
0 PLEISTOCENE
a PLIOCENE .H
-100 I
Zz ____20
> -300 Ll
-J
<_ L
LU
0 z LUI 0 2 -200 <50
0
Cr
LL
IL
Li
A -300 I-
LU
LJ
LL
z LUI
z 0
H Z LU 1-- z -.
LU o
(.9 i "
I LUJ
z
Cn
-5001__ _Figure 9. Graph showing well-exploration data for well 43-26-4.
The hydrograph of well 42-19-1 (fig. 27) shows the seasonal fluctuations and regional trend of the artesian pressure head from August 1951 to December 1956. The seasonal use of water i:s indicated by the declines in head during periods of least rainfall, when large quantities of water were being used for irrigation. The rises in head, corresponding to periods of greater rainfall, are due primarily to a decrease in discharge but at times may




REPORT OF INVESTIGATIONS No. 21 27
FORMA- WELL VELOCITY CHLORIDE CONTENT
AGE TION 43-26-7 (rpm of Current meter) (ports per million)
0 50 100 1 0 50 10O 0- PLEISTOCENE
SPLIOCENE
zz
-100
>i z
- i-0
-300
o z
Q 2
Li
z -200 a
U
LLi
-00
I-- w
Ld
U-)
" W
z z
0 w
IE W
U z
_ 0 0 1--500'Figure 10. Graph showing well-exploration data for well 43-26-7.
indicate an increase in recharge. The hydrograph indicates that the magnitude of seasonal fluctuations has increased from about four feet in 1952 to about eight feet in 1956. The lowest recorded water level- in this well was 29.6 feet, in April 1956. The progressive increase in the magnitude of seasonal fluctuations and the general downward trend of the artesian pressure head throughout the period of record reflect the regional increase in both seasonal and perennial use of water.
The hydrograph of well-44-25-39 (fig. 27) shows the effects of seasonal differences in local withdrawals. The slight downward




! VELOCITY OF WATER 'CHLORIDE CONTENT OF WATER AGE FORMA' SELF-POTENTIAL RELATIVE RESISTIVITY (rpm of current meter) (pOrt per million)
TON 10 my p2h j 0 50 00 10 2 0 00 10 20 2.
0-0 ..-.N -- --_ --SPLIOCEN9
.. -200 ...
-100
z
-a U
-J w
- 00
EOCENE
.j-_200- _dC( j2
-300
Figure 11. Graph showing well-expl]oration data for well 43-26-12. M w
W -J
0
z
- 0
0
-500
EOCENE
-600
Figure 11. Graph showing well -exploration data for well 43-26-12.




REPORT OF INVESTIGATIONS No. 21 29
trend of the artesian pressure head from 1950 to 1952 probably reflects the increased use of water resulting from expansion of agriculture during this period. The hydrograph indicates that local use of water has been relatively stable since 1952.
The hydrographs in figures 28-33 also show seasonal fluctuations due to local discharge. Some hydrographs indicate that discharge has remained relatively stable since about 1952, whereas others show a general upward trend of the artesian pressure head since 1953, thus indicating a decrease in local use of water.
Although the principal fluctuations of artesian head in the Ruskin area -are caused by changes in the rate of withdrawal of water from wells, observable changes are caused by earthquakes, atmospheric-pressure changes, and other factors.
Earthquake waves passing through the earth's crust cause a relatively rapid expansion and contraction of artesian aquifers, which results in fluctuations of the artesian pressure head. The magnitude of these fluctuations in a particular well may range from a few hundredths of a foot to several feet, according to the intensity of the earthquake and the distance of the epicenter from
VEIIOCITY OF WATER ~ MORIDE
AGEFORMA- SELF-POTENTIAL r RELATIVE RESISTIVITY V OCT OF WATER AETON 20 m a (rpm of c urrent meei o p
TION 20 my, 25 ohms
- ~ *0 50 100 I50 200 250 0- PLEiSTOCENE- f F
8 PLIOCENEf
ZZ -__o-___z z
-100
- 4
-500
Figure 12. Graph showing well-exploration data for well 43-26-26.




DEPTH, IN FEET REFERRED TO MEAN SEA LEVEL
II I I (i (J
0 0 0 0 0
0 0 0 0 0 0 EOCENE 0 LI GO CE NE M 10 CEN E ur- 0 OCALA HAWTHORN me GROUP SUWANNEE LIMESTONE TAMPA FORMATION z FORMATION n
, (.71 ,_-_ -_-_ --_._- --_______--_..___..___ ___ I
6" casing
O
F Me
u
Figure 13. Graph showing well-exploration data for well 44-24-15.




REPORT- or INVESTIGATIONS No. 21 3
WEL VELOCITY OF WATER CH4LORIDE CONTENT OF WATER RESISTIVITY OF WATER 44E 25RM2 W L rmacurent meter) (parts per million) mlihs
0 LPLEISTOCENE -__S PLIOCENE
4:z A
-J-to
W
0
I -____Iii
L I_ 13
- Z W z a. 0 W
0
Figure 14. Graph showing well-exploration data for well 44-25-42.
w HOFIE WCOEN AEFRA SELF-POTENTIAL j 6 RELATIVE RESISTIVITY VELOCITY OF WATER CHOIEATE T
TION ~ W' (0m e 2 hs rpm of curreent meler) Ipols per MAO"~)
_ I.m .4 L5 hs 0 5O 1O 150 50 100 10
0 PLEISTOCENE- ______ =
9PL IOCENEf
-too
0-100Jd 0 z 0 W 0
0
Fiur 154 rp hwn elepoain aafrwl 42-0




C4
vE:LOcIr" OF WAFE H CHLORIDE WCOTENT RESISrIvITY AGE FORMA SELF- POTENTIAL RELATIVE RESISTIVITY (rprn of current meier) (parps per m WonR
A TION IQ' POMNY A Rq ATV (m lhohmt
0. ______- _-. 50 100 150 -350 400 150 00
&PLIOCEtNE
00
z
W 0 0 to 3: 200 Iz
l--0,
300----
z
0
Figure 16. Graph showing well-exploration data for well 44-26-31.




REPORT OF INVESTIGATIONS NO. 21 33
FOR WELL VELOCITY OF WATER CHLORIDE
!AGE O(rpm of current meter) CONTENT
TION 45-24-13 ppm)I
0 50 KOO 50 101
0- PLEISTOCENE --
B PLIOCENE
100 0
o o
0 c_,
X
-J 0
400- a
w
O
z
z w 0
0
M 0
30
X LW I- J il
wW
-300 - - _Iz W 0
0 _j "
j Z'
0 <0
U)
oiur 17 rp hwn elepoato aafrwl 52-




34 FLORIDA GEOLOGICAL SURVEY
the well. The effects of earthquakes on water levels in wells 4219-1 and 44-25-39 are shown on the hydrographs in figure 34, which were traced from the charts of continuous recording gages. An earthquake in southern California, which occurred on July 21, 1952, had a magnitude of 7.5 (based on a comparative scale that ranges from a minimum intensity of 1 to a maximum intensity of 10) and caused maximum water-level fluctuations of 0.85 foot in well 42-19-1 and 0.46 foot in well 44-25-39. An earthquake of 8.5 intensity near the east coast of Kamchatka, in Siberia, on November 4, 1952, caused maximum water-level fluctuations of
0.86 foot in well 42-19-1 and 1.24 feet in well 44-25-39.
Daily changes in atmospheric pressure cause minor fluctuations of artesian pressure head which are observable in most wells, but these changes may be masked or modified by fluctuation due to tides, local pumping, or other factors. The effects of atmospheric-pressure changes on the water level in well 44-25-39 may be seen on the hydrographs in figure 34, even though these fluctuations are probably modified somewhat by effects of ocean tides and local discharge. The effects of changes in atmospheric pressure on the water level in well 42-19-1, which is not affected by local pumping or ocean tides, are shown also in figure 34. The
FCRMA- SELF-POTENTIAL ; RELATIVE RESISTIVITY VELOCITY OF WATER C HLORI
TONm 25ohms. (rp o curntolo mele150 tppm o
O 'LElyr0CEMESIO E 1 dt for wel 45-24-17.
.A 0
1C 'u&.
300 ...... .... .
Figure 18. Graph showing well-exploration data for well 45-24-17.




REPORT OF INVESTIGATIONS NO. 21 35
periods of low atmospheric pressure in the early morning and late afternoon are represented by high water levels. The highest atmospheric pressures occur about noon and midnight and are represented by the lowest water levels. The magnitude of the fluctuations caused by changes in atmospheric pressure is generally
WELL VELOCITY OF WATER CHLORIDE CONTENT z WELL OFWAT E.
AGE 'o (rpm of current meter) (parts per million)
o_ 45-24-23 0 50 100 0 50 IC00
0- PLEISTOCENE
&PLIOCENE
zz
0 00
OM
JO- ---__ -- ,w E2
10
.J
> iLJ
0
4200- o m--
F
W
0
00-
iur 1a
U)
- /
4i 00- ~ W -_ _.1
U_0
- z
Fig 1U
500- -- U__ _ _ _ .1_ _
Figure 19. Graph showing well-exploration data for well 45-24-23.




36 FLORIDA GEOLOGICAL SURVEY
less than 0.1 foot but may be considerably greater during a hurricane, when extremely low pressure may cause water levels to rise several tenths of a foot.
Piezometric Surface: The contours on the map in figure 35 show the configuration of the piezometric surface of the Floridan aquifer in October 1952. The piezometric surface at that time was more than 45 feet above mean sea level (msl) in the southeastern part of the area and from there sloped northwestward to sea level in the vicinity of East Tampa, indicating a general movement of the artesian water from southeast to northwest. In the eastern part of the area, where interference by discharging wells is negligible, the gradient of the piezometric surface is about three to five feet per mile. The depressions in the piezometric surface along the coast reveal the areas in which water was being discharged from the aquifer. The deepest depressions, and hence the areas of greatest discharge, are indicated by the closed contours north of Ruskin and northwest of Sun City.
The depressions in the piezometric surface are probably the result of discharge from wells. However, as most of the wells are cased to depths of less than 50 feet, the depressions may reflect, in addition, losses of artesian pressure head caused by upward leakage of water from the Floridan aquifer into the shallow formations through unused wells. The relatively large depression indicated by the contours north of Adamsville is probably the result of perennial withdrawal of large quantities of water for industrial use and also some natural discharge from springs and seeps.
?1VELOCIty OF WATER CLRD
FORMA- SELF POTENTIAL J RELATIVE RESISTIVITY (rpm o current mter) CORTE toO' 25 ohms150 5 ..I e 2 0m dt0 50 100 45- 5
0PLEISTOCENE 0.
Ii X6,
Ai 2
So Li
S 0a
w 200
X
z
Figure 20. Graph showing well-exploration data for well 45-25-20.




WI FRMA- SELF POTENTIAL RELATIVE RESISTIVITY VLCT WER C HLORIDE CONTENT OF WATER I~m 25ohm (rpm of current motor) (ports per mili~on)
9 0LITCN 100~. 50 10 IO 20 ol
0- I,
100. 0
J 0
W 0 2
40-
W -'
a. P.
z U ~ -.--
______ il0_ 1
Fiur 21 rp hwn vl-xlraindt o el462




38 FLORIDA GEOLOGICAL SURVEY
The contours on the map in figure 36 represent the piezometric surface in May 1953, during an extended period of dry weather when large quantities of ground water were being withdrawn for irrigation. The altitude of the piezometric surface ranged from more than 40 feet above msl in the southeastern part of the area to sea level in the vicinity of East Tampa. A comparison of figures 35 and 36 shows that the piezometric surface was generally about 5 feet lower in May than in October CHLORIDE CONTENT Sz WELL VELOCITY OF WATER CHLORIDE WATENT
S45-26-3 (rpm of current meter) (parts per million)
0- 45-26-3
50 100 150 0 50 0- PLE1OT'DCENE
PUOCENE z
(to
U,
U1U
- zz '
O
-o
,00
Fisl LLI
4'z z
SLL
,U
z z -_0
Lu
o
~200 car:
0
LiL
-300
- zr
0
F i
400- cD z ______-z d
Figure 22. Graph showing well-exploration data for well 45-26-3.




TFORMA- SELF POTENTIAL --' RELATIVE RESISTIVITY VELOCITY OF WATER CLORIOECONTENT I TION 10 my 25 ohms (rpm of current meter) (ports per million))
6- -J 0 50 100 150 200 250 0 50
o PLEISTOCENE
Pt. OCENE
22 z
-OR
_j 100- z
w z
W0 *
CJ:o I.J 0
R:200O
090
-W -00. <__ It LU,
L
o W
o o
- w
_j 2 400 0
Figure 23. Graph showing well-exploration data for well 46-24-7.




40 FLORIDA GEOLOGICAL SURVEY
as a result of the combined drawdown of several hundred irrigation wells.
Depth of Water Levels Below Land Surface: The area of artesian flow and the approximate depth to water below the land surface in wells that penetrate the Floridan aquifer, based on the piezometric surface in May 1953, are shown in figure 37. The area of flow includes a zone about one to three miles wide along the coast, south of the Alafia River, and extends completely across the Ruskin area along the valley of the Little Manatee River. It includes also a narrow zone along the Alafia River in the vicinity of Riverview. The depth to water below the land surface is
VELOCITY OF WATER AGE TIFORMA- WELL46-24-8 (rpm of current meter)
,ETION 46-24-8
0 5o 100 150 200 250
0 PLEISTOCENE
& PLIOCENE
dc
Z Z )
0
400 40 Li
i 0
-.J 0
oo
F Gio dl
1
w Z
Lj
o
300
wy
LiJ
U
spoZ
C1,
I Li
Figure 24. Graph showing well-exploration data for well 46-24-8.




DEPTHIN FEET BELOW MEAN SEA LEVEL
o 0 o
o 0 0 0
1 1 1 1 I I
O'IGO- M I 0 C E N E ,r AGE
CENE rm
SFORMA
_____ _z__ jTION
< -tp TAMPA FORMATION -' zO TION
6"CASING, G
ror
2_ In 0 000 TA
o co
3-:
400
c-I
DEPTH, IN FEET BELOW MEAN SEA LEVEL
0
0 L I 05 W c .) 0
LIMESTONE M I 0 C ENNE TIO
eoo
I03 6"CASING I
tjN Ir m
0 -0
0
0
o Mo
E,~ gTZ-0N SNOI1VDI.L9A9I O I. aIOJIn.




VELOCITY OF WATER VELOCITY OF WATER CHORIDE CONTENT
AGE FORMA WELL (rpm of current meiter) AGE WELL (rpmof current moetr) (ports per million .]NTR
TiON 47-23-8 0 50 1 TION 48-23-15 0 50 100 0 5 0 0- PLEISTOCENE 0 PLEITOCENE =0
a PLIOCENE PLIOCENE
LiJJ
-100* i i -oo 10 -100 2J a 5e 0 =
0 -50*- -" 100J
a 0 UJ 4
-200 -200 -10
-250 - -250 20
- 00-O -300
E
-- w
W -25o- -a5 o =0hi7
z W 0 m
z n
Fu 26. G sw -300 dld
0 ,
S Figure 26. Graphs showing well-exploration data for wells 47-23-8 and 48-23-15.




40 il lill i i iIIII 111I I I' I I I 1 i l 1 1 1 1 1 I l illl l i I ii I i T .l"' i ] i 38 A
432
.o
100 U, 30
SWell 42-19-1, I MILE WEST OF WIMAUMA
W
/ !___________________w0 0
cr > 18__ _ _ _ __ _
wo
u- 14I
LL 12
z
-10 '_ _ WelI44-25-59,2 MILES NORTH OFRU KIN
1950 1951 1952 1953 1954 955 1956
Figure 27. Hydrographs of wells 42-19-1 and 44-25-39.




44 FLORIDA GEOLOGICAL SURVEY
greatest in the east-central part of the area, where it is 50 feet or more. Throughout most of the area, however, it is less than 25 feet.
Wells: About 650 wells were inventoried during this investigation, and the information obtained is given in Information Circular No. 22. As shown in plate 1, most of the wells are in a zone about three to five miles wide along the coast, and most of them flow, at least intermittently. They range in depth from 60 to more than 700 feet, but most of them are between 300 alnd
' fIl li t i i l i l fI l II l'j I i I l i I I I I I I I l l''" ) I l I I I' 1 I I I I Il I I I I I
.2
20
16
Well 39-30-1, 2)MILES SOUTHWEST OF SUN CITY
24 A
J Z2 -/
> t A / /
LIi 2 I------- -- i_Well 40-27-7. MILE EAST OF SUN CITY

W V \1 4>
20
W 14 1 .
Well 41-30-5, 2 MILES NEST OF SUN CITY I
tal LL i l. L i ti l 11 .111 1 1 11 1 11 1 11 1 1 1 1
14 - _-,,Well 42130-9 2 MILESl WSRTH OF. SUN CIT
19i 1 1953 -9 __.. 4 1954 -955
Figure 28. Hydrographs of wells 39-30-1, 40-27-7, 41-30-5, and 42-28-9.




REPORT OF INVESTIGATIONS No. 21 45
500 feet deep. They range in diameter from 2 inches to 18 inches, but most of them are 6 to 8 inches in diameter. Surface casings are generally seated in the Hawthorn formation, at depths of 20 to 75 feet, although some wells contain as much as 200 feet of surface casing. In addition to the surface casing,
22 r -'l rII I" II I TIrl IT I II I I Imr r Trr'rI I'Ill'Tl- rrITI I
20
' A A A
16
14
12
SWell 43-26-2, MILE W1ST OF RUSKI
.. 20
-J
-J 16
. 14
LaJ ._ _. z 12
W Well 44-25-5, I MILE NORT-I OF RU KIN I
W 20
>
0
1 8
19 1959319415
i- 12 H
1Well 46-24-7,,4.MILES NORTHEAST OF RUSKIN ...
8 W/ell124' 2A9i 1 I. MILE_ WEST ,YI I ,, ,,-, , ,
95 1952 1953 1954 1955
Figure 29. Hydrographs of wells 43-26-2, 44-25-5, 46-24-7,-and 52-20-1.




46 FLORIDA GEOLOGICAL SURVEY
many wells are equipped with an inner casing extending to greater depth to shut off caving sands.
The yields of the wells differ because of difference in the permeability and thickness of the aquifer penetrated, the artesian pressure head, and the size of the well bore. The irrigation wells six inches or more in diameter, in the area of perennial artesian flow, generally yield about 100 to 400 gpm.
Temperature: Measurements of the temperature of artesian water from several hundred wells are given in Information Circular No. 22 and a few are included in table 5. The temperature of the water from the Hawthorn formation is generally between 740 and 76 F, and that from the Tampa formation is generally between 76 and 77.50F, depending upon the depth to the principal producing zones. The temperature of the water from wells that penetrate the Suwannee limestone and older formations is generally about 780 to 790F, but it ranges from about 77.50 to 82: F, according to the depth and proportionate yield of the various producing zones in these formations.
1! 1 1 I I I
, 10
WATER LEVEL
Well 43-26-12, I MILE NORTHWEST OF RUSKIN
CHLORIDE CONT NT
50
14
~ WATER LEVEL I_____ _____ _____ ____Well 43-26-26, a MILE NORTHWEST OF RUSKIN
200
a CHLORIDE CONT NT
100 . tr ll-LLi IIfIII ILL I I I I1 11111
1951 1952 1953 1954 1955
Figure 30. Hydrographs of and chloride content of water from wells 43-26-12 and 43-26-26.




REPORT OF INVESTIGATIONS NO. 21 47
QUANTITATIVE STUDIES
The withdrawal of water from an artesian aquifer creates a depression in the piezometric surface in the vicinity of the point of withdrawal. This depression generally has the approximate form of an inverted cone and is referred to as the cone of depression. The distance the piezometric surface is lowered at any given point within this cone is known as the drawdown at
- J
,, I6 C -. ..
wA
Cd
0W 12
WATER LEVEL
" Well 44- 25-38, 2 MILES NORTHEAST OF RUSKIN
200
b CHLORIDE CONTENT 100 20
U)
' A
co
50 --V--\ k," -J '-
,W ,,ATER .EVEL
U. Well 44-26-31, 2 MILES NORTH OF RUSKIN
400
300 ..
200
700 6cr 00 20D
CHLORIDE CONTENT
1951 1952 1953 1954 1955
Figure 31. Hydrographs of and chloride content of water from wells 44-25-38 and 44-26-31.




48 FLORIDA GEOLOGICAL SURVEY
that point. The size, shape, and rate of growth of the cone of depression depends on several factors, including (1) the rate of pumping, (2) the water-transmitting and storage capacities of the aquifer, (3) the increase in recharge resulting from the lowering of the piezometric surface, and (4) the decrease in natural discharge due to the lowering of the piezometric surface. The perennial yield of the artesian aquifer in the Ruskin area is limited by the extent to which the piezometric surface can be lowered without impairing the quality of the water or making the cost of obtaining the water prohibitive.
The principal hydraulic properties of an aquifer are its capacities to transmit and store water, for all aquifers serve as
S 20 | 1 i i Ii-1T 1 I I 111111 II ITI III TII nI I II I II FII TI TTII TITTll
i 0
4
8
U WATER LEVEL
8Well 46-24-4, 3* MILES NORTHEAST OF RUSKIN
350 .r-. . .. ..
CHLORIDE CONTENT
300 .
2 250
-j
U,
200 150
1OO
uJ
2 WATER LEVE
1 50 1951 195 15}199
- ,0
and 46-24-4.




REPORT OF INVESTIGATIONS No. 21 49
both conduits and reservoirs. An artesian aquifer functions primarily as a conduit, transmitting water from places of recharge to places of discharge; however, it is capable of storing water, by expansion, or releasing water, by compression.
The coefficient of transmissibility is a measure of the capacity of an aquifer to transmit water. In units commonly used by the U. S. Geological Survey, it is the quantity of water, in gallons per day (gpd), that will flow through a vertical section of the aquifer one foot wide and extending the full saturated height, under a unit hydraulic gradient, at the prevailing temperature of the water. The coefficient of storage is a measure of the capacity of an aquifer to store water, and is defined as the volume of water released from or taken into storage per unit surface area of the aquifer per unit change in head normal to that surface.
1S 1 1 1 1 1i 7 T 7 7 I I I I I I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 1I 1 1 1 1 1 1 1 1
-j
w
Wz
WATER LEVEL
8
Well 48-23-19, + MILE WEST OF ADAMSVILLE
1501
50 CHLORIDE, CONTENT
16 i__ _ _ _ _
10
WATER LEVEL
0
U
Well 47-23-22, I-MILES SOUTHWEST OF ADAMSVILLE
150
CHLORIDE CON ENT
00
, 50 I I l l i a I I I I I l liJ.I I I I I I I I I I I t s
.1951 1952 53 1954 1955
Figure 38. Hydrographs of and chloride content bf water from wells 47-23-22 and 48-23-19.




50 FLORIDA GEOLOGICAL SURVEY
JULY 1952
18 19 20 21 22 23
37 37
Well 42-19-1
36 36
> 14 14
13 13
< Well 44-25-39
I 12 12
w NOVEMBER 1952
> I 2 3 4 5 6
0
o
39 39
I- 1
U
z
L Well 42-19- l
>91
U38 _38
_j
n, 14 14
W
I
13 13
Well 44-25-39
12 t 112
Figure 34. Effects of earthquakes and atmospheric-pressure changes on the
water levels in wells 42-19-1 and 44-25-39.




REPORT OF INVESTIGATIONS No. 21 51
In order to determine the transmissibility and storage coefficients of the Floridan aquifer in the Ruskin area, a pumping test was made in August 1955. Well 40-27-6, one-half mile east of Sun City, was pumped at the rate of 650 gpm for a period of 31 hours, beginning at 9:15 a.m. on August 18 and ending at 4:12 p.m. on August 19. Throughout the period of pumping, waterlevel measurements were made periodically in well 40-27-7, which
e230 '{\. o2 '
-2255
6F
B0 0 N
Go
EXPLANATION v w I W
12.3AST TAMPA
Well in which water-level measurement
was mode. Number represents the ASS NT N
altitude of water level, in feet above 0
mean sea level.
27*5d 2/--- 7k 65d Contour line represents approximate height,
in feet above mean sea level, that water 10
will rise in lightly cased wells. Broken lines '0 DAsvL represent inferred position of contour, t
Note change in contour interval. 12 4
4 MILES /1so
1 4.9
2!0154 14.0
2745 57 27 5
20.9/24.
Sl.e 4 HtIL S9OROUGH COUNYUNTY
MANATEE 2*COUNTY
is 1,--Z
Figure 35. Map of the Ruskin area showing the piezometric surface of the Floridan aquifer in October 1952.




52 FLORIDA GEOLOGICAL SURVEY
is 0.12 mile northwest of the pumped well, to determine the rate and magnitude of drawdown. The coefficients obtained are not necessarily correct for all parts of the area, but they are considered to be representative.
The Theis graphical method, as described by Wenzel (1942, p. 87-89), was used to compute the transmissibility and storage coefficients from the drawdown produced in well 40-27-7. This
@ *30'
HILL B N, \30
EXPLANATION ST\ TA EAST TAMPA
-'Z3
Well in which water-level measurement
was made Number represents the sC 7
attitude of water level.in feet above
mean sea level.
Contour line represents approximate height,
in feet above mean sea level, that water
will rise in tightly cased wells. Broken ines svILLE
represent inferred position of contour
Note change in contour interval. 22
3 4 5 LES 10 274
4 / *
Z755
1455 RUSK, S?
t 57H 5 G HSC O U C O U N T
MANATEE 64 CIMAUM 343
82*30 8 "251/0
Figure 36. Map of the Ruskin area showing the piezometric surface of the Floridan aquifer in May 1953.
;43 267




REPORT OF INVESTIGATIONS NO. 21 53
method relates the drawdown in the vicinity of a pumping well to the rate and duration of discharge and is based on several simplifying assumptions which include the following: (1) the aquifer has an indefinite areal extent, (2) the aquifer is homogeneous and transmits water with equal facility in all directions, (3) the discharge well obtains water from the full thickness of the aquifer, (4) the coefficient of transmissibility is
27*55'
- 25"i,/..., G/
s oo0N \
0 At Qj
L S
i EXPLANATION
AREA OF
ARTESIAN FLOW
WATER LEVEL. IN FEET
27'5so BELOW LAND SURFACE .- k ,
0-10o
-PADAMSV LLE
10-25 4j
25-50
MORE THAN 50
0 2 3 4 5 MILES
27 45' 27-45 .
-7 .
SUN
CITY
?7 40 "
S 1. 4_HILLSB0 OUGH OUTY -.
MANATEE COUNTY
I-- ,. : t Iu I I -,- -- ,,I _,, 2-o 8.25'
Figure 37. Map of the Ruskin area showing area of artesian flow and depth of water level below land surface.




54 FLORIDA GEOLOGICAL SURVEY
constant at all places and at all times, (5) the discharge well has an infinitesimal diameter, and (6) water taken from storage by the decline in water level is discharged instantaneously with the decline in head.
The observed data for well 40-27-7 matched against the type curve, as shown in figure 38, yielded the following figures:
Where W (u) = 1.0, s = 0.65
and where u = 0.1, t/r2 = 1.0 x 10114.6 QW (u)
These figures inserted in the formulas T = 114.6 QW(u)
s
uTt
and S = 1.87 r give a transmissibility coefficient of 114,600 gpd/ft and a storage coefficient of .0006.
QUALITY OF WATER
The water that falls on the earth's surface as rain or snow is practically free of mineral matter except for very small quantities of atmospheric gases and dust. Therefore, the mineral constituents and the degree of mineralization of ground water depends generally
1.0
0 650gpm
W(u) 114.6QI W(u) 2z s
0T 114.6 x650x 1.0 o 0.65 Te114,600 gpd/fI.
l uT. 0.1xi04,6000x0xid .1 187ra 1.87
S2.0006
igu 10-La l T 10"
t/ra (days/fta
Figure 38. Logarithmic plot of drawdown in well 40-27-7 versus t/r2.




REPORT OF INVESTIGATIONS No. 21 55
upon the composition and solubility of the soil and rocks through which the water passes. In some places, mineralization of ground water may result from the mixing of relatively fresh water with highly mineralized, residual sea water within the water-bearing formations.
Chemical analyses of water samples from 29 selected wells in the Ruskin area (fig. 39) were made by the Quality of Water
82 130 Cou~ewcy B
FEAST TAMPA
EXPLANATION 4
Well sampled for
chemical analysis
II
2- j% . . .1*
98
-1- 06 *2RUSKIN
4
('4
"HILSBOROUGH COUNT MANATEE 4OUTY
Figure 39 Map of the Ruskin area showing wells sampled for chemical analysis.




56 FLORIDA GEOLOGICAL SURVEY
Branch of the U. S. Geological Survey. The results of these analyses are shown in table 5 and are discussed briefly-below. The concentrations of mineral constituents are given in parts per million (ppm)-1 ppm is approximately equivalent to 8.34 pounds per million gallons of water. The specific conductance is expressed in micromhos at 250 C, and the hydrogen-ion content in standard pH units. The concentration limits given for the ions, unless otherwise stated, are taken from standards for drinking water prescribed by the U. S. Public Health Service (1946).
Calcium (Ca) is dissolved principally from limestone, which is predominantly calcium carbonate, by water containing carbon dioxide. Calcium is a principal cause of hardness in water.- As indicated by the analyses, the water from the Floridan aquifer in the Ruskin area has a calcium content ranging from 81 to 275 ppm.
Magnesium (Mg) is dissolved principally from dolomite or dolomitic limestone and, like calcium, is a major cause of hardness in water. As magnesium is one of the principal mineral constituents of sea water, ground water that has been contaminated by sea water usually has a relatively high magnesium content. The water from the Floridan aquifer in the Ruskin area has a magnesium content ranging from 33 to 109 ppm. (See table 5.)
Sodium (Na) and potassium (K) are dissolved in small amounts from many types of rocks, but they constitute only a small to moderate part of the total mineral content of fresh ground water. The sodium content of water that has been contaminated by sea water is generally high, as sea water is principally a solution of sodium chloride. Water from the Floridan aquifer in southwestern Hillsborough County contained 7 to more than 100 ppm of sodium and potassium.
Bicarbonate (HCO,) in ground water results from the solution of limestone and other carbonate rocks. Hardness caused by calcium and magnesium equivalent to the carbonate and bicarbonate is known as carbonate hardness in water. The bicarbonate content of water from the Floridan aquifer is relatively high, ranging from about 150 to more than 225 ppm.
Sulfate (SO,) in ground water may be due to the oxidation of sulfide minerals or the solution of sulfate salts in the formations. Large quantities of sulfates in water may impart a bitter taste. and have a laxative effect. Sulfates of calcium and magnesium cause boiler scale. The concentration limit of sulfate in drinking and culinary water is considered to be about 250 ppm. The sulfate content of water from the Floridan aquifer in southwestern




TABLE 5. Chemical Analyses of Artesian Water from Wells in the Ruskin Area (Analyses by U. S. Geological Survey; chemical constituents in parts per million)
89-18-1 4-4-55 _... ...... 81 83 6.7 158 192 16 .... .... 480 338 696 8.1 82
39-80-5 4-8-55 .... ...... 110 50 8.3 178 300 28 .... .... 692 480 950 7.8 78.3
40-27-3 4-7-55 .... ... 104 48 18 182 275 35 .... .... 656 457 894 7.7 78.2 t-.
40-29-4 4-8-55 .... ...... 101 48 16 188 260 28 .... .... 684 429 876 1.9 77
40-29-5 4-8-55 .... ...... 84 89 25 200 215 25 .... .... 554 370 806 7.9 76
40-29-24 4-7-55 .... .... 90 44 12 194 232 22 .... .... 594 406 827 7.9 77
41-80-5 4-7-55 .... ...... 110 50 17 182 820 24 .... .... 706 480 943 7.9 77
42-28-8 4-7-55 .... ..... 97 48 14 190 255 21 .... .... 606 419 846 7.9 77
42-28-9 4-7-55 .... ...... 117 52 12 188 832 28 ... .... 718 506 987/ 7.9 78.5 2
43-24-6 4-14-55 .... ...... 105 46 9.9 190 272 24 .... .... 682 451 885 7.9 78.1 r
48-24-9 4.14-55 .... ...... 83 38 10 198 185 22 .... .... 586 863 745 8.0 76
43-26-2 4-7-55 .... ...... 115 51 11 180 330 21 ... .... 702 496 950 7.8 78 ,
48-26-12 8-9-53 21 0.10 234 96 74 170 678 202 0.7 0.9 1,560 978 1,920 7.5 79 43-27-6 4-14-55 .... ...... 185 59 10 182 405 22 .... .... 854 580 1,000 7.9 78
48-28-4 4-14-55 .... ...... 104 58 12 190 805 22 .... .... 674 478 988 7.9 77
44-24-1 7-27-55 .... ...... 81 86 21 210 165 26 .... .... 484 850 686 7.3 76.5
44-25-1 4-8-55 .... ...... 95 48 7.4 192 232 22 .... .... 590 414 825 7.9 77
44-25-88 4-8-55 ... ...... 177 75 43 172 475 148 .... .... 1,280 750 1,590 7.6 79
44-26-25 7-27-55 .... ...... 185 55 18 186 388 25 .... .... 800 568 1,010 7.4 77.5
44-26.21 n-5-58 17 .69 lan981 89 168 582 190 .9 .8 1.350 830 1.780 7.3 80 ...
0 A
r=U
rk 4j
39-18-1 4-4-55 ---- 81 33 6.7 158 192 16 ... ... 480 338 696 8.1 82 o
89-3 0-5 4-8-55-----------110 50 8.3 178 300 28 .... .... 692 480 950 7.8 78.3 '
40-27-3 4-7-55 *. 104 48 13 182' 275 35 .... ... 656 457 894 7.7 78.2
40-29-4 4-8-55-------------101 43 16 188 260 28 .... 684 429 876 7.9 77
40-29-5 4-8-55--------------84 39 25 200 215 25------------554 370 806 7.9 76
40-29-24 4-7-55----------90 44 12 194 232 22 .... 594 406 827 7.9 77
41-30-5 4-7-55-------------110 50 17 182 320 24 .. ... 706 480 943 7.9 77
42-28-8 4-7-55-------- 97 43 14 190 255 21 ---- .... 606 419 846 7.9 77 0
42-28-9 4-7-55-------------117 52 12 188 832 23 ... 718 506 987 7.9 78.5 Z
43-24-6 4-14-55--------------105 46 9.9 190 272 24 .... 632 451 885 7.9 78.1 w
43-24-9 4-14-55--------------83 38 10 198 185 22 .. .. 536 363 745 8.0 76
43-26-2' 4-7-55-------------115 51 11 180 330 21 ... 702 496 950 7.8 78
43-26-12 3-9-53 21 0.10 234 96 74 170 678 202 0.7 0.9 1,560 978 1,920 7.5 79 43-27-6 4-14-55 ..... 135 59 10 182 405 22 .. ... 854 580 1,090 7.9 78
43-28-4 4-14-55 .. ... 104 53 12 190 305 2 2 .... ... 674 478 938 7.9 77
44-24-1 7-27-55 ... ... 81 36 21 210 165 26 .. .. 484 850 686 7.8 76.5
44-25-1 4-8-55 .. ... 95 43 7.4 192 232 22 .... .. 590 414 825 7.9 77
44-25-88 4-8-55 ... 177 75 43 172 475 148 .. .... 1,230 750 1,590 7.6 79
44-26-25 7-27-55 ------------135 55 18 186 888 25 .... 800 563 1,010 7.4 77.5
44-26-31 3-5-53 17 .69 199 81 89 168 582 190 .9 .8 1,350 830 1,780 7.3 80




Table 5 (Continued)
a ~ ,W Z
45-24-7 7-27-55 105 47 16 156 812 25 --... 658 456 870 8.0 78
46-24-4 8-6-58 18 .6 276 109 108 162 821 270 1.2 .6 1,840 1,140 2,800 7.4 -..
46-24-7 8-10-58 19 .14 122 52 16 178 864 19 .4 .2 750 518 956 7.4 -47-20-1 8-6-58 28 0.06 87 88 14 228 188 14 0.6 0.7 581 878 718 7.4 47-28-22 4-8-55 .. 162 69 36 170 475 94 ... .... 1,100 688 1,420 7.8 77.5
48-22-5 7-27-55 .... 161 60 15 198 455 28 .... .... 909 648 1,110 7.4 76
48-22-7 7-27-55 ... .... 177 68 16 181 525 26 .... .. 1,010 721 1,220 7.8 77
48-28-8 7-27-55 ... 206 79 76 176 610 157 .... .... 1,840 889 1,720 7.4 79.5
48-28-19 8-6-58 21 .28 170 65 52 172 510 88 .4 .4 1,080 693 1,870 7.8 77




REPORT OF INVESTIGATIONS NO. 21 59
Hillsborough County is relatively high, ranging from about 165 to more than 800 ppm. Throughout the coastal area, the sulfate content is more than 250 ppm (fig. 40).
Chloride (Cl) in small quantities is dissolved from most soils and rocks and is found in large quantities in ground water that has been contaminated by sea water. Chloride salts do not generally decrease the potability of water except when present in
Cousea Blv 82-2d
* 0 o30
/ i L L S B/
H I RIVE VIW EAST TAMPA
EXPLANATION
SULFATE IN PPM 'oi
Less than 250
250-500 v .LL
MANATEE COUNTY
8230 b2-I 1 1'
Figure 40. Map of the Ruskin area showing-the sulfate content of water from the Floridan aquifer.




60 FLORIDA GEOLOGICAL SURVEY
quantities sufficient to cause a salty taste. The chloride content of water from the Floridan aquifer in the Ruskin area ranges from about 15 ppm to more than 1,000 ppm. The chloride content of water from the Tampa formation is shown in figure 41, and that from the Suwannee and older formations is shown in Jigure 42. The chloride content of the artesian water is discussed in more detail under the heading "Salt-Water Contamination."
Iron (Fe) occurs in almost all rocks, but the quantity of iron
IL
EXPLANATION E^S ,
CHLORIDE IN PPM CAs30 or leis
31-100
lot -250 AA, ILLE
251 -500 19
More t".a 500oo ~
_ //
. HILLSMOROUGH COUNTY o3 M0U
Figure 41. Map of the Ruskin area showing the chloride content of water from the Tampa formation.




REPORT OF INVESTIGATIONS No. 21 61
dissolved by ground water is relatively small in comparison with the quantity of more soluble minerals. Water containing more than about 0.3 ppm of iron causes stains on fixtures, utensils, and clothing; and water containing 0.5 to 1.0 ppm has an objectionable taste. Iron can generally be removed from water by aeration and filtration. The iron content of water from six wells in the Ruskin area ranged from 0.06 to 0.69 ppm (table 5).
Fluoride (F) is present in minor amounts in most ground
-27*ss 0 27*5ss
GC
" 0 00
RIVER C S EXPLANATION EAST TAMP
CHLORIDE IN PPM
O 850SNT,
0
30 or test
27*so a -_2* 31 100 101-250
251- 500
8 Bnd Road
More thon 500
0 I ... 4 5 MILES
o
'/" ,'27*45'0 0
-27400
O o oo o
; o HILLSBOROUGH COUNTYo
' MANATEE COUNTY
82*30 8225
Figure 42. Map of the Ruskin area showing the chloride content of water from the Suwannee limestone and older formations.




62 FLORIDA GEOLOGICAL SURVEY
water. Water containing fluoride in excess of 1.5 ppm may cause mottling of children's teeth during their formation (Cox and Ast, 1951, p. 641-648). In concentrations of 1.5 ppm or less, fluoride is recognized as being beneficial to dental health through reducing tooth decay and is added to many public water supplies for this reason. As shown in table 5, the fluoride content of water from six wells that penetrate the Floridan aquifer ranged from 0.4 ppm to 1.2 ppm.
The dissolved-solids content of ground water represents the approximate amount of mineral matter in solution. Water containing less than 500 ppm of dissolved solids is generally of good chemical quality, according to the U. S. Public Health Service drinking-water standards, and water containing as much as 1,000 ppm may be used for public supplies if a less mineralized water is not available. The concentration of dissolved solids in water from the Floridan aquifer in the Ruskin area ranges from slightly less than 500 ppm to more than 1,800 ppm. (See fig. 43 and table 5.)
The hardness of water is due principally to the salts of calcium and magnesium. The most noticeable effects of hardness are the formation of curds and the lack of suds when soap is added to the water, and the formation of a scale in vessels in which the water is heated. Water having a hardness of 60 ppm or less is generally satisfactory for most purposes. Water having a hardness between 60 and 120 ppm requires treatment for many industrial uses. Water having a hardness of more than 200 ppm is commonly softened for domestic and some other uses, although many private and some public supplies having a hardness of more than 500 ppm are not treated. The hardness of water from the Floridan aquifer in the Ruskin area ranges from about 350 ppm in the eastern part to more than 1,100 ppm near the coast (fig. 44).
The specific conductance of water is a measure of its capacity to conduct an electric current and depends upon the concentration and ionization of the minerals in solution. It indicates in a general way the relative mineralization of the water. As shown in table 5, the specific conductance of water from the Floridan aquifer in the Ruskin area ranged from 686 to 2,300 micromhos.
Hydrogen sulfide (H2S) is a gas that gives water an objectionable odor and may cause corrosion of plumbing. Water containing it is often referred to as "sulfur water." Aeration is generally the most practical method of treatment. No analyses were made of the hydrogen sulfide content of water from the Floridan aquifer in the Ruskin area, but the odor of the gas is detectable in water from most wells.




REPORT OF INVESTIGATIONS No. 21 63
The pH of a water indicates the instantaneous concentration of hydrogen ions. Water that has a pH of 7.0 is said to be neutral. Water having a pH of less than 7.0 is acidic and may be corrosive; water having a pH greater than 7.0 is alkaline and not generally corrosive. The water from the Floridan aquifer in the Ruskin area is slightly alkaline, the pH ranging from 7.3 to 8.1.
82*3 820
03
H IL LS 0 0
L9 L S/
EXPLANATION REI\ DISSOLVED SOLIDS r ,
IN PPM
Le Ihon 500
500-750
oxo
MANTE COUNTY C'
751- 000 -Sv_.
Mote I te f 1,000 rm h Fo d a o ife r.
77
",11,LLSR0UG OU, ,TyW. NATEE CUNTY
82 I 82:25
Figure e 43. Map of the Ruskin area showing the dissolved-solids content of water from the Floidan aquifer.




64 FLORIDA GEOLOGICAL SURVEY
SALT-WATER CONTAMINATION
In coastal areas underlain by permeable water-bearing formations that are hydraulically connected to the sea, the depth to salt water is directly related to the height of the fresh ground water above sea level. The density of fresh water is slightly less than that of sea water, so that fresh water floats on sea water in
82*30 82 20
S0 R 0
030
e Ls N
L L
RIVERVIEW
EAST TAMPA
EXPLANATION T
HARDNESS IN PPM
300-500
4I 750
DAMSWLL
More than 150
5 MILDend noo
f ,
WIMAU
301
SSUN CT
yANArr(
4 HILLSBOROUGH UNTY
MANATEE COUNTY
' -' 8 3d" a~zd,,82'2V
Figure 44. Map of the Ruskin area showing the hardness of water from the Floridan aquifer.




REPORT OF INVESTIGATIONS No. 21 65
much the same way that ice floats on water. The specific gravity of sea water is generally about 1.025, whereas that of fresh water, for practical purposes, is 1.000. Thus, with these specific gravities a column of sea water 40 feet high will exactly balance a column of fresh water 41 feet high. This principle was first applied to the hydrology of coastal areas by Badon Ghyben and Alexander Herzberg (Brown, 1925, p. 16) who found that for each foot of fresh water above sea level there was approximately 40 feet of fresh water below sea level. Although the 40-to-1 ratio is strictly applicable only under a condition of static equilibrium, it applies approximately in coastal aquifers, except in areas very close to the shore.
Salty water is present in the Floridan aquifer at relatively shallow depths throughout most of the coastal area of Florida. At some places, the lowering of the artesian head by withdrawal of large quantities of water from wells has caused the encroachment of sea water into the aquifer. In most of the area, however, the artesian pressure head is sufficiently high to prevent encroachment of water directly from the sea; thus, the widespread salty water probably represents residual sea water that entered the aquifer prior to Recent time.
The Floridan aquifer was partly filled with sea water several times during the interglacial stages of the Pleistocene epoch, when the sea rose above the present level. Since the last recession of the sea, the circulation of fresh water through the aquifer has been gradually diluting and flushing out the salty water. In much of the coastal area, however, a part or all of the water-bearing formations still contain water that is too salty for most uses, although it is considerably less salty than sea water. Excessive lowering of the head may reverse the flushing action and cause lateral migration of sea water into the aquifer. It may also cause an upward migration of the salty water from the lower zones of the aquifer into the tipper part, except where such migration is retarded by relatively impermeable strata.
RELATIVE SALINITY OF THE ARTESIAN WATER
The dissolved mineral constituents of sea water consist predominantly of chloride salts; thus, an abnormally high chloride content of ground water is generally a reliable indicator of saltwater contamination. Water samples from about 400 wells were analyzed in order to determine the chloride content of the water from the Floridan aquifer in the Ruskin area. The results of




66 FLORIDA GEOLOGICAL SURVEY
these analyses are included in table 5 and are shown by symbols in figures 41 and 42.
The chloride content of the water from the Floridan aquifer is about 10 ppm in western Polk County and about 15 ppm in eastern Hillsborough County. It increases gradually toward Tampa Bay, in the direction in which the water is moving. Throughout most of the Ruskin area, the chloride content of water from the Floridan aquifer is about 20 to 30 ppm, but in some parts of the coastal area it ranges from 31 to more than 500 ppm.
The chloride content of water from the Tampa formation is shown in figure 41. Most of the wells that yield water of relatively high chloride content are in a narrow zone that extends along, the coast from the vicinity of Adamsville to the northern boundary of the area. The chloride content of water from these wells ranges from less than 50 to more than 500 ppm. A few wells south of Adamsville yield water from the Tampa containing about 35 to 40 ppm of chloride. The relatively high chloride content of the water from these wells may represent contamination from nearby wells that penetrate the deeper formations.
Figure 42 shows the chloride content of water from wells that penetrate the Suwannee limestone, the Ocala group, and the Avon Park limestone. Most of the wells that yield water of relatively high chloride content are in a zone about a mile wide that extends along the coast from the Little Manatee River to the northern boundary of the area. Wells that penetrate the Suwannee limestone in this zone yield water having a chloride content ranging from about 30 ppm to more than 800 ppm, and wells that penetrate the Ocala group and Avon Park limestone yield water having a chloride content of more than 1,000 ppm. A few wells south of the Little Manatee River yield water whose chloride content is 35 to 65 ppm.
In order to determine the relative salinity of the water from the different producing zones in the aquifer, water samples were collected at several depths in selected wells with a deep-well sampler and measurements of the electrical resistivity of the water at different depths were made in several wells. The chloride content of water samples collected in wells is shown graphically in figures 9-12, 14-18, 20-23, 26, and 45-47. The results of resistivity measurements also are included in figures 14, 16, and 45.
As indicated by these graphs, the salty water enters the wells from the deep producing zones and is diluted by fresher water from other producing zones as it moves up the well bore. For example, the analyses of samples collected in well 44-25-42 (fig. 14) show that the chloride content of the water from the Suwannee




- CHLORIDE CONTENT OF WATER RESISTIVITY OF *WATER AGE FORMA SELF-POTENTIAL RELATIVE RESISTIVITY (parts per million) (milliohms)
TION 1O my 2ohms
150 200 250 300 150 200 250 300 O- PLEISTOCENE
& PLIOCENE
22
W,
U.1
" 0 2 1
LLJ L
w
L- I
U.
zr
0j m
300w
F
LU
z
0 C) Z
4001 0 ___Figure 45. Graph showing well-exploration data for well 44-25-28.




68 FLORIDA GEOLOGICAL SURVEY
FORMA- SELF- POTENTIAL j cy RLTIVE RESISTIVITY CHLORIDE CONTENT OF WATER
A TION ww(parts per million)
TN ___ _25 om 100 150 200 2 0
PLEtS QEllE La
I ___-
II 0
.%O o :,, ]
0 0
Figure 46. Graph showing well-exploration data for well 47-23-22.
AEFRM-SELF- POTENTIAL -j.I RELATIVE RESISTIVITY CHLORIDE CONTENT
T 10 myL2 oms (parts per million)
0 PLEISTOCENE- 200 25 30 5
PLIOC ENE .
4ATHR I
LIJ TION
t" ,Jt
Z t
olX 0
z Ol Figure 47. Graph showing well-exploration data for well 4-23-8.




REPORT OF INVESTIGATIONS NO. 21 69
limestone was 225 ppm at a depth of 370 feet and 135 ppm at a depth of 320 feet. The sharp increase in the resistivity from about 207 milliohms at 330 feet to about 256 milliohms at 315 feet indicates that most of the fresh water entered the well in this interval.
Periodic analysis of water samples shows that the chloride content of the water varies with changes in artesian pressure head. A decrease in head is generally accompanied by an increase in chloride content, and vice versa. This relationship indicates that the lowering of the head causes a vertical movement of salty water from the deeper formations. It may also reflect variations in the proportion of the total yield of the well that is obtained from each formation or producing zone. During periods of heavy withdrawal, the artesian head of the Tampa formation may be slightly less in some places than the head of the Suwannee limestone or deeper formations. This difference in head would increase the proportional yield of the deeper formations and increase the chloride content of the water obtained.
SOURCES OF CONTAMINATION
As indicated by the contours in figures 35 and 36, the mean artesian head along the coast ranges from about sea level in the area north of the Alafia River to about 18 feet above sea level near the Manatee County line. If the 40-to-1 ratio applies, the depth below sea level to salt water in the aquifer would be nearly zero at East Tampa and more than 600 feet south of the Little Manatee River. In the area south of Adamsville, the mean artesian head is sufficiently high to prevent encroachment of water from the sea into the Suwannee limestone (see fig. 4) ; thus, the occurrence of relatively salty water in the Suwannee or in the Tampa formation probably represents residual sea water that entered the formations during Pleistocene time.
Studies of current-meter traverses show that the Floridan aquifer contains permeable zones separated by relatively impermeable beds of considerable thickness. The permeable zones tapped by most wells in the area are generally less than 450 feet below sea level. The relatively impermeable beds beneath the principal water-bearing zones retard or prevent upward migration of salty water from the deeper formations.
The salinity of the water in the Suwannee limestone and Tampa formation in the area north of Adamsville is probably due in part to residual Pleistocene sea water and in part to encroachment of water from Tampa Bay during recent years.




70 FLORIDA GEOLOGICAL SURVEY
The Tampa formation is at or near the land surface in the northern Tampa Bay area, and in 1955 large quantities of artesian water were being discharged from the formation through springs and seeps. The northern part of Tampa Bay is apparently the center of a large area of natural discharge which has existed for many thousands of years. The withdrawal of large quantities of water from wells during recent years has lowered the piezometric surface to sea level at some places, permitting salt water from Tampa Bay to enter the upper part of the aquifer.
The withdrawal of large quantities of salt water at East Tampa, through wells that penetrate the Avon Park limestone, has created a cone of depression which extends below sea level in the vicinity of the pumped wells but is relatively small in areal extent. The limited extent of this cone is probably due to the salvage of natural discharge and the induction of recharge from Tampa Bay. The quantity of water discharged from the wells is apparently near equilibrium with the recharge from Tampa Bay and the intercepted natural discharge, so that the artesian head is relatively stable; however, salt water is steadily encroaching.
SUMMARY AND CONCLUSIONS
The investigation of the ground-water resources of the Ruskin area of Hillsborough County involved collecting and evaluating data from about 650 wells. The principal results of the study are summarized below:
1. The Ruskin area is underlain by a thick section of Tertiary limestones whose upper surface ranges in depth from about sea level in the northern part of the area to about 250 feet below sea level in the southern part. The limestone formations penetrated by water wells include the Avon Park limestone and Ocala group of Eocene age, the Suwannee limestone of Oligocene age, and the Tampa formation of early Miocene age. The Tampa is overlain by the Hawthorn formation of middle Miocene age which consists of sandy, calcareous clay and thin beds of limestone and sand.
2. The Suwannee limestone and Tampa formation are the principal sources of artesian water in the area, although the deeper limestones yield water to a few wells. The water in these formations occurs in permeable zones which are generally separated by relatively impermeable layers of considerable thickness. The water is replenished by rainfall in western Polk County and eastern Hillsborough County and is confined under pressure by the relatively impermeable strata within the formations and by




REPORT OF INVESTIGATIONS No. 21 71
the overlying Hawthorn formation. The beds of limestone and sand in the Hawthorn are the source of many domestic water supplies.
3. Water-level records show that significant fluctuations of artesian pressure head result from the daily and seasonal variations in withdrawal of water from wells. During periods of heaviest withdrawal, the piezometric surface is lowered about 4 feet throughout the area and more than 8 feet at some places. The artesian pressure head declined progressively in the coastal area during a period of extensive agricultural development from 1950 to 1952. Since 1952 the seasonal fluctuations in the coastal area have decreased in magnitude and a slight progressive increase in artesian pressure head has occurred locally as a result of a decrease in withdrawals. In wells not affected by local use of water the artesian pressure head declined progressively in 1955-56.
4. Analysis of data collected during a pumping test indicates that the artesian aquifer has a transmissibility coefficient of about 115,000 gpd/ft and a storage coefficient of 0.0006.
5. Chemical analyses show that the mineral content of the water in the Suwannee limestone and Tampa formation is lowest in the eastern part of the area and progressively higher toward Tampa Bay, in the direction in which the water is moving. Concentrations of dissolved solids range from less than 500 ppm in the eastern part of the area to more than 1,800 at some places along the coast, and the hardness ranges from about 350 ppm to more than 1,000 ppm. The water in the Suwannee limestone is somewhat more mineralized than the water in the Tampa, and that in the Eocene formations probably is much more mineralized than the water in the Suwannee limestone, particularly in the coastal area.
6. The chloride content of the artesian water is about 20 to 30 ppm throughout most of the area. In a narrow zone along the coast north of the Little Manatee River, many wells yield water having a considerably higher chloride content, indicating that the artesian water has been contaminated to some extent by salty water.
In the area south of Adamsville, salt-water contamination is apparently due to residual sea water that entered the aquifer during Pleistocene time, as the mean artesian head along the coast is sufficiently high to prevent encroachment of water from Tampa Bay into the Suwannee limestone and Tampa formation. The circulation of fresh water through the aquifer has flushed most of the sea water from these formations, although some water from the




72 FLORIDA GEOLOGICAL SURVEY
Suwannee limestone has a chloride content of several hundred ppm. The water in the Tampa formation generally contains about 30 ppm of chloride or less.
Contamination in the vicinity of Adamsville and northward is probably due to both residual Pleistocene sea water and encroachment of water from Tampa Bay during recent decades. The northern part of Tampa Bay is the approximate center of an area of natural discharge that has existed for many thousands of years. The withdrawal of water through wells in recent decades has lowered the artesian head to sea level at some places, permitting water from Tampa Bay to enter the upper part of the Floridan aquifer. Some wells that penetrate the Eocene limestones yield water as salty as sea water.
Periodic analysis of water from selected wells shows that the chloride content varies with significant changes in artesian pressure head. The chloride content generally increases as the artesian head declines, and vice versa. This relationship may reflect variations in the proportion of the total yield of the well that is obtained from each formation or producing zone, or it may indicate that a decline in artesian pressure head results in upward encroachment of salty water from the deeper formations. The relatively impermeable strata in the aquifer probably retard or prevent an upward movement of the salty water throughout most of the area, as only a few wells have yielded water that has shown a progressive increase in chloride content and the contaminated zone has not expanded during the period of record. An appreciable lowering of the artesian pressure head in the coastal area, however, would eventually result in lateral encroachment. It might result also in vertical encroachment in areas where the impermeable strata are breached or absent.
REFERENCES
Applin, Esther R. (see Applin, Paul L.)
Applin, Pau! L.
1944 (and Applin, Esther R.) Regional subsurface stratigraphy and
structure of Florida and southern Georgia: Am. Assoc. Petroleum
Geologists Bull., v. 28, no. 12, p. 1673-1753. Ast, D. B. (see Cox, C. R.)
Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters:
Florida State Board of Cons., Division Water Survey and Research Paper 6.




REPORT OF INVESTIGATIONS NO. 21 73
Brown, Eugene (see Black, A. P.) Brown, J. S.
1925 A study of coastal ground water, with special reference to Connecticut: U. S. Geol. Survey Water-Supply Paper 537. Collins, W. D.
1928 (and Howard, C. S.) Chemical character of waters of Florida:
U. S. Geol. Survey Water-Supply Paper 596-G. Cooke, C. W. (also see Parker, G. C.)
1945 Geology of Florida: Florida Geol. Survey Bull. 29.
Cox, C. R.
1951 (and Ast, D. B.) Water fluoridation-a sound public health practice: Am. Water Works Assoc. Jour., v. 43, no. 8, p. 641-648. Ferguson, G. E. (see Parker G. G.)
Gunter, Herman (see Sellards, E. H.)
Howard, C. S. (see Collins, W. D.) Love, S. K. (see Parker G. G.)
MacNeil, F. S.
1949 Pleistocene shorelines in Florida and Georgia: U. S. Geol. Survey
Prof. Paper 221-F.
Matson, G. C.
1913 (and Sanford, Samuel) Geology and ground waters of Florida:
U. S. Geol. Survey Water-Supply Paper 319. Parker, G. G.
1944 (and Cooke, C. W.) Late Cenozoic geology of southern Florida
with a discussion of the ground water: Florida Geol. Survey
Bull. 27.
1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides,
winds, and atmospheric pressure changes on water in the geologic formations of southern Florida: Econ. Geology, v. 45, no.
51, p. 441-460.
1955 (and Ferguson, G. E., Love, S. K., and others) Water resources
of southeastern Florida, with special reference to the geology and ground water of the Miami area: U. S. Geol. Survey WaterSupply Paper 1255.
Puri, Harbans
1953 Zonation of the Ocala group in peninsular Florida: Jour. Sedimentary Petrology, v. 23, p. 130.
Sanford, Samuel (see Matson, G. C.)
Sellards, E. H.
1913 (and Gunter, Herman) The artesian water supply of eastern and
southern Florida: Florida Geol. Survey 5th Ann. Rept.




74 FLORIDA GEOLOGICAL SURVEY
Stringfield, V. T. (also see Parker, G. C.)
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey
Water-Supply Paper 773-C.
U. S. Public Health Service
1946 Drinking water standards: Public Health Repts., v. 61, no. 11,
p. 371-384.
Vernon, R. O.
1951 Geology of Citrus and Levy counties, Florida: Florida Geol. Survey Bull. 33.
Wenzel, LI K.
1942 Methods for determining permeability of water-bearing materials,
with special reference to discharging-well methods, with a section on direct laboratory methods and bibliography on permeability and laminar flow, by V. C. Fishel: U. S. Geol. Survey
Water-Supply Paper 887.




TABLE 6. Measurements of Water Levels in Wells in the Ruskin Area (All measurements shown in feet above or below' (-) measuring point) Well Date Water Date Water Date Water Date Water Number level level level level 38-81-5 8-22-52 4.2 12-28-52 8.2 8-17-53 12.6
9-29-52 8.6 5-18-58 5.8 9-14-54 12.0 89-18-1 9- 7-51 10.6 5-18-58 4.9 4- 4-55 8.0
7- 2-52 9.0 9-80-54 11.1
89-81-5 2- 1-51 11.8 8-28-51 10.7 5-18-52 8.6
40-20-1 2-19-51 -28.5 3-26-51 -24.2 6-11-51 -25.75 8- 4-53 -28.9
2-26-51 -24.5. 4-17-51 -28.0 7-11-51 -24.84 4-14-58 -25.7
8-16-51 -25.8 5- 4-51 -22.7 9- 8-51 -22.80 5-21-58 -26.75
40-24-1 2-19-51 20.1 8-16-51 22.9 4-27-51 22.5 9- 7-51 25.9
2-26-51 24.9 8-26-51 24.0 6-11-51 20.6 5-16-52 18.9
40-27-4 5-18-52 -8.75 10-10-52 1.8 8-17-53 0.7 6- 8-55, -8.18
40-28-2 11-26-51 -6.15 12- 3-51 -8.27 12-14-51 -10.50 9-29-52 -11.25
40-30-1 8-28-51 8.1 5-18-52 8.8 5-18-53 5.6
9- 7-51 7.0 10-18-52 18.2




Table (1, (Continued)
(All measurements shown in feet above or below (-.) measuring point)
Well Date Water Date Water Date Water Date Water Number level level level level
41-24-1 9- 7-51 --11.52 6-23-52 -14.65 5-18-58 -19.2
5-16-52 -18.7 10-10-52 -12.3
41-29-23 8-28-51 0.7 10-22-52 6.5 1-80-53 1.4 10-15-58 1.2
5-18-52 -4.57 11-18-52 0.3 5-21-58 1.0 11-20-58 3.2
10-10-52 5.7 12-22-58 1.3 8-17-58 7.0 6- 8-55 4.62
41,80-6 2-19-51 9.3 3-16-51 9.9 4-17-51 14.6 9- 7-51 12.2
2-26-51 8.8 3-26-51 12.7 6-11-51 9.9 10-10-52 13.7
41-80-18 9- 7-51 7.4 5-18-52 2.5 10-10-52 9.2 10-22-52 10.3
42-25-13 2- 1-51 3.0 10-10-52 6.8 9-27-55 5.7
9- 6-51 4.6 6- 8-55 2.45
42-26-12 9- 6-51 10.1 10-13-52 11.2 5-18-53 2.9
5-14-52 1.78 5-14-58 3.5
48-24-6 2- 1-51 8.9 6-23-52 4.6 10-22-52 7.6 7-27-55 6.1
3-28-51 4.2 8-25-52 2.5 1-30-58 5.5 9- 6-51 4.6 9-29-52 5.7 9-30-54 8.0 5-18-52 -2.15 10-10-52 7.0 6- 8-55 '1.05




Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point) Well Date Water Date Water Date Water Date Water Number level level level level
43-24-17 2- 1-51 0.8 2-26-51 -4.1 4-17-51 6.9 5- 4-51 0.1
2-19-51 1.8 3-26-51 1.9 4-25-51 6.8 6-11-51 -1.6
48-25-3 9- 6-51 8.5 5-14-52 -0.5 10-10-52 9.2 10-22-52 9.7
48-25-18 2- 1-51 4.4 3-28-51 3.9 9- 6-51 6.8 5-18-52 -0.2
43-27-4 2- 1-52 9.9 9- 6-51 10.0 5-15-52 5.4 10- 9-52 11.1
4-27-6 2-19-51 9.9 8-26-51 12.2 6-11-51 9.1 5-15-53 8.0
S2-26-51 9.9 4-17-51 14.8 9- 6-51 8.8 5-21-58 8.5
3-16-51 11.8 4-24-51 13.2 10-13-52 12.1
,
43-27-11 2- 1-51 11.9 9- 6-51 10.7 10-13-52 18.2
8-27-51 12.5 5-15-52 7.9
44-24-1 9- 6-51 4.1 5-15-53 -4.4 10-15-58 1.95
10-18-52 8.7 8-17-52 3.4
44-24-17 2- 1-51 4.4 8-27-51 1.7 9- 6-51 8.4 10-13-52 5.8




Table 0, (Continued) 1 (All measurements shown in feet above or below ( ) measuring point) Well Date Water Date Water Date Water Date Water Number level level level level 44-24-20 2- 1-51 4,9 9- 6-51 9,9 10-18-52 5.6
8-27-51 2.8 5-14-52 -0.15 10-22-52 6.6
44-25-1 2- 1-51 5.6 4- 2-52 10.1 9-29-52 6.1 1-80-58 6.5
3-27-51 4.5 7-25-52 8.95 10- 9-52 8.5 11-20-58 4.1
9- 6-51 9.0 8-22-52 6.2 10-22-52 9.2
44-25-9 2- 1-51 5.7 8-27-51 8.9 9- 6-51 9.1 5-15-52 0.85
44-26-9 8-26-51 11.6 9- 6-51 12.0 5-15-52 6.9 10- 9-52 12.0
45-23-8 1-81-51 4.2 3-26-51 7.6 9- 5-51 6.6 5-21-53 -1.1
45-24-6 1-81-51 5.2 5-15-52 0.8 10- 9-52 6.4 10-21-52 7.5
45-25-10 9- 7-51 8.5 10- 9-52 9.7 10-21-52 10.8 12-22-52 6.1
45-25-15 1-31-51 7.7 3-26-51 9.0 9- 5-51 7.2 5-15-538 2.0
45-25-18 1-31-51 9.6 9- 5-51 8.5 10- 9-52 10.1
3-26-51 11.4 5-15-52 4.15 5-21-53 5.2




Table 6. (Continued)
(All measurements shown in feet above or below (-) measuring point)
Well Date Water Date Water Date Water Date Water Number level level level level
46-28-2 1-81-51 8.2 9- 5-51 6.5 9-30-54 5.8
8-26-51 6.8 10-10-52 5.1
.... 0
46-24-9 9- 5-51 10.0 10- 9-52 10.4 10-22-52 10.6 11-19-58 5.5
46-24-12 1-81-51 10.2 8-26-51 11.1 9- 5-51 11.5 10- 9-52 11.0
46-24-15 9- 5-51 11.1 5-15-52 3.25 8-25-52 8.5
4- 2-52 10.0 6-23-52 8.3 9-29-52 9.0
47-20-1 6-11-51 -36.65 8-23-54 -29.20 2- 1-55 -80.75 6- 8-55 -3388.0
11-20-53 -29.15 9-30-54 -28.65 3-10-55 -832.50 7-27-55 -30.45
6-28-54 -29.40 12-28-54 -29.30 4- 8-55 -81.72 10-25-55 -30.50
47-22-2 1-81-51 2.3 9- 5-51 7.1 5-21-53 -1.65
8-26-51 4.3 10-10-52 7.0
47-22-6 5-15-53 -7.5 8-17-53 -5.85 4- 8-55 -6.60
5-21-53 -9.1 2-25-54 -6.45 6- 8-55 -6.55
47-22-12 8-26-51 5.4 4-27-51 6.7 6-11-51 3.0
4-17-51 7.5 5- 4-51 2.3 9- 5-51 5.6




Table 6, (Continued) (All measurements shown in feet above or below ( -) measuring point)
Well Date Water Date Water Date Water Date Water Number level level level level
47-22-18 2-19-51 0.6 2-26-51 2.1 8-16-51 3,8 3-26-51 5.1
47-28-19 9- 5-51 6-7 10-10-52 5.4 5-21-53 -0.5
5-14-52 0.2 10-21-52 5.6
47-28-21 1-31-51 3.9 9- 5-51 6.6 4-14-58 5.5
3-27-51 6.8 10-10-52 5.7 5-21-53 0.9
47-23-31 1-31-51 3.9 3-27-51 6.8 9- 5-51 6.1 5-14-52 1.25
48-22-5 3-27-51 3.7 10-10-52 2.8 11-20-52 0.25 9-30-54 1.80
9- 5-51 4.2 5-21-53 --2.5 2-25-54 0.70 7-27-55 1.80
5-14-52 -1.7 8-17-538 2.2 6-28-54 0.90
6-23-52 1.1 10-14-53 2.0 8-24-54 1.1
48-23-10 1-81-51 4.2 9- 5-51 3.6 2- 6-53 5.7
3-27-51 6.6 5-14-52 2.24 5-21-53 2.3
49-22-1 2-19-51 0.1 3-22-51 0.8 5- 4-51 0.4 9- 5-51 1.87
2-26-51 0.0 4-17-51 1.4 6-11-51 -0.8 3-16-51 0.3 4-27-51 1.3 8-13-51 1.30




REPORT OF INVESTIGATIONS NO. 21 81
TABLE 7. Logs of Selected Wells in the Ruskin Area
Well 40-28-2
(Florida Geol. Survey No. W-2323)
Lithology Depth Below Land Surface
Pleistocene and Pliocene
Sand, white, quartz, fine to medium, subrounded to wellrounded, carbonaceous. 0- 10
Sand, brown, quartz, fine to coarse, subrounded to wellrounded, carbonaceous. 10- 20
Sand, brown, quartz, carbonaceous, fine to medium. 20- 35 Sand, as above; peat; wood; amber. _35- 40
Sand, as above; abundant shells and fragments; carbonaceous
material; gray silty clay. 40- 50
Shell fragments and sand; quartz pebbles and black phosphate
pebbles, rounded and frosted. 50- 60
Hawthorn formation
Clay, gray, sandy, calcareous, phosphatic; quartz and phosphate pebbles, as above; a few shell fragments. 60- 70
Clay, gray-white, chalky, phosphatic, sandy in part. 70- 90 Clay, as above, with some gray impure limestone. 90-100 Clay, as above. 100-110 No sample. 110-120 Clay, white, chalky, sandy iin part, phosphatic. 120-125 No sample. 125-130
Clay, white, chalky, sandy; gray-white sandy limestone, with
a few mollusk molds and casts. ._ 130-140 Clay, greenish gray calcareous, sandy, phosphatic. 140-145 No sample. 145-150 Clay, as above but very sandy; much chert. 150-155 No sample. 155-160
Clay, gray-white calcareous, sandy, phosphatic; gray-white
sandy limestone; some chert. ___160-165
Clay, greenish gray, calcareous, sandy, phosphatic; some chert. 165-170 Limestone, gray-white, impure, porous. 170-175 No sample. 175-180 Clay and limestone, with some chert. 180-185 No sample. 185-210 Clay, gray-white, sandy, phosphatic; some chert. 210-215
Tampa formation
Limestone, white to cream, hard to soft, very sandy; some
chert. Archaias sp. and Sorites sp. 215-220
Limestone, creamy white, gray, and tan, soft to hard, granular, porous, granular to dense, sandy, fossiliferous; crystalline calcite. Archaias sp. and Sorites sp. 220-230
Limestone, as above. 230-250




82 FLORIDA GEOLOGICAL SURVEY
Table 7. (Continued)
Lithology Depth Below Land Surface
No sample. 250-270 Limestone, white to tan, granular to dense, sandy; some chert. 270-275
Limestone, buff and tan, soft to hard, dense to granular,
sandy; crystalline calcite in solution cavities. 275-285
No sample. 285-300
Limestone, buff and tan, soft to hard, dense to granular, fossiliferous; contains numerous fragments of gastropod molds
and casts. 300-305
No sample. 305-310
Limestone, white to brown, soft to hard, chalky, porous,
sandy in part, fossiliferous. 310-315
No sample. 315-325 Limestone, as above; also dark brown, hard, porous. 325-330 Limestone, as above, and some chert. -330-340 No sample. 340-345 Limestone, as above, Archaias sp. 345-350 Limestone, as above. 350-360 Limestone, as above, but no chert. 360-370 No sample. 370-380
Limestone, white, tan, and brown, granular to dense, porous,
dolomitic in part, fossiliferous; crystalline calcite and some
chert. 380-385
No sample. 385-400 Sawannee limestone
Limestone, creamy white to white, soft, granular to chalky,
porous, fossiliferous, calcitic. 400-410
Limestone, as above. Rotalia mexicana and other foraminifers. 410-420
Limestone, creamy white, soft, granular, calcitic, porous,
chalky matrix, fossiliferous, abundant molds, casts, spines,
and foraminifers. Rotalia mexicana. 420-425
No sample. 425-430 Limestone, as above. 430-460 No sample. 460-470
Limestone, buff and tan to white, fairly soft, porous, chalky;
brown crystalline dolomite; some chert. Rotalia mexicana,
Dictyoconus cookei and other foraminifers present. 470-475
No sample. 475-480 Limestone, as above. 480-485 No sample. 485-490
Limestone, white to tan, granular, porous, dolomitic in part,
fossiliferous. Abundant Dictyoconus cookei, Coskinolina
floridana and Rotalia mexicana. 490-500
Limestone, as above, and brown shaly, carbonaceous clay. 500-510' Limestone, as above. 510-520
Limestone, white, soft, granular, porous, fossiliferous; hard
brown crystalline dolomite; Dictyoconus cookei and other
foraminifers poorly preserved. 520-525




REPORT OF INVESTIGATIONS NO. 21 83
Table 7. (Continued)
Lithology Depth Below Land Surface
No sample. -_ .525-530 Dolomite, brown, hard, crystalline.- .- 530-535
Dolomite, as above, with some soft granular porous fossiliferous limestone. Dictyoconus cookei and Coskinolina
floridana. -- - - 535-550
No sample. 550-560
Limestone, white, granular, soft to hard, porous to dense;
small amount of fossiliferous dolomite. Dictyoconus cookei
and Coskinolina floridana. 560-565
No sample. 565-575 Limestone, as above, but dolomite not present. 575-580 No sample. 580-600
Limestone, white, finely granular, soft, porous, fossiliferous;
abundant foraminifers, echinoid spines. 600-605
No sample. -_____ 605-615
Ocala group
Limestone, white, chalky, soft, finely granular, porous, fossiliferous. Lepidocyclina ocalana, L. floridana, Nummulites sp., Gypsina globula, and other foraminifers.---. 615-642
Well 42-23-1
(Florida Geol. Survey No. W-2675)
Pleistocene and Pliocene
Soil and sand. 0- 5 Sand, brown stained, quartz, fine to coarse. 5- 40
Clay, gray, calcareous, very sandy with phosphate; frosted
gray and brown, quartz grains and pebbles; fish teeth; pyrite. 40- 45
Clay, gray, very sandy, calcareous, phosphatic; coarse to fine
sand; frosted rounded quartz pebbles. 45- 55
Hawthorn formation
Clay, gray-white, calcareous, chalky, sandy, phosphatic. 55- 70 Clay, as above, with some gray, sandy, impure limestone. --------70- 85
Clay, as above; limestone, white, hard, sandy, fossiliferous,
phosphatic. 85- 90
No sample. 90- 95 Clay, as above, with some impure limestone. 95-115 No sample. 115-125
Clay, gray-green to white, waxy to chalky, calcareous, sandy
in part; impure limestone with a few mollusk fragments;
phosphate and some chalcedony. 125-135




84 FLORIDA GEOLOGICAL SURVEY
Table 7. (Continued)
Lithology Depth Below Land Surface
Tempa formation
Clay, olive green to gray, calcareous, sandy; gray, sandy
limestone; some crystalline calcite; chert and phosphate .... 135-145
Limestone, gray-white, fairly hard, sandy, dolomitic in part;
chert; a few mollusk fragments and foraminifers, Archaias
and Sorites. 145-165
No sample. 165-170
Limestone, gray-white, fairly hard, sandy, porous in part,
fossiliferous, dolomitic in part; chert and pyrite. Archaias
and Sorites. ------- -- 170-180
No sample. 180-185 Limestone, as above. 185-195 No sample. 195-205 Limestone, as above. 205-215 No sample. ----- 215-225
Limestone, gray-white, tan and brown, hard, dense, dolomitic
and crystalline in part, sandy, porous in part, fossiliferous; crystalline calcite and chert; mollusks and foraminifers.
A rchaias. ------225-235
No sample. 235-240 Limestone, as above. 240-250 No sample. 250-255
Limestone, gray-white to brown, fairly soft to hard, granular
to dense, porous, dolomitic in part, sandy in part; crystalline calcite and pyrite; mollusk molds and casts, foraminifers. Archaias. 255-275
No sample. -------- ------ 275-300
Suwannee limestone
Limestone, white to buff, soft, granular to somewhat chalky,
very porous, fossiliferous; chert; echinoid spines and plates, mollusk molds and casts, many small foraminifers.
Rotalia mexicana. -300-310
No sample. 310-320 Limestone, as above. 320-345 No sample. 345-350 Limestone, as above, but more chalky and less porous. 350-360 No sample. 360-365 Limestone, as above. 365-375
Well 42-25-3
(Florida Geol. Survey No. W-2796)
Pleistocene and Pliocene
Sand, white, fine to coarse. -_.0- 10 Sand, brown, fine to coarse, carbonaceous, shells. - 10- 20




REPORT OF INVESTIGATIONS No. 21 85
Table 7. (Continued)
Lithology Depth Below Land Surface
Sand, quartz and phosphate, fine to coarse. 20- 23
Hawthorn formation
Clay, gray-white, calcareous, chalky, phosphatic; few mollusk
molds and casts. -__ 23- 25
Clay, white, chalky, sandy, calcareous, phosphatic; gray-white
impure sandy limestone; pyrite. -........... ... 25- 35
No sample. ___ 35- 45
Clay, gray-white, calcareous, sandy, phosphatic; gray impure
sandy fossiliferous limestone; pyrite; chert; mollusk molds
and casts. __45- 50
No sample. 50- 60 Clay, white to gray, chalky, sandy; chert and phosphate. 60- 70 No sample. 70- 75
Clay, greenish gray, sticky, sandy, calcareous; phosphate
grains and pebbles; gray impure sandy limestone, oolitic
in part, phosphatic. 75- 85
No sample. ------ ---- 85- 90
Clay, gray-white, chalky; phosphatic sand and pebbles; gray
hard impure limestone; phosphatic sand. 90-100
No sample. 100-110
Clay, gray-white, calcareous, very sandy; white to buff sandy
limestone; phosphate and pyrite. 110-120
No sample. 120-140
Clay, as above; gray to buff, hard, dense sandy limestone;
phosphate; chalcedony; dolomite ........ ..... .. 140-150
Clay, gray-green, calcareous, very sandy, phosphatic. 150-153
Tampa formation
Limestone, white, chalky, soft, fossiliferous, fairly porous.
Archaias. --- --- 153-155
No sample. 155-165 Limestone, gray-white, fairly hard, sandy, fossiliferous; chert. 165-170 No sample. -....-.-----.. 170-175
Limestone, gray-white, hard, porous to dense, crystalline,
sandy; chert; mollusk fragments. Abundant Archaias
and Sorites.- ------ ----- ----- 175-185
No sample. 185-190
Limestone, gray to tan, hard, porous to dense, dolomitic in
part, sandy in part; gray and tan chert; crystalline calcite; mollusks and foraminifers. Sorites. 190-200
No sample. 200-210
Limestone, gray-white to brown, granular, sandy, porous to
dense, hard, dolomitic, and crystalline in part, fossiliferous; chert. Archaias. 210-245
No sample. 245-255




86 FLORIDA GEOLOGICAL SURVEY
Table 7. (Continued)
Lithology Depth Below Land Surface
Limestone, as above. 255-275
Limestone, gray-white to dark brown, soft to hard, granular,
porous to dense, fossiliferous, dolomitic, slightly sandy;
crystalline calcite, chert; mollusks and foraminifers. 275-285
No sample. 285-290 Limestone, as above but no chert. ----- - 290-300
Limestone, gray-white to brown, fairly soft to hard, granular,
porous to dense, fossiliferous, dolomitic in part, slightly
sandy; gray and brown chert; crystalline calcite. 300-305
No sample. 305-310
Limestone, white and buff, fairly soft, granular, porous in
part, fossiliferous; crystalline calcite; chert; Sorites. ____ 310-315
No sample. 315-320 Limestone, as above, but dolomitic in part. 320-330 No sample. 330-340 Suwannee limestone
Limestone, white, soft, granular to chalky, porous, fossiliferous; crystalline calcite; mollusks, echinoid spines, foraminifers. 340-345
No sample. 345-365
Limestone, creamy white, soft, granular, porous, finely crystalline in part; crystalline calcite. Rotalia mexicana. .. 365-375
No sample. ---- 375-380 Limestone, as above. 380-390 No sample. 390-415
Limestone, creamy white to buff, soft, granular to chalky, porous; fossils abundant but poorly preserved. Rotalia mexicana, Dictyoconus cookei. 415-425
No sample. 425-435
Limestone, gray-tan, fairly hard, granular with a chalky
matrix, not very porous, fossiliferous as above. 435-445
No sample. 445-460
Limestone, gray-tan, soft, granular, porous, fossiliferous;
crystalline in part. Rotalia mexicana, Dictyoconus cookei. 460-470
No sample. 470-480
Limestone, white, soft, granular, fossiliferous; dolomite, tan
and brown, hard, crystalline; chert. Rotalia mexicana,
Dictyoconus cookei, Coskinolina floridana. 480-490
Limestone, gray-tan, fairly hard, granular, impure, dolomitic
in part, fairly porous; chert. Rotalia mexicana, Dictyoconus cookei, Coskinolina floridana, Gypsina globula. Top
of Ocala group apparently in this interval.- - 490-500 Ocala group
Limestone, gray-white to tan, granular, fairly porous, fossilferous, dolomitic in part; chert; crystalline calcite. Gypsina globula abundant. 500-510




REPORT OF INVESTIGATIONS No. 21 87
Table 7. (Continued)
Lithology Depth Below Land Surface
Limestone, gray-white to buff, fairly soft, granular to chalky,
porous, fossiliferous; chert and crystalline calcite. Gypsina globula, Nummulites sp., Operculinoides sp., Heterostegina ocalana. 510-520
Limestone, predominantly a coquina of mollusk fragments
and poorly preserved foraminifers in a finely granular to chalky matrix. Nummulites sp., Gypsina globula, Lepidocyclina ocalana. _.._520-550
Well 45-25-8
(Florida Geol. Survey No. W-2546)
No sample. ---- 0- 30
Hawthorn formation
Clay, white, chalky, sandy, calcareous, phosphatic. 30- 35 Limestone, gray-white, dense, sandy with chert; pyrite; phosphate. 35- 40 Clay, light green, waxy, sandy, calcareous, phosphatic; some chert. 40- 50 As above. __ __ _50- 65
Clay, as above; limestone, white, dense, sandy; some chert and
a few mollusk fragments. 65- 85
As above. __ 85- 95
Tampa formation
Limestone, gray-white, hard, dense, sandy, fossiliferous;
crystalline calcite in solution cavities; dolomite, gray-tan,
hard, dense, crystalline. ... 95-100
No sample. 100-110
Limestone, white and gray, hard, sandy; chert fragments;
mollusk molds and casts. __110-120
Limestone, white and gray, granular, porous, chalky, sandy in
part; chert; mollusk molds and casts. Archaias and other
foraminifers. _____120-130
Limestone, as above but more porous. Sorites, abundant Archaias. 130-140 No sample. .- 140-150
Limestone, white, gray, and tan, fairly hard, dense to porous,
sandy in part, fossiliferous; chert. --- -- 150-160
No sample. 160-170
Limestone, white to tan, fairly hard, dense, sandy in part;
chert; pyrite and crystalline calcite. 170-180
No sample. 180-200 Limestone, as above, but dolomitic in part. ...200-210 No sample. 210-240
Limestone, white to tan, fairly hard, dense to granular, porous; contains a few foraminifers. -240-250
No sample. ---- 250-270




88 FLORIDA GEOLOGICAL SURVEY
Table 7. (Continued)
Lithology Depth Below Land Surface
Suwannee limestone
Limestone, white, chalky, granular, porous; abundant small
foraminifers and echinoid fragments. 270-275
Limestone, creamy white to tan, soft, granular, porous,
fossiliferous. 275-285
No sample. 285-315 Limestone, as above. 315-325 No sample. 325-340
Limestone, as above. Rotalia mexicana and Dictyoconus
cookei. ___ ________340-350
As above. 350-365 No sample. 365-415
Limestone, buff and tan, soft, granular, porous, fossiliferous.
Dictyoconus cookei. 415-425
Well 42-27-6
(Florida Geol. Survey No. W-2674)
Pleistocene and Pliocene
Sand and shells. .._0- 38
Hawthorn formation
Clay, gray, calcareous, sandy, phosphatic. ________ 38- 45 No sample. .._.__..45-140
Clay, gray, sandy, calcareous, waxy in part; phosphate grains
and pebbles; chert. _... ___140-165
Tampa formation
Limestone, white, gray, buff and tan, fairly soft, granular,
fossiliferous; chert; Sorites. .. 165-170
Limestone, gray-white to buff, soft, granular, porous, sandy;
chert; crystalline calcite in solution cavities; mollusk
fragments, small foraminifers. Sorites. -_.. 170-175
No sample. 175-210
Well 43-26-4
(Florida Geol. Survey No. W-2414)
Pleistocene and Pliocene
Sand. 0- 5 Sand and shells. 5- 15 Sand, shells, clay, gray, calcareous, sandy, phosphatic. 15- 20




REPORT OF INVESTIGATIONS NO. 21 89
Table 7. (Continued)
Lithology Depth Below Land Surface
Hawthorn formation
Clay, gray, sandy, calcareous, phosphatic. 20- 40
Clay, gray-green, white, calcareous, sandy, phosphate grains
and pebbles; large quartz grains ...... .. .......---------- 40- 50
Clay, gray-white, calcareous, sandy, phosphatic; white to tan,
impure, sandy limestone; chert. - 50- 60
Clay, as above, with pyrite fragments ..... ........... ......... 60- 80
Clay, as above, with some impure limestone and chert. 80- 85 Clay, blue-gray, calcareous, sandy; phosphate and chert. 85-100 Clay, white to blue-gray, chalky, sandy; phosphate and chert. -. 100-110
Clay, white to green, chalky, shaly, sandy, calcareous; phosphate and chert -.. ........ . ........... .......... .-- 110-115
Clay, green, calcareous, very sandy; phosphate and chert...... 115-125
Clay, green, calcareous, shaly, slightly sandy; phosphate and
chert. 125-130
No sample. ----------------- -_ 130-135
Tampa formation
Limestone, white to tan, fairly hard, granular to dense, porous, sandy in part, fossiliferous; chert; mollusks and
foraminifers. Archaias and Sorites. .----------- ..... 135-140
Limestone, white to dark gray, hard, very sandy, crystalline
calcite in solution cavities; chert; few mollusk molds and
casts. Archaias and Sorites. ------------------------.. .... .... __. 140-170
Limestone, white, chalky, granular, slightly sandy in part,
porous; crystalline calcite in cavities; mollusk fragments.
Archaias and Sorites.----------- --------------------- --- --- ...170-180
No sample. ---------..-------------- -------------- ------ --.. 180-190
Limestone, as above. - ------ 190-195
Limestone, gray-white, granular to tan, hard, dense, sandy;
crystalline calcite; chert. Archaias and Sorites. .... ... 195-220
Limestone, tan to dark gray, very hard, dense, slightly sandy
in part, dolomitic; chert ... ......-......... _........ 220-235
Limestone, gray-white, fairly hard, sandy, chalky; crystalline
calcite in solution cavities; mollusk molds and casts. ------.. ... 235-240
No sample. 240-250
Limestone, white, gray, and tan, hard, dense, sandy; chert
and crystalline calcite. ---- -------- - ----- 250-265
N o sam ple --- -- -- -- ------------ -- 265-275
Limestone, as above. ----------------------------------------- 275-280
Limestone, white, soft, granular, chalky, sandy; crystalline
calcite; mollusk molds and echinoid spines. ----- --280-290
Limestone, buff, fairly soft, granular, slightly sandy, crystalline in part; chert and calcite. 290-295
No sample. 295-300




90 FLORIDA GEOLOGICAL SURVEY
Table 7. (Continued)
Lithology Depth Below Land Surface
Limestone, gray-white, tan, and brown, hard, dense, dolomitic,
slightly sandy . --.. .........-... ... ... ........... ... ------------............................ 300-305
Limestone, gray-white, tan, soft to hard, granular to dense,
dolomitic in part; chert and calcite; mollusk fragments ........... 305-315
No sample. .-------.------.---------------------------................................. 315-325
Suwannee limestone
Limestone, creamy white, buff, and tan, soft, granular,
porous fossiliferous; chert and calcite ........ ------------------......................---......... 325-345
Limestone, as above, somewhat harder. Rotalia mexicana ........... --------345-355
Limestone, white, soft, granular, somewhat chalky, fairly porous; mollusks, echinoids and foraminifers. Rotalia mexicana. _. 355-435
Limestone, white to tan, soft, granular, somewhat chalky, not
very porous, fossiliferous; crystalline calcite. Rotalia mexicana and Dictyoconus cookei ................................................--------------------------------..... 435-455
Limestone, white to tan, soft to hard, granular to dense, fossiliferous. Rotalia mexicana, Dictyoconu8 cookei, Coskinolina floridana...- ----...-... ---------------------.............. ................ -------------------455-465
Limestone, tan, gray, and brown, soft to hard, granular to
dense, crystalline in part, fossilferous. Dictyoconus cookei,
and Coakinolina floridana ........................ ...........----------------------------- ----- 465-475
Limestone, gray-brown, fairly soft, granular, crystalline in
part, fossiliferous. Dictyoconus cookei and Coskinolina
fioridana -- -..----------..........................5........... ................ ..- 475-510
Well 46-23-5
(Florida Geol. Survey No. W-2668)
Pleistocene and Pliocene
No sample. -------- -- ------------........................... ----.............. 0- 20
Sand, gray-brown, fine to coarse, rounded, carbonaceous. ----------20- 27
Hawthorn formation
Clay, gray, waxy, sandy in part, calcareous, phosphatic .........-.... ---------27- 30
Clay, gray, calcareous, sandy, phosphatic ........................................... ----------------------30- 40
Clay, as above; limestone, gray-white, sandy, chalky, impure;
chert and phosphate ...................................................................... ------------------------------------ 40- 70
Clay, gray-green, waxy, calcareous, sandy in part; chert and
phosphate ----.. ... ...... ................... ...............- -- -............ ..... 70- 80
Tampa formation
Limestone, dark gray to brown, hard, sandy, silicified in part,
dolomitic in part ---...................---------..........-----------------------................................... 80-100
Limestone, gray-white, fairly hard, sandy, porous, fossiliferous; dolomite, brown, crystalline; chert. Archaias and Sorites. .. 100-120




REPORT OF INVESTIGATIONS NO. 21 91
Table 7. (Continued)
Lithology Depth Below Land Surface
Limestone, white, soft, chalky, slightly sandy, granular porous; gray-brown hard, dense, splintery, sandy limestone;
brown crystalline dolomite. Archaias and Soritcs. ..........---.....-- 120-130
Limestone, gray-white, sandy, hard, porous to dense; dolomite,
as above; chert and a few poorly preserved fossils ............ .--------- 130-140
Limestone, gray-white to tan, fairly soft, chalky; hard dense,
porous in part, sandy, fossiliferous limestone; dolomite,
as above, and some chert. Sorites and other foraminifers . 140-150
Limestone, gray to tan, hard, sandy; gray-brown hard, crystalline dolomite; chert ..................................................... ...--------------- -------- --------150-170
Limestone, gray-white, tan, fairly hard, sandy, dolomitic,
fossiliferous; chert. Sorites. ........... ............................... ---------170-180
Limestone, white, gray and brown, hard, sandy; gray-brown
hard crystalline dolomite, porous in part .. ------------................ .. ------- 180-200
Limestone, gray-white, tan, brown, hard, dense, sandy in
part, dolomitic in part; chert; few poorly preserved fossils. 200-220
Limestone, white, soft, granular, porous, fossiliferous; dolomite, gray-brown; echinoid spines. Archaias .................... ---------------220-230
Limestone, as above, also gray-brown, sandy, dolomitic. Sorites. 230-250
Limestone, creamy white, buff, and tan, soft, granular, fossiliferous- ------ .............. ............... ........... .................... 250-260
Well 46-23-8
(Florida Geol. Survey No. W-2671)
No sample ..........................-. ....-------........ ---------------------------------------- 0- 30
Hawthorn formation
Clay, gray-white, calcareous, sandy; phosphate grains and
pebbles, interbedded with gray hard sandy, fossiliferous
limestone ------------------------------------------ -. .. ---------- ------- 30- 55
Tampa formation
Limestone, gray to white, fairly soft to hard, granular, porous
to dense, sandy; brown dolomite; chert; mollusk fragments and foraminifers. Sorites- ..........-- ....----_.---------- --.......... .. 55- 70
Limestone, gray-brown, hard, dense, sandy, dolomitic in part,
porous in part, fossiliferous; chert. Sorites- .........-..-- --------------... 70-100
Limestone, white, soft, granular, having chalky matrix, porous, fossiliferous; much chert. Sorites, Archaias. ------------......... 100-110
Limestone, gray, white, tan, fairly soft, porous, sandy; chert;
mollusks, echinoids, foraminifers .............................------------ -----......... 110-120
No sample ................ -- -------------------------------- ---------------------- ......................... 120-130
Limestone, gray-white, tan, hard, dense, sandy to soft, chalky,
porous; chert; mollusks, milliolids. Sorites ....................----.............. 130-140