<%BANNER%>
HIDE
 Front Cover
 Florida State Board of Conserv...
 Transmittal letter
 Table of contents
 Abstract and introduction
 Biscayne Aquifer
 Ground-water occurrence
 Hydrologic characteristics of the...
 Salt-water contamination
 Adequacy of supply
 Selected references


FGS







STATE OF FLORIDA

STATE BOARD OF CONSERVATION


~r.
- /


Ernest Mitts, Director


FLORIDA GEOLOGICAL SURVEY

Herman Gunter, Director




REPORT OF INVESTIGATIONS NO. 17




BISCAYNE AQUIFER OF

DADE AND BROWARD COUNTIES, FLORIDA




By
Melvin C. Schroeder, Howard Klein, and Nevin D. Hoy

U. S. Geological Survey




Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
DADE COUNTY
CITIES OF MIAMI, MIAMI BEACH and FORT LAUDERDALE




TALLAHASSEE, FLORIDA
1958










FLORIDA STATE BOARD

OF

CONSERVATION







LEROY COLLINS
Governor


R. A. GRAY
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation






LETTER OF TRANSMITTAL


Tallahassee

December 5, 1957





Mr. Ernest Mitts, Director
Florida State Board of Conservation
Tallahassee, Florida

Dear Mr. Mitts:

I am forwarding to you a report entitled, BISCAYNE AQUIFER
OF DADE AND BROWARD COUNTIES, FLORIDA, which was pre-
pared by Melvin C. Schroeder, Howard Klein, and Nevin D. Hoy,
Geologists of the United States Geological Survey. The report was sub-
mitted for publication March 15, 1956, and it is recommended that it
be published as Report of Investigations No. 17.

The Biscayne Aquifer is the principal source of water for the heavily
populated area in the vicinity of West Palm Beach and Miami. The
publication of this data is timely and will assist in the intelligent devel-
opment of the water resources of the area.

Respectfully submitted,
HERMAN GuNTER, Director







TABLE OF CONTENTS


Page,
A abstract .............................................................. 1


Introduction .....................................
Location and geography of area ...............
Purpose and scope of investigation .............
Previous investigations .......................
Personnel and acknowledgments ...............

Biscayne aquifer .................................
D definition ...................................
Areal extent and thickness .....................


Geologic formations composing the
General features ...........
Miocene series .............
Tamiami formation .....
Pliocene series ........... .
Caloosahatchee marl ....
Pleistocene series ...........


Biscayne



.........


aquifer
. .. .. ,


Fort Thompson formation .
Key Largo limestone .....
Anastasia formation .....
Miami oolite ...........
Pamlico sand ...........


11
11
11
20
21
23
24

24
24
25
26
36


Ground-water occurrence .....................
General features ...................... .
Shape and slope of the water table .........
Fluctuation of the water table ............
Recharge and discharge .................

Hydrologic characteristics of the Biscayne aquifer


Quality of the water ................................


Salt-water contamination ............................................... 42

Adequacy of supply .................................................. 45

Selected references .................................................... 55


. . . . .
. . . . .


..


. ..... ...00.0. 0. .000 *0 .. 0 0






ILLUSTRATIONS

Figure Page
1 Map of Florida showing location of Dade and Broward
Counties and the approximate extent of the Biscayne
aquifer ....................................................... 2
2 Structure-contour map of Dade and Broward Counties
showing base of the Biscayne aquifer ............................ 6
3 Geologic map of southern Florida ............................. 8
4 West-east geologic cross section in western Broward County ............ 13
5 West-east geologic cross section in Dade County .............. Facing 14
6 North-south geologic cross section in the Everglades ............ Facing 14
7 Map of Broward and Dade Counties showing location of
geologic cross sections and certain test wells ...................... 15
8 West-east geologic cross section near Krome Avenue at
Tamiami Trail ........................... ................... 17
9 North-south geologic cross section on the coastal ridge ................. 22
10 Map of Dade County showing average water levels in
eastern part, 1940-50 .......................................... 27
11 Graphs showing fluctuation of water level in well S196 and
rainfall at University of Florida Subtropical Experiment
Station during 1947 ............................................ 28
12 Chart of comparative average monthly water levels in
selected wells ............. .... ................................ 30
13 Map showing location of certain observation wells and
location of large municipal well fields ........................... 31
14 Low-stage water-level map of eastern and southern Dade
County, May-June 1945 ..................................... 33
15 Low-stage water-level map of eastern Broward County,
April 14, 1945 ................................................ 34
16 High-stage water-level map of Dade County, October
11-12, 1947 ................................................. 35
17 Map showing progressive salt-water encroachment in the
Miami area from 1904 through 1953 ............................. 44
18 Map showing location of chloride profiles of figures 19
through 24 ................................................... 46
19 Profile of the 1,000-ppm isochlor along the Biscayne Canal
in 1946 and 1950 .............................................. 47
20 Profile of the 1,000-ppm isochlor along the Little River
Canal in 1946 and 1950 ........................................ 48
21 Profile of the 1,000-ppm isochlor along the Miami Canal
in 1946 and 1950 ............................................. 49
22 Profile of the 1,000-ppm isochlor along the Tamiami Canal
in 1946 and 1950 ................... ....................... 50
23 Profile of the 1,000-ppm isochlor along the South Fork of
the Tamiami Canal in 1946 and 1950 ........................... 51
24 Profile of the 1,000-ppm isochlor along the Coral Gables
Canal in 1946 and 1950 ................ ........................ 52













BISCAYNE AQUIFER OF DADE AND
BROWARD COUNTIES, FLORIDA


ABSTRACT

The Biscayne aquifer is the only source of fresh ground water in
Dade and Broward counties, Florida. Composed of highly permeable
limestone and sand mainly of Pleistocene age, the aquifer supplies large
quantities of water, of excellent quality except for hardness, for munici-
pal, industrial, and. irrigational use. The aquifer attains its maximum
thickness in the Atlantic coastal areas and wedges out in western Dade
and Broward counties.

Water-table conditions prevail in the Biscayne aquifer, and the water
table fluctuates with variations in rainfall, evapotranspiration, and pump-
ing. High ground-water levels occur during the fall months and'low
levels during spring and early summer. The highest water levels of
record occurred in Qctoher-.1947, when intense rainfall accompanying
a hurricane flooded large areas throughout the two counties. Major dis-
charge from the aquifer occurs by natural outflow and evapptranspira-
tion. The average daily pumpage from the Biscayne aquifer in 1950 is
estimated to have been 1380 million gallons.

Permeability tests show that the limestones of the Biscayne aquifer
rank among the most productive aquifers ever investigated by the U. S.
Geological Survey.

Salt-water encroachment in the aquifer has taken place in coastal.
areas of southeastern Florida. The greatest inland advance of salt-water
intrusion has occurred as tongues along tidal drainage canals and rivers.

INTRODUCTION

LOCATION AND GEOGRAPHY OF AREA
Dade and Broward counties are in southeastern Florida, bordering
the Atlantic Ocean (fig. 1). The Atlantic Coastal Ridge, whose av-
erage elevation is between 8 and 10 feet above mean sea level, occupies
the eastern portion of the area from the coast to a few miles inland. Maxi-
mum elevatiobs at isolated highs range from 20 to 25 feet above sea






FLORIDA GEOLOGICAL SURVEY


.4 (


I /


/4


0


xC


SCALE IN MILES
2S 0 25 0 75 100


Figure 1. Map of Florida showing location of Dade and Broward counties
approximate extent (shaded area) of the Biscayne aquifer.


the






REPORT OF INVESTIGATIONS No. 17


level. In Dade County the ridge is composed principally of limestone,
but in Broward County it is composed of both sand and limestone. Most
of the population in the two counties is concentrated in the coastal and
ridge areas. The Florida Everglades, and area of organic soils, lies west
of the ridge and is devoted chiefly to agriculture and conservation areas.
The climate is semitropical to tropical. Rainfall averages 60 inches per
year, about 75 percent of the total falling in the period from May through
QOptber. The average temperature is about 750F.

PURPOSE AND SCOPE OF INVESTIGATION
The ground-water resources of Dade and Broward counties are one
of the greatest natural assets of the region. This report describes the
geology and hydrologic characteristics of the Biscayne aquifer and de-
fines its geographic distribution. The factors involved in the adequacy
of the supply are discussed and an evaluation of data on fluctuations
in water level is presented.

PREVIOUS INVESTIGATIONS
The surface geology in Dade and Broward counties was first investi-
gated by Sanford (1909). Sellards (1919) added considerable data when
the drainage canals were cut across the Everglades. The geologic for-
mations in southern Florida were described by Cooke and Mossom
(1929). Matson and Sanford (1913), Parker (1942), and Parker and
others (1944) described the geology and occurrence of water in the
water-table (Biscayne) aquifer. Parker and Cooke (1944) presented
physiographic and geologic descriptions of southern Florida, with spe-
cial reference to the late Cenozoic material in southeastern Florida.
The major part of the aquifer was then identified as belonging to the
TamiamFUiiforma iiParer (1951) proposed the name Biscayne aquifer
for the shallow materials and revised the geologic correlations of the
formations in the aquifer. A report by Parker, Ferguson, Love, and oth-
ers (1955) presents hydrologic data on the Biscayne aquifer in greater
detail than does this report.
Data on fluctuations of water levels in wells in Dade and Broward
counties have been reported in the following U. S. Geological Survey
Water-Supply Papers for the years 1939-1952 inclusive: 886, 907, 937,
945, 987, 1017, 1024, 1072, 1097, 1127, 1157, 1166, 1192, and 1222. Sub-
sequent data will be published in the water-supply papers entitled "Wa-
ter Levels and Artesian Pressures in Observation Wells in the United
states Part 2, Southeastern States."





FLORIDA GEOLOGICAL SURVEY


PERSONNEL AND ACKNOWLEDGMENTS
The data presented in this report cover the results of studies made
by the U. S. Geological Survey in cooperation with the Florida Geologi-
cal Survey, Dade County, the cities of Miami, Miami Beach, Coral
Gables, and Fort Lauderdale, and the Central and Southern Florida Flood
Control District. The continued interest and help of the officials of these
agencies have made it possible to develop the necessary program to study
the aquifer and the fluctuations of the ground-water levels.
The investigation was made under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, U. S. Geological Survey. V. T. String-
field and Garald G. Parker of the U. S. Geological Survey gave valuable
advice. The Corps of Engineers, U. S. Army, cooperated by permitting
examination of the cores and records of a great number of core borings.

BISCAYNE AQUIFER
DEFINITION
Meinzer (1923, p. 52, 53) has defined an aquifer as a rock formation
or stratum that will yield water in sufficient quantity to be of conse-
quence as a source of supply. A formation yielding meager amounts of
water might not be considered to be an aquifer in an area where there
are other formations that yield prolifically but might be considered to
be one in an area where little water is available.
Wherever possible, an aquifer is identified by the name or names of
the stratigraphic units composing it. Where an aquifer crosses strati-
graphic lines, or where its stratigraphy is uncertain, yet it is well known
to constitute a hydrologic unit, an aquifer may be given a proper name.
The principal aquifer in this area is such a unit.

The name Biscayne aquifer was proposed by Parker (1951, p. 820-823)
for the hydrologic unit of water-bearing rocks that carries unconfined
ground water in southeastern Florida. The aquifer is a single hydrologic
unit of permeable materials ranging in age from late Miocene through
Pleistocene. The boundaries of the aquifer, both horizontal and vertical,
are set not by formational contacts or age restrictions but by djfferegces-
in the hydrologic properties of the sediments. The lowermost component
of the Biscayne aquifer is a limestone or shelly calcareous sand-
stone of the upper part of the Tamiami formation in the northeastern
part of Dade County and the southeastern part of Broward County. The
remaining and major portion of the Biscayne aquifer is composed of rocks
ranging in age from Pliocene through Pleistocene in the following





REPORT OF INVESTIGATIONS No. 17 5

sequence from bottom to top: Caloosahatchee marl (as erosion rem-
nants), Fort Thompson formation, Key Largo limestone, Anastasia for-
ination, Miami oolite, and Pamlico sand. The aquifer is underlain by
a relatively impermeable greenish marl of the Tamiami formation. The
contact between the marl and the limestone of the Tamiami, Fort Thomp-
son, or Anastasia formations, or the Key Largo limestone, forms the lower
boundary of the aquifer.

In the Miami area the base of the Biscayne aquifer is easily deter-
mined by the occurrence of the impervious marl of the Tamiami forma-
tion. However, it is more difficult to define the basal or lateral limits in
Broward County where clastic sediments rather than limestones consti-
tute a major part of the Pleistocene sequence. The interfingering and
the vertical and horizontal gradation of sands and calcareous materials
present a problem similar to determining the demarcation between two
different lithologic facies of the same geologic time unit. In an aquifer
the ground water should be free to move in any direction, under the
proper hydraulic gradient. In northwesternmost Broward County (fig. 1)
the water in sands whose elevation and stratigraphic position are similar
to those in the Biscayne aquifer to the southeast apparently does not
move freely, as shown by its high mineralization. These sands, therefore,
are not considered a part of the Biscayne aquifer.

AREAL EXTENT AND THICKNESS

The Biscayne aquifer underlies all the coastal areas and most of the
Everglades to and a little beyond the Broward-Palm Beach county line
(fig. 1).

The thickness of the aquifer is greatest along the coast in the Miami
area and northward in the vicinity of Fort Lauderdale, where it is 200
fee.t-i,places. The aquifer decreases in thickness gradually .southwfird
from Miami, and rapidly westward into the Everglades; beyond its
thickest portion in the Everglades it thins out to a featheredge in eastern
Collier and Monroe counties.

Figure 2 shows contours on the base of the highly permeable rock
in Dade and Broward counties. The base of the Biscayne aquifer is
commonly drawn at the base of 'the formations of Pleistocene age ex-
cept for the coastal area in Broward County and in northeastern Dade
County, where the boundary occurs within the Tamiami formation, and
other isolated areas where the base is placed at the bottom of limestone






FLO A GEOLOGICAL SURVEY
FLORIDA GEOLOGICAL SUIRvEY


D A/

/


R D


FORT


(3


"I


HOME


S' EXPLANATION
) WELL USED IN DRAWING CONTOURS
CONTOUR LINES REPRESENT
APPROXIMATELY THE BASE
OF THE BISCAYNE AQUIFER
IN FEET BELOW SEA LEVEL
CONTOUR INTERVAL 10 FEET

SCALE IN MILES


Figure 2. Structure contour map of Dade and Broward counties showing base of
Biscayne aquifer.


W


0
0
0
0
- o


/















I 4)O$


0


/
0o






REPORT OF INVESTIGATIONS No. 17


that perhaps is the Caloosahatchee marl. Subsurface geologic data in
southern Dade County are scanty because very few core holes have been
drilled.

The areal extent of the Biscayne aquifer as shown in figure 1 is
based upon the available data, and collection of additional information
concerning the geology and the hydrologic characteristics may either in-
crease or decrease the areal extent shown.

GEOLOGIC FORMATIONS COMPOSING
THE BISCAYNE AQUIFER

GENERAL FEATURES
The Biscayne aquifer includes the following stratigraphic units: the
upper part of the Ta~miamiJformation in the coastal areas of Broward
County and northeastern Dade County; the small erosional remnants
of the Caloosahatchee marl in southern Broward County; the Anastasia
formation in Broward County and southern Palm Beach County; the
Fort Thompson formation in Dade and Broward counties, except the
western part of Dade County north of the Tamiami Trail and north-
west Broward County where the formation is relatively impermeable;
the Key Largo limestone in Dade and Monroe counties; and the Miami
oolite and the Pamlico sand in Broward and Dade counties. The Lake
Flirt marl and more recent deposits, including the organic soils of the
Everglades and marine marls bordering the coast, are excluded from
the Biscayne aquifer.
The generalized surface distribution of the various geologic forma-
tions is shown on figure 3. The map is based upon recent observations
of both surface exposures and well cuttings and is adapted and revised
from geologic maps of Florida by Cooke (1945, pl. 1) and R. 0. Vernon
(in Black and Brown, 1951, p. 7) and of southern Florida by Parker
and Cooke (1944, pl. 15). The field notes of Mr. Parker have been used
extensively for descriptions of exposures and borrow pits no longer in
existence.
The formations appearing on the geologic map and mentioned in the
report are as follows:










FLORIDA GEOLOGICAL SURVEY


0- 7
-


LAKE
OKEECHOBEE


EXPLANATION



MIdAMIOOkllf






LWII N"W"



FORT THOMdPSON FORMdATION
AII~NJIT'4OWAINKSANDI SNACIIIK AND 1IRISH-
04110 NA~k, iN N)I NALKNAND N"lioLDID%


81 CALOOSAHAYCHEE MARL



TAMIAMI FORMATION
CLAVAINNA*&. NlLlN SAND AND NSOFTIILIY*
SAONVNlNtIO4NI LOCALiI CAIWIARD11490.


.06


G(otOdy AVISF0 TO M C. SCHRO0(ro.
HOWARD KLEIN, AND N.D 0 F ONOM
maPS 1 Asy PARDIR AlSAND COOK&
ItS41, Cw COOE li1945), AND R. 0.
VISION (IN LACK ANID ROWN, I1l)


SCALE IN MILES
to 0 0 20 30


Figure 3. Geologic map of southern Florida.


,9r"'




REPORT OF INVESTIGATIONS No. 17


LATE CENOZOIC FORMATIONS OF DADE AND BROWARD COUNTIES


Formation


Soils
Lake Flirt
marl


Characteristics


Peat and muck; laterite.
White to gray calcareous mud, rich with
shells of Helisoma sp., a fresh-water gas-
tropod. In some places casehardened to
a dense limestone. Relatively imperme-


Liable.


Pleistocene
(Formations
are contem-
poraneous
in part)


Pliocene


Miocene


Pamlico
sand


Miami
oolite


Anastasia
formation


Quartz sand, white to black or red, depend-
ing upon nature of staining materials,
very fine to coarse, average medium.
Mantles large areas underlain by Miami
oolite and Anastasia formation.


Limestone, oolitic, soft, white to yellowish,
containing streaks or thin layers of cal-
cite, massive to crossbedded and strati-
fied; generally perforated with vertical
solution holes. Fair to good aquifer.
Coquina, sand, calcareous sandstone, sandy
limestone, and shell marl. Probably com-
posed of deposits equivalent in age to
marine members of Fort Thompson
formation. Fair to good aquifer.


Key Largo Coralline reef rock, ranging from hard and
limestone dense to soft and cavernous. Probably
interfingers with the marine members of
the Fort Thompson formation. Crops out
along southeastern coast line of Florida
from Soldier Key in Biscayne Bay to
Bahia Honda. Excellent aquifer.
Fort Alternating marine, brackish-water and
Thompson fresh-water marls, limestones, and sand-
formation stone. A major component of the highly
permeable Biscayne aquifer of coastal
Dade and Broward counties, which yields
copious supplies of ground water.


Caloosa-
hatchee
marl
Tamiami
formation


Sandy marl, clay, silt, sand, and shell beds.
Yields ground water less abundantly than
most other parts of the Biscayne aquifer.
Cream, white, and greenish-gray clayey
marl, silty and shelly sands, and shell
marl, locally hardened to limestone. Up-
per part, where permeability is high,
forms the lower part of the Biscayne
aquifer. Lower and major part of forma-
tion is of low permeability and forms the
upper beds of the aquiclude that confines
water in the Floridan aquifer (Ocala and
associated limestones) below.


Age


Recent
and
Pleistocene


Thickness
(feet)
0-12
0-6


0-40


0-40


0-120





0-60







0-150






0-25


0-100


--i--


I\ --~----~-- -





FLORIDA GEOLOGICAL SURVEY


MIOCENE SERIES

TAMIAMI FORMATION

The Tamiami formation as redefined by Parker (1951, p. 823) in-
cludes all the upper Miocene materials in southern Florida, including
the Tamiami limestone of Mansfield (1939, p. 8). Excluded from the
formation is the "Tamiami" formation of Parker and Cooke (1944, p.
62-65) in Dade County. Parker and Cooke correlated the limestone that
Mansfield found cropping out along the Tamiami Trail in Collier and
Monroe counties with the highly permeable limestones and sandstones
which unconformably underlie the Miami oolite of Pleistocene age in the
eastern Everglades and Miami area. Their correlation was based on cut-
tings from percussion-type or cable-tool drilled wells, which penetrated
the aquifer, but the comminuted condition of the cuttings prevented
identification of any fresh-water limestones intercalated with marine lime-
stones. Subsequent exploratory core drillings in the Everglades and Mi-
ami area by the Corps of Engineers, U. S. Army, and the U. S. Geological
Survey revealed the occurrence of fresh-water gastropods in limestone
beds underlying the Miami oolite to a depth of 55 feet below sea level.
Because the oldest known fresh-water limestones in this region are of
Pleistocene age, most of the material underlying the eastern Everglades
and the Miami area has been tentatively referred to the Pleistocene, by
Parker (1951, p. 822, 823), and Hoy and Schroeder (1952, p. 283-285).
The Tamiami formation is divisible lithologically and hydrologically
into two units: a relatively impermeable clastic imit, and a permeable
limestone and sandstone unit. The two units have no stratigraphic signifi-
cance, although in many places the plastics form the base and sandstones
or limestones the uppermost part of the formation. However, the units
are primarily geographic. Limestone is commonly exposed at the surface
in the outcrop of the Tamiami formation in the Big Cypress Swamp and
the Sunniland area; permeable sandstone composes the upper part of
the formation in the subsurface of the coastal area of Broward County
and northeastern Dade County. The subsurface Tamiami formation near
Carnestown, Sunniland, and Immokalee in Collier County is a creamy-
white, clayey, shelly marl, which in part has been indurated to a per-
meable limestone as a result of water-table fluctuation and ground-water
percolation. Toward the east the formation increases in sand and marl
content, and in Dade and Broward counties most of the formation con-
sists of relatively impermeable plastics composing the upper part of the
aquiclude that confines water in the Floridan aquifer, the principal ar-
tesian aquifer of the Florida Peninsula and adjacent area.





REPORT OF INVESTIGATIONS No. 17


PLIOCENE SERIES
CALOOSAHATCHEE MARL
The Caloosahatchee marl is the only Pliocene material found in south-
ern Florida. It was named by Matson and Clapp (1909, p. 123) for the
soft, semiconsolidated sediments that form low bluffs along the Caloo-
sahatchee River between La Belle and Denaud in Hendry County.
The Caloosahatchee marl is commonly a light greenish-gray silty,
shelly marl, with varying amounts of sand. Sand and shells, occurring
both in beds and in lenses, locally form a shell marl. Ground-water move-
ment and exposure to air have locally casehardened and cemented the
more sandy and shelly material to a calcareous rock which subsequently
has been made permeable by solution of limestone and washing out of
elastic material. Generally the formation is relatively impermeable, ex-
cept locally where very shelly layers or lenses predominate.
The Caloosahatchee marl is known to extend 25 miles southward
from Lake Okeechobee where it underlies Pleistocene rocks in the form
of thin permeable limestone and sandstone reefs or "shoestring" sands.
Present data are not yet sufficient to determine the extent of Pliocene
deposits beneath the lower Everglades, but faunal evidence from a well
near Kendall suggests the possibility of the occurrence in Dade County
of isolated remnants of the Caloosahatchee marl.
It was previously thought by Parker and Cooke (1944, p. 59) that,
south of Lake Okeechobee between the Dade-Broward county line and
the approximate latitude of Twenty-Six Mile Bend of the North New
River Canal, the Caloosahatchee and Tamiami formations were possibly
contemporaneous and interfingered in the subsurface. However, more re-
cent exploratory drilling has indicated that this material to about 60 feet
below sea level is probably of Pleistocene age. This would mean that
the Caloosahatchee marl, which is 30 to 50 feet thick near Lake Okee-
chobee, thins to 6 feet at a place a mile south of the Broward-Palm Beach
county line and the North New River Canal. The marl has not been defi-
nitely recognized in well cuttings south of that place in Broward or
Dade counties.

PLEISTOCENE SERIES
FORT THOMPSON FORMATION
The Fort Thompson formation is the name applied to the alternating
fresh-water and marine limestones and marl beds which unconformably
overlie the Caloosahatchee marl at old Fort Thompson 1% miles east of
La Belle. Originally referred to as the Fort Thompson beds by Sellards





FLORIDA GEOLOGICAL SURVEY


(1919, p. 71, 72), the unit was later named the Fort Thompson forma-
tion by Cooke and Mossom (1929, p. 211-215), and was defined to
include the overlying marine Coffee Mill Hammock marl. In the lower
Everglades the Fort Thompson formation overlies the Tamiami forma-
tion, or, where present, erosional remnants of the Caloosahatchee marl,
and underlies the Miami oolite unconformably. In the northern part of
the area the Fort Thompson is overlain by the younger portion of the
Anastasia formation, the Lake Flirt marl, or the Pamlico sand.
The Fort Thompson formation at the type locality is a succession
of shelly marine and nonmarine limestones and marls, including three
distinct marine beds. The uppermost, the Coffee Mill Hammock mem-
ber, is a shell marl, consisting chiefly of shells of Chione cancellata. The
marine marl members are separated by gray, shelly, marl beds, in
part indurated to limestone, containing the fresh-water gastropods Heli-
soma and Ameria. The fresh-water beds are pierced by vertical and
lateral solution cavities formed by ground-water percolations. Subsequent
filling of the cavities by marine marls has produced a network of inter-
connected and isolated marine and fresh-water marls and limestones. In
places, holes penetrate the entire thickness of the formation so that the
Coffee Mill Hammock member lies directly upon the Caloosahatchee
marl of Pliocene age as a solution-hole filling. The alternation of marine
and fresh-water beds indicates, according to Parker and Cooke (1944,
p. 94-96, fig. 4), onlapping and offlapping seas from the end of Pliocene
time through the Sangamon interglacial stage of the Pleistocene.
Core borings of the thick section of permeable limestone and sand-
stone in the lower Everglades, between the Miami oolite and the Tami-
ami formation, similarly show interbeds and cavity fillings of fresh-water
limestone with marine limestone (figs. 4-9). This interbedded material
forms the major part of the Biscayne aquifer and, as previously men-
tioned, has been tentatively correlated by Hoy and Schroeder (1952, p.
283-286) with the Fort Thompson formation.
The Fort Thompson formation in the Dade-Broward county area
is predominantly light gray to cream, fossiliferous, marine, sandy lime-
stone and calcareous sandstone, with a few thin beds of gray and tan
fresh-water limestone. The entire section has been subjected to solution
by ground water,,and the result is a cavity-riddled mass of permeable
rock. Solution cavities are as much as several feet in diameter; some are
filled or partially filled with fine and medium quartz sand. Some sand
filling possibly occurred during flooding by Pleistocene seas. Loose sand
such as this decreases the permeability of the aquifer, but if wells are
heavily pumped much of the sand will be removed and a high perme-
ability adjacent to a well will result.





REPORT OF INVESTIGATIONS No. 17


Figure 4. West-east geologic cross section in western Broward County.

Cementation and redeposition of materials by ground-water move-
ment are very much in evidence throughout the Fort Thompson for-
mation. Cementation of sand bodies by calcium carbonate has produced
layers of hard, dense sandstone. Locally the cement is siliceous, pro-
ducing a very hard quartzitic sandstone. An examination of limestone
cores frequently shows secondary deposits of calcite crystals inside cav-
ities or within concavities of marine shells. Fossils are preserved chiefly
as molds and casts, rarely in their original form. Some cores of the Fort
Thompson formation show indications of bedding planes which provide
zones of weakness along which ground-water solution takes place. Part
of the Fort Thompson formation is composed of very dense, hard non-
fossiliferous limestone exhibiting little or no effect of ground-water
action. In general, highly fossiliferous beds are markedly pitted with so-
lution holes.
Because no unconformable relationship has been noted between the
Fort Thompson and older formations, the contact is normally placed


__ ____





FLORIDA GEOLOGICAL SURVEY


beneath the lowest sandy marine limestone which underlies fresh-water
beds. It is recognized that a part of this basal material in some places
may include formations of either Pliocene or late Miocene age.
The contact between the Fort Thompson formation and the Miami
oolite, as observed in spoil banks along canals in the Everglades, is un-
conformable and is usually placed at the maximum depth at which oolites
appear. The upper surface of the Fort Thompson is uneven and is char-
acterized by solution pits and depressions and vertical solution holes.
Oolitic material admixed with loose, sandy detritus from the Fort Thomp-
son was deposited on this eroded surface and filled depressions to depths
a few feet below the actual contact. These cavity fillings are easily dis-
cerned in core samples because the filling material is heterogeneous and
shows a color contrast. A layer of very hard, dense, cream to gray,
sandy limestone, which is peculiarly mottled or banded with brown
and tan limestone, occurs in the Fort Thompson below the contact. In
places the material appears to be a conglomerate containing weathered
pebbles of the Fort Thompson formation, but in at least some of these
places the "conglomerate" is the result of irregular deposition of iron
oxide in interstices of the Fort Thompson, along with differential cemen-
tation of those areas. The banding may denote an old eroded surface
or may be the result of water-table fluctuations.
The occurrence of fresh-water limestones in a great number of core
borings that penetrate the aquifer west of the coastal ridge has been
plotted in cross sections (figs. 4-6), the locations being shown on figure
7. In addition, a series of shallower borings, 25 to 30 feet below mean
sea level, along U. S. Highway 27 (Miami Canal northward to North
New River Canal) across Broward County between the Dade and Palm
Beach county lines, were examined. Fresh-water limestones are pres-
ent at shallow depth along U. S. Highway 27 where it adjoins the South
New River Canal north to the Palm Beach county line. In another series
of holes bored to a depth of about 20 to 25 feet below mean sea level
and extending from the North New River Canal to the Hillsboro Canal,
along a line approximately 8 miles west of Florida Highway 7, no fresh-
water material was noted in the cores. Obviously, it is difficult to deter-
mine exactly where the Fort Thompson and Anastasia formations merge,
but they seem to merge near the eastern edge of the Everglades.
A similar situation exists in Dade County where fresh-water lime-
stones are not known to occur in coastal areas. Along the western edge
of the coastal ridge, a few beds of fresh-water limestone are present, as
well as some indications of reef corals. The fresh-water limestones, rang-
ing in thickness from 1 to 3 feet, were noted in the following wells (fig.
7) which are not included in the cross sections:









































































































































.1

































- '--


B t i






65 SO%


FORT THOMPSON





i10





TAMIAMI


35 .


MIAIWM

LITT~


FORMATION


FORMATION


EXPLANATION


PEAT AND UGCK


OOLITIO LIMtSTONR

$AND


SANDSTONE OR SANDY LIMISTON('


LIMESTONE


IRSiN.*VWAI LIMESTONE


SHELLS

EMA
MARL


0 AO


V q C
It c 0


NOIASTEM OR
UN CONFORM NIT Y


TAMIAMI


R EC EI N T O R OA N I C ( 1 1 L 9


FORT


THOMPSON


FORMATION


SCALE IN MILIS
0 I S J A _


.-----J1. ..- _


Figure 5. West-east geologic cross section in Dadc County.


%0 ut
o' o "


ANI


iAtLS


MIAMI


QOLITE


FORMATION


CORAL


'A-
C'
1~~
(II


_ __ ___~__I__UI


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~~~-- -~--'---`~--^--~--`~'"--1-1------1-1--~ ---







































min# 4514M



11 16MillS p
all MANI4. 4






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FORMATION


Vo 1 3 9.4 .413 .


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MIAM)


FORT


THOMPSON


NISNT


44
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ONOANI


FORMATION


"1


1171
GAVITYYI
USIIINg Lit


VI:I


FORT


STAMIAM


FI


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oilIV
0
.4 .4 .4 .4
.4


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F RM 0


avs ~Q~F---^ --^a-'-' -- ... -- =ia ---_te


EXPLANAT ION
P14Y AND 5WONI
M-1ISNPTD


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Figure 6. North-south geologic cross section in the Everglades,


*1t


S OIL#,


cPP


-5'4

-SO


____1_~__ __ __~I __I_____ I_____~___ __1_______1~_ __


I -~------~I-"pl-_-"~=m-`~""~'~"~'~E~i~E` _I


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REPORT OF INVESTIGATIONS No. 17


-I
C'


AEI..









B'


G552


HOMESTEAD
*


N


EXPLANATION
* TEST WELL, CORE BORING
0 TEST WELL, CABLE TOOL G2(O
TEST WELL, PENETRATING RECOGNIZED
FRESH-WATER LIMESTONE
TEST WELL, PENETRATING RECOGNIZED
CORALLINE LIMESTONE


*11


SCALE IN
0


MILES


Figure 7. Map of Broward and Dade counties showing location of geologic
cross sections and certain test wells.


m,&!6Q~r


I






FLORIDA GEOLOGICAL SURVEY


Well Depth to top of fresh-water lime-
No. stone, in feet below msl
G 448-- .---..............- .................... -.... ............ ....... ........------------- 41
G 551 --..---------................-.........................------......----------.----------...................... 87 and 50
G 553 .......---------------..............-.....--..--.--..--------... ...... ........ -- --.... --.......-.. 42
G 552 ..... ......................... --..........--- .......-- ... ...------....... ..--...........------ .------. 10
S 24 .....--------..- ..------ --------- ----..........................................---.. 40 to 45
(depth uncertain)
S 986 ............. ......................--------------- --------------....................... ..... ........... .. 89

Reference to the section on the Anastasia formation, and to figure 7
showing wells that have penetrated coralline rocks, makes it evident
that the Fort Thompson, Key Largo, and Anastasia formations inter-
finger. Pleistocene marine limestones in certain areas of coastal Dade
County cannot be definitely assigned to one of the three formations, be-
cause of their transitional character. In some instances the limestone has
been arbitrarily placed in the Fort Thompson formation, although it does
not contain fresh-water beds, but in others the limestone is placed in
the Key Largo, although it is not coralline.

Figures 4 and 5 show west-east geologic sections across the lower
Everglades, and figure 6 shows a north-south section at the longitude
of Krome Avenue. Figure 8 shows a short west-east section along the
Tamiami Trail east of Krome Avenue, where wells were closely spaced,
and a possible correlation of fresh-water limestones. Several zones of
fresh-water limestone are apparent between wells G 670 and G 624,
shown in figure 6, where the uppermost zone occurs between the base of
the Miami oolite and a position 8 feet below mean sea level. The most
persistent zone and one that definitely appears to be a single layer oc-
curs between 8 and 15 feet below mean sea level and extends south-
ward from well G 670 to well G 653, and possibly farther. The thickness
of the fresh-water limestone of this zone ranges from 1 to nearly 5 feet,
although the greater thickness may be due to filling of solution holes.
This fresh-water limestone is not found at comparable depths in wells
G 657 and G 656. Possibly the core pierced a marine cavity fill within
the fresh-water limestone, or the bed has been eroded and subsequently
covered by younger marine limestone. However, limestone beds plotted
a few feet below the minus 15-foot mean-sea-level horizon in these 2 wells
may indicate that this bed was deposited in a locally depressed area or
a wide solution hole.

A second fresh-water limestone occurs approximately 20 to 30 feet
below sea level. This zone extends between wells G 661 and G 6538,
and wells G 669, G 667, and G 664 farther north containing fresh-water





REPORT OF INVESTIGATIONS No. 17


Figure 8. West-east geologic cross section near Krome Avenue at Tamiami Trail.
limestones, at slightly lower elevations, which are probably a continua-
tion of this zone. A similar situation may be true of the wells south of
G 653, although these limestones are generally at slightly higher ele-
vations.


17






FLORIDA GEOLOGICAL SURVEY


Cores from wells G 667, G 664, G 624, and G 757 indicate that 2 or
possibly 3 zones of fresh-water limestone may be present between the
second zone and the base of the Fort Thompson formation, but definite
correlation between wells cannot be made with the information available.
In well C 667 the highest fresh-water limestone is associated with
oolitic material and may be part of the Miami oolite. North of the Dade-
Broward county line the distribution of fresh-water material was such
that it could not be correlated with the more uniformly bedded strata
to the south.
Figure 8 shows a locality east of Krome Avenue along the Tamiami
Trail, where some of the closely spaced core borings penetrate the en-
tire thickness of the highly permeable aquifer. This section again shows
a possible correlation of 6 fresh-water limestone zones similar to that
shown in figures 5 and 6. Well G 607 (fig. 5) penetrated 6 beds of
fresh-water limestone and a well 42 feet east pentrated the same 6 beds.

At least four limestone beds of fresh-water origin occur within the
Pleistocene section at the Palm Beach-Broward county line and the North
New River Canal (fig. 7), as shown by the following log of well G 725:


Description
Peat and muck, dark brown .. --- .....--- ..... ..- ..........-.-.
Clay, m ucky, black .. -.-- ....................
Limestone, fresh-water, brown, dense, shelly .----.....................
Marl, sandy, marine, in places indurated to sandstone ................
Limestone, fresh-water, dense, brown ......... ..-.... ... ............
Sandstone, calcareous, fossiliferous, marine ...........................
Limestone, fresh-water, cream .-----...-..--..--.........................
Sandstone, shelly, marine, calcareous -..-....-. ......-.................-
limestone, cream, shelly, probably fresh-water (?) .................
Marl, very sandy, shelly, tan, marine, with a few fresh-water
shells .. .-----.....................
Marl, tresh-water, sandy, shelly ---...-------- -----....-.- ......... ...
Marl, fresh-water, partially shelly, indurated to limestone ..........
Sand, marly, tan, very shelly, fresh-water gastropods from
11.5 to 12.0, apparently as savings, containing some
marine shells (Chione cancellata) ......------------...................
Sandstone, cream to tan, very shelly, mixed marine and fresh-
water at bottom ---......--------..---...........-------..................


Depth, in feet, with
reference to msl
+ 10.9 to + 6.1
+ 6.1 to + 4.8
+ 4.8 to + 4.7
+ 4.7 to -- 1.7
+ 1.7 to + 1.1
+ 1.1 to 0.0
0.0 to 1.0
1.0 to 6.0
6.0 to 6.5


- 6.5
- 8.6
- 10.7


- 8.6
-10.7
- 11.5


- 11.5 to 13.5

- 13.5 to 16.5


A glance at the geologic sections indicates that each fresh-water bed
was probably deposited on an undulating and solution-pitted marine
limestone. The beds range in thickness from 0.2 foot to nearly 5 feet.
Their upper surfaces were probably eroded to some extent by shallow
encroaching seas which removed less resistant materials. It is recognized






REPORT OF INVESTIGATIONS No. 17


that a few of the fresh-water limestones as plotted are cavity fillings which
were deposited in what is definitely marine material. Fresh-water mate-
rials could easily have been washed in and deposited in subsurface cavi-
ties as well as at the surface.
It is possible that, during major portions of the Pleistocene glacial
stages, the lower Everglades was a low-lying marginal area bounded on
the west by slightly higher land and on the east by the coastal ridge
composed of reef materials. Because of the marginal character of the
area, slight rises in sea level would bring about marine floods during
which thin marine limestones were deposited. However, with a fall in
sea level, the land emerged so that the resulting weathering and erod-
ing of the marine limestones accompanied the deposition of some thin
fresh-water limestone. A major advance of the continental ice sheet would
cause an extended lowering of sea level, thus allowing a greater thick-
ness of fresh-water limestone to be deposited over a larger area. On the
other hand, a major or complete retreat of the ice sheet probably re-
sulted in inundation of the area for a long period, and in deposition of
a greater thickness of marine limestone in which were thin, isolated
I bodies of reworked older material.
The lower Everglades appears to have been a depressed area which,
during Pleistocene time, was intermittently shut off from the sea by a
barrier along the coastal ridge of southeastern Florida. This barrier was
formed by the deposition of the Anastasia formation, the Key Largo
limestone, and the Miami oolite. During times of lowered sea level the
Everglades lay exposed and contained swamps and fresh-water lakes,
and fresh-water limestones were deposited as fills in the lower materials
and as beds. The sea level probably was not stable during the glacial
stages but rose and fell with relatively short retreats and advances of
the ice. Such activity produced thin layers of marine limestone during
short sea floodings, interbedded with thin fresh-water or brackish-water
deposits during recessions. However, after a complete retreat of the
continental ice sheet, the resulting rise of sea level would permit thick
marine sections to be deposited. Optimum conditions for the most wide-
spread deposition of fresh-water limestone in the lower Everglades prob-
ably occurred at times between the beginning of a glacial stage and of
maximum advance of the continental ice sheet. Times of maximum ad-
vance of the ice and lowering of sea level were most favorable for chan-
nel cutting, resulting in draining of the land.
Correlation of the six postulated beds of fresh-water limestone with
specific glacial stages of the Pleistocene is a more difficult problem than
the correlation by Parker and Cooke (1944, p. 89) of the beds at the






FLORIDA GEOLOGICAL SURVEY


site of old Fort Thompson. The data suggests that the tentative correla-
tion by Parker and Cooke of individual beds with specific glacial and
interglacial stages may need revision.
KEY LARGO LIMESTONE
The Key Largo limestone, named and described by Sanford (1909,
p. 214-218), is a dead coral reef that makes up the Florida Keys from
Soldier Key southwest to Bahia Honda. The Key Largo limestone is
a part of the Biscayne aquifer along the coastal area of Dade County.
It constitutes the whole of the aquifer in the part of the Florida Keys
described. The rest of the Keys southwest from Bahia Honda are com-
posed of the Miami oolite and there the Key Largo limestone may con-
stitute only a small part of the aquifer. The aquifer in the Keys yields
saline water to wells.
The Key Largo limestone consists chiefly of recemented reef detritus
and precipitated limestone surrounding coral heads of the old reef. The
corals were subjected to wave action, which eroded the softer parts and
deposited the waste in the openings along with other bioherm material.
The formation in general is very permeable, containing solution cavities
which were produced in the same manner as in the Fort Thompson
formation.
Corals, most of them of the reef-building type, have been found in
material from the following wells (fig. 7), at the noted depths:
Well Depth, in feet
No. below msl
G 10 1 ......... .................... ...... .................. ......... 20 to 56
G 186 ----------------------.. ...........---- -------- 9 to 43
G 189 -----------------...----- ....--- ............-..........-------------- 13 to 32, and
41 to 48
G 193 ---------------------------------------- ............................ ... 35 to 43
G 196 ...----------------------..........................................-----............................--------... 41 to 54
G 210 .....-------------------.. ---------.. ........ ----..---..........--.....----- 13 to 19
G 216 ----------.............................----------...............------.............................----------.............--- 15 to 20,
24 to 33, and
44 to 60
G 224 -- --- .- ..- -----------------------...............................----... 18 to 44
G 429 .------...........------...---------------------------......-----------.....................--- 18 to 23
G 448 .----- ... ..----- ...........................................-------------------------................ 1 to 40
G 756 ... ..-- ---------.......................---------------------------------------------- 56
G 757 ---.. .-- ... ......-- -------................. ....................................... 44 and 49
G 758 -. .. ----------------------------.. --......-......-..---- --..... .... 52 and 56
S 986 (and nearby wells)-....-------------------------------------........................... 38,40,60, and 70
All except the last four wells, which were cored, were drilled by
the cable-tool method. The coralline material in well G 448 directly






REPORT OF INVESTIGATIONS No. 17


overlies fresh-water limestone, whereas in well S 986 a fresh-water lime-
stone bed at 89 feet is overlain and underlain by reef-limestone material.
Coral was noted in wells G 756 and G 757 below the lowest fresh-water
limestone. In many wells that were not cored the coralline limestone
appears to be discontinuous, because only a trace of coralline limestone
was noted in the samples from wells G 101 and G 224. The comminution
of the material by the bit action prevents any possible identification of
fresh-water limestone in such samples. However, along the eastern part
of the coastal ridge, fresh-water limestones are not apparent in the under-
lying limestones and only an occasional bed is penetrated in the western
part of the coastal ridge. The occurrence of coral in the vicinity of the
western part of the ridge demarks the area of interfingering between
the Key Largo limestone and the Fort Thompson formation. The nature
of this interfingering is not known nor is the western limit of coralline
limestone. An abundance of reef coral was excavated from the borrow
ditch for the levee which crosses the Tamiami Trail a mile west of Krome
Avenue. The corals apparently are from the top part of the Fort Thomp-
son formation, although it is possible that they are in the Miami oolite also.
A great number of wells along the coastal ridge penetrate Pleistocene
limestones that apparently include neither fresh-water limestones nor
coralline limestone. These limestones have been placed in the Anastasia
formation.
The upper part of the Key Largo limestone, according to Parker and
Cooke (1944, p. 68), interfingers with the lower part of the Miami oolite.
ANASTASIA FORMATION
The Anastasia formation was named by Sellards (1912) from its typi-
cal development of coquina on Anastasia Island, near St. Augustine,
Florida, and as defined in this report includes all pre-Pamlico marine
sand, limestone, and shell beds of Pleistocene age along the coastal area.
The Anastasia formation represents the chief component of the Bis-
cayne aquifer in the vicinity of Fort Lauderdale and along the coastal
ridge as far north as Delray Beach in Palm Beach County. In the area
to the west, the Anastasia is equivalent to the marine portions of the
Fort Thompson formation, and to the south the upper part of the An-
astasia merges with the Miami oolite and the lower part merges and
interfingers with the Key Largo limestone (fig. 9). The formation
is composed of marine sandy limestone, calcareous sandstone, in part
coquinoid, and shelly sand. It was initially laid down in a shallow beach
environment as an offshore bar which was exposed from time to time
by eustatic sea-level fluctuations during the Pleistocene. An outcrop of














E Ei


r*c Ie--V FL


ANASTASIA


HAWTHORN FORMATION


OOLITE


FORMATION


FORMATION


EXPLANATION

PiAT MUil

ODUTIC LMfTOas
ES





**skss
*MITOWl
ESa


SCALE m


Figure 9. North-south geologic cross section on the coastal ridge.


0


eg

0






REPORT OF INVESTIGATIONS No. 17


the Anastasia formation at Palm Beach shows younger eolian crossbed-
ded sandstone lying unconformably on marine calcareous sandstone. The
unconformity is characterized by brown sandy soil which fills solution
holes in the older material. The Anastasia formation represents sediments
deposited throughout all or a major part of the Pleistocene, according
to Parker and Cooke (1944, p. 66).
The permeability of the Anastasia formation ranges widely from place
to place. Away from the coastal areas, where it is well indurated, ground-
water action has produced large solution cavities and the permeability
high. Adjacent to the coast the material contains more sand and silt so
that the permeability is markedly reduced.

MIAMI OOLITE
The Miami oolite was named by Sanford (1909, p. 211-214). Cooke
and Mossom (1929, p. 204-207) redefined the formation to include all
the oolitic limestone of southern Florida, including that on the Keys.
The Miami oolite is the surface rock that blankets nearly all of Dade
County, parts of eastern and southern Broward County, the southern
mainland area of Monroe County, the Florida Keys from Big Pine Key
to Key West, and a triangular area extending from Dade County west-
ward along the Collier-Monroe county line. The formation thins out
at its western extremity and gradually thickens to the east, attaining a
maximum thickness of about 40 feet.
In the lower Everglades the Miami oolite unconformably overlies and
fills cavities in the upper surface of the Fort Thompson formation. Along
the coast the formation interfingers with the upper portions of the Fort
Thompson, Anastasia, and Key Largo formations. Where not exposed at
the surface in the lower Everglades, it is covered by Recent organic
materials. In northwest Dade County and southwest Broward County,
it is overlain unconformably by the Pamlico sand, a terrace deposit of
Pleistocene age, or by the Lake Flirt marl of Pleistocene and Recent age.
The Miami oolite is typically a white to yellowish massive crossbedded
oolitic limestone containing varying amounts of sand, usually in solution
holes. Where exposed to weathering, as in the Silver Bluff area, the
surface of the oolite turns a dull gray color. Crossbedding and cone-in-
cone structures are outstanding features. The angle of dip of the cross-
bedded material changes from place to place, and the material is ap-
parently a dune or beach-ridge deposit. The high angle crossbeds in
places are beveled by flat-lying oolitic material containing marine shells.
In the Silver Bluff area large pieces of crossbedded oolitic limestone are
4A


23






FLORIDA GEOLOGICAL SURVEY


incorporated in portions of oolite which show no evidence of bedding.
This is definite evidence of reworking of younger oolite deposits and,
according to Parker and Cooke (1944, p. 71), might indicate either that
the Miami oolite represents deposits of two or more interglacial stages
or that the deposition, reworking, and redeposition occurred during a
single stage. In either case, oscillation of the sea level was involved. At
many places in Broward County the formation is composed almost
entirely of calcareous oolitic sand or of mixtures of calcareous and quartz
sand.

PAMLICO SAND
The Pamlico sand is a late Pleistocene terrace deposit of marine origin
(Parker and Cooke, 1944, p. 75). Parker and Cooke (p. 74, 75) extended
the term Pamlico sand from North Carolina to southern Florida, and
defined it to include all the marine Pleistocene deposits younger than
the Anastasia formation.
The Pamlico sand blankets much of the Everglades north of the
latitude of Fort Lauderdale and covers the coastal area as far south as
Coral Gables. It unconformably overlies and fills cavities in the Miami
oolite, the Fort Thompson formation, and the Anastasia formation. In
the northern part of the region the sand is covered by Recent marls and
organic soils.
The Pamlico sand is chiefly a quartz sand ranging in color from
light gray or white to red and gray-black, depending on the amount of
incorporated iron oxide or carbonaceous material. In localities where
shells are admixed, the Pamlico sand may be semiconsolidated as a result
of solution and redeposition of calcium carbonate. The quartz sand
ranges in size from very fine to coarse, the medium-sized grains predomi-
nating. Where the material is medium to coarse, and well sorted, it will
furnish adequate fresh-water supplies for domestic purposes.
The Pamlico sand lies below the 25-foot contour; areas within its
outcrop that lie at higher elevations represent dunes or shore ridges
formed during the Recent. The formation increases in thickness from a
featheredge to perhaps 40 feet, the greatest thickness being along the
coastal ridge.

GROUND-WATER OCCURRENCE
GENERAL FEATURES
All the water that recharges the Biscayne aquifer is derived from
local rainfall. When rain falls to the surface, a part is evaporated, a part






REPORT OF INVESTIGATIONS No. 17


is used by plants, another portion runs off as surface water, in streams
or to fill lakes and ponds, and the remainder percolates rapidly through
the thin sandy mantle to the water table. Only in the Everglades does
any major surface runoff occur.
The water table is the upper surface of the zone of saturation except
in areas (rare in southern Florida) where that zone is formed by an
impermeable body. The water table is open to the atmosphere and is
marked by the level at which water stands in wells. It is an undulating
surface which in a general way conforms to the topography, being at
higher elevations under hills and lower under valleys. The water table
in the Biscayne aquifer normally lies within the Miami oolite, the Pamlico
sand, or the organic soils of Recent age. Parker (in Parker and others,
1955), in relating precipitation to water-table rises, estimates that about
two-thirds of the annual rainfall reaches the water table in southern
Dade County.
The water table fluctuates in response to local rainfall in the area
and to natural discharge (seepage into streams or canals or to the sea,
and evapotranspiration), and pumping.
Water for small domestic supplies is derived through small diameter
sand-point wells from the Pamlico sand. The Miami oolite is more per-
meable than the Pamlico sand, and the contained water is obtained by
means of shallow open-hole unscreenedd) wells. Large supplies of water
are obtainable from uncased wells in this formation in the grove area of
southern Dade County. The Key Largo limestone, the Anastasia forma-
tion, and the Fort Thompson formation in Dade County will yield large
amounts of water to open wells. For example, an 18-inch well southwest
of Miami yielded 7,600 gallons per minute, or about 11 million gallons a
day, with a drawdown of only 7 feet. Along the coastal areas of Broward
County, the water in the Anastasia formation generally is obtained by
means of screened wells. At Fort Lauderdale the Tamiami formation,
which is a friable; very calcareous sandstone, yields large quantities of
water to both open-hole and screened wells.

SHAPE AND SLOPE OF THE WATER TABLE
The water table of the Biscayne aquifer may be mapped at any given
time by determining its elevation in a network of wells. Eastern Dade
County has a large number of control wells, whereas those in Broward
County are relatively few and scattered. Irregularities in the shape and
slope of the water table are common and are produced chiefly by rainfall
and to a lesser extent by pumping, both of which are highly variable from
place to place. The water table in Broward and Dade counties commonly




FLORIDA GEOLOGICAL SURVEY


slopes eastward toward the coast, although in the central part of the
Everglades it slopes southward. In wet periods the water table may slope
both east and west from the coastal ridge.
Water-table contour maps have been prepared for the eastern part
of Dade County. These show modifications and changes in the shape of
the water table brought about by the various drainage canals and the
heavy local rains. The maps were prepared principally from records of
the present network of observation wells that are equipped with auto-
matic recording gages; however, when interpreted in conjunction with
maps showing high, intermediate, and low water stages, these records
give coverage that is nearly as complete as that of the much larger number
of wells measured for preparing a detailed water-table contour map.
Figure 10, which represents the average elevation of the water table for
the period 1940-1950, shows the general shape and slope of the water
table in Dl)ade County. Although several maps of different water stages
have been made, the maps of the lowest (fig. 14) and highest (fig.
16) ground-water stages of record in Dade County emphasize the
irregularities.

FLUCTUATIONS OF THE WATER TABLE
Major fluctuations of the water table are caused by recharge and
natural or artificial discharge. The magnitude of water-level fluctuation
during any one year in Dade County varies from 2 to 8 feet, depending
upon the amount and distribution of the rainfall in the local area. Figure
11 shows a hydrograph of well S 196 compared with a graph of rainfall.
The water table in the coastal areas fluctuates in response to
ocean tides, the time lag increasing and the magnitude of fluctuations
decreasing with distance inland. The greatest observed inland distance
of the tidal effect on water levels is 6,700 feet in well F 179, in Miami,
where the fluctuation amounted to 0.01 foot. Although the Biscayne
aquifer generally shows nonartesian characteristics, pumping tests indi-
cate that the aquifer temporarily responds as an artesian aquifer hav-
ing a very leaky roof. Thus, water levels in many wells respond to
earthquake shocks and to changes in barometric pressure. The effect
of barometric pressure is usually slight and is commonly masked by other
fluctuations. Parker and Stringfield (1950) have discussed the effects
of earthquakes, winds, tides, and atmospheric pressure changes on
ground-water levels in southern Florida.
High and low water-table conditions are of economic importance in
both rural and urban areas. Extremely high water-table conditions cause
the flooding of the low-lying lands in southern Florida, destroying crops,


26







REPORT OF INVESTIGATIONS No. 17


BROWARD COUNTY

RA NOES E,'A s r .$


IUR


It~

N II I


si la I


rLORIO A~
lvz

SCALE IN MILES
0 1 t 3 4 5 6 1 0 3 10


Figure 10. Map of Dade County showing average water levels in
eastern part, 1940-1950.







FLORIDA GEOLOGICAL SURVEY


PRECIPITATION,
IN INCHES


WATER LEVEL, IN FEET
ABOVE MEAN SEA LEVEL


0PO CO (NO ()o 4W OD ( O 4 a 0


Figure 11. Graphs showing fluctuation of water level in well S 196 and
rainfall at University of Florida Subtropical Experiment Station
during 1947.





REPORT OF INVESTIGATIONS No. 17


damaging buildings and other structures, and delaying the planting of
crops. Low water conditions cause nonirrigated crops to die, allow the
organic soils to shrink or to be destroyed by fire, and permit the en-
croachment of salt water at accelerated rates. The difference between
the highest and lowest water levels of record (1940-1951), as recorded
in observation wells, ranges from 6 to 11 feet along the coastal ridge and
from 7 to 8 feet in the Everglades.
The duration of water-level peaks resulting from rapid rises is
generally only a few minutes; hence, an average water level for a month
is a better guide to use in evaluating high water-level conditions. The
average monthly water level in a well is computed by averaging the
daily water-level readings. The range between the highest and lowest
average monthly water levels of record is about 7 to 7.5 feet in the
upper Everglades and 4.5 to 8.5 feet along the coastal ridge. The maxi-
mum, minimum, and mean of the average monthly water levels in
selected wells are shown in figure 12.
The net of observation wells equipped with recording instruments
in operation in Dade County since 1949 is adequate to determine the
annual average water-level conditions in the eastern part of the county.
The average water level in 1949 in Dade County was approximately the
same as the average water level in the period from 1940-1950 in those
wells for which water-level records were available during this 11-year
period. Therefore, the map showing average water levels for the period
1940-1950 represents average water levels in 1949.
In Broward County, the average water level for a 10-year period in
well S 829 (see fig. 13 for location) is about 4 feet above mean sea level.
This coincides fairly well with the average water level in 1949, and it
is inferred that the 1940-1950 average for other wells on the coastal ridge
may be nearly the same as the 1949 average. The 1949 average levels in
wells F 291 and G 561 were about 2 and 1.5 feet above mean sea level,
respectively.
The lowest water levels of record (1934-1951) occurred during May
and June 1945. The total rainfall during the years 1944-1945 scarcely
exceeded that of one normal year, so that the recharge to the aquifer
was well below normal. For the most part the numerous drainage canals
were uncontrolled during 1944 and only partially controlled in 1945.
These canals accelerated the lowering of water levels by the continuous
draining of ground water during the drought.
In the southern part of Dade County, in an area centering west and
southwest of Florida City, the water table declined to almost 3 feet below


29








FLORIDA GEOLOGICAL SURVEY


J F M A M J J A S O N D

G596 ..
4 YEARS / 6
f REORO -




X1


'4.t


Figure 12. Chart of comparative average monthly water levels in selected wells.


F 291
5 YEARS
*o RECORD


LLLL1~LIA


~


F M A M J J A S 0 N 0
---T---r-
F 210
0 YEARS
OF RECORD


Afl







REPORT OF INVESTIGATIONS No. 17


A


I *ir
a C%
I I 1'H


PERMANENT
SOUTHWEST
G


1%


SCALE IN MILES
0 0


Figure 18. Map showing location of certain observation wells and locations
of large municipal well fields.


/


D A





FLORIDA GEOLOGICAL SURVEY


the average level in Biscayne Bay (the average level in the Bay being
about 0.5 foot above U. S. Coast and Geodetic Survey mean-sea-level
datum). Parker, Cooper, and Hoy (1948, p. 16) state: "This lowering of
the water table below ocean level was largely brought about by the ex-
ceedingly high rate of evapo-transpiration acting upon a water table
already reduced to sea level by lack of rainfall and by drainage. But, in
addition to the natural withdrawal of ground water by evapo-transpira-
tion, irrigation helps reduce water levels still lower. The greater the
drought the greater the withdrawal of ground water for irrigation and,
thus, the greater the lowering of the water table. It should be empha-
sized, however, that irrigation withdrawal had very little to do with the
development of the large area of below-ocean-level water table in the
area centering west and south of Florida City evapo-transpiration,
which may possibly account for more than 71 inches of water a year in
this area, was principally responsible. The U. S. Weather Bureau reports
the evaporation of 70.704 inches from the Hialeah pan in 1945." A
ground-water contour map of Dade County for May 19, 1945, is shown
in figure 14.

The lowest stage of record was reached during the period June 17-20,
1945, a month after the detailed measurements used for figure 14 were
made, and estimated contours for that period also are shown in figure
14. The position of the contours is based on a few isolated measurements
and records from wells equipped with recording instruments. Water
levels ranged between 0.3 and 0.4 foot lower than those recorded on
May 19 except in the Miami area and the area southwest of Florida City,
where they remained the same. A slight amount of rainfall southwest of
Florida City maintained the same water levels there.

The lowest ground-water levels of record (1940-1951) in Broward
County occurred in 1945 also. Water-level measurements in a number of
wells in the eastern part of the county were made on April 14, 1945. The
lowest water level probably did not occur until late May; however, the
low water levels shown in figure 15, as interpreted from the measure-
ments of April 14, probably were not significantly different from those
reached several weeks later.

The highest water-table conditions of record in Dade County occurred
during October 1947 (fig. 16). At the end of September the water table
along the coastal ridge, especially in the Miami area, was the highest
of record (1940-1947) for September, owing to excessive rainfall. The
rainfall at Miami in the month of September was 13.65 inches, 5.00 inches
above normal for the month. The intense rainfall accompanying a small







REPORT OF INVESTIGATIONS No. 17


BROWARD COUNTY
0



TI11 aSakf CN

-0.5 0. -OPA LOCKA N T MAIJ


It'
sill MIku
I ~s PT. IN S.
I. I 'o \ *0) I


i NOR l LINst C I -





II
------ ----- ---4. -

"II Y --
I Su CSETE R IVE








I I o.o 7UA
I *OS.-ol
SI L.o" "

III"E

W l i E
I-----------------ARANJA~

I -I MODLL I



.0 1010 ---1 o


IT,













^-- I' 7

5 Waler lv,


SCALE IN MILES
t I 4 4 5 6 7 ,l 0 10


It
h 4-mi


IlO.LOI IiT


LANATION


vel on May 19

lI on June 19


Figure 14. Low stage water-level map of eastern and southern Dade County,
May, June 1945.


33














W 8. POMPANO :
I




I \LAUDERDALE

"DANIA

HOLLYWOOD





EXPLANATION
4.8 CANAL STAGE, IN FEET
ABOVE M.SL.
SCALE IN MILES O0 WATER TABLE CONTOUR
2 0 2 4 6 8 IN FEET ABOVE MS.L.
Figure 15. Low stage water-level map of eastern Broward County, April 14, 1945.









REPORT OF INVESTIGATIONS No. 17


BROWARO


COUNTY


High stage water-level map of eastern Dade County, October 11, 12, 1947.


SCALE IN MILES
aI 5I 4 1 o10


Figure 16.







36 FLORIDA GEOLOGICAL SURVEY

hurricane on October 11, 12 resulted in water levels reaching what are
probably the highest stages that have occurred since the major Everglades
canals were completed in 1913.
Rainfall at representative stations in southern Florida ranged as
follows:
January 1-October 30, 1947............................................. 65.9 to 96.1 inches
June 1-October 30, 1947................................................. 50.0 to 74.2 inches
Normal yearly rainfall..................................................... 53.8 to 62.6 inches
Rainfall on October 11 ranged from 5 to 15 inches and averaged about
10 inches in northern Dade County.
Practically the entire area west of the coastal ridge that was not
already flooded became inundated, and the already large overland flow
south in the Everglades was increased. The Miami Canal was out of its
banks as far east as Hialeah and Miami Springs. Outflow across U. S.
Highway 27 occurred from a mile northwest of Pennsuco to the vicinity
of the Russian Colony Canal. Other canals were similarly out of their
banks. The actual peak lasted several hours at the most, although many
areas remained flooded for several weeks.
The water-level map for October 11, 12 showing the peak (fig. 16)
was prepared from records of observation wells equipped with recorders,
and from measurements made during the flood period, leveled measure-
ments of flood marks, and interpolation of the measurements made in a
large number of wells on or about October 7. In a few places the water
levels are estimated. However, the map is believed to be a good approxi-
mation of actual conditions. In the area between Snapper Creek and
Krome Avenue, south of the Tamiami Canal, the presence of several small
ground-water mounds and the network of canals make it difficult to
visualize the actual shape of the water table, but the general slope was as
indicated.
RECHARGE AND DISCHARGE
Local rainfall is the principal source of recharge to the Biscayne
aquifer. The amount of rainfall varies within relatively short distances,
but it averages about 60 inches annually in.Dade County. In Broward
County, rainfall records for periods ranging from 5 to 25 years indicate
an average annual rainfall ranging from 51 to 65 inches. The lower
averages commonly pertain to the Everglades, and the higher ones to the
coastal ridge.
A small amount of ground water moves into the aquifer in Broward
County from Palm Beach County and from the North New River Canal.
In areas where canals are controlled by dams and in areas where the
ground-water levels are lowered by pumping, as in the well field in Miami
Springs, the canals provide recharge to the Biscayne aquifer.






REPORT OF INVESTIGATIONS No. 17


Discharge from the Biscayne aquifer occurs by ground-water flow into
the canals, the Atlantic Ocean, or Biscayne Bay, by evapotranspiration,
and by pumping.
Of the 60 inches of average annual rainfall in the coastal ridge
area of Dade County, Parker (1951, p. 825) estimates that 22 inches is
discharged by evapotranspiration and surface runoff without reaching
the water table and 38 inches reaches the water table. Of this, 20 inches
is discharged as ground-water flow, and 18 inches is discharged by
evapotranspiration of ground water and by pumping from wells. It is
estimated that, as of 1950, approximately 4 inches gross was discharged
by wells. In areas where heavy pumping forms significant cones of de-
pression, ground water is salvaged because of the decreased evapo-
transpiration resulting from the lowered water levels.
Ground water is utilized for municipal, industrial, domestic, and
irrigation supplies. The estimated pumpage in Dade County, in 1945
and 1950 in gallons per day, is as follows:
1945 1950
Municipal supplies 35,000,000 65,000,000
Industrial use 12,000,000 20,000,000
Rural use and irrigation 11,000,000 15,000,000

Total average daily pumpage 58,000,000 100,000,000
These estimates do not include the amounts from wells used for air-
conditioning and then returned to the ground. In 1954 about 28 mgd was
being pumped in this way, although an unknown part of this was saline
water. One new hotel under construction in the Miami Beach area will
pump 4 mgd of saline water from the ground for air-conditioning and
will discharge it into the ocean.
In Broward County sufficient data are not available to estimate the
total ground-water withdrawal, but the municipal supplies in the county
delivered about 4 billion gallons (11 mgd) in 1951. Percentagewise, the
industrial and agricultural uses are about the same as in Dade County;
however, a smaller percentage of the people obtain their domestic water
from municipal supplies. The total withdrawal probably was not in
excess of 80 mgd.

HYDROLOGIC CHARACTERISTICS
OF THE BISCAYNE AQUIFER
Ground water is stored in joints, pore spaces, and solution cavities
in the rock. In the Biscayne aquifer the major portion of the ground
,water is stored in cavities formed by the dissolving action of percolating


87






FLORIDA GEOLOGICAL SURVEY


ground water. Ground water moves laterally and vertically under gravi-
tational influence to points of discharge in streams, canals, lakes, and
the ocean, and carries, in both solution and suspension, materials removed
from the rock.
The permeability of a rock is a measure of its ability to transmit
water. Porosity is the property of containing openings. or interstices.
Materials such as clay or marl are highly porous but relatively imper-
meable because the components are so finely divided that the molecular
attraction between the clay-sized particles tends to hold the contained
water in place, thereby restricting movement. High permeability is
usually associated with clean, well-sorted gravel or open shell beds. The
material that forms the Biscayne aquifer has a permeability equivalent
to that of coarse, well-sorted gravel, because the interconnected solution
cavities greatly facilitate ground-water movement.
Several pumping tests have been made on wells penetrating the Bis-
cayne aquifer in the Greater Miami area. The purpose of these tests
was to determine values for the coefficients of transmissibility and
storage of the aquifer at different localities. The coefficient of transmis-
sibility may be defined as the number of gallons of water per day that
will move through a complete section of the aquifer one mile wide,
under a hydraulic gradient of one foot per mile. A value for the field
coefficient of permeability may be determined by dividing the coefficient
of transmissibility by the saturated thickness of the aquifer, in feet;
thus, the coefficient of permeability refers to the hydrologic character-
istic of a unit of the water-bearing rock, whereas transmissibility refers
to that characteristic of the aquifer as a whole. The coefficient of
storage of an aquifer is defined as the volume of water it releases from
or takes into storage per unit surface area of the aquifer per unit change
in the component of head normal to that surface. The Biscayne aquifer
on a long-term basis behaves as an unconfined or water-table aquifer
(although in short tests it may behave as an artesian aquifer having a
leaky roof), and the coefficient of storage is essentially equal to the
specific yield 0.10 to 0.35.

The average transmissibility (T) of the Biscayne aquifer, as stated
by Parker (1951), is about 5 million gallons per day per foot, the lowest
value observed being about 3 million. The storage coefficient (S) ranges
from 0.10 to 0.35 and averages about 0.20.

Pumping rates for these tests were about 8,500 gpm, except for the
test on well G 218 which was at a rate of about 1,500 gpm. The results
of these tests computed by the Theis nonequilibrium formula (1935,






REPORT OF INVESTIGATIONS No. 17


p. 519-524) and as reported by Parker (Parker, Ferguson,. Love, and
others, 1955, p. 239-274) are summarized in the following table (see fig.
14 for location of test sites).
Test Range in computed
site coefficient of transmissibility
(gpd/ft)
Lowest Highest
S 1 .......................................................... 3,250,000 4,300,000
G 551 .............................................................. 9,000,000 14,000,000
G 552 .............................................................. 2,800,000 5,700,000
G 553 .......................................................... 2,500,000 3,900,000
G 218 -----...-----........--..-.. --..-.......--. ...-------. 8,900,000 4,400,000
At all the test sites the Miami oolite forms the upper part of the
Biscayne aquifer, and at most of them it is underlain by a bed of sand.
The permeability of the oolite and sand is lower than that of the under-
lying cavernous limestone of the Fort Thompson formation and thus acts
as a leaky roof during the pumping of a well, and the formation initially
acts as an artesian aquifer. The Bessel function then can be used in
the computations using formulas developed by Jacob (1945, p. 198-208).
John G. Ferris (1950, personal communication) determined the following
values from the test data:
Well Coefficient of transmissibility
No. (gpd/ft)
S 1 ............................................................................ .. 3,200,000
G 551 ......................................................................... ...... 9,700,000
G 552 ....................................................... 3,200,000
G 553 ............................... ........................................... 3,200,000

The T value of the test for well G 551 by both calculations is incon-
sistent with the values for the other tests. The results of the other
three tests using the Bessel function are extraordinarily consistent con-
sidering the character of the aquifer. The permeability of the Biscayne
aquifer probably averages between 50,000 and 70,000 gallons per day per
square foot, according to Parker (1951). No satisfactory computation
of the storage coefficient has yet been obtained.

Several assumptions concerning the aquifer must be applied in using
formulas to determine these coefficients: (1) the aquifer is homogeneous
and isotropic and transmits water with equal readiness in all directions;
(2) the discharging well penetrates the. entire thickness of the aquifer;
(3) there is no turbulent flow within the aquifer, and during the pumping
there is no vertical convergence of flow lines toward the pumped well;
and (4) water is discharged from storage instantaneously with reduction
in head.


39






FLORIDA GEOLOGICAL SURVEY


Inaccuracies in these tests must be assumed because the Biscayne
aquifer does not conform adequately to ideal conditions. Owing to the
size of the cavities in the aquifer, turbulent flow develops near the
pumped wells. Sand-filled cavities locally reduce the flow within the
aquifer, so that the permeability is not the same in all directions.
Ground-water movement is significantly less through the Miami oolite
than through the Fort Thompson formation. Also, within the Miami
oolite itself the rate of movement is less in a horizontal than in a vertical
direction.
Slight errors or differences in drawdown due to irregularities in the
aquifer can cause errors in the value of T. The aquifer is so permeable
that pumping causes only small drawdowns; hence, even small obser-
vational errors produce large errors in the computed values. However,
the various determinations indicate that the general order of magnitude
of the value of T is correct, although its value at any specific place is
difficult to determine exactly and its value from place to place cannot
be estimated without field tests.
By far the most permeable unit within the Biscayne aquifer is the
Fort Thompson formation. It is from this formation that most of the
irrigation, industrial, and public supply wells in Dade County draw
water. Wells may be pumped at high rates for extended intervals with
small drawdowns. The character of the rock is such that in many cases
short pieces of surface casing are all that are :required to complete a
well. The remainder of the hole stands open with no danger of caving.
However, in some of the coastal ridge areas and in localities a few
miles inland from the ridge, sand is more prevalent than it is farther
to the west, so that greater lengths of casing are required. Sand occurs
in most places as residual fills in solution cavities, although at the coast
it occurs as beds of variable thickness, depth, and areal extent. The
aquifer grades into a predominantly sandy phase in the Fort Lauderdale
area and contains so much unconsolidated material that wells often must
be cased to the main water horizon, at which depth screens provide the
well finish.
The Biscayne aquifer at Fort Lauderdale, in the vicinity of well
G 221, is composed of the Pamlico sand, Miami oolite, Anastasia forma-
tion, and Tamiami formation. The Tamiami formation is the most im-
portant component. The coefficient of transmissibility of the Biscayne
aquifer there was calculated by Vorhis (1948, p. 20, 21), using the
graphical method of Cooper and Jacob, to be about 1,200,000. The nature
of the test suggests that the value of the coefficient is only tentative but
that the general magnitude of the coefficient is valid. The small


40






REPORT OF INVESTIGATIONS No. 17


coefficient, as compared with coefficients at Miami, reflects the uncon-
solidated character and predominance of sandy material in the Fort
Lauderdale area.
Water levels in many water-table wells in southern Florida respond
to earthquake shocks in a manner similar to that of an artesian well.
The Miami oolite or the sand separating the oolite from the limestone
of the Fort Thompson formation acts as a shallow semiconfining layer.
These layers, where locally present, do not affect normal water-table
conditions within the aquifer. However, they indicate that the com-
ponents of the aquifer have variable hydrologic characteristics. They
cause a difference in water levels immediately after pumping has started
or stopped in two adjacent wells, one ending in the Miami oolite or sand
and one penetrating the deeper Fort Thompson formation.

QUALITY OF THE WATER
The quality of the water, rather than the quantity, which is very
large, is the limiting factor in the use of water from the Biscayne aquifer.
Parker and others (1944, p. 13-22) state that unconfined ground water
in southeastern Florida may be grouped into three general divisions:
(1) the highly mineralized water in the sands that underlie a part of the
Everglades in the area north of the margin of the Biscayne aquifer
(fig. 1), (2) the fresh water from the highly permeable rocks of the
Biscayne aquifer beneath the Everglades and coastal ridge, and (3)
the water that has been contaminated by salt-water encroachment.
The ground water from the uncontaminated part of the aquifer is
fairly uniform in quality, although along the coastal ridge north and
south of Miami it contains somewhat less dissolved minerals and is
slightly softer than elsewhere. The hardness generally ranges from
200 to 300 ppm, averaging 250 ppm. The chloride concentration normally
ranges from about 20 to 30 ppm. Nearly all the ground water is colored
with either organic material or iron, or both. As rainfall percolates down
to the water table, it carries small amounts of minerals dissolved from
the surface organic soils. Usually the water obtained from the upper
portion of the aquifer is the most highly colored, the color decreasing
with depth.
One of the most troublesome mineral constituents in water from the
Biscayne aquifer is iron. Generally most of the iron can be removed
by aeration and settling or filtration, but when not removed it stains
clothing and fixtures, and the water has an objectionable taste. There
is no apparent consistency in the amount of iron present in the ground






FLORIDA GEOLOGICAL SURVEY


water, and predictions cannot be made as to the localities and depths
at which water will have a high content of dissolved iron. Analyses of
water from wells only a few hundred feet apart, and penetrating the
aquifer to the same depth, may show large differences in iron content.

SALT-WATER CONTAMINATION
Salt-water encroachment along the coastal area in Broward County
is not yet a critical problem except in the vicinity of certain canals.
The high water levels in the northern part of the coastal area have
prevented intrusion of salt water from the ocean into the aquifer. Wells
drilled to depths of 200 feet at Pompano, three miles inland, show no
indication of salt-water encroachment.
In the southern part of Broward County, in the vicinity of Hollywood
and Dania, salt water has not yet encroached as far inland as U. S. High-
way 1, which is about 1.5 miles from the ocean. The water levels in that
area are apparently lower than in the Pompano area, averaging about 2.0
feet above sea level near well F 291. Because of the greater thickness
of the aquifer there, an average fresh-water head of 4 to 5 feet above
sea level is theoretically required to prevent the intrusion of salt water
into the lower part of the aquifer. However, the salt front does not
appear to be moving inland at present; therefore, the actual position
of equilibrium between salt water and fresh water in the aquifer may be
east of the theoretical position. It may be that, if no detrimental change
in the present water-table conditions occurs, the salt front in that area
will not progress any farther inland.
Salt-water encroachment in the Fort Lauderdale area may have
progressed inland about two miles in the vicinity of the North New River
and South New River canals; however, in most of that area it is believed
to have progressed only a mile or so from the shore.
Salt-water contamination due to direct encroachment from the ocean
certainly has not advanced as far as the Fort Lauderdale well field,
which is six miles inland. However, Vorhis (1948) indicates that the well
field is underlain at a depth of 200 feet by salty connate (or residual)
water. He points out also that chloride encroachment into the aquifer
underlying the well field can be from any of four sources: (1) the ocean,
(2) salt-water tongues along the canals extending from the ocean,
(3) brackish water, residual from Pleistocene encroachment seeping into
the canals from parts of the Fort Thompson formation in the Everglades,
and (4) the salty connate or residual water underlying the well field at
depth. The most serious threat of well-field contamination is from the


42






REPORT OF INVESTIGATIONS No. 17


North New River Canal. When the salt-water tongue extends up the
canal during low-water stages, lateral movement of salt water from the
canal into the aquifer can occur.
Although salt-water encroachment is important in Broward County,
it is of greater importance in Dade County. The physical and theoretical
aspects of encroachment in Dade County have been studied in detail
continuously since 1939.
The encroachment of salt water into the aquifer in Dade County
has been described in detail by Brown and Parker (1945) and Parker
(1945). Parker (1951, p. 826, 827) states that in the Miami area "The
canals have effectively induced encroachment by two chief means:
"1. They have served to drain off fresh water stored in. the aquifer
in the coastal zone.
"2. They have acted during certain dry periods as inland extensions
of the sea, carrying salty water inland for several miles and allowing
it to leak out to contaminate the aquifer all along their course.
"Lowering the water table nearly to sea level under the coastal
ridge has caused a loss in head in some places of approximately 5 ft.
compared with the original head before drainage began. Not only is
this a-large actual loss of fresh water in storage, but it is the factor that
led to the inland movement of a salt water wedge from Biscayne Bay,
operating in accordance with the Ghyben-Herzberg principle.
"The five maps in Fig. 5 [extended through 1953 in fig. 17 of this
report] show the general pattern of encroachment into the Biscayne
aquifer in the Miami area for a period of 47 years. They show that the
major spread of the salt water wedge occurred between 1943 and 1946.
During that time, a lengthy drought occurred, and in 1945, water levels
fell to all time lows in this area. Parker [1945, p. 526] reckoned, on the
basis of studies in the Silver Bluff area, that the rate of encroachment
until 1943 had been approximately 235 ft. per year. In a 27-month period
that overlapped 1943-44, the front of the salt wedge advanced 2,000 ft.,
or at a rate of approximately 890 ft. a year."
Dams were placed in the Miami, Biscayne, and Little River canals,
with the result that there was an actual seaward retreat of the salt-water
tongue from 1946 to 1951. Dams were placed also in the Tamiami Canal
and Coral Gables Canal, but they were so far inland that they had little,
if any, effect in opposing the salt-water encroachment; salt-water con-
tamination continues to spread in those two areas. Figures 19 through
24 show profiles along the canals, indicating the relative positions of the






FLORIDA GEOLOGICAL SURVEY


Figure 17. Map showing progressive salt-water encroachment in the Miami area
from 1904 through 1953. (Note: stippling shows extent of areas that have chloride
concentration approximating 1,000 ppm or more, at the base of the aquifer.)






REPORT OF INVESTIGATIONS No. 17


salt-water front (defined as the point where the water contains 1,000
ppm of chloride) in 1946 and 1950, based upon the interpolation of
chloride analysis of wells at varying distances from the canals. Figure 18
is an index map showing the location of the profiles.
The dams, where placed in effective positions, have largely prevented
the inland intrusion of salt water up the canals during the dry seasons
and have raised the fresh-water head in the aquifer to some degree. The
wedge of salt water in the intercanal area is in the same relative position
as in 1946 (fig. 17), probably as a result of the water-control program
and increased rainfall since 1947 which have maintained the average
water levels in those areas at higher stages than in 1946.

The depth of the base of the aquifer is shown in figure 2. In the
areas in Dade County where salt-water encroachment is a threat, the base
of the aquifer is about 100 feet below sea level. Relatively impermeable
materials floor the aquifer, thus making only lateral encroachment pos-
sible. Under strict application of the Ghyben-Herzberg principle, a
2.5-foot head of fresh water above bay level or 3.0-feet above mean sea
level is required to hold salt water out completely; however, modifying
factors make the required fresh-water head somewhat less. The progres-
sive ,reduction in the depth to the bottom of the aquifer westward from
the bay means that progressively less fresh-water head is needed inland.

ADEQUACY OF SUPPLY
The area underlain by the aquifer, excluding the part that now
contains salt water, is about 3,000 square miles. The average water-
saturated thickness in that area is about 72 feet. There is about 9,000
billion gallons of fresh water stored in the aquifer, if the average
storage coefficient is assumed to be 0.2. At a low-water stage, such as
that in 1945, the storage is reduced by only about 5 to 7 percent.
Although the storage is large and there is a large area where water
supplies could be located, the economics related to transmission make
it most desirable that the supplies be located as close as possible to the
area of use. Therefore, most of the present and future pumping will
be on and closely adjacent to the coastal ridge, an area of about 700
square miles.

In considering the potential of the aquifer in the eastern parts of
Dade and Broward counties, flow of ground water into the coastal area
from the Everglades must be considered. There is a lack of information,
however, concerning the direction of movement in much of the area of the
Everglades. In the coastal ridge and part of the adjacent Everglades,


45






FLORIDA GEOLOGICAL SURVEY


\


SCALE IN MILES
0 I 2, Z


Figure 18. Map showing location of chloride profiles of figures 19 through 24.


LITTLE


46






REPORT OF INVESTIGATIONS No. 17


o o


o 0


DEPTH, IN FEET BELOW M.S.L,


CANAL SPUR
NO. 4


CONTROL DAM


W. DIXIE HWY.


N.E. 6TH AVE.


F.E.C. RY.


U S. HWY.
NO. I


BISCAYNE
BAY


Figure 19. Profile of the 1,000 ppm isochlor along the Biscayne Canal
in 1946 and 1950.


(I


o 0


o N .
o 0 .


~Cs


, ,/






FLORIDA GEOLOGICAL SURVEY
N IaIII


N.W. 95TH ST.


N.W. 7TH AVE.









N. MIAMI AVE.


N.E. 2ND AVE.



F.E.C. RY.







BISCAYNE
BOULEVARD


-N
0t


Figure 20. Profile of the


1,000 ppm isochlor a
in 1946 and 1950.


Long the Little River Canal


oEPrH, t# PErer


I
BELOW


I:


N


/


II


BISCAYNE
BAY


- ---







REPORT OF INVESTIGATIONS No. 17


0 0
DEPTH, IN FEET


N.W. 36TH
STREET



















TAMIAMI
CANAL


N.W. 27TH
AVENUE


N3
0


I I I I


Figure 21. Profile of the


IN.W.


ITTH AVE.


1,000 ppm isochlor along the Miami Canal
in 1946 and 1950.


0
BELOW


N-T
0~


L


I


---


49






FLORIDA GEOLOGICAL SURVEY


DEPTH, IN FEEr


I
0,
BELOW


0
Mz. S.


\0


I
0


RED ROAD


SOUTH FORK
TAMIAMI CANAL


LE JEUNE RD.





DOUGLAS RD.








MIAMI
CANAL


N.W. 27TH
AVENUE


I


Figure 22. Profile of the 1,000 ppm isochlor algng the Tamjnami Canal
in 1946 and 1950.


50






REPORT OF INVESTIGATIONS No. 17
I I I
o o o o
0 0 0 ET BELOW M.S.L
DEPTH, IN FEET BELOW M.S.L. r


\


S0


M..


RED ROAD


DOUGLAS RD.


N.W. 27TH
AVENUE


MIAMI CANAL


, Figure 23. Profile of the 1,000 ppm isochlor along the South Fork of the
Tamiami Canal in 1946 and 1950.


I I -


I I I


6 \ \


\\






FLORIDA GEOLOGICAL SURVEY


o 0 0 0
oEPrH, IN FEET BELOW M.S.L.


RED ROAD


BIRD ROAD


BLUE ROAD


F. E.C. RY.

MILLER RD.


HARDEE RD.


LE JEUNE RD.


8 BISCAYNE
I I I I I I IB Y


Figure 24. Profile of the 1,000 ppm isochlor along the
in 1946 and 1950.


Coral Gables Canal


6


N


21 I


!





REPORT OF INVESTIGATIONS No. 17


an area which composes about one-third of the extent of the aquifer, the
ground-water flow is to the east and southeast during most of the year.
In the remainder of the Everglades ground water presumably flows to the
south, and, under the conditions that were prevalent in 1950, this flow
was not a direct source of water for the coastal ridge. However, flood
control structures and the establishment of proposed conservation areas
in the western two-thirds of the area may make large additional quantities
of water available for recharge, thus changing the water-table gradient
and increasing ground-water flow from the Everglades toward the coast.
An estimate of the ground-water potential of the aquifer requires an
inventory of the recharge that would include rainfall, the inflow from
Palm Beach County to the conservation areas, and the recharge from
drainage wells, septic tanks, and irrigation; and the discharge, consisting
of evapotranspiration, ground-water outflow to the ocean directly from
the aquifer and from the canals, and losses due to pumping. The lack of
detailed data, particularly canal discharge data, makes a complete water
inventory impossible at this time. Rainfall over the 8,000 square miles
ranges from about 54 to 64 inches, averaging 60 inches. Computations
for the coastal ridge area indicate that about one-third of this rainfall, or
about 1,000 billion gallons a year, is eventually discharged from the
aquifer by ground-water flow. The total amount of this annual water
might be pumped if the aquifer were not bound by salt water on the
eastern and southern sides.
The lowering of water levels due to pumping in an area salvages some
of the water that might otherwise be lost by evapotranspiration. The
southwest well field (fig. 3) of the city of Miami, as planned, will
eventually withdraw 100 mgd. It is estimated by Parker and others (1955,
p. 287) that 15 mgd may be salvaged from reduced evapotranspiration.
The estimated pumpage of 100 mgd in Dade County is about 20
percent of the estimated ground-water discharge into the ocean and
canals. At present a large part of the use is not consumptive and the
water recharges the aquifer through irrigation, septic tank drains, and
drainage wells. Enlargement of the sewer system for the city of Miami,
and the construction of similar but smaller systems in other municipalities,
will diminish this type of recharge. It appears likely that, under the
present system of canal control, additional wells so located as to leave
a buffer strip (an area in which water levels are not affected by pumping)
between them and the ocean could withdraw 10 times the amount of
water pumped in 1950 without causing salt-water encroachment. It is
estimated that at least 2 billion gpd could be pumped from areas west of
,the coastal ridge, if the ridge were used as a buffer zone. These estimates


53





FLORIDA GEOLOGICAL SURVEY


are based partly on the fact that more water would be available because
of reduced evapotranspiration when the water table is lowered, and that
more of the aquifer would be available for storage of rainwater that is
normally rejected when the aquifer is full or nearly full, and on the
possibility of recharge in the flood control conservation areas by water
diverted from Palm Beach County. These factors increase the amount
of water computed as available for withdrawal.
A large supply of ground water is available in the part of the aquifer
lying west of the salt-water front in Dade County and west of U. S.
Highway 1 in Broward County. To protect this supply, salt-water en-
croachment must be strictly controlled by maintaining proper placement
of dams or locks in canals, by proper control of water levels in the canals,
and by locating well fields and other centers of large withdrawals so that
pumping will not lower water levels below the minimum stage required
to prevent additional encroachment. Storage in the aquifer should be
continually measured and evaluated, and future development of the
ground-water resources carried out in accordance with the principles
outlined.


54






REPORT OF INVESTIGATIONS No. 17

SELECTED REFERENCES


Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters-1951:
Florida State Board Cons., Div. Water Survey and Research, Paper 6,
November 30, 117 p.
Brown, Eugene (see Black, A. P.)
Brown, R. H.
1945 (and Parker, Garald G.) Salt-water encroachment in limestone at Silver
Bluff, Miami, Florida: Econ. Geology, vol. 40, no. 4, p. 235-262.
Clapp, F. G. (see Matson, G. C., 1909)
Cooke, C. W. (see also Parker, Garald G., 1944)
1929 (and Mossom, Stuart) Geology of Florida: Florida Geol. Survey 20th
Ann. Rept., p. 29-227, 29 pl., geol. map.
1945 Geology of Florida: Florida Geol. Survey Bull. 29, 339 p., 1 pl., 47 fig.,
geol. maps.
Cooper, H. H., Jr. (see Parker, Garald G., 1948)
Hoy, N. D. (see Parker, Garald G., 1948)
1952 (and Schroeder, M. C.) Age of subsurface "Tamiami" formation near
Miami, Florida: Jour. Geology, vol. 60, no. 3, p. 283-286.
Jacob, C. E.
1946 Radial flow in a leaky artesian aquifer: Am. Geophys. Union Trans.,
vol. 27, no. 2, p. 198-208.
Love, S. K. (see Parker, Garald G., 1944, 1955)
Mansfield, W. C.
1939 Notes on the upper Tertiary and Pleistocene mollusks of Peninsular
Florida: Florida Geol. Survey Bull. 18, 75 p., 3 pl., 1 fig.
Matson, G. C.
1909 (and Clapp, F. G.) A preliminary report on the geology of Florida, with
special reference to the stratigraphy: Florida Geol. Survey 2nd Ann. Rept.,
p. 25-173, map.
1913 (and Sanford, Samuel) Geology and ground waters of Florida: U. S.
Geol. Survey Water-Supply Paper 319, 445 p.
Meinzer, 0. E.
1923 The occurrence of ground water in the United States, with a discussion
of principles: U. S. Geol. Survey Water-Supply Paper 489, 321 p.
Mossom, Stuart (see Cooke, C. W., 1929)
Parker, Garald G. (see also Brown, R. H., 1945)
1942 Notes on the geology and ground water of the Everglades in southern
Florida: Soil Sci. Soc. Florida. Proc., vol. 4A, p. 47-76.
1944 (and Cooke, C. W.) Late Cenozoic geology of southern Florida, with a
discussion of the ground water: Florida Geol. Survey Bull. 27, 119 p.
(Ferguson, G. E., and Love, S. K.) Interim report of water-resources
investigation in southeastern Florida, with special reference to the Miami
area in Dade County: Florida Geol. Survey Rept. Inv. 4, 39 p., 9 pl.
1945 Salt water encroachment in southern Florida: Am. Water Works Assoc.
Jour., vol. 37, no. 6, p. 526-542.
1948 (Cooper, H. H., Jr., and Hoy, N. D.) Water levels and artesian pressure
in observation wells in the United States in 1945, Pt. 2, Southeastern
. States: U. S. Geol. Survey Water-Supply Paper 1024, p. 11-81.





FLORIDA GEOLOGICAL SURVEY


1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides, winds, and
atmospheric pressure changes on water in geologic formations of south-
ern Florida: Econ. Geology, vol. 45, no. 5, p. 441-460.
1951 Geologic and hydrologic factors in the perennial yield of the Biscayne
aquifer: Am. Water Works Assoc. Jour., vol. 43, p. 817-834.
1955 (Ferguson, G. E., Love, S. K., and others) Water resources of south-
eastern Florida, with special reference to the geology and ground water
of the Miami area: U. S. Geol. Survey Water-Supply Paper 1255, 965 p.
Sanford, Samuel (see Matson, G. C., 1913)
1909 The topography and geology of southern Florida: Florida Geol. Survey
2nd Ann. Rept., p. 175-231.
Schroeder, M. C. (see Hoy, N. D.)
Sellard, E. H.
1912 The soils and other surface residual materials of Florida, their origin,
character, and the formations from which derived: Florida Geol. Survey
4th Ann. Rept., p. 1-79.
1919 Geologic section across the Everglades of Florida: Florida Geol. Survey
12th Ann. Rept., p. 67-76.
Stringfield, V. T. (see Parker, Garald G., 1950)
Theis, C. V.
1935 The relation between the lowering of the piezometric surface and the
rate and duration of discharge of a well using ground-water storage:
Am. Geophys. Union Trans., vol. 16, p. 519-524.
Vorhis, R. C.
1948 Geology and ground water of the Fort Lauderdale area, Florida: Florida
Geol. Survey Rept. Inv. 6, 32 p.


56




Biscayne aquifer of Dade and Broward Counties, Florida ( FGS: Report of investigations 17 )
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 Material Information
Title: Biscayne aquifer of Dade and Broward Counties, Florida ( FGS: Report of investigations 17 )
Series Title: ( FGS: Report of investigations 17 )
Physical Description: v, 56 p. : maps, diagrs. ; 23 cm.
Language: English
Creator: Schroeder, Melvin C ( Melvin Carrell ), 1917-
Geological Survey (U.S.)
Florida -- Bureau of Geology
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1958
 Subjects
Subjects / Keywords: Groundwater -- Florida -- Miami-Dade County   ( lcsh )
Groundwater -- Florida -- Broward County   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Melvin C. Schroeder, Howard Klein, and Nevin D. Hoy.
Bibliography: Bibliography: p. 55-56.
General Note: "Prepared by the United States Geological Survey in cooperation with the Florida Geological Survey, Central and Southern Florida Flood Control District, Dade County, Cities of Miami Beach, and Fort Lauderdale."
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Table of Contents
    Front Cover
        Page i
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
    Table of contents
        Page iv
        Page v
        Page vi
    Abstract and introduction
        Page 1
        Page 2
        Page 3
        Page 4
    Biscayne Aquifer
        Page 5
        Page 6
        Page 4
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Ground-water occurrence
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 26
    Hydrologic characteristics of the Biscayne Aquifer
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 39
    Salt-water contamination
        Page 45
        Page 46
        Page 47
        Page 44
    Adequacy of supply
        Page 48
        Page 49
        Page 47
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
    Selected references
        Page 57
        Page 58
        Copyright
            Copyright
Full Text




STATE OF FLORIDA

STATE BOARD OF CONSERVATION


~r.
- /


Ernest Mitts, Director


FLORIDA GEOLOGICAL SURVEY

Herman Gunter, Director




REPORT OF INVESTIGATIONS NO. 17




BISCAYNE AQUIFER OF

DADE AND BROWARD COUNTIES, FLORIDA




By
Melvin C. Schroeder, Howard Klein, and Nevin D. Hoy

U. S. Geological Survey




Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
DADE COUNTY
CITIES OF MIAMI, MIAMI BEACH and FORT LAUDERDALE




TALLAHASSEE, FLORIDA
1958










FLORIDA STATE BOARD

OF

CONSERVATION







LEROY COLLINS
Governor


R. A. GRAY
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation






LETTER OF TRANSMITTAL


Tallahassee

December 5, 1957





Mr. Ernest Mitts, Director
Florida State Board of Conservation
Tallahassee, Florida

Dear Mr. Mitts:

I am forwarding to you a report entitled, BISCAYNE AQUIFER
OF DADE AND BROWARD COUNTIES, FLORIDA, which was pre-
pared by Melvin C. Schroeder, Howard Klein, and Nevin D. Hoy,
Geologists of the United States Geological Survey. The report was sub-
mitted for publication March 15, 1956, and it is recommended that it
be published as Report of Investigations No. 17.

The Biscayne Aquifer is the principal source of water for the heavily
populated area in the vicinity of West Palm Beach and Miami. The
publication of this data is timely and will assist in the intelligent devel-
opment of the water resources of the area.

Respectfully submitted,
HERMAN GuNTER, Director







TABLE OF CONTENTS


Page,
A abstract .............................................................. 1


Introduction .....................................
Location and geography of area ...............
Purpose and scope of investigation .............
Previous investigations .......................
Personnel and acknowledgments ...............

Biscayne aquifer .................................
D definition ...................................
Areal extent and thickness .....................


Geologic formations composing the
General features ...........
Miocene series .............
Tamiami formation .....
Pliocene series ........... .
Caloosahatchee marl ....
Pleistocene series ...........


Biscayne



.........


aquifer
. .. .. ,


Fort Thompson formation .
Key Largo limestone .....
Anastasia formation .....
Miami oolite ...........
Pamlico sand ...........


11
11
11
20
21
23
24

24
24
25
26
36


Ground-water occurrence .....................
General features ...................... .
Shape and slope of the water table .........
Fluctuation of the water table ............
Recharge and discharge .................

Hydrologic characteristics of the Biscayne aquifer


Quality of the water ................................


Salt-water contamination ............................................... 42

Adequacy of supply .................................................. 45

Selected references .................................................... 55


. . . . .
. . . . .


..


. ..... ...00.0. 0. .000 *0 .. 0 0






ILLUSTRATIONS

Figure Page
1 Map of Florida showing location of Dade and Broward
Counties and the approximate extent of the Biscayne
aquifer ....................................................... 2
2 Structure-contour map of Dade and Broward Counties
showing base of the Biscayne aquifer ............................ 6
3 Geologic map of southern Florida ............................. 8
4 West-east geologic cross section in western Broward County ............ 13
5 West-east geologic cross section in Dade County .............. Facing 14
6 North-south geologic cross section in the Everglades ............ Facing 14
7 Map of Broward and Dade Counties showing location of
geologic cross sections and certain test wells ...................... 15
8 West-east geologic cross section near Krome Avenue at
Tamiami Trail ........................... ................... 17
9 North-south geologic cross section on the coastal ridge ................. 22
10 Map of Dade County showing average water levels in
eastern part, 1940-50 .......................................... 27
11 Graphs showing fluctuation of water level in well S196 and
rainfall at University of Florida Subtropical Experiment
Station during 1947 ............................................ 28
12 Chart of comparative average monthly water levels in
selected wells ............. .... ................................ 30
13 Map showing location of certain observation wells and
location of large municipal well fields ........................... 31
14 Low-stage water-level map of eastern and southern Dade
County, May-June 1945 ..................................... 33
15 Low-stage water-level map of eastern Broward County,
April 14, 1945 ................................................ 34
16 High-stage water-level map of Dade County, October
11-12, 1947 ................................................. 35
17 Map showing progressive salt-water encroachment in the
Miami area from 1904 through 1953 ............................. 44
18 Map showing location of chloride profiles of figures 19
through 24 ................................................... 46
19 Profile of the 1,000-ppm isochlor along the Biscayne Canal
in 1946 and 1950 .............................................. 47
20 Profile of the 1,000-ppm isochlor along the Little River
Canal in 1946 and 1950 ........................................ 48
21 Profile of the 1,000-ppm isochlor along the Miami Canal
in 1946 and 1950 ............................................. 49
22 Profile of the 1,000-ppm isochlor along the Tamiami Canal
in 1946 and 1950 ................... ....................... 50
23 Profile of the 1,000-ppm isochlor along the South Fork of
the Tamiami Canal in 1946 and 1950 ........................... 51
24 Profile of the 1,000-ppm isochlor along the Coral Gables
Canal in 1946 and 1950 ................ ........................ 52













BISCAYNE AQUIFER OF DADE AND
BROWARD COUNTIES, FLORIDA


ABSTRACT

The Biscayne aquifer is the only source of fresh ground water in
Dade and Broward counties, Florida. Composed of highly permeable
limestone and sand mainly of Pleistocene age, the aquifer supplies large
quantities of water, of excellent quality except for hardness, for munici-
pal, industrial, and. irrigational use. The aquifer attains its maximum
thickness in the Atlantic coastal areas and wedges out in western Dade
and Broward counties.

Water-table conditions prevail in the Biscayne aquifer, and the water
table fluctuates with variations in rainfall, evapotranspiration, and pump-
ing. High ground-water levels occur during the fall months and'low
levels during spring and early summer. The highest water levels of
record occurred in Qctoher-.1947, when intense rainfall accompanying
a hurricane flooded large areas throughout the two counties. Major dis-
charge from the aquifer occurs by natural outflow and evapptranspira-
tion. The average daily pumpage from the Biscayne aquifer in 1950 is
estimated to have been 1380 million gallons.

Permeability tests show that the limestones of the Biscayne aquifer
rank among the most productive aquifers ever investigated by the U. S.
Geological Survey.

Salt-water encroachment in the aquifer has taken place in coastal.
areas of southeastern Florida. The greatest inland advance of salt-water
intrusion has occurred as tongues along tidal drainage canals and rivers.

INTRODUCTION

LOCATION AND GEOGRAPHY OF AREA
Dade and Broward counties are in southeastern Florida, bordering
the Atlantic Ocean (fig. 1). The Atlantic Coastal Ridge, whose av-
erage elevation is between 8 and 10 feet above mean sea level, occupies
the eastern portion of the area from the coast to a few miles inland. Maxi-
mum elevatiobs at isolated highs range from 20 to 25 feet above sea






FLORIDA GEOLOGICAL SURVEY


/

(


/ 1


-4
A,


(.
-1\


0


I -. -~
~( I


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0


SCALE IN MILES
25 0 25 O T70 5 100


the


Figure 1. Map of Florida showing location of Dade and Broward counties al
approximate extent (shaded area) of the Biscayne aquifer.






REPORT OF INVESTIGATIONS No. 17


level. In Dade County the ridge is composed principally of limestone,
but in Broward County it is composed of both sand and limestone. Most
of the population in the two counties is concentrated in the coastal and
ridge areas. The Florida Everglades, and area of organic soils, lies west
of the ridge and is devoted chiefly to agriculture and conservation areas.
The climate is semitropical to tropical. Rainfall averages 60 inches per
year, about 75 percent of the total falling in the period from May through
QOptber. The average temperature is about 750F.

PURPOSE AND SCOPE OF INVESTIGATION
The ground-water resources of Dade and Broward counties are one
of the greatest natural assets of the region. This report describes the
geology and hydrologic characteristics of the Biscayne aquifer and de-
fines its geographic distribution. The factors involved in the adequacy
of the supply are discussed and an evaluation of data on fluctuations
in water level is presented.

PREVIOUS INVESTIGATIONS
The surface geology in Dade and Broward counties was first investi-
gated by Sanford (1909). Sellards (1919) added considerable data when
the drainage canals were cut across the Everglades. The geologic for-
mations in southern Florida were described by Cooke and Mossom
(1929). Matson and Sanford (1913), Parker (1942), and Parker and
others (1944) described the geology and occurrence of water in the
water-table (Biscayne) aquifer. Parker and Cooke (1944) presented
physiographic and geologic descriptions of southern Florida, with spe-
cial reference to the late Cenozoic material in southeastern Florida.
The major part of the aquifer was then identified as belonging to the
TamiamFUiiforma iiParer (1951) proposed the name Biscayne aquifer
for the shallow materials and revised the geologic correlations of the
formations in the aquifer. A report by Parker, Ferguson, Love, and oth-
ers (1955) presents hydrologic data on the Biscayne aquifer in greater
detail than does this report.
Data on fluctuations of water levels in wells in Dade and Broward
counties have been reported in the following U. S. Geological Survey
Water-Supply Papers for the years 1939-1952 inclusive: 886, 907, 937,
945, 987, 1017, 1024, 1072, 1097, 1127, 1157, 1166, 1192, and 1222. Sub-
sequent data will be published in the water-supply papers entitled "Wa-
ter Levels and Artesian Pressures in Observation Wells in the United
states Part 2, Southeastern States."





FLORIDA GEOLOGICAL SURVEY


PERSONNEL AND ACKNOWLEDGMENTS
The data presented in this report cover the results of studies made
by the U. S. Geological Survey in cooperation with the Florida Geologi-
cal Survey, Dade County, the cities of Miami, Miami Beach, Coral
Gables, and Fort Lauderdale, and the Central and Southern Florida Flood
Control District. The continued interest and help of the officials of these
agencies have made it possible to develop the necessary program to study
the aquifer and the fluctuations of the ground-water levels.
The investigation was made under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, U. S. Geological Survey. V. T. String-
field and Garald G. Parker of the U. S. Geological Survey gave valuable
advice. The Corps of Engineers, U. S. Army, cooperated by permitting
examination of the cores and records of a great number of core borings.

BISCAYNE AQUIFER
DEFINITION
Meinzer (1923, p. 52, 53) has defined an aquifer as a rock formation
or stratum that will yield water in sufficient quantity to be of conse-
quence as a source of supply. A formation yielding meager amounts of
water might not be considered to be an aquifer in an area where there
are other formations that yield prolifically but might be considered to
be one in an area where little water is available.
Wherever possible, an aquifer is identified by the name or names of
the stratigraphic units composing it. Where an aquifer crosses strati-
graphic lines, or where its stratigraphy is uncertain, yet it is well known
to constitute a hydrologic unit, an aquifer may be given a proper name.
The principal aquifer in this area is such a unit.

The name Biscayne aquifer was proposed by Parker (1951, p. 820-823)
for the hydrologic unit of water-bearing rocks that carries unconfined
ground water in southeastern Florida. The aquifer is a single hydrologic
unit of permeable materials ranging in age from late Miocene through
Pleistocene. The boundaries of the aquifer, both horizontal and vertical,
are set not by formational contacts or age restrictions but by djfferegces-
in the hydrologic properties of the sediments. The lowermost component
of the Biscayne aquifer is a limestone or shelly calcareous sand-
stone of the upper part of the Tamiami formation in the northeastern
part of Dade County and the southeastern part of Broward County. The
remaining and major portion of the Biscayne aquifer is composed of rocks
ranging in age from Pliocene through Pleistocene in the following





REPORT OF INVESTIGATIONS No. 17 5

sequence from bottom to top: Caloosahatchee marl (as erosion rem-
nants), Fort Thompson formation, Key Largo limestone, Anastasia for-
ination, Miami oolite, and Pamlico sand. The aquifer is underlain by
a relatively impermeable greenish marl of the Tamiami formation. The
contact between the marl and the limestone of the Tamiami, Fort Thomp-
son, or Anastasia formations, or the Key Largo limestone, forms the lower
boundary of the aquifer.

In the Miami area the base of the Biscayne aquifer is easily deter-
mined by the occurrence of the impervious marl of the Tamiami forma-
tion. However, it is more difficult to define the basal or lateral limits in
Broward County where clastic sediments rather than limestones consti-
tute a major part of the Pleistocene sequence. The interfingering and
the vertical and horizontal gradation of sands and calcareous materials
present a problem similar to determining the demarcation between two
different lithologic facies of the same geologic time unit. In an aquifer
the ground water should be free to move in any direction, under the
proper hydraulic gradient. In northwesternmost Broward County (fig. 1)
the water in sands whose elevation and stratigraphic position are similar
to those in the Biscayne aquifer to the southeast apparently does not
move freely, as shown by its high mineralization. These sands, therefore,
are not considered a part of the Biscayne aquifer.

AREAL EXTENT AND THICKNESS

The Biscayne aquifer underlies all the coastal areas and most of the
Everglades to and a little beyond the Broward-Palm Beach county line
(fig. 1).

The thickness of the aquifer is greatest along the coast in the Miami
area and northward in the vicinity of Fort Lauderdale, where it is 200
fee.t-i,places. The aquifer decreases in thickness gradually .southwfird
from Miami, and rapidly westward into the Everglades; beyond its
thickest portion in the Everglades it thins out to a featheredge in eastern
Collier and Monroe counties.

Figure 2 shows contours on the base of the highly permeable rock
in Dade and Broward counties. The base of the Biscayne aquifer is
commonly drawn at the base of 'the formations of Pleistocene age ex-
cept for the coastal area in Broward County and in northeastern Dade
County, where the boundary occurs within the Tamiami formation, and
other isolated areas where the base is placed at the bottom of limestone






FLO A GEOLOGICAL SURVEY
FLORIDA GEOLOGICAL SUIRvEY


D A/

/


R D


FORT


(3


"I


HOME


S' EXPLANATION
) WELL USED IN DRAWING CONTOURS
CONTOUR LINES REPRESENT
APPROXIMATELY THE BASE
OF THE BISCAYNE AQUIFER
IN FEET BELOW SEA LEVEL
CONTOUR INTERVAL 10 FEET

SCALE IN MILES


Figure 2. Structure contour map of Dade and Broward counties showing base of
Biscayne aquifer.


W


0
0
0
0
- o


/















I 4)O$


0


/
0o





FLORIDA GEOLOGICAL SURVEY


PERSONNEL AND ACKNOWLEDGMENTS
The data presented in this report cover the results of studies made
by the U. S. Geological Survey in cooperation with the Florida Geologi-
cal Survey, Dade County, the cities of Miami, Miami Beach, Coral
Gables, and Fort Lauderdale, and the Central and Southern Florida Flood
Control District. The continued interest and help of the officials of these
agencies have made it possible to develop the necessary program to study
the aquifer and the fluctuations of the ground-water levels.
The investigation was made under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, U. S. Geological Survey. V. T. String-
field and Garald G. Parker of the U. S. Geological Survey gave valuable
advice. The Corps of Engineers, U. S. Army, cooperated by permitting
examination of the cores and records of a great number of core borings.

BISCAYNE AQUIFER
DEFINITION
Meinzer (1923, p. 52, 53) has defined an aquifer as a rock formation
or stratum that will yield water in sufficient quantity to be of conse-
quence as a source of supply. A formation yielding meager amounts of
water might not be considered to be an aquifer in an area where there
are other formations that yield prolifically but might be considered to
be one in an area where little water is available.
Wherever possible, an aquifer is identified by the name or names of
the stratigraphic units composing it. Where an aquifer crosses strati-
graphic lines, or where its stratigraphy is uncertain, yet it is well known
to constitute a hydrologic unit, an aquifer may be given a proper name.
The principal aquifer in this area is such a unit.

The name Biscayne aquifer was proposed by Parker (1951, p. 820-823)
for the hydrologic unit of water-bearing rocks that carries unconfined
ground water in southeastern Florida. The aquifer is a single hydrologic
unit of permeable materials ranging in age from late Miocene through
Pleistocene. The boundaries of the aquifer, both horizontal and vertical,
are set not by formational contacts or age restrictions but by djfferegces-
in the hydrologic properties of the sediments. The lowermost component
of the Biscayne aquifer is a limestone or shelly calcareous sand-
stone of the upper part of the Tamiami formation in the northeastern
part of Dade County and the southeastern part of Broward County. The
remaining and major portion of the Biscayne aquifer is composed of rocks
ranging in age from Pliocene through Pleistocene in the following






REPORT OF INVESTIGATIONS No. 17


that perhaps is the Caloosahatchee marl. Subsurface geologic data in
southern Dade County are scanty because very few core holes have been
drilled.

The areal extent of the Biscayne aquifer as shown in figure 1 is
based upon the available data, and collection of additional information
concerning the geology and the hydrologic characteristics may either in-
crease or decrease the areal extent shown.

GEOLOGIC FORMATIONS COMPOSING
THE BISCAYNE AQUIFER

GENERAL FEATURES
The Biscayne aquifer includes the following stratigraphic units: the
upper part of the Ta~miamiJformation in the coastal areas of Broward
County and northeastern Dade County; the small erosional remnants
of the Caloosahatchee marl in southern Broward County; the Anastasia
formation in Broward County and southern Palm Beach County; the
Fort Thompson formation in Dade and Broward counties, except the
western part of Dade County north of the Tamiami Trail and north-
west Broward County where the formation is relatively impermeable;
the Key Largo limestone in Dade and Monroe counties; and the Miami
oolite and the Pamlico sand in Broward and Dade counties. The Lake
Flirt marl and more recent deposits, including the organic soils of the
Everglades and marine marls bordering the coast, are excluded from
the Biscayne aquifer.
The generalized surface distribution of the various geologic forma-
tions is shown on figure 3. The map is based upon recent observations
of both surface exposures and well cuttings and is adapted and revised
from geologic maps of Florida by Cooke (1945, pl. 1) and R. 0. Vernon
(in Black and Brown, 1951, p. 7) and of southern Florida by Parker
and Cooke (1944, pl. 15). The field notes of Mr. Parker have been used
extensively for descriptions of exposures and borrow pits no longer in
existence.
The formations appearing on the geologic map and mentioned in the
report are as follows:











FLORIDA GEOLOGICAL SURVEY


a ANASTASIA FORMATIONI
0 0


14(Y LARGO LIMISIONE 0



FORT THOMPSON FORMdATION
*LI 'IN I"O ARI NINI AD@AINIS 450 ANDIoo 5(0



1 CALOOSAHATCHEE MARL 1





SjCLVIWINA*&. ILlS SAND AND SOFT SKIV.O
SA*O NL10ISONI. t600111C~1WCISIMSSIN(.


.0


Gl(00040 vsEtoSCOGY kt C.SC 050(05.
HOWARD KLEIN, AND N.D0. lHOY (50.
maps SI NO.G.P550(0 AND C a COOKIS
110441. wC V 011 i45I*AND R. 0.
VISION (INI BLACK AND $650 VS* 11"l)




SCALE INI MILES


10 20 30


Figure 3. Geologic map of southern Florida.


to 0


CI'I --PI ---~- -~~ -----'"


I


,9r"'


y wt




REPORT OF INVESTIGATIONS No. 17


LATE CENOZOIC FORMATIONS OF DADE AND BROWARD COUNTIES


Formation


Soils
Lake Flirt
marl


Characteristics


Peat and muck; laterite.
White to gray calcareous mud, rich with
shells of Helisoma sp., a fresh-water gas-
tropod. In some places casehardened to
a dense limestone. Relatively imperme-


Liable.


Pleistocene
(Formations
are contem-
poraneous
in part)


Pliocene


Miocene


Pamlico
sand


Miami
oolite


Anastasia
formation


Quartz sand, white to black or red, depend-
ing upon nature of staining materials,
very fine to coarse, average medium.
Mantles large areas underlain by Miami
oolite and Anastasia formation.


Limestone, oolitic, soft, white to yellowish,
containing streaks or thin layers of cal-
cite, massive to crossbedded and strati-
fied; generally perforated with vertical
solution holes. Fair to good aquifer.
Coquina, sand, calcareous sandstone, sandy
limestone, and shell marl. Probably com-
posed of deposits equivalent in age to
marine members of Fort Thompson
formation. Fair to good aquifer.


Key Largo Coralline reef rock, ranging from hard and
limestone dense to soft and cavernous. Probably
interfingers with the marine members of
the Fort Thompson formation. Crops out
along southeastern coast line of Florida
from Soldier Key in Biscayne Bay to
Bahia Honda. Excellent aquifer.
Fort Alternating marine, brackish-water and
Thompson fresh-water marls, limestones, and sand-
formation stone. A major component of the highly
permeable Biscayne aquifer of coastal
Dade and Broward counties, which yields
copious supplies of ground water.


Caloosa-
hatchee
marl
Tamiami
formation


Sandy marl, clay, silt, sand, and shell beds.
Yields ground water less abundantly than
most other parts of the Biscayne aquifer.
Cream, white, and greenish-gray clayey
marl, silty and shelly sands, and shell
marl, locally hardened to limestone. Up-
per part, where permeability is high,
forms the lower part of the Biscayne
aquifer. Lower and major part of forma-
tion is of low permeability and forms the
upper beds of the aquiclude that confines
water in the Floridan aquifer (Ocala and
associated limestones) below.


Age


Recent
and
Pleistocene


Thickness
(feet)
0-12
0-6


0-40


0-40


0-120





0-60







0-150






0-25


0-100


--i--


I\ --~----~-- -





FLORIDA GEOLOGICAL SURVEY


MIOCENE SERIES

TAMIAMI FORMATION

The Tamiami formation as redefined by Parker (1951, p. 823) in-
cludes all the upper Miocene materials in southern Florida, including
the Tamiami limestone of Mansfield (1939, p. 8). Excluded from the
formation is the "Tamiami" formation of Parker and Cooke (1944, p.
62-65) in Dade County. Parker and Cooke correlated the limestone that
Mansfield found cropping out along the Tamiami Trail in Collier and
Monroe counties with the highly permeable limestones and sandstones
which unconformably underlie the Miami oolite of Pleistocene age in the
eastern Everglades and Miami area. Their correlation was based on cut-
tings from percussion-type or cable-tool drilled wells, which penetrated
the aquifer, but the comminuted condition of the cuttings prevented
identification of any fresh-water limestones intercalated with marine lime-
stones. Subsequent exploratory core drillings in the Everglades and Mi-
ami area by the Corps of Engineers, U. S. Army, and the U. S. Geological
Survey revealed the occurrence of fresh-water gastropods in limestone
beds underlying the Miami oolite to a depth of 55 feet below sea level.
Because the oldest known fresh-water limestones in this region are of
Pleistocene age, most of the material underlying the eastern Everglades
and the Miami area has been tentatively referred to the Pleistocene, by
Parker (1951, p. 822, 823), and Hoy and Schroeder (1952, p. 283-285).
The Tamiami formation is divisible lithologically and hydrologically
into two units: a relatively impermeable clastic imit, and a permeable
limestone and sandstone unit. The two units have no stratigraphic signifi-
cance, although in many places the plastics form the base and sandstones
or limestones the uppermost part of the formation. However, the units
are primarily geographic. Limestone is commonly exposed at the surface
in the outcrop of the Tamiami formation in the Big Cypress Swamp and
the Sunniland area; permeable sandstone composes the upper part of
the formation in the subsurface of the coastal area of Broward County
and northeastern Dade County. The subsurface Tamiami formation near
Carnestown, Sunniland, and Immokalee in Collier County is a creamy-
white, clayey, shelly marl, which in part has been indurated to a per-
meable limestone as a result of water-table fluctuation and ground-water
percolation. Toward the east the formation increases in sand and marl
content, and in Dade and Broward counties most of the formation con-
sists of relatively impermeable plastics composing the upper part of the
aquiclude that confines water in the Floridan aquifer, the principal ar-
tesian aquifer of the Florida Peninsula and adjacent area.





REPORT OF INVESTIGATIONS No. 17


PLIOCENE SERIES
CALOOSAHATCHEE MARL
The Caloosahatchee marl is the only Pliocene material found in south-
ern Florida. It was named by Matson and Clapp (1909, p. 123) for the
soft, semiconsolidated sediments that form low bluffs along the Caloo-
sahatchee River between La Belle and Denaud in Hendry County.
The Caloosahatchee marl is commonly a light greenish-gray silty,
shelly marl, with varying amounts of sand. Sand and shells, occurring
both in beds and in lenses, locally form a shell marl. Ground-water move-
ment and exposure to air have locally casehardened and cemented the
more sandy and shelly material to a calcareous rock which subsequently
has been made permeable by solution of limestone and washing out of
elastic material. Generally the formation is relatively impermeable, ex-
cept locally where very shelly layers or lenses predominate.
The Caloosahatchee marl is known to extend 25 miles southward
from Lake Okeechobee where it underlies Pleistocene rocks in the form
of thin permeable limestone and sandstone reefs or "shoestring" sands.
Present data are not yet sufficient to determine the extent of Pliocene
deposits beneath the lower Everglades, but faunal evidence from a well
near Kendall suggests the possibility of the occurrence in Dade County
of isolated remnants of the Caloosahatchee marl.
It was previously thought by Parker and Cooke (1944, p. 59) that,
south of Lake Okeechobee between the Dade-Broward county line and
the approximate latitude of Twenty-Six Mile Bend of the North New
River Canal, the Caloosahatchee and Tamiami formations were possibly
contemporaneous and interfingered in the subsurface. However, more re-
cent exploratory drilling has indicated that this material to about 60 feet
below sea level is probably of Pleistocene age. This would mean that
the Caloosahatchee marl, which is 30 to 50 feet thick near Lake Okee-
chobee, thins to 6 feet at a place a mile south of the Broward-Palm Beach
county line and the North New River Canal. The marl has not been defi-
nitely recognized in well cuttings south of that place in Broward or
Dade counties.

PLEISTOCENE SERIES
FORT THOMPSON FORMATION
The Fort Thompson formation is the name applied to the alternating
fresh-water and marine limestones and marl beds which unconformably
overlie the Caloosahatchee marl at old Fort Thompson 1% miles east of
La Belle. Originally referred to as the Fort Thompson beds by Sellards





FLORIDA GEOLOGICAL SURVEY


(1919, p. 71, 72), the unit was later named the Fort Thompson forma-
tion by Cooke and Mossom (1929, p. 211-215), and was defined to
include the overlying marine Coffee Mill Hammock marl. In the lower
Everglades the Fort Thompson formation overlies the Tamiami forma-
tion, or, where present, erosional remnants of the Caloosahatchee marl,
and underlies the Miami oolite unconformably. In the northern part of
the area the Fort Thompson is overlain by the younger portion of the
Anastasia formation, the Lake Flirt marl, or the Pamlico sand.
The Fort Thompson formation at the type locality is a succession
of shelly marine and nonmarine limestones and marls, including three
distinct marine beds. The uppermost, the Coffee Mill Hammock mem-
ber, is a shell marl, consisting chiefly of shells of Chione cancellata. The
marine marl members are separated by gray, shelly, marl beds, in
part indurated to limestone, containing the fresh-water gastropods Heli-
soma and Ameria. The fresh-water beds are pierced by vertical and
lateral solution cavities formed by ground-water percolations. Subsequent
filling of the cavities by marine marls has produced a network of inter-
connected and isolated marine and fresh-water marls and limestones. In
places, holes penetrate the entire thickness of the formation so that the
Coffee Mill Hammock member lies directly upon the Caloosahatchee
marl of Pliocene age as a solution-hole filling. The alternation of marine
and fresh-water beds indicates, according to Parker and Cooke (1944,
p. 94-96, fig. 4), onlapping and offlapping seas from the end of Pliocene
time through the Sangamon interglacial stage of the Pleistocene.
Core borings of the thick section of permeable limestone and sand-
stone in the lower Everglades, between the Miami oolite and the Tami-
ami formation, similarly show interbeds and cavity fillings of fresh-water
limestone with marine limestone (figs. 4-9). This interbedded material
forms the major part of the Biscayne aquifer and, as previously men-
tioned, has been tentatively correlated by Hoy and Schroeder (1952, p.
283-286) with the Fort Thompson formation.
The Fort Thompson formation in the Dade-Broward county area
is predominantly light gray to cream, fossiliferous, marine, sandy lime-
stone and calcareous sandstone, with a few thin beds of gray and tan
fresh-water limestone. The entire section has been subjected to solution
by ground water,,and the result is a cavity-riddled mass of permeable
rock. Solution cavities are as much as several feet in diameter; some are
filled or partially filled with fine and medium quartz sand. Some sand
filling possibly occurred during flooding by Pleistocene seas. Loose sand
such as this decreases the permeability of the aquifer, but if wells are
heavily pumped much of the sand will be removed and a high perme-
ability adjacent to a well will result.





REPORT OF INVESTIGATIONS No. 17


Figure 4. West-east geologic cross section in western Broward County.

Cementation and redeposition of materials by ground-water move-
ment are very much in evidence throughout the Fort Thompson for-
mation. Cementation of sand bodies by calcium carbonate has produced
layers of hard, dense sandstone. Locally the cement is siliceous, pro-
ducing a very hard quartzitic sandstone. An examination of limestone
cores frequently shows secondary deposits of calcite crystals inside cav-
ities or within concavities of marine shells. Fossils are preserved chiefly
as molds and casts, rarely in their original form. Some cores of the Fort
Thompson formation show indications of bedding planes which provide
zones of weakness along which ground-water solution takes place. Part
of the Fort Thompson formation is composed of very dense, hard non-
fossiliferous limestone exhibiting little or no effect of ground-water
action. In general, highly fossiliferous beds are markedly pitted with so-
lution holes.
Because no unconformable relationship has been noted between the
Fort Thompson and older formations, the contact is normally placed


__ ____





FLORIDA GEOLOGICAL SURVEY


beneath the lowest sandy marine limestone which underlies fresh-water
beds. It is recognized that a part of this basal material in some places
may include formations of either Pliocene or late Miocene age.
The contact between the Fort Thompson formation and the Miami
oolite, as observed in spoil banks along canals in the Everglades, is un-
conformable and is usually placed at the maximum depth at which oolites
appear. The upper surface of the Fort Thompson is uneven and is char-
acterized by solution pits and depressions and vertical solution holes.
Oolitic material admixed with loose, sandy detritus from the Fort Thomp-
son was deposited on this eroded surface and filled depressions to depths
a few feet below the actual contact. These cavity fillings are easily dis-
cerned in core samples because the filling material is heterogeneous and
shows a color contrast. A layer of very hard, dense, cream to gray,
sandy limestone, which is peculiarly mottled or banded with brown
and tan limestone, occurs in the Fort Thompson below the contact. In
places the material appears to be a conglomerate containing weathered
pebbles of the Fort Thompson formation, but in at least some of these
places the "conglomerate" is the result of irregular deposition of iron
oxide in interstices of the Fort Thompson, along with differential cemen-
tation of those areas. The banding may denote an old eroded surface
or may be the result of water-table fluctuations.
The occurrence of fresh-water limestones in a great number of core
borings that penetrate the aquifer west of the coastal ridge has been
plotted in cross sections (figs. 4-6), the locations being shown on figure
7. In addition, a series of shallower borings, 25 to 30 feet below mean
sea level, along U. S. Highway 27 (Miami Canal northward to North
New River Canal) across Broward County between the Dade and Palm
Beach county lines, were examined. Fresh-water limestones are pres-
ent at shallow depth along U. S. Highway 27 where it adjoins the South
New River Canal north to the Palm Beach county line. In another series
of holes bored to a depth of about 20 to 25 feet below mean sea level
and extending from the North New River Canal to the Hillsboro Canal,
along a line approximately 8 miles west of Florida Highway 7, no fresh-
water material was noted in the cores. Obviously, it is difficult to deter-
mine exactly where the Fort Thompson and Anastasia formations merge,
but they seem to merge near the eastern edge of the Everglades.
A similar situation exists in Dade County where fresh-water lime-
stones are not known to occur in coastal areas. Along the western edge
of the coastal ridge, a few beds of fresh-water limestone are present, as
well as some indications of reef corals. The fresh-water limestones, rang-
ing in thickness from 1 to 3 feet, were noted in the following wells (fig.
7) which are not included in the cross sections:

































- '--


B t i






65 SO%


FORT THOMPSON





i10





TAMIAMI


35 .


MIAIWM

LITT~


FORMATION


FORMATION


EXPLANATION


PEAT AND UGCK


OOLITIO LIMtSTONR

$AND


SANDSTONE OR SANDY LIMISTON('


LIMESTONE


IRSiN.*VWAI LIMESTONE


SHELLS

EMA
MARL


0 AO


V q C
It c 0


NOIASTEM OR
UN CONFORM NIT Y


TAMIAMI


R EC EI N T O R OA N I C ( 1 1 L 9


FORT


THOMPSON


FORMATION


SCALE IN MILIS
0 I S J A _


.-----J1. ..- _


Figure 5. West-east geologic cross section in Dadc County.


%0 ut
o' o "


ANI


iAtLS


MIAMI


QOLITE


FORMATION


CORAL


'A-
C'
1~~
(II


_ __ ___~__I__UI


I---I I --


- 1' -~ hT1 ~t ~-f~Y a k~d IN-,


~~~-- -~--'---`~--^--~--`~'"--1-1------1-1--~ ---







































min# 4514M



11 16MillS p
all MANI4. 4






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4.0
YAMAM


I


0sla


AND


0.F4IAMILif


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FORMATION


Vo 1 3 9.4 .413 .


.4.4.4.4.4.4.4
MIAM)


FORT


THOMPSON


NISNT


44
.4 S o
I' III


ONOANI


FORMATION


"1


1171
GAVITYYI
USIIINg Lit


VI:I


FORT


STAMIAM


FI


W6 )A


THOMPS1


oilIV
0
.4 .4 .4 .4
.4


. ---


F RM 0


avs ~Q~F---^ --^a-'-' -- ... -- =ia ---_te


EXPLANAT ION
P14Y AND 5WONI
M-1ISNPTD


%sCLE NNIF


Figure 6. North-south geologic cross section in the Everglades,


*1t


S OIL#,


cPP


-5'4

-SO


____1_~__ __ __~I __I_____ I_____~___ __1_______1~_ __


I -~------~I-"pl-_-"~=m-`~""~'~"~'~E~i~E` _I


Y1-^ ul~~ra


-T


A-


0 m R m R 9 JS


" "'' '"` """~` "" """'- "


I,


- II-- ~'~--~--~----- -


I


P--


lo


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I I






REPORT OF INVESTIGATIONS No. 17


AA sou


G552


HOMESTEAD, /
G 216dEa


EXPLANATION
* TEST WELL, CORE BORING G210
o TEST WELL, CABLE TOOL
TEST WELL, PENETRATING RECOGNIZED
FRESH-WATER LIMESTONE
TEST WELL, PENETRATING RECOGNIZED
CORALLINE LIMESTONE


SCALE IN MILES


N


Figure 7. Map of Broward and Dade counties showing location of geologic
cross sections and certain test wells.


e






FLORIDA GEOLOGICAL SURVEY


Well Depth to top of fresh-water lime-
No. stone, in feet below msl
G 448-- .---..............- .................... -.... ............ ....... ........------------- 41
G 551 --..---------................-.........................------......----------.----------...................... 87 and 50
G 553 .......---------------..............-.....--..--.--..--------... ...... ........ -- --.... --.......-.. 42
G 552 ..... ......................... --..........--- .......-- ... ...------....... ..--...........------ .------. 10
S 24 .....--------..- ..------ --------- ----..........................................---.. 40 to 45
(depth uncertain)
S 986 ............. ......................--------------- --------------....................... ..... ........... .. 89

Reference to the section on the Anastasia formation, and to figure 7
showing wells that have penetrated coralline rocks, makes it evident
that the Fort Thompson, Key Largo, and Anastasia formations inter-
finger. Pleistocene marine limestones in certain areas of coastal Dade
County cannot be definitely assigned to one of the three formations, be-
cause of their transitional character. In some instances the limestone has
been arbitrarily placed in the Fort Thompson formation, although it does
not contain fresh-water beds, but in others the limestone is placed in
the Key Largo, although it is not coralline.

Figures 4 and 5 show west-east geologic sections across the lower
Everglades, and figure 6 shows a north-south section at the longitude
of Krome Avenue. Figure 8 shows a short west-east section along the
Tamiami Trail east of Krome Avenue, where wells were closely spaced,
and a possible correlation of fresh-water limestones. Several zones of
fresh-water limestone are apparent between wells G 670 and G 624,
shown in figure 6, where the uppermost zone occurs between the base of
the Miami oolite and a position 8 feet below mean sea level. The most
persistent zone and one that definitely appears to be a single layer oc-
curs between 8 and 15 feet below mean sea level and extends south-
ward from well G 670 to well G 653, and possibly farther. The thickness
of the fresh-water limestone of this zone ranges from 1 to nearly 5 feet,
although the greater thickness may be due to filling of solution holes.
This fresh-water limestone is not found at comparable depths in wells
G 657 and G 656. Possibly the core pierced a marine cavity fill within
the fresh-water limestone, or the bed has been eroded and subsequently
covered by younger marine limestone. However, limestone beds plotted
a few feet below the minus 15-foot mean-sea-level horizon in these 2 wells
may indicate that this bed was deposited in a locally depressed area or
a wide solution hole.

A second fresh-water limestone occurs approximately 20 to 30 feet
below sea level. This zone extends between wells G 661 and G 6538,
and wells G 669, G 667, and G 664 farther north containing fresh-water






REPORT OF INVESTIGATIONS No. 17


Figure 8. West-east geologic cross section near Krome Avenue at Tamiami Trail.
limestones, at slightly lower elevations, which are probably a continua-
tion of this zone. A similar situation may be true of the wells south of
G 653, although these limestones are generally at slightly higher ele-
vations.


17






FLORIDA GEOLOGICAL SURVEY


Cores from wells G 667, G 664, G 624, and G 757 indicate that 2 or
possibly 3 zones of fresh-water limestone may be present between the
second zone and the base of the Fort Thompson formation, but definite
correlation between wells cannot be made with the information available.
In well C 667 the highest fresh-water limestone is associated with
oolitic material and may be part of the Miami oolite. North of the Dade-
Broward county line the distribution of fresh-water material was such
that it could not be correlated with the more uniformly bedded strata
to the south.
Figure 8 shows a locality east of Krome Avenue along the Tamiami
Trail, where some of the closely spaced core borings penetrate the en-
tire thickness of the highly permeable aquifer. This section again shows
a possible correlation of 6 fresh-water limestone zones similar to that
shown in figures 5 and 6. Well G 607 (fig. 5) penetrated 6 beds of
fresh-water limestone and a well 42 feet east pentrated the same 6 beds.

At least four limestone beds of fresh-water origin occur within the
Pleistocene section at the Palm Beach-Broward county line and the North
New River Canal (fig. 7), as shown by the following log of well G 725:


Description
Peat and muck, dark brown .. --- .....--- ..... ..- ..........-.-.
Clay, m ucky, black .. -.-- ....................
Limestone, fresh-water, brown, dense, shelly .----.....................
Marl, sandy, marine, in places indurated to sandstone ................
Limestone, fresh-water, dense, brown ......... ..-.... ... ............
Sandstone, calcareous, fossiliferous, marine ...........................
Limestone, fresh-water, cream .-----...-..--..--.........................
Sandstone, shelly, marine, calcareous -..-....-. ......-.................-
limestone, cream, shelly, probably fresh-water (?) .................
Marl, very sandy, shelly, tan, marine, with a few fresh-water
shells .. .-----.....................
Marl, tresh-water, sandy, shelly ---...-------- -----....-.- ......... ...
Marl, fresh-water, partially shelly, indurated to limestone ..........
Sand, marly, tan, very shelly, fresh-water gastropods from
11.5 to 12.0, apparently as savings, containing some
marine shells (Chione cancellata) ......------------...................
Sandstone, cream to tan, very shelly, mixed marine and fresh-
water at bottom ---......--------..---...........-------..................


Depth, in feet, with
reference to msl
+ 10.9 to + 6.1
+ 6.1 to + 4.8
+ 4.8 to + 4.7
+ 4.7 to -- 1.7
+ 1.7 to + 1.1
+ 1.1 to 0.0
0.0 to 1.0
1.0 to 6.0
6.0 to 6.5


- 6.5
- 8.6
- 10.7


- 8.6
-10.7
- 11.5


- 11.5 to 13.5

- 13.5 to 16.5


A glance at the geologic sections indicates that each fresh-water bed
was probably deposited on an undulating and solution-pitted marine
limestone. The beds range in thickness from 0.2 foot to nearly 5 feet.
Their upper surfaces were probably eroded to some extent by shallow
encroaching seas which removed less resistant materials. It is recognized






REPORT OF INVESTIGATIONS No. 17


that a few of the fresh-water limestones as plotted are cavity fillings which
were deposited in what is definitely marine material. Fresh-water mate-
rials could easily have been washed in and deposited in subsurface cavi-
ties as well as at the surface.
It is possible that, during major portions of the Pleistocene glacial
stages, the lower Everglades was a low-lying marginal area bounded on
the west by slightly higher land and on the east by the coastal ridge
composed of reef materials. Because of the marginal character of the
area, slight rises in sea level would bring about marine floods during
which thin marine limestones were deposited. However, with a fall in
sea level, the land emerged so that the resulting weathering and erod-
ing of the marine limestones accompanied the deposition of some thin
fresh-water limestone. A major advance of the continental ice sheet would
cause an extended lowering of sea level, thus allowing a greater thick-
ness of fresh-water limestone to be deposited over a larger area. On the
other hand, a major or complete retreat of the ice sheet probably re-
sulted in inundation of the area for a long period, and in deposition of
a greater thickness of marine limestone in which were thin, isolated
I bodies of reworked older material.
The lower Everglades appears to have been a depressed area which,
during Pleistocene time, was intermittently shut off from the sea by a
barrier along the coastal ridge of southeastern Florida. This barrier was
formed by the deposition of the Anastasia formation, the Key Largo
limestone, and the Miami oolite. During times of lowered sea level the
Everglades lay exposed and contained swamps and fresh-water lakes,
and fresh-water limestones were deposited as fills in the lower materials
and as beds. The sea level probably was not stable during the glacial
stages but rose and fell with relatively short retreats and advances of
the ice. Such activity produced thin layers of marine limestone during
short sea floodings, interbedded with thin fresh-water or brackish-water
deposits during recessions. However, after a complete retreat of the
continental ice sheet, the resulting rise of sea level would permit thick
marine sections to be deposited. Optimum conditions for the most wide-
spread deposition of fresh-water limestone in the lower Everglades prob-
ably occurred at times between the beginning of a glacial stage and of
maximum advance of the continental ice sheet. Times of maximum ad-
vance of the ice and lowering of sea level were most favorable for chan-
nel cutting, resulting in draining of the land.
Correlation of the six postulated beds of fresh-water limestone with
specific glacial stages of the Pleistocene is a more difficult problem than
the correlation by Parker and Cooke (1944, p. 89) of the beds at the






FLORIDA GEOLOGICAL SURVEY


site of old Fort Thompson. The data suggests that the tentative correla-
tion by Parker and Cooke of individual beds with specific glacial and
interglacial stages may need revision.
KEY LARGO LIMESTONE
The Key Largo limestone, named and described by Sanford (1909,
p. 214-218), is a dead coral reef that makes up the Florida Keys from
Soldier Key southwest to Bahia Honda. The Key Largo limestone is
a part of the Biscayne aquifer along the coastal area of Dade County.
It constitutes the whole of the aquifer in the part of the Florida Keys
described. The rest of the Keys southwest from Bahia Honda are com-
posed of the Miami oolite and there the Key Largo limestone may con-
stitute only a small part of the aquifer. The aquifer in the Keys yields
saline water to wells.
The Key Largo limestone consists chiefly of recemented reef detritus
and precipitated limestone surrounding coral heads of the old reef. The
corals were subjected to wave action, which eroded the softer parts and
deposited the waste in the openings along with other bioherm material.
The formation in general is very permeable, containing solution cavities
which were produced in the same manner as in the Fort Thompson
formation.
Corals, most of them of the reef-building type, have been found in
material from the following wells (fig. 7), at the noted depths:
Well Depth, in feet
No. below msl
G 10 1 ......... .................... ...... .................. ......... 20 to 56
G 186 ----------------------.. ...........---- -------- 9 to 43
G 189 -----------------...----- ....--- ............-..........-------------- 13 to 32, and
41 to 48
G 193 ---------------------------------------- ............................ ... 35 to 43
G 196 ...----------------------..........................................-----............................--------... 41 to 54
G 210 .....-------------------.. ---------.. ........ ----..---..........--.....----- 13 to 19
G 216 ----------.............................----------...............------.............................----------.............--- 15 to 20,
24 to 33, and
44 to 60
G 224 -- --- .- ..- -----------------------...............................----... 18 to 44
G 429 .------...........------...---------------------------......-----------.....................--- 18 to 23
G 448 .----- ... ..----- ...........................................-------------------------................ 1 to 40
G 756 ... ..-- ---------.......................---------------------------------------------- 56
G 757 ---.. .-- ... ......-- -------................. ....................................... 44 and 49
G 758 -. .. ----------------------------.. --......-......-..---- --..... .... 52 and 56
S 986 (and nearby wells)-....-------------------------------------........................... 38,40,60, and 70
All except the last four wells, which were cored, were drilled by
the cable-tool method. The coralline material in well G 448 directly






REPORT OF INVESTIGATIONS No. 17


overlies fresh-water limestone, whereas in well S 986 a fresh-water lime-
stone bed at 89 feet is overlain and underlain by reef-limestone material.
Coral was noted in wells G 756 and G 757 below the lowest fresh-water
limestone. In many wells that were not cored the coralline limestone
appears to be discontinuous, because only a trace of coralline limestone
was noted in the samples from wells G 101 and G 224. The comminution
of the material by the bit action prevents any possible identification of
fresh-water limestone in such samples. However, along the eastern part
of the coastal ridge, fresh-water limestones are not apparent in the under-
lying limestones and only an occasional bed is penetrated in the western
part of the coastal ridge. The occurrence of coral in the vicinity of the
western part of the ridge demarks the area of interfingering between
the Key Largo limestone and the Fort Thompson formation. The nature
of this interfingering is not known nor is the western limit of coralline
limestone. An abundance of reef coral was excavated from the borrow
ditch for the levee which crosses the Tamiami Trail a mile west of Krome
Avenue. The corals apparently are from the top part of the Fort Thomp-
son formation, although it is possible that they are in the Miami oolite also.
A great number of wells along the coastal ridge penetrate Pleistocene
limestones that apparently include neither fresh-water limestones nor
coralline limestone. These limestones have been placed in the Anastasia
formation.
The upper part of the Key Largo limestone, according to Parker and
Cooke (1944, p. 68), interfingers with the lower part of the Miami oolite.
ANASTASIA FORMATION
The Anastasia formation was named by Sellards (1912) from its typi-
cal development of coquina on Anastasia Island, near St. Augustine,
Florida, and as defined in this report includes all pre-Pamlico marine
sand, limestone, and shell beds of Pleistocene age along the coastal area.
The Anastasia formation represents the chief component of the Bis-
cayne aquifer in the vicinity of Fort Lauderdale and along the coastal
ridge as far north as Delray Beach in Palm Beach County. In the area
to the west, the Anastasia is equivalent to the marine portions of the
Fort Thompson formation, and to the south the upper part of the An-
astasia merges with the Miami oolite and the lower part merges and
interfingers with the Key Largo limestone (fig. 9). The formation
is composed of marine sandy limestone, calcareous sandstone, in part
coquinoid, and shelly sand. It was initially laid down in a shallow beach
environment as an offshore bar which was exposed from time to time
by eustatic sea-level fluctuations during the Pleistocene. An outcrop of


































ANASTASIA


HAWTHORN FORMATION


SCALC 10 WLg


Figure 9. North-south geologic cross section on the coastal ridge.


OOLITI


FORMATION


FORMATION


E XPLANATION




0@UTIC L.MmY@S6

ASD

S=s~w
Lo00070u5

mSO?0


1_ I


I __ _






REPORT OF INVESTIGATIONS No. 17


the Anastasia formation at Palm Beach shows younger eolian crossbed-
ded sandstone lying unconformably on marine calcareous sandstone. The
unconformity is characterized by brown sandy soil which fills solution
holes in the older material. The Anastasia formation represents sediments
deposited throughout all or a major part of the Pleistocene, according
to Parker and Cooke (1944, p. 66).
The permeability of the Anastasia formation ranges widely from place
to place. Away from the coastal areas, where it is well indurated, ground-
water action has produced large solution cavities and the permeability
high. Adjacent to the coast the material contains more sand and silt so
that the permeability is markedly reduced.

MIAMI OOLITE
The Miami oolite was named by Sanford (1909, p. 211-214). Cooke
and Mossom (1929, p. 204-207) redefined the formation to include all
the oolitic limestone of southern Florida, including that on the Keys.
The Miami oolite is the surface rock that blankets nearly all of Dade
County, parts of eastern and southern Broward County, the southern
mainland area of Monroe County, the Florida Keys from Big Pine Key
to Key West, and a triangular area extending from Dade County west-
ward along the Collier-Monroe county line. The formation thins out
at its western extremity and gradually thickens to the east, attaining a
maximum thickness of about 40 feet.
In the lower Everglades the Miami oolite unconformably overlies and
fills cavities in the upper surface of the Fort Thompson formation. Along
the coast the formation interfingers with the upper portions of the Fort
Thompson, Anastasia, and Key Largo formations. Where not exposed at
the surface in the lower Everglades, it is covered by Recent organic
materials. In northwest Dade County and southwest Broward County,
it is overlain unconformably by the Pamlico sand, a terrace deposit of
Pleistocene age, or by the Lake Flirt marl of Pleistocene and Recent age.
The Miami oolite is typically a white to yellowish massive crossbedded
oolitic limestone containing varying amounts of sand, usually in solution
holes. Where exposed to weathering, as in the Silver Bluff area, the
surface of the oolite turns a dull gray color. Crossbedding and cone-in-
cone structures are outstanding features. The angle of dip of the cross-
bedded material changes from place to place, and the material is ap-
parently a dune or beach-ridge deposit. The high angle crossbeds in
places are beveled by flat-lying oolitic material containing marine shells.
In the Silver Bluff area large pieces of crossbedded oolitic limestone are
4A


23






FLORIDA GEOLOGICAL SURVEY


incorporated in portions of oolite which show no evidence of bedding.
This is definite evidence of reworking of younger oolite deposits and,
according to Parker and Cooke (1944, p. 71), might indicate either that
the Miami oolite represents deposits of two or more interglacial stages
or that the deposition, reworking, and redeposition occurred during a
single stage. In either case, oscillation of the sea level was involved. At
many places in Broward County the formation is composed almost
entirely of calcareous oolitic sand or of mixtures of calcareous and quartz
sand.

PAMLICO SAND
The Pamlico sand is a late Pleistocene terrace deposit of marine origin
(Parker and Cooke, 1944, p. 75). Parker and Cooke (p. 74, 75) extended
the term Pamlico sand from North Carolina to southern Florida, and
defined it to include all the marine Pleistocene deposits younger than
the Anastasia formation.
The Pamlico sand blankets much of the Everglades north of the
latitude of Fort Lauderdale and covers the coastal area as far south as
Coral Gables. It unconformably overlies and fills cavities in the Miami
oolite, the Fort Thompson formation, and the Anastasia formation. In
the northern part of the region the sand is covered by Recent marls and
organic soils.
The Pamlico sand is chiefly a quartz sand ranging in color from
light gray or white to red and gray-black, depending on the amount of
incorporated iron oxide or carbonaceous material. In localities where
shells are admixed, the Pamlico sand may be semiconsolidated as a result
of solution and redeposition of calcium carbonate. The quartz sand
ranges in size from very fine to coarse, the medium-sized grains predomi-
nating. Where the material is medium to coarse, and well sorted, it will
furnish adequate fresh-water supplies for domestic purposes.
The Pamlico sand lies below the 25-foot contour; areas within its
outcrop that lie at higher elevations represent dunes or shore ridges
formed during the Recent. The formation increases in thickness from a
featheredge to perhaps 40 feet, the greatest thickness being along the
coastal ridge.

GROUND-WATER OCCURRENCE
GENERAL FEATURES
All the water that recharges the Biscayne aquifer is derived from
local rainfall. When rain falls to the surface, a part is evaporated, a part






REPORT OF INVESTIGATIONS No. 17


is used by plants, another portion runs off as surface water, in streams
or to fill lakes and ponds, and the remainder percolates rapidly through
the thin sandy mantle to the water table. Only in the Everglades does
any major surface runoff occur.
The water table is the upper surface of the zone of saturation except
in areas (rare in southern Florida) where that zone is formed by an
impermeable body. The water table is open to the atmosphere and is
marked by the level at which water stands in wells. It is an undulating
surface which in a general way conforms to the topography, being at
higher elevations under hills and lower under valleys. The water table
in the Biscayne aquifer normally lies within the Miami oolite, the Pamlico
sand, or the organic soils of Recent age. Parker (in Parker and others,
1955), in relating precipitation to water-table rises, estimates that about
two-thirds of the annual rainfall reaches the water table in southern
Dade County.
The water table fluctuates in response to local rainfall in the area
and to natural discharge (seepage into streams or canals or to the sea,
and evapotranspiration), and pumping.
Water for small domestic supplies is derived through small diameter
sand-point wells from the Pamlico sand. The Miami oolite is more per-
meable than the Pamlico sand, and the contained water is obtained by
means of shallow open-hole unscreenedd) wells. Large supplies of water
are obtainable from uncased wells in this formation in the grove area of
southern Dade County. The Key Largo limestone, the Anastasia forma-
tion, and the Fort Thompson formation in Dade County will yield large
amounts of water to open wells. For example, an 18-inch well southwest
of Miami yielded 7,600 gallons per minute, or about 11 million gallons a
day, with a drawdown of only 7 feet. Along the coastal areas of Broward
County, the water in the Anastasia formation generally is obtained by
means of screened wells. At Fort Lauderdale the Tamiami formation,
which is a friable; very calcareous sandstone, yields large quantities of
water to both open-hole and screened wells.

SHAPE AND SLOPE OF THE WATER TABLE
The water table of the Biscayne aquifer may be mapped at any given
time by determining its elevation in a network of wells. Eastern Dade
County has a large number of control wells, whereas those in Broward
County are relatively few and scattered. Irregularities in the shape and
slope of the water table are common and are produced chiefly by rainfall
and to a lesser extent by pumping, both of which are highly variable from
place to place. The water table in Broward and Dade counties commonly




FLORIDA GEOLOGICAL SURVEY


slopes eastward toward the coast, although in the central part of the
Everglades it slopes southward. In wet periods the water table may slope
both east and west from the coastal ridge.
Water-table contour maps have been prepared for the eastern part
of Dade County. These show modifications and changes in the shape of
the water table brought about by the various drainage canals and the
heavy local rains. The maps were prepared principally from records of
the present network of observation wells that are equipped with auto-
matic recording gages; however, when interpreted in conjunction with
maps showing high, intermediate, and low water stages, these records
give coverage that is nearly as complete as that of the much larger number
of wells measured for preparing a detailed water-table contour map.
Figure 10, which represents the average elevation of the water table for
the period 1940-1950, shows the general shape and slope of the water
table in Dl)ade County. Although several maps of different water stages
have been made, the maps of the lowest (fig. 14) and highest (fig.
16) ground-water stages of record in Dade County emphasize the
irregularities.

FLUCTUATIONS OF THE WATER TABLE
Major fluctuations of the water table are caused by recharge and
natural or artificial discharge. The magnitude of water-level fluctuation
during any one year in Dade County varies from 2 to 8 feet, depending
upon the amount and distribution of the rainfall in the local area. Figure
11 shows a hydrograph of well S 196 compared with a graph of rainfall.
The water table in the coastal areas fluctuates in response to
ocean tides, the time lag increasing and the magnitude of fluctuations
decreasing with distance inland. The greatest observed inland distance
of the tidal effect on water levels is 6,700 feet in well F 179, in Miami,
where the fluctuation amounted to 0.01 foot. Although the Biscayne
aquifer generally shows nonartesian characteristics, pumping tests indi-
cate that the aquifer temporarily responds as an artesian aquifer hav-
ing a very leaky roof. Thus, water levels in many wells respond to
earthquake shocks and to changes in barometric pressure. The effect
of barometric pressure is usually slight and is commonly masked by other
fluctuations. Parker and Stringfield (1950) have discussed the effects
of earthquakes, winds, tides, and atmospheric pressure changes on
ground-water levels in southern Florida.
High and low water-table conditions are of economic importance in
both rural and urban areas. Extremely high water-table conditions cause
the flooding of the low-lying lands in southern Florida, destroying crops,


26







REPORT QF INVESTIGATIONS No. 17


BROWARD COUNTY


3? 3


I OMESTC AD

I VLONIDAc


SCALE IN MILES
0 & 4 5 6 7 6 1 10


Figure 10. Map of Dade County showing average water levels in
eastern part, 1940-1950.







FLORIDA GEOLOGICAL SURVEY


PRECIPITATION,
IN INCHES


WATER LEVEL, IN FEET
ABOVE MEAN SEA LEVEL


0PO CO (NO ()o 4W OD ( O 4 a 0


Figure 11. Graphs showing fluctuation of water level in well S 196 and
rainfall at University of Florida Subtropical Experiment Station
during 1947.





REPORT OF INVESTIGATIONS No. 17


damaging buildings and other structures, and delaying the planting of
crops. Low water conditions cause nonirrigated crops to die, allow the
organic soils to shrink or to be destroyed by fire, and permit the en-
croachment of salt water at accelerated rates. The difference between
the highest and lowest water levels of record (1940-1951), as recorded
in observation wells, ranges from 6 to 11 feet along the coastal ridge and
from 7 to 8 feet in the Everglades.
The duration of water-level peaks resulting from rapid rises is
generally only a few minutes; hence, an average water level for a month
is a better guide to use in evaluating high water-level conditions. The
average monthly water level in a well is computed by averaging the
daily water-level readings. The range between the highest and lowest
average monthly water levels of record is about 7 to 7.5 feet in the
upper Everglades and 4.5 to 8.5 feet along the coastal ridge. The maxi-
mum, minimum, and mean of the average monthly water levels in
selected wells are shown in figure 12.
The net of observation wells equipped with recording instruments
in operation in Dade County since 1949 is adequate to determine the
annual average water-level conditions in the eastern part of the county.
The average water level in 1949 in Dade County was approximately the
same as the average water level in the period from 1940-1950 in those
wells for which water-level records were available during this 11-year
period. Therefore, the map showing average water levels for the period
1940-1950 represents average water levels in 1949.
In Broward County, the average water level for a 10-year period in
well S 829 (see fig. 13 for location) is about 4 feet above mean sea level.
This coincides fairly well with the average water level in 1949, and it
is inferred that the 1940-1950 average for other wells on the coastal ridge
may be nearly the same as the 1949 average. The 1949 average levels in
wells F 291 and G 561 were about 2 and 1.5 feet above mean sea level,
respectively.
The lowest water levels of record (1934-1951) occurred during May
and June 1945. The total rainfall during the years 1944-1945 scarcely
exceeded that of one normal year, so that the recharge to the aquifer
was well below normal. For the most part the numerous drainage canals
were uncontrolled during 1944 and only partially controlled in 1945.
These canals accelerated the lowering of water levels by the continuous
draining of ground water during the drought.
In the southern part of Dade County, in an area centering west and
southwest of Florida City, the water table declined to almost 3 feet below


29








FLORIDA GEOLOGICAL SURVEY


J F M A M J J A S O N D

G596 ..
4 YEARS / 6
f REORO -




X1


'4.t


Figure 12. Chart of comparative average monthly water levels in selected wells.


F 291
5 YEARS
*o RECORD


LLLL1~LIA


~


F M A M J J A S 0 N 0
---T---r-
F 210
0 YEARS
OF RECORD


Afl







REPORT OF INVESTIGATIONS No. 17 81


I I NAL







SB\R 0 W AR
^f^ WELL FIELD 9 FORT
p lS5329
I DALE
SOUrH NEW RIVER CANAL D56*

C'% /
S- 291'

L.-"--- ----------------------------
072 SI
I -Z


IA MIAMI SPRINGS E I MA
SWELL FIELDo
BEACH
TAMIAMI CANAL
I T AMIAMI TRAIL w U
I PERMANENT SITE
SOUTHWEST WELL FIELD F 31
S596 TEMPORARY
SI0 WEL FIELD
W S182

K D A E

S196
HOMESTEAD
S KEYWEST
I y c: WELL FIELD


INGRAHAM





0

* to 0
SCALE IN MILES
10 0 10

Figure 18. Map showing location of certain observation wells and locations
of large municipal well fields.





FLORIDA GEOLOGICAL SURVEY


the average level in Biscayne Bay (the average level in the Bay being
about 0.5 foot above U. S. Coast and Geodetic Survey mean-sea-level
datum). Parker, Cooper, and Hoy (1948, p. 16) state: "This lowering of
the water table below ocean level was largely brought about by the ex-
ceedingly high rate of evapo-transpiration acting upon a water table
already reduced to sea level by lack of rainfall and by drainage. But, in
addition to the natural withdrawal of ground water by evapo-transpira-
tion, irrigation helps reduce water levels still lower. The greater the
drought the greater the withdrawal of ground water for irrigation and,
thus, the greater the lowering of the water table. It should be empha-
sized, however, that irrigation withdrawal had very little to do with the
development of the large area of below-ocean-level water table in the
area centering west and south of Florida City evapo-transpiration,
which may possibly account for more than 71 inches of water a year in
this area, was principally responsible. The U. S. Weather Bureau reports
the evaporation of 70.704 inches from the Hialeah pan in 1945." A
ground-water contour map of Dade County for May 19, 1945, is shown
in figure 14.

The lowest stage of record was reached during the period June 17-20,
1945, a month after the detailed measurements used for figure 14 were
made, and estimated contours for that period also are shown in figure
14. The position of the contours is based on a few isolated measurements
and records from wells equipped with recording instruments. Water
levels ranged between 0.3 and 0.4 foot lower than those recorded on
May 19 except in the Miami area and the area southwest of Florida City,
where they remained the same. A slight amount of rainfall southwest of
Florida City maintained the same water levels there.

The lowest ground-water levels of record (1940-1951) in Broward
County occurred in 1945 also. Water-level measurements in a number of
wells in the eastern part of the county were made on April 14, 1945. The
lowest water level probably did not occur until late May; however, the
low water levels shown in figure 15, as interpreted from the measure-
ments of April 14, probably were not significantly different from those
reached several weeks later.

The highest water-table conditions of record in Dade County occurred
during October 1947 (fig. 16). At the end of September the water table
along the coastal ridge, especially in the Miami area, was the highest
of record (1940-1947) for September, owing to excessive rainfall. The
rainfall at Miami in the month of September was 13.65 inches, 5.00 inches
above normal for the month. The intense rainfall accompanying a small







REPORT OF INVESTIGATIONS No. 17


BROWARD COUNTY
0



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-0.5 0. -OPA LOCKA N T MAIJ


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SCALE IN MILES
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vel on May 19

lI on June 19


Figure 14. Low stage water-level map of eastern and southern Dade County,
May, June 1945.


33














-II



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EXPLANATION

4.8 CANAL STAGE, IN
ABOVE MSJ..


FEET


SCALE IN MILES
2 o 2 4 6 s


O- WATER TABLE CONTOUR
*,' IN FEET ABOVE M.SL.


Figure 15. Low stage water-level map of eastern Broward County, April 14, 1945.


,8.0


FORT
LAUDERDALE


L14



t14








REPORT OF INVESTIGATIONS No. 17


BROWARO COUNTY


VI


vII


High stage water-level map of eastern Dade County, October 11, 12, 1947.


35


SCALE IN MILES
OttS4n^^testo


Figure 16.







36 FLORIDA GEOLOGICAL SURVEY

hurricane on October 11, 12 resulted in water levels reaching what are
probably the highest stages that have occurred since the major Everglades
canals were completed in 1913.
Rainfall at representative stations in southern Florida ranged as
follows:
January 1-October 30, 1947............................................. 65.9 to 96.1 inches
June 1-October 30, 1947................................................. 50.0 to 74.2 inches
Normal yearly rainfall..................................................... 53.8 to 62.6 inches
Rainfall on October 11 ranged from 5 to 15 inches and averaged about
10 inches in northern Dade County.
Practically the entire area west of the coastal ridge that was not
already flooded became inundated, and the already large overland flow
south in the Everglades was increased. The Miami Canal was out of its
banks as far east as Hialeah and Miami Springs. Outflow across U. S.
Highway 27 occurred from a mile northwest of Pennsuco to the vicinity
of the Russian Colony Canal. Other canals were similarly out of their
banks. The actual peak lasted several hours at the most, although many
areas remained flooded for several weeks.
The water-level map for October 11, 12 showing the peak (fig. 16)
was prepared from records of observation wells equipped with recorders,
and from measurements made during the flood period, leveled measure-
ments of flood marks, and interpolation of the measurements made in a
large number of wells on or about October 7. In a few places the water
levels are estimated. However, the map is believed to be a good approxi-
mation of actual conditions. In the area between Snapper Creek and
Krome Avenue, south of the Tamiami Canal, the presence of several small
ground-water mounds and the network of canals make it difficult to
visualize the actual shape of the water table, but the general slope was as
indicated.
RECHARGE AND DISCHARGE
Local rainfall is the principal source of recharge to the Biscayne
aquifer. The amount of rainfall varies within relatively short distances,
but it averages about 60 inches annually in.Dade County. In Broward
County, rainfall records for periods ranging from 5 to 25 years indicate
an average annual rainfall ranging from 51 to 65 inches. The lower
averages commonly pertain to the Everglades, and the higher ones to the
coastal ridge.
A small amount of ground water moves into the aquifer in Broward
County from Palm Beach County and from the North New River Canal.
In areas where canals are controlled by dams and in areas where the
ground-water levels are lowered by pumping, as in the well field in Miami
Springs, the canals provide recharge to the Biscayne aquifer.






REPORT OF INVESTIGATIONS No. 17


Discharge from the Biscayne aquifer occurs by ground-water flow into
the canals, the Atlantic Ocean, or Biscayne Bay, by evapotranspiration,
and by pumping.
Of the 60 inches of average annual rainfall in the coastal ridge
area of Dade County, Parker (1951, p. 825) estimates that 22 inches is
discharged by evapotranspiration and surface runoff without reaching
the water table and 38 inches reaches the water table. Of this, 20 inches
is discharged as ground-water flow, and 18 inches is discharged by
evapotranspiration of ground water and by pumping from wells. It is
estimated that, as of 1950, approximately 4 inches gross was discharged
by wells. In areas where heavy pumping forms significant cones of de-
pression, ground water is salvaged because of the decreased evapo-
transpiration resulting from the lowered water levels.
Ground water is utilized for municipal, industrial, domestic, and
irrigation supplies. The estimated pumpage in Dade County, in 1945
and 1950 in gallons per day, is as follows:
1945 1950
Municipal supplies 35,000,000 65,000,000
Industrial use 12,000,000 20,000,000
Rural use and irrigation 11,000,000 15,000,000

Total average daily pumpage 58,000,000 100,000,000
These estimates do not include the amounts from wells used for air-
conditioning and then returned to the ground. In 1954 about 28 mgd was
being pumped in this way, although an unknown part of this was saline
water. One new hotel under construction in the Miami Beach area will
pump 4 mgd of saline water from the ground for air-conditioning and
will discharge it into the ocean.
In Broward County sufficient data are not available to estimate the
total ground-water withdrawal, but the municipal supplies in the county
delivered about 4 billion gallons (11 mgd) in 1951. Percentagewise, the
industrial and agricultural uses are about the same as in Dade County;
however, a smaller percentage of the people obtain their domestic water
from municipal supplies. The total withdrawal probably was not in
excess of 80 mgd.

HYDROLOGIC CHARACTERISTICS
OF THE BISCAYNE AQUIFER
Ground water is stored in joints, pore spaces, and solution cavities
in the rock. In the Biscayne aquifer the major portion of the ground
,water is stored in cavities formed by the dissolving action of percolating


87






FLORIDA GEOLOGICAL SURVEY


incorporated in portions of oolite which show no evidence of bedding.
This is definite evidence of reworking of younger oolite deposits and,
according to Parker and Cooke (1944, p. 71), might indicate either that
the Miami oolite represents deposits of two or more interglacial stages
or that the deposition, reworking, and redeposition occurred during a
single stage. In either case, oscillation of the sea level was involved. At
many places in Broward County the formation is composed almost
entirely of calcareous oolitic sand or of mixtures of calcareous and quartz
sand.

PAMLICO SAND
The Pamlico sand is a late Pleistocene terrace deposit of marine origin
(Parker and Cooke, 1944, p. 75). Parker and Cooke (p. 74, 75) extended
the term Pamlico sand from North Carolina to southern Florida, and
defined it to include all the marine Pleistocene deposits younger than
the Anastasia formation.
The Pamlico sand blankets much of the Everglades north of the
latitude of Fort Lauderdale and covers the coastal area as far south as
Coral Gables. It unconformably overlies and fills cavities in the Miami
oolite, the Fort Thompson formation, and the Anastasia formation. In
the northern part of the region the sand is covered by Recent marls and
organic soils.
The Pamlico sand is chiefly a quartz sand ranging in color from
light gray or white to red and gray-black, depending on the amount of
incorporated iron oxide or carbonaceous material. In localities where
shells are admixed, the Pamlico sand may be semiconsolidated as a result
of solution and redeposition of calcium carbonate. The quartz sand
ranges in size from very fine to coarse, the medium-sized grains predomi-
nating. Where the material is medium to coarse, and well sorted, it will
furnish adequate fresh-water supplies for domestic purposes.
The Pamlico sand lies below the 25-foot contour; areas within its
outcrop that lie at higher elevations represent dunes or shore ridges
formed during the Recent. The formation increases in thickness from a
featheredge to perhaps 40 feet, the greatest thickness being along the
coastal ridge.

GROUND-WATER OCCURRENCE
GENERAL FEATURES
All the water that recharges the Biscayne aquifer is derived from
local rainfall. When rain falls to the surface, a part is evaporated, a part






FLORIDA GEOLOGICAL SURVEY


ground water. Ground water moves laterally and vertically under gravi-
tational influence to points of discharge in streams, canals, lakes, and
the ocean, and carries, in both solution and suspension, materials removed
from the rock.
The permeability of a rock is a measure of its ability to transmit
water. Porosity is the property of containing openings. or interstices.
Materials such as clay or marl are highly porous but relatively imper-
meable because the components are so finely divided that the molecular
attraction between the clay-sized particles tends to hold the contained
water in place, thereby restricting movement. High permeability is
usually associated with clean, well-sorted gravel or open shell beds. The
material that forms the Biscayne aquifer has a permeability equivalent
to that of coarse, well-sorted gravel, because the interconnected solution
cavities greatly facilitate ground-water movement.
Several pumping tests have been made on wells penetrating the Bis-
cayne aquifer in the Greater Miami area. The purpose of these tests
was to determine values for the coefficients of transmissibility and
storage of the aquifer at different localities. The coefficient of transmis-
sibility may be defined as the number of gallons of water per day that
will move through a complete section of the aquifer one mile wide,
under a hydraulic gradient of one foot per mile. A value for the field
coefficient of permeability may be determined by dividing the coefficient
of transmissibility by the saturated thickness of the aquifer, in feet;
thus, the coefficient of permeability refers to the hydrologic character-
istic of a unit of the water-bearing rock, whereas transmissibility refers
to that characteristic of the aquifer as a whole. The coefficient of
storage of an aquifer is defined as the volume of water it releases from
or takes into storage per unit surface area of the aquifer per unit change
in the component of head normal to that surface. The Biscayne aquifer
on a long-term basis behaves as an unconfined or water-table aquifer
(although in short tests it may behave as an artesian aquifer having a
leaky roof), and the coefficient of storage is essentially equal to the
specific yield 0.10 to 0.35.

The average transmissibility (T) of the Biscayne aquifer, as stated
by Parker (1951), is about 5 million gallons per day per foot, the lowest
value observed being about 3 million. The storage coefficient (S) ranges
from 0.10 to 0.35 and averages about 0.20.

Pumping rates for these tests were about 8,500 gpm, except for the
test on well G 218 which was at a rate of about 1,500 gpm. The results
of these tests computed by the Theis nonequilibrium formula (1935,






REPORT OF INVESTIGATIONS No. 17


p. 519-524) and as reported by Parker (Parker, Ferguson,. Love, and
others, 1955, p. 239-274) are summarized in the following table (see fig.
14 for location of test sites).
Test Range in computed
site coefficient of transmissibility
(gpd/ft)
Lowest Highest
S 1 .......................................................... 3,250,000 4,300,000
G 551 .............................................................. 9,000,000 14,000,000
G 552 .............................................................. 2,800,000 5,700,000
G 553 .......................................................... 2,500,000 3,900,000
G 218 -----...-----........--..-.. --..-.......--. ...-------. 8,900,000 4,400,000
At all the test sites the Miami oolite forms the upper part of the
Biscayne aquifer, and at most of them it is underlain by a bed of sand.
The permeability of the oolite and sand is lower than that of the under-
lying cavernous limestone of the Fort Thompson formation and thus acts
as a leaky roof during the pumping of a well, and the formation initially
acts as an artesian aquifer. The Bessel function then can be used in
the computations using formulas developed by Jacob (1945, p. 198-208).
John G. Ferris (1950, personal communication) determined the following
values from the test data:
Well Coefficient of transmissibility
No. (gpd/ft)
S 1 ............................................................................ .. 3,200,000
G 551 ......................................................................... ...... 9,700,000
G 552 ....................................................... 3,200,000
G 553 ............................... ........................................... 3,200,000

The T value of the test for well G 551 by both calculations is incon-
sistent with the values for the other tests. The results of the other
three tests using the Bessel function are extraordinarily consistent con-
sidering the character of the aquifer. The permeability of the Biscayne
aquifer probably averages between 50,000 and 70,000 gallons per day per
square foot, according to Parker (1951). No satisfactory computation
of the storage coefficient has yet been obtained.

Several assumptions concerning the aquifer must be applied in using
formulas to determine these coefficients: (1) the aquifer is homogeneous
and isotropic and transmits water with equal readiness in all directions;
(2) the discharging well penetrates the. entire thickness of the aquifer;
(3) there is no turbulent flow within the aquifer, and during the pumping
there is no vertical convergence of flow lines toward the pumped well;
and (4) water is discharged from storage instantaneously with reduction
in head.


39






FLORIDA GEOLOGICAL SURVEY


Inaccuracies in these tests must be assumed because the Biscayne
aquifer does not conform adequately to ideal conditions. Owing to the
size of the cavities in the aquifer, turbulent flow develops near the
pumped wells. Sand-filled cavities locally reduce the flow within the
aquifer, so that the permeability is not the same in all directions.
Ground-water movement is significantly less through the Miami oolite
than through the Fort Thompson formation. Also, within the Miami
oolite itself the rate of movement is less in a horizontal than in a vertical
direction.
Slight errors or differences in drawdown due to irregularities in the
aquifer can cause errors in the value of T. The aquifer is so permeable
that pumping causes only small drawdowns; hence, even small obser-
vational errors produce large errors in the computed values. However,
the various determinations indicate that the general order of magnitude
of the value of T is correct, although its value at any specific place is
difficult to determine exactly and its value from place to place cannot
be estimated without field tests.
By far the most permeable unit within the Biscayne aquifer is the
Fort Thompson formation. It is from this formation that most of the
irrigation, industrial, and public supply wells in Dade County draw
water. Wells may be pumped at high rates for extended intervals with
small drawdowns. The character of the rock is such that in many cases
short pieces of surface casing are all that are :required to complete a
well. The remainder of the hole stands open with no danger of caving.
However, in some of the coastal ridge areas and in localities a few
miles inland from the ridge, sand is more prevalent than it is farther
to the west, so that greater lengths of casing are required. Sand occurs
in most places as residual fills in solution cavities, although at the coast
it occurs as beds of variable thickness, depth, and areal extent. The
aquifer grades into a predominantly sandy phase in the Fort Lauderdale
area and contains so much unconsolidated material that wells often must
be cased to the main water horizon, at which depth screens provide the
well finish.
The Biscayne aquifer at Fort Lauderdale, in the vicinity of well
G 221, is composed of the Pamlico sand, Miami oolite, Anastasia forma-
tion, and Tamiami formation. The Tamiami formation is the most im-
portant component. The coefficient of transmissibility of the Biscayne
aquifer there was calculated by Vorhis (1948, p. 20, 21), using the
graphical method of Cooper and Jacob, to be about 1,200,000. The nature
of the test suggests that the value of the coefficient is only tentative but
that the general magnitude of the coefficient is valid. The small


40






REPORT OF INVESTIGATIONS No. 17


coefficient, as compared with coefficients at Miami, reflects the uncon-
solidated character and predominance of sandy material in the Fort
Lauderdale area.
Water levels in many water-table wells in southern Florida respond
to earthquake shocks in a manner similar to that of an artesian well.
The Miami oolite or the sand separating the oolite from the limestone
of the Fort Thompson formation acts as a shallow semiconfining layer.
These layers, where locally present, do not affect normal water-table
conditions within the aquifer. However, they indicate that the com-
ponents of the aquifer have variable hydrologic characteristics. They
cause a difference in water levels immediately after pumping has started
or stopped in two adjacent wells, one ending in the Miami oolite or sand
and one penetrating the deeper Fort Thompson formation.

QUALITY OF THE WATER
The quality of the water, rather than the quantity, which is very
large, is the limiting factor in the use of water from the Biscayne aquifer.
Parker and others (1944, p. 13-22) state that unconfined ground water
in southeastern Florida may be grouped into three general divisions:
(1) the highly mineralized water in the sands that underlie a part of the
Everglades in the area north of the margin of the Biscayne aquifer
(fig. 1), (2) the fresh water from the highly permeable rocks of the
Biscayne aquifer beneath the Everglades and coastal ridge, and (3)
the water that has been contaminated by salt-water encroachment.
The ground water from the uncontaminated part of the aquifer is
fairly uniform in quality, although along the coastal ridge north and
south of Miami it contains somewhat less dissolved minerals and is
slightly softer than elsewhere. The hardness generally ranges from
200 to 300 ppm, averaging 250 ppm. The chloride concentration normally
ranges from about 20 to 30 ppm. Nearly all the ground water is colored
with either organic material or iron, or both. As rainfall percolates down
to the water table, it carries small amounts of minerals dissolved from
the surface organic soils. Usually the water obtained from the upper
portion of the aquifer is the most highly colored, the color decreasing
with depth.
One of the most troublesome mineral constituents in water from the
Biscayne aquifer is iron. Generally most of the iron can be removed
by aeration and settling or filtration, but when not removed it stains
clothing and fixtures, and the water has an objectionable taste. There
is no apparent consistency in the amount of iron present in the ground






FLORIDA GEOLOGICAL SURVEY


water, and predictions cannot be made as to the localities and depths
at which water will have a high content of dissolved iron. Analyses of
water from wells only a few hundred feet apart, and penetrating the
aquifer to the same depth, may show large differences in iron content.

SALT-WATER CONTAMINATION
Salt-water encroachment along the coastal area in Broward County
is not yet a critical problem except in the vicinity of certain canals.
The high water levels in the northern part of the coastal area have
prevented intrusion of salt water from the ocean into the aquifer. Wells
drilled to depths of 200 feet at Pompano, three miles inland, show no
indication of salt-water encroachment.
In the southern part of Broward County, in the vicinity of Hollywood
and Dania, salt water has not yet encroached as far inland as U. S. High-
way 1, which is about 1.5 miles from the ocean. The water levels in that
area are apparently lower than in the Pompano area, averaging about 2.0
feet above sea level near well F 291. Because of the greater thickness
of the aquifer there, an average fresh-water head of 4 to 5 feet above
sea level is theoretically required to prevent the intrusion of salt water
into the lower part of the aquifer. However, the salt front does not
appear to be moving inland at present; therefore, the actual position
of equilibrium between salt water and fresh water in the aquifer may be
east of the theoretical position. It may be that, if no detrimental change
in the present water-table conditions occurs, the salt front in that area
will not progress any farther inland.
Salt-water encroachment in the Fort Lauderdale area may have
progressed inland about two miles in the vicinity of the North New River
and South New River canals; however, in most of that area it is believed
to have progressed only a mile or so from the shore.
Salt-water contamination due to direct encroachment from the ocean
certainly has not advanced as far as the Fort Lauderdale well field,
which is six miles inland. However, Vorhis (1948) indicates that the well
field is underlain at a depth of 200 feet by salty connate (or residual)
water. He points out also that chloride encroachment into the aquifer
underlying the well field can be from any of four sources: (1) the ocean,
(2) salt-water tongues along the canals extending from the ocean,
(3) brackish water, residual from Pleistocene encroachment seeping into
the canals from parts of the Fort Thompson formation in the Everglades,
and (4) the salty connate or residual water underlying the well field at
depth. The most serious threat of well-field contamination is from the


42






REPORT OF INVESTIGATIONS No. 17


Discharge from the Biscayne aquifer occurs by ground-water flow into
the canals, the Atlantic Ocean, or Biscayne Bay, by evapotranspiration,
and by pumping.
Of the 60 inches of average annual rainfall in the coastal ridge
area of Dade County, Parker (1951, p. 825) estimates that 22 inches is
discharged by evapotranspiration and surface runoff without reaching
the water table and 38 inches reaches the water table. Of this, 20 inches
is discharged as ground-water flow, and 18 inches is discharged by
evapotranspiration of ground water and by pumping from wells. It is
estimated that, as of 1950, approximately 4 inches gross was discharged
by wells. In areas where heavy pumping forms significant cones of de-
pression, ground water is salvaged because of the decreased evapo-
transpiration resulting from the lowered water levels.
Ground water is utilized for municipal, industrial, domestic, and
irrigation supplies. The estimated pumpage in Dade County, in 1945
and 1950 in gallons per day, is as follows:
1945 1950
Municipal supplies 35,000,000 65,000,000
Industrial use 12,000,000 20,000,000
Rural use and irrigation 11,000,000 15,000,000

Total average daily pumpage 58,000,000 100,000,000
These estimates do not include the amounts from wells used for air-
conditioning and then returned to the ground. In 1954 about 28 mgd was
being pumped in this way, although an unknown part of this was saline
water. One new hotel under construction in the Miami Beach area will
pump 4 mgd of saline water from the ground for air-conditioning and
will discharge it into the ocean.
In Broward County sufficient data are not available to estimate the
total ground-water withdrawal, but the municipal supplies in the county
delivered about 4 billion gallons (11 mgd) in 1951. Percentagewise, the
industrial and agricultural uses are about the same as in Dade County;
however, a smaller percentage of the people obtain their domestic water
from municipal supplies. The total withdrawal probably was not in
excess of 80 mgd.

HYDROLOGIC CHARACTERISTICS
OF THE BISCAYNE AQUIFER
Ground water is stored in joints, pore spaces, and solution cavities
in the rock. In the Biscayne aquifer the major portion of the ground
,water is stored in cavities formed by the dissolving action of percolating


87






REPORT OF INVESTIGATIONS No. 17


North New River Canal. When the salt-water tongue extends up the
canal during low-water stages, lateral movement of salt water from the
canal into the aquifer can occur.
Although salt-water encroachment is important in Broward County,
it is of greater importance in Dade County. The physical and theoretical
aspects of encroachment in Dade County have been studied in detail
continuously since 1939.
The encroachment of salt water into the aquifer in Dade County
has been described in detail by Brown and Parker (1945) and Parker
(1945). Parker (1951, p. 826, 827) states that in the Miami area "The
canals have effectively induced encroachment by two chief means:
"1. They have served to drain off fresh water stored in. the aquifer
in the coastal zone.
"2. They have acted during certain dry periods as inland extensions
of the sea, carrying salty water inland for several miles and allowing
it to leak out to contaminate the aquifer all along their course.
"Lowering the water table nearly to sea level under the coastal
ridge has caused a loss in head in some places of approximately 5 ft.
compared with the original head before drainage began. Not only is
this a-large actual loss of fresh water in storage, but it is the factor that
led to the inland movement of a salt water wedge from Biscayne Bay,
operating in accordance with the Ghyben-Herzberg principle.
"The five maps in Fig. 5 [extended through 1953 in fig. 17 of this
report] show the general pattern of encroachment into the Biscayne
aquifer in the Miami area for a period of 47 years. They show that the
major spread of the salt water wedge occurred between 1943 and 1946.
During that time, a lengthy drought occurred, and in 1945, water levels
fell to all time lows in this area. Parker [1945, p. 526] reckoned, on the
basis of studies in the Silver Bluff area, that the rate of encroachment
until 1943 had been approximately 235 ft. per year. In a 27-month period
that overlapped 1943-44, the front of the salt wedge advanced 2,000 ft.,
or at a rate of approximately 890 ft. a year."
Dams were placed in the Miami, Biscayne, and Little River canals,
with the result that there was an actual seaward retreat of the salt-water
tongue from 1946 to 1951. Dams were placed also in the Tamiami Canal
and Coral Gables Canal, but they were so far inland that they had little,
if any, effect in opposing the salt-water encroachment; salt-water con-
tamination continues to spread in those two areas. Figures 19 through
24 show profiles along the canals, indicating the relative positions of the






FLORIDA GEOLOGICAL SURVEY


Figure 17. Map showing progressive salt-water encroachment in the Miami area
from 1904 through 1953. (Note: stippling shows extent of areas that have chloride
concentration approximating 1,000 ppm or more, at the base of the aquifer.)






REPORT OF INVESTIGATIONS No. 17


salt-water front (defined as the point where the water contains 1,000
ppm of chloride) in 1946 and 1950, based upon the interpolation of
chloride analysis of wells at varying distances from the canals. Figure 18
is an index map showing the location of the profiles.
The dams, where placed in effective positions, have largely prevented
the inland intrusion of salt water up the canals during the dry seasons
and have raised the fresh-water head in the aquifer to some degree. The
wedge of salt water in the intercanal area is in the same relative position
as in 1946 (fig. 17), probably as a result of the water-control program
and increased rainfall since 1947 which have maintained the average
water levels in those areas at higher stages than in 1946.

The depth of the base of the aquifer is shown in figure 2. In the
areas in Dade County where salt-water encroachment is a threat, the base
of the aquifer is about 100 feet below sea level. Relatively impermeable
materials floor the aquifer, thus making only lateral encroachment pos-
sible. Under strict application of the Ghyben-Herzberg principle, a
2.5-foot head of fresh water above bay level or 3.0-feet above mean sea
level is required to hold salt water out completely; however, modifying
factors make the required fresh-water head somewhat less. The progres-
sive ,reduction in the depth to the bottom of the aquifer westward from
the bay means that progressively less fresh-water head is needed inland.

ADEQUACY OF SUPPLY
The area underlain by the aquifer, excluding the part that now
contains salt water, is about 3,000 square miles. The average water-
saturated thickness in that area is about 72 feet. There is about 9,000
billion gallons of fresh water stored in the aquifer, if the average
storage coefficient is assumed to be 0.2. At a low-water stage, such as
that in 1945, the storage is reduced by only about 5 to 7 percent.
Although the storage is large and there is a large area where water
supplies could be located, the economics related to transmission make
it most desirable that the supplies be located as close as possible to the
area of use. Therefore, most of the present and future pumping will
be on and closely adjacent to the coastal ridge, an area of about 700
square miles.

In considering the potential of the aquifer in the eastern parts of
Dade and Broward counties, flow of ground water into the coastal area
from the Everglades must be considered. There is a lack of information,
however, concerning the direction of movement in much of the area of the
Everglades. In the coastal ridge and part of the adjacent Everglades,


45






FLORIDA GEOLOGICAL SURVEY


water, and predictions cannot be made as to the localities and depths
at which water will have a high content of dissolved iron. Analyses of
water from wells only a few hundred feet apart, and penetrating the
aquifer to the same depth, may show large differences in iron content.

SALT-WATER CONTAMINATION
Salt-water encroachment along the coastal area in Broward County
is not yet a critical problem except in the vicinity of certain canals.
The high water levels in the northern part of the coastal area have
prevented intrusion of salt water from the ocean into the aquifer. Wells
drilled to depths of 200 feet at Pompano, three miles inland, show no
indication of salt-water encroachment.
In the southern part of Broward County, in the vicinity of Hollywood
and Dania, salt water has not yet encroached as far inland as U. S. High-
way 1, which is about 1.5 miles from the ocean. The water levels in that
area are apparently lower than in the Pompano area, averaging about 2.0
feet above sea level near well F 291. Because of the greater thickness
of the aquifer there, an average fresh-water head of 4 to 5 feet above
sea level is theoretically required to prevent the intrusion of salt water
into the lower part of the aquifer. However, the salt front does not
appear to be moving inland at present; therefore, the actual position
of equilibrium between salt water and fresh water in the aquifer may be
east of the theoretical position. It may be that, if no detrimental change
in the present water-table conditions occurs, the salt front in that area
will not progress any farther inland.
Salt-water encroachment in the Fort Lauderdale area may have
progressed inland about two miles in the vicinity of the North New River
and South New River canals; however, in most of that area it is believed
to have progressed only a mile or so from the shore.
Salt-water contamination due to direct encroachment from the ocean
certainly has not advanced as far as the Fort Lauderdale well field,
which is six miles inland. However, Vorhis (1948) indicates that the well
field is underlain at a depth of 200 feet by salty connate (or residual)
water. He points out also that chloride encroachment into the aquifer
underlying the well field can be from any of four sources: (1) the ocean,
(2) salt-water tongues along the canals extending from the ocean,
(3) brackish water, residual from Pleistocene encroachment seeping into
the canals from parts of the Fort Thompson formation in the Everglades,
and (4) the salty connate or residual water underlying the well field at
depth. The most serious threat of well-field contamination is from the


42






FLORIDA GEOLOGICAL SURVEY


\


SCALE IN MILES
0 I 2 3


Figure 18. Map showing location of chloride profiles of figures 19 through 24.


LITTLE


46






REPORT OF INVESTIGATIONS No. 17


o o


o 0


DEPTH, IN FEET BELOW M.S.L,


CANAL SPUR
NO. 4


CONTROL DAM


W. DIXIE HWY.


N.E. 6TH AVE.


F.E.C. RY.


U S. HWY.
NO. I


BISCAYNE
BAY


Figure 19. Profile of the 1,000 ppm isochlor along the Biscayne Canal
in 1946 and 1950.


(I


o 0


o N .
o 0 .


~Cs


, ,/






REPORT OF INVESTIGATIONS No. 17


salt-water front (defined as the point where the water contains 1,000
ppm of chloride) in 1946 and 1950, based upon the interpolation of
chloride analysis of wells at varying distances from the canals. Figure 18
is an index map showing the location of the profiles.
The dams, where placed in effective positions, have largely prevented
the inland intrusion of salt water up the canals during the dry seasons
and have raised the fresh-water head in the aquifer to some degree. The
wedge of salt water in the intercanal area is in the same relative position
as in 1946 (fig. 17), probably as a result of the water-control program
and increased rainfall since 1947 which have maintained the average
water levels in those areas at higher stages than in 1946.

The depth of the base of the aquifer is shown in figure 2. In the
areas in Dade County where salt-water encroachment is a threat, the base
of the aquifer is about 100 feet below sea level. Relatively impermeable
materials floor the aquifer, thus making only lateral encroachment pos-
sible. Under strict application of the Ghyben-Herzberg principle, a
2.5-foot head of fresh water above bay level or 3.0-feet above mean sea
level is required to hold salt water out completely; however, modifying
factors make the required fresh-water head somewhat less. The progres-
sive ,reduction in the depth to the bottom of the aquifer westward from
the bay means that progressively less fresh-water head is needed inland.

ADEQUACY OF SUPPLY
The area underlain by the aquifer, excluding the part that now
contains salt water, is about 3,000 square miles. The average water-
saturated thickness in that area is about 72 feet. There is about 9,000
billion gallons of fresh water stored in the aquifer, if the average
storage coefficient is assumed to be 0.2. At a low-water stage, such as
that in 1945, the storage is reduced by only about 5 to 7 percent.
Although the storage is large and there is a large area where water
supplies could be located, the economics related to transmission make
it most desirable that the supplies be located as close as possible to the
area of use. Therefore, most of the present and future pumping will
be on and closely adjacent to the coastal ridge, an area of about 700
square miles.

In considering the potential of the aquifer in the eastern parts of
Dade and Broward counties, flow of ground water into the coastal area
from the Everglades must be considered. There is a lack of information,
however, concerning the direction of movement in much of the area of the
Everglades. In the coastal ridge and part of the adjacent Everglades,


45






FLORIDA GEOLOGICAL SURVEY
N IaIII


N.W. 95TH ST.


N.W. 7TH AVE.









N. MIAMI AVE.


N.E. 2ND AVE.



F.E.C. RY.







BISCAYNE
BOULEVARD


-N
0t


Figure 20. Profile of the


1,000 ppm isochlor a
in 1946 and 1950.


Long the Little River Canal


oEPrH, t# PErer


I
BELOW


I:


N


/


II


BISCAYNE
BAY


- ---







REPORT OF INVESTIGATIONS No. 17


0 0
DEPTH, IN FEET


N.W. 36TH
STREET



















TAMIAMI
CANAL


N.W. 27TH
AVENUE


N3
0


I I I I


Figure 21. Profile of the


IN.W.


ITTH AVE.


1,000 ppm isochlor along the Miami Canal
in 1946 and 1950.


0
BELOW


N-T
0~


L


I


---


49






FLORIDA GEOLOGICAL SURVEY


DEPTH, IN FEEr


I
0,
BELOW


0
Mz. S.


\0


I
0


RED ROAD


SOUTH FORK
TAMIAMI CANAL


LE JEUNE RD.





DOUGLAS RD.








MIAMI
CANAL


N.W. 27TH
AVENUE


I


Figure 22. Profile of the 1,000 ppm isochlor algng the Tamjnami Canal
in 1946 and 1950.


50






REPORT OF INVESTIGATIONS No. 17
I I I
o o o o
0 0 0 ET BELOW M.S.L
DEPTH, IN FEET BELOW M.S.L. r


\


S0


M..


RED ROAD


DOUGLAS RD.


N.W. 27TH
AVENUE


MIAMI CANAL


, Figure 23. Profile of the 1,000 ppm isochlor along the South Fork of the
Tamiami Canal in 1946 and 1950.


I I -


I I I


6 \ \


\\






FLORIDA GEOLOGICAL SURVEY


o 0 0 0
oEPrH, IN FEET BELOW M.S.L.


RED ROAD


BIRD ROAD


BLUE ROAD


F. E.C. RY.

MILLER RD.


HARDEE RD.


LE JEUNE RD.


8 BISCAYNE
I I I I I I IB Y


Figure 24. Profile of the 1,000 ppm isochlor along the
in 1946 and 1950.


Coral Gables Canal


6


N


21 I


!





REPORT OF INVESTIGATIONS No. 17


an area which composes about one-third of the extent of the aquifer, the
ground-water flow is to the east and southeast during most of the year.
In the remainder of the Everglades ground water presumably flows to the
south, and, under the conditions that were prevalent in 1950, this flow
was not a direct source of water for the coastal ridge. However, flood
control structures and the establishment of proposed conservation areas
in the western two-thirds of the area may make large additional quantities
of water available for recharge, thus changing the water-table gradient
and increasing ground-water flow from the Everglades toward the coast.
An estimate of the ground-water potential of the aquifer requires an
inventory of the recharge that would include rainfall, the inflow from
Palm Beach County to the conservation areas, and the recharge from
drainage wells, septic tanks, and irrigation; and the discharge, consisting
of evapotranspiration, ground-water outflow to the ocean directly from
the aquifer and from the canals, and losses due to pumping. The lack of
detailed data, particularly canal discharge data, makes a complete water
inventory impossible at this time. Rainfall over the 8,000 square miles
ranges from about 54 to 64 inches, averaging 60 inches. Computations
for the coastal ridge area indicate that about one-third of this rainfall, or
about 1,000 billion gallons a year, is eventually discharged from the
aquifer by ground-water flow. The total amount of this annual water
might be pumped if the aquifer were not bound by salt water on the
eastern and southern sides.
The lowering of water levels due to pumping in an area salvages some
of the water that might otherwise be lost by evapotranspiration. The
southwest well field (fig. 3) of the city of Miami, as planned, will
eventually withdraw 100 mgd. It is estimated by Parker and others (1955,
p. 287) that 15 mgd may be salvaged from reduced evapotranspiration.
The estimated pumpage of 100 mgd in Dade County is about 20
percent of the estimated ground-water discharge into the ocean and
canals. At present a large part of the use is not consumptive and the
water recharges the aquifer through irrigation, septic tank drains, and
drainage wells. Enlargement of the sewer system for the city of Miami,
and the construction of similar but smaller systems in other municipalities,
will diminish this type of recharge. It appears likely that, under the
present system of canal control, additional wells so located as to leave
a buffer strip (an area in which water levels are not affected by pumping)
between them and the ocean could withdraw 10 times the amount of
water pumped in 1950 without causing salt-water encroachment. It is
estimated that at least 2 billion gpd could be pumped from areas west of
,the coastal ridge, if the ridge were used as a buffer zone. These estimates


53





FLORIDA GEOLOGICAL SURVEY


are based partly on the fact that more water would be available because
of reduced evapotranspiration when the water table is lowered, and that
more of the aquifer would be available for storage of rainwater that is
normally rejected when the aquifer is full or nearly full, and on the
possibility of recharge in the flood control conservation areas by water
diverted from Palm Beach County. These factors increase the amount
of water computed as available for withdrawal.
A large supply of ground water is available in the part of the aquifer
lying west of the salt-water front in Dade County and west of U. S.
Highway 1 in Broward County. To protect this supply, salt-water en-
croachment must be strictly controlled by maintaining proper placement
of dams or locks in canals, by proper control of water levels in the canals,
and by locating well fields and other centers of large withdrawals so that
pumping will not lower water levels below the minimum stage required
to prevent additional encroachment. Storage in the aquifer should be
continually measured and evaluated, and future development of the
ground-water resources carried out in accordance with the principles
outlined.


54






REPORT OF INVESTIGATIONS No. 17

SELECTED REFERENCES


Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters-1951:
Florida State Board Cons., Div. Water Survey and Research, Paper 6,
November 30, 117 p.
Brown, Eugene (see Black, A. P.)
Brown, R. H.
1945 (and Parker, Garald G.) Salt-water encroachment in limestone at Silver
Bluff, Miami, Florida: Econ. Geology, vol. 40, no. 4, p. 235-262.
Clapp, F. G. (see Matson, G. C., 1909)
Cooke, C. W. (see also Parker, Garald G., 1944)
1929 (and Mossom, Stuart) Geology of Florida: Florida Geol. Survey 20th
Ann. Rept., p. 29-227, 29 pl., geol. map.
1945 Geology of Florida: Florida Geol. Survey Bull. 29, 339 p., 1 pl., 47 fig.,
geol. maps.
Cooper, H. H., Jr. (see Parker, Garald G., 1948)
Hoy, N. D. (see Parker, Garald G., 1948)
1952 (and Schroeder, M. C.) Age of subsurface "Tamiami" formation near
Miami, Florida: Jour. Geology, vol. 60, no. 3, p. 283-286.
Jacob, C. E.
1946 Radial flow in a leaky artesian aquifer: Am. Geophys. Union Trans.,
vol. 27, no. 2, p. 198-208.
Love, S. K. (see Parker, Garald G., 1944, 1955)
Mansfield, W. C.
1939 Notes on the upper Tertiary and Pleistocene mollusks of Peninsular
Florida: Florida Geol. Survey Bull. 18, 75 p., 3 pl., 1 fig.
Matson, G. C.
1909 (and Clapp, F. G.) A preliminary report on the geology of Florida, with
special reference to the stratigraphy: Florida Geol. Survey 2nd Ann. Rept.,
p. 25-173, map.
1913 (and Sanford, Samuel) Geology and ground waters of Florida: U. S.
Geol. Survey Water-Supply Paper 319, 445 p.
Meinzer, 0. E.
1923 The occurrence of ground water in the United States, with a discussion
of principles: U. S. Geol. Survey Water-Supply Paper 489, 321 p.
Mossom, Stuart (see Cooke, C. W., 1929)
Parker, Garald G. (see also Brown, R. H., 1945)
1942 Notes on the geology and ground water of the Everglades in southern
Florida: Soil Sci. Soc. Florida. Proc., vol. 4A, p. 47-76.
1944 (and Cooke, C. W.) Late Cenozoic geology of southern Florida, with a
discussion of the ground water: Florida Geol. Survey Bull. 27, 119 p.
(Ferguson, G. E., and Love, S. K.) Interim report of water-resources
investigation in southeastern Florida, with special reference to the Miami
area in Dade County: Florida Geol. Survey Rept. Inv. 4, 39 p., 9 pl.
1945 Salt water encroachment in southern Florida: Am. Water Works Assoc.
Jour., vol. 37, no. 6, p. 526-542.
1948 (Cooper, H. H., Jr., and Hoy, N. D.) Water levels and artesian pressure
in observation wells in the United States in 1945, Pt. 2, Southeastern
. States: U. S. Geol. Survey Water-Supply Paper 1024, p. 11-81.





FLORIDA GEOLOGICAL SURVEY


1950 (and Stringfield, V. T.) Effects of earthquakes, trains, tides, winds, and
atmospheric pressure changes on water in geologic formations of south-
ern Florida: Econ. Geology, vol. 45, no. 5, p. 441-460.
1951 Geologic and hydrologic factors in the perennial yield of the Biscayne
aquifer: Am. Water Works Assoc. Jour., vol. 43, p. 817-834.
1955 (Ferguson, G. E., Love, S. K., and others) Water resources of south-
eastern Florida, with special reference to the geology and ground water
of the Miami area: U. S. Geol. Survey Water-Supply Paper 1255, 965 p.
Sanford, Samuel (see Matson, G. C., 1913)
1909 The topography and geology of southern Florida: Florida Geol. Survey
2nd Ann. Rept., p. 175-231.
Schroeder, M. C. (see Hoy, N. D.)
Sellard, E. H.
1912 The soils and other surface residual materials of Florida, their origin,
character, and the formations from which derived: Florida Geol. Survey
4th Ann. Rept., p. 1-79.
1919 Geologic section across the Everglades of Florida: Florida Geol. Survey
12th Ann. Rept., p. 67-76.
Stringfield, V. T. (see Parker, Garald G., 1950)
Theis, C. V.
1935 The relation between the lowering of the piezometric surface and the
rate and duration of discharge of a well using ground-water storage:
Am. Geophys. Union Trans., vol. 16, p. 519-524.
Vorhis, R. C.
1948 Geology and ground water of the Fort Lauderdale area, Florida: Florida
Geol. Survey Rept. Inv. 6, 32 p.


56










FLRD GEOLIOWC( ICA SURflViEWY~


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