U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5029

Prepared in cooperation with Broward County, Florida

Hydrogeologic Framework and Salinity Distribution of the 

Floridan Aquifer System of Broward County, Florida
Cover. Aerial view of well drilling operations for G-2984, adjacent to the Hillsboro Canal in northern Broward County, 

Florida. Photo provided by Broward County Natural Resources Planning and Management Division.
Hydrogeologic Framework and Salinity 

Distribution of the Floridan Aquifer System 

of Broward County, Florida

By Ronald S. Reese and Kevin J. Cunningham

Prepared in cooperation with Broward County, Florida

Scientific Investigations Report 2014–5029

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Reese, R.S., and Cunningham, Kevin, 2014, Hydrogeologic framework and salinity distribution of the Floridan 

aquifer system of Broward County, Florida: U.S. Geological Survey Scientific Investigations Report 2014–5029, 60 p., 

http://dx.doi.org/10.3133/sir20145029.

ISSN 2328-0328 (online)
Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Hydrogeologic Setting .........................................................................................................................3

Previous Investigations........................................................................................................................4

Methods of Investigation..............................................................................................................................5

Collection and Compilation of Well Data ..........................................................................................5

Delineation of Lithostratigraphic, Sequence-Stratigraphic, and 

Hydrogeologic Frameworks .................................................................................................6

Marine Seismic Acquisition, Processing, and Interpretation .......................................................7

Stratigraphic Framework..............................................................................................................................7

Geologic Units and Lithology ..............................................................................................................7

Stratigraphic Markers..........................................................................................................................8

Structure and Thickness of Lithostratigraphic Units....................................................................17

Sequence-Stratigraphic Analysis....................................................................................................20

Sequence Stratigraphy at Test Corehole G-2984..................................................................22

Upper-Middle to Upper Avon Park Formation..............................................................22

Lower Arcadia Formation................................................................................................24

Correlation of Sequences Within the Study Area ................................................................24

Seismic Stratigraphy and Structure ................................................................................................25

Hydrogeologic Framework.........................................................................................................................28

Upper Floridan Aquifer.......................................................................................................................29

Middle Semiconfining Unit 1.............................................................................................................34

Avon Park Permeable Zone...............................................................................................................34

Middle Semiconfining Unit 2.............................................................................................................34

Uppermost Permeable Zone of the Lower Floridan Aquifer........................................................34

Conceptualization of Groundwater Flow Within the Floridan Aquifer System.........................38

Distribution of Salinity in the Upper Part of the Floridan Aquifer System..........................................45

Summary and Conclusions.........................................................................................................................48

References Cited .........................................................................................................................................53

Appendix 1.....................................................................................................................................................57

Plates

[Available for download at http://dx.doi.org/10.3133/sir20145029]

1. Stratrigraphic and hydrogeologic section A–A’ ................................................................. link

2. Stratigraphic and hydrogeologic section C–C’................................................................... link

3. Stratigraphic and hydrogeologic section Z–Z’ ................................................................... link
iv

Figures

1. Map showing location of the study area in southeastern Florida, wells used 

in the study, and lines of hydrogeologic sections...................................................................2

2. Chart showing lithostratigraphic units in the study area, generalized lithology, 

and correlation to hydrogeologic units.....................................................................................4

3. Explanation for figures 4 through 8, 14, 25 and 29.................................................................10

4. Borehole geophysical logs and lithologic data collected for well PB-1775 

at site 16 .......................................................................................................................................12

5. Borehole geophysical logs and lithologic data collected for well G-2938 at site 6.........13

6. Borehole geophysical logs and lithologic data collected for well CS-I2 at site 5 ...........14

7. Borehole geophysical logs and lithologic data collected for well G-2945 at 

site 23............................................................................................................................................15

8. Borehole geophysical logs, lithologic data, and depositional cycles and 

sequences for test corehole G-2984 at site 18.......................................................................16

9. Map showing altitude of the upper contact surface of the Avon Park Formation ..........18

10. Map showing thickness of the upper Avon Park Formation ...............................................19

11. Map showing thickness of the lower Arcadia Formation....................................................21

12. Uninterpreted seismic-reflection profile acquired along the Hillsboro Canal 

and locations of wells PB-1766, PB-1775, and G-2984 projected onto the profile...........26

13. Seismic-reflection profile displayed in figure 12 showing interpreted

lithostratigraphic and sequence-stratigraphic boundaries, hydrostratigraphy,

and seven seismic-sag structures...........................................................................................27

14. Borehole geophysical data including fluid properties and flowmeter logs, 

lithology, hydrogeologic units, and flow zones for test corehole G-2984..........................30

15. Map showing altitude of the upper surface of the Upper Floridan aquifer......................31

16. Map showing thickness of the Upper Floridan aquifer........................................................32

17. Map showing distribution of transmissivity in the Upper Floridan aquifer.......................33

18. Map showing altitude of the upper boundary of the Avon Park permeable zone...........35

19. Map showing thickness of the Avon Park permeable zone................................................36

20. Map showing distribution of transmissivity of the Avon Park permeable zone...............37

21. Borehole geophysical log data for test corehole G-2984, from 955 to 968 ft bls,

including optical and acoustic images, flowmeter and fluid properties, flow

zones, and relation to high frequency depositional cycles .................................................39

22. Borehole geophysical log data for test corehole G-2984, from 1,102 to 1,115 ft bls,

including optical and acoustic images, flowmeter and fluid properties, flow

zones, and relation to high frequency depositional cycles .................................................40

23. Photographs showing microscopic images of G-2984 at 1,109.45 ft bls............................41

24. Borehole geophysical log data for test corehole G-2984, from 1,165 to 1,178 ft bls,

including optical and acoustic image, flowmeter and fluid properties, flow

zones, and relation to high frequency depositional cycles .................................................42

25. Borehole geophysical log data, including fluid properties and flowmeter log 

data, lithology, hydrogeologic units, and flow zones, for monitoring well G-2940 

at site 6, from 900 to 1,220 ft bls................................................................................................43

26. Borehole geophysical log data for well G-2940, from 1,024 to 1,038 ft bls, 

including optical image, flowmeter and fluid properties, and flow zones ........................44

27. Map showing distribution of salinity as dissolved-solids concentration in the

Upper Floridan aquifer...............................................................................................................46
v

28. Map showing distribution of salinity as dissolved-solids concentration in the 

Avon Park permeable zone .......................................................................................................47

29. Water-quality data, resistivity geophysical log data, salinity zones, and

lithostratigraphic and hydrogeologic units for wells at site 5.............................................49

30. Map showing greatest depth of groundwater with dissolved solids concentration

of less than or equal to 10,000 mg/l..........................................................................................50

31. Schematic diagram showing perched zone of elevated salinity in the Upper

Floridan aquifer in the west central part of the study area.................................................51

32. Graph showing relation between transmissivity and salinity in the Upper 

Floridan aquifer...........................................................................................................................51

Tables

1. Lithostratigraphic and geophysical-log units identified or defined in the study ...............9

2. Nomenclature of stratigraphic cycle hierarchies and order of cyclicity..........................20

3. Avon Park Formation lithofacies in well G-2984. ...................................................................23

4. Horizontal hydraulic conductivity values for major permeable zones and

semiconfining units based on data from aquifer and packer tests in the 

study area ....................................................................................................................................34

Appendix Tables

[Appendix tables 1–1 to 1–8 available for download at http://dx.doi.org/10.3133/sir20145029 in 

MS Excel format]

1–1. Well identifiers, locations, and construction information for all wells 

used in the study...................................................................................................................... link

1–2. Sources for well data compiled for this study.................................................................... link

1–3. Types of data compiled for wells used in study.................................................................. link

1–4. Stratigraphic boundaries identified from well data in the study area. ........................... link

1–5. Hydrogeologic boundaries identified from well data in the study area ......................... link

1–6. Hydraulic well tests descriptions and results..................................................................... link

1–7. Water-quality data collected from the Floridan aquifer system...................................... link

1–8. Salinity boundary depths determined in this study............................................................ link
vi

Conversion Factors

Inch/Pound to SI and cubic feet to gallons

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

cubic foot (ft3) 7.479 gallons (gal)

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

Hydraulic conductivity

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per day (ft/d) 0.3048 meter per day (m/d)

foot per day (ft/d) 7.479 gallon per day per feet squared (gal/d/ft2)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d) 

foot squared per day (ft2/d) 7.479 gallon per day per foot (gal/d/ft)

Leakance

foot per day per foot [(ft/d)/ft] 1 meter per day per meter

foot per day per foot [(ft/d)/ft] 7.479 gallon per day per cubic foot (gal/d/ft3)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27) 

or North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L) 
Abbreviations

bls below land surface

ABI acoustic borehole image (log)

AIV average interval velocity

ASR aquifer storage and recovery

DGPS differential global positioning system

GR gamma-ray

GWSI Groundwater Site Inventory (database)

HFC high-frequency cycle

kHz kilohertz

LFA Lower Floridan aquifer

μsec/ft microsecond per foot

MAP middle Avon Park

OBI optical borehole image (log)

ohm-m ohm-meter

RASA Regional Aquifer System Analysis

SFWMD South Florida Water Management District

Δt sonic borehole geophysical log interval transit time, 

in microseconds per foot

USDW underground source of drinking water

USGS U.S. Geological Survey

vii

Abstract

Concerns about water-level decline and seawater 

intrusion in the surficial Biscayne aquifer, currently the 

principal source of water supply to Broward County, prompted 

a study to refine the hydrogeologic framework of the underlying Floridan aquifer system to evaluate its potential as an 

alternative source of supply. This report presents cross sections 

that illustrate the stratigraphy and hydrogeology in eastern 

Broward County; maps of the upper surfaces and thicknesses 

of several geologic formations or units within the Floridan 

aquifer system; and maps of two of the potentially productive 

water-bearing zones within the system, the Upper Floridan 

aquifer and the Avon Park permeable zone.

An analysis of data on rock depositional textures, 

associated pore networks, and flow zones in the Floridan 

aquifer system shows that groundwater moves through the 

system in two ways. These data support a conceptual, dualporosity model of the system wherein groundwater moves 

either as concentrated flow in discrete, thin bedding-plane 

vugs or zones of vuggy megaporosity, or as diffuse flow 

through rocks with primarily interparticle and moldic-particle 

porosity. Because considerable exchange of groundwater 

may occur between the zones of vuggy and matrix-dominated 

porosity, understanding the distribution of that porosity and 

flow zone types is important to evaluating the suitability of the 

several units within the Floridan aquifer system for managing 

the water through practices such as aquifer storage and 

recovery (ASR). 

The salinity of the water in the Floridan aquifer system is 

highest in the central part of the study area, and lower toward 

the north and south. Although salinity generally increases with 

depth, in the western part of the study area a zone of relatively 

high saline water is perched above water of lower salinity in 

the underlying Avon Park permeable zone. Overall, the areas 

of highest salinity in the aquifer system coincide with those 

with the lowest estimated transmissivity, so that the occurrence 

of perched saline water in the system may be the consequence 

of incompletely flushed connate water or intruded seawater. 

A seismic reflection profile along the Hillsboro Canal, at 

the northern edge of the study area, shows seven seismic-sag 

structures that are interpreted as downward deformation of 

overlying strata into collapsed deep cave systems. These 

structures may compromise the integrity of the confinement 

created by the underlying strata by allowing upconing of 

saline water from depth, which has implications for successful 

application of ASR and use of the Floridan aquifer system as 

an alternative water supply.

Introduction

The Biscayne aquifer is shallow and prolific, and has 

provided most of the water supply in eastern Broward County, 

Florida (fig. 1), during the last century. Concerns about 

water-level declines and saltwater intrusion in the Biscayne 

aquifer have prompted limits on municipal withdrawals and 

on new water-supply well-field permits. Consequently, the 

county is examining the potential for the use of the Floridan 

aquifer system as an alternative water supply, either directly, 

by pumping and treating water from wells completed in the 

aquifers, or indirectly, by aquifer storage and recovery (ASR).

The Floridan aquifer system has not been used 

historically for water supply in southeastern Florida because of 

elevated groundwater salinity (Sprinkle, 1989). Brackish water 

in the aquifer system may be treated for public supply by using 

reverse-osmosis desalination technologies, or by mixing it 

with freshwater from the surficial aquifer system. Knowledge 

of the distribution of salinity and hydraulic properties within 

the aquifer system, such as hydraulic conductivity and degree 

of confinement, may improve the predictability of finding an 

alternative water supply with low salinity and high yield. 

Aquifer storage and recovery has been implemented 

in the Floridan aquifer system for water-supply storage in 

Broward County and other counties in southeastern Florida 

with varying degrees of success (Reese and AlvarezZarikian, 2007). The objective of ASR is to increase available 

Hydrogeologic Framework and Salinity Distribution of the 

Floridan Aquifer System of Broward County, Florida

By Ronald S. Reese and Kevin J. Cunningham
2 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian -83 ̊00’

EXPLANATION

G-2989

G-2916

2

Hillsboro Canal marine 

 seismic profile tract

Hydrogeologic section 

 line—For this study

Hydrogeologic section 

 line (or part thereof)—

 From Reese and 

 Richardson, 2008

Well location and—

 Site number 

 Well number

 Well number for well 

 on section 

A Aʹ

Y Yʹ

Study

area

F l o r i d

a

Z

Zʹ

Aʹ

Cʹ

A

C

D

Dʹ

E

Eʹ

Y

Yʹ

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

5 MILES

17 16

18

8

9

2

28

21

5

33

6

10

27

30

31

32

25

26 14 13

7

12

11

19

29

20

15

23

24 22

4

1

3

G-2970

G-2978

G-2979

G-2982

G-2983

G-2942

G-2943

D-365

G-2887

G-2968

G-2969

S-567

CS-I1

CS-I2

CS-M2

SUN-I3

SUN-M1

SUN-M1A

SUN-M2

SUN-M3

G-2980

PLT-I1

PLT-I2

PLT-M1

PBP-I1

PBP-I2

PBP-M1

G-2944

G-2945

G-2946

G-2989

G-2961

G-2962

G-2975

G-2917

G-2918 G-2914

G-2292

MAR-I2

MAR-M2

G-2889

G-2916

FTL-I1

FTL-I3

FTL-I4

FTL-M1

FTL-M2

G-2938

G-2939

G-2940

BCN-I1

BCN-I2

BCN-I3

BCN-I4

BCN-I5

BCN-I6

BCN-M2

BCN-M3

BCN-M4

PB-1775

PB-1776

PB-1765

PB-1766

PB-1841

G-2981

G-2988

HOL-RO1

G-2966

G-2967

PLT-ROI1

PLT-ROM1

G-2971

G-2972

G-2984

G-2987

G-2986

G-2985

G-2991

G-2963

G-2964

G-2976

G-2973

G-2974

HAL-RO1

75

95

595

1

441

Figure 1. Location of the study area in southeastern Florida, wells used in the study, and lines 

of hydrogeologic sections. Site numbers and names and types of wells are provided in appendix 

table 1–1.
Introduction 3

supply by diverting relatively fresher water to displace 

native, brackish groundwater in the Upper Floridan aquifer 

of the Floridan aquifer system for subsequent recovery. In 

Palm Beach County, the cumulative recovery efficiency 

at the Boynton Beach East Water Treatment Plant, about 

15 miles (mi) north of Broward County, has reached more 

than 60 percent, which is considered a successful level of 

recovery efficiency. In contrast, cycle testing at three ASR 

projects in Broward County has not demonstrated cumulative 

recovery efficiencies greater than about 30 percent as of the 

end of 2004. The success of ASR is largely dependent on 

(1) the presence of an optimal range in the transmissivity 

of the storage zone and an optimal distribution of hydraulic 

conductivity of the aquifer materials; (2) geologic structure 

that substantially limits or prevents migration of injected 

freshwater away from an ASR well or storage zone, both 

horizontally and vertically; and (3) low salinity in the aquifer. 

High salinity groundwater (water with a dissolved-solids 

concentration of about 5,000 milligrams per liter [mg/L] or 

greater) in the Floridan aquifer system may adversely affect 

the utility of ASR, because the resulting mix of injected 

water with the brackish-to-saline groundwater may result in 

recovered water that is too saline to be used for public supply. 

The ability to predict the physical properties of an aquifer that 

will be conducive to ASR requires a refined hydrogeologic 

framework; conversely, poor definition of the hydrogeologic 

framework increases the risk for planning and design failures.

A sequence-stratigraphic analysis can be used to refine 

the hydrogeologic framework of the Floridan aquifer system 

and delineate the spatial distribution and hydraulic connectivity of permeable zones. Carbonate sequence stratigraphy 

differs from traditional lithostratigraphy in that unconformities 

or their relative conformities related to relative fall or rise 

in sea level are correlated (Schlager, 2005). Because these 

surfaces are present at the top and bottom of depositional 

cycles and sequences, and are related to widespread physical 

events, they are assumed to have time significance. Correlation 

of these surfaces provides a more accurate method of correlation of rock units between the surfaces than lithostratigraphic 

analyses alone. The recognition of the vertical arrangement of 

lithostratigraphic successions and stratal patterns bounded by 

these surfaces also helps to correlate flow zones and confining 

units, and to estimate the thickness, porosity, and permeability 

of the hydrologic units.

To provide information about the Floridan aquifer system 

that would help water-resource managers evaluate it as an 

alternative water supply, for imminent use with reverseosmosis desalination or blending, and for storage with ASR, 

the U.S. Geological Survey (USGS), in cooperation with 

Broward County, initiated a study to refine the delineation of 

the hydrogeologic framework of the Floridan aquifer system in 

Broward County. As part of this study, a test hole was continuously cored penetrating about 350 feet (ft) of the uppermost 

Floridan aquifer in northeastern Broward County along 

Hillsboro Canal. Data collected from this test corehole were 

interpreted using both a traditional lithostratigraphic approach 

and, over the deeper intervals, a sequence-stratigraphic 

approach, and correlated with existing borehole data across 

the eastern part of the county. Seismic-reflection data 

collected along the Hillsboro Canal were used to illustrate the 

hydrogeologic framework in two dimensions, assist with the 

sequence-stratigraphic analysis, and identify structural features 

that intersect hydrogeologic units and provide potential 

pathways for vertical groundwater movement in the Floridan 

aquifer system. Water-quality data from the test borehole 

provided information about the distribution of salinity in the 

aquifer system. Information in this report can be used by 

water-resource managers to identify areas in eastern Broward 

County that would be favorable for water-supply development 

in the Floridan aquifer system. 

Purpose and Scope

The purpose of this report is to (1) refine the 

hydrogeologic framework of the Floridan aquifer system from 

the lower Avon Park Formation to the upper surface of the 

aquifer system in eastern Broward County, using borehole 

geophysical log data and, where appropriate, integrating 

those data with lithostratigraphic and sequence-stratigraphic 

analyses; (2) evaluate hydraulic properties of major permeable 

units; and (3) characterize salinity distribution of major permeable units. The study area encompasses the developed part of 

Broward County, east of the Everglades, and an adjacent part 

of southeastern Palm Beach County (fig. 1). More specifically, 

the report (1) distinguishes the major permeable zones and 

semiconfining units of part of the Floridan aquifer system, 

and delineates their configuration, thickness, and extent; 

(2) estimates hydraulic properties of these units; (3) describes 

the distribution of salinity within these units; and (4) suggests 

hypotheses to explain the distributions of hydraulic 

properties and salinity.

Borehole geophysical data, lithologic information, 

hydraulic property data, and water-quality data collected in 

other studies and used in this analysis are included herein. 

This report includes three hydrogeologic cross sections 

extending across the county, maps of subsurface altitudes and 

thicknesses of major permeable zones in the Floridan aquifer 

system, maps of transmissivity and salinity of major permeable zones, and a map of the greatest depth of brackish water 

within the Floridan aquifer system. Additionally, this report 

presents data collected from the cored test hole (G–2984) in 

northeastern Broward County, and 14.3 mi of high-resolution, 

multichannel, water-based seismic-reflection data acquired 

along the Hillsboro Canal (fig. 1). 

Hydrogeologic Setting

The Floridan aquifer system is the deepest of three 

principal hydrogeologic units present in the study area, and 

is overlain by the shallow surficial aquifer system, and the 

intermediate confining unit, which separates the system from 
4 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

the surficial aquifer system (fig. 2). The heavily-used Biscayne 

aquifer composes a part of the surficial aquifer system. The 

Floridan aquifer system in South Florida includes a thick 

sequence of highly permeable, carbonate strata of Tertiary 

age, and is part of the Florida Platform (Hine, 2013). The 

Floridan aquifer system has generally been divided into the 

Upper Floridan aquifer, the underlying middle confining 

unit or middle semi-confining units, and the Lower Floridan 

aquifer (LFA) (Miller, 1986). Locally, permeable units have 

been identified within the confining unit between the Upper 

Floridan aquifer and the Lower Floridan aquifer, specifically, 

the Avon Park permeable zone (Reese and Richardson, 2008), 

and below the middle confining unit, the uppermost permeable 

zone of the Lower Floridan aquifer.

Previous Investigations

A comprehensive regional investigation of the Floridan 

aquifer system hydrogeology for Florida and parts of Georgia, 

Alabama and South Carolina was conducted in the 1980s as 

part of the USGS Regional Aquifer System Analysis (RASA) 

Program (USGS Professional Paper 1403 series reports). The 

hydrogeologic framework of the Floridan aquifer system for 

the entire RASA study area was described by Miller (1986). 

The groundwater hydraulics, regional flow, and groundwater 

development of the aquifer system were described for the 

same region by Bush and Johnston (1988), and Meyer (1989) 

described the hydrogeology and delineated groundwater 

movement patterns in southern Florida.

Series Geologic formation or

lithostratigraphic unit Lithology Hydrogeologic unit Approximatethickness, in feet 

Holocene 

to 

Pliocene

Holocene-age undifferentiated

 and 

Pleistocene-age formations1

Quartz sand; silt; clay; shell; 

limestone; sandy shelly limestone

Surficial 

aquifer system

Biscayne aquifer

200–450 

Confining beds

Gray limestone aquifer

Confining unit

Intermediate confining unit 

35–210 

Upper Floridan 

aquifer (UFA)

40–350 

700–1,200 

Lower 

Floridan 

aquifer 

(includes 

permeable zones 

and confining units)

Boulder

Zone 400–650

1,700–2,000

Miocene 

to 

possibly 

Late 

Oligocene

Eocene 

Middle

Paleocene Cedar Keys 

Formation

Dolomite and dolomitic 

limestone

Massive anhydrite beds Sub-Floridan confining unit

Tamiami 

Formation2

Stock Island 

Formation3

Silt; sandy clay; sandy, shelly

limestone; calcareous sandstone; and quartz sand/ planktic

foraminiferal limestone

Hawthorn Group

Peace

River

Formation

Interbedded sand, silt,

gravel, clay, carbonate,

and phosphatic sand

Arcadia Formation

Carbonate mudstone 

to grainstone; claystone; 

shell beds; dolomite; 

phosphatic and quartz 

sand; silt; and clay 

Sandy, molluscan limestone; phosphatic 

quartz sand, sandstone, and limestone

 Floridan aquifer system

Avon Park Formation

Fossiliferous, lime mudstone

to packstone and grainstone; 

dolomitic limestone; and

dolomite; abundant 

cone-shaped benthic 

foraminifera

Oldsmar Formation

500–830

1,200?

Avon Park permeable zone

Early

Middle semiconfining 

unit 2 (MC2)

Upper

Lower 

Upper

LF1 35–310

 Middle 

semiconfining 

unit 1 (MC1)

Lower

Lower

Focus of this study

Upper

Middle

Micritic limestone, dolomitic limestone, 

and dolomite

344–670 

150–500 

EXPLANATION

Uppermost major permeable zone 

 of the Lower Floridan aquifer 

LF1

? ? ? 

1

Pleistocene-age formations in southeastern Florida (Pamlico Sand, Miami Limestone, Anastasia Formation, Fort Thompson Format

2 Tamiami Formation (Pinecrest Sand Member, Ochopee Limestone Member). 3

Stock Island Formation, after Cunningham and others, 1998.

Figure 2. Lithostratigraphic units in the study area, generalized lithology, and correlation to hydrogeologic units. Subdivisions of the 

Arcadia and Avon Park Formations are defined in this study and are informal.
Methods of Investigation 5

More recent hydrogeologic studies of the Floridan 

aquifer system in southeastern Florida include those of the 

hydrogeology and distribution of salinity within the upper 

part of the Floridan aquifer system in Miami-Dade and 

Broward Counties (Reese, 1994), Palm Beach County (Reese 

and Memberg, 2000), and in Martin and St. Lucie Counties 

(Reese, 2004). Reese and Richardson (2008) synthesized 

previous studies on the Floridan aquifer system in central and 

southern Florida and introduced a revised regional hydrogeologic framework, linking hydrogeologic nomenclature and previously mapped hydrogeologic units between central and southern 

Florida and between the western and eastern coastal areas.

Test-well drilling and hydrogeologic investigations of 

the Floridan aquifer system have been conducted by both 

the USGS and South Florida Water Management District 

(SFWMD) in Broward County and southern Palm Beach 

County since the 1980s. Two sites with multiple wells drilled 

by SFWMD are within the current study area (Bennett and 

others, 2001; Lukasiewicz, 2003). The USGS drilled and 

completed a deep well in the Floridan aquifer system in westernmost Broward County and correlated formation boundaries 

with water-bearing zones in the aquifer system (Meyer, 1988). 

Sequence-stratigraphic analyses have been made in 

previous studies on the basis of data collected from test 

coreholes completed in the Floridan aquifer system in southern 

Florida. Cunningham and others (1998) characterized the 

lithostratigraphy and sequence stratigraphy of the Suwannee 

Limestone and Arcadia Formation south of the study area in 

southern Miami-Dade County and in the Florida Keys. Guertin 

and others (2000) subsequently used chronostratigraphic 

methods to determine the duration of major sequence boundaries at the upper boundaries of the Suwannee Limestone 

and Arcadia Formation in southern Florida. Hammes (1992) 

defined the sequence stratigraphy and sedimentology of the 

Suwannee limestone (referred to as Suwannee Formation in 

Hammes, 1992) in southwestern Florida. Missimer (2002) 

identified lithofacies, sequences, and supersequences that 

compose the Arcadia Formation in southwestern Florida. 

Ward and others (2003) analyzed the sequence stratigraphy 

of the upper part of the Avon Park Formation and Ocala 

Limestone using core description and other data (including 

digital optical borehole imaging) collected from a well north 

of the study area in south-central Florida (Highlands County). 

Budd and Vacher (2004) defined depositional cycles in the 

Avon Park Formation in a well in west-central Florida. Maliva 

and others (2009) used a micro-resistivity imaging log to 

identify a stacked, cyclic depositional pattern in the Avon 

Park Formation in a test well in south-central Florida (Glades 

County). An inventory and review of existing ASR wells 

utilizing the Floridan aquifer system of southern Florida was 

conducted by Reese (2002), and Reese and Alvarez-Zarikian 

(2007) made a more complete comparative analysis of aquifer 

system ASR wells in southern Florida that included ASR site 

performance and hydrogeologic framework definition. Ward 

and others (2003) showed that integrating carbonate sequence 

stratigraphy and hydraulic data can be a valuable approach for 

evaluating areas suitable for ASR in southern Florida.

Methods of Investigation

Data collected for this study and existing data from 

the study area were used to construct lithostratigraphic and 

sequence-stratigraphic frameworks for the upper part of the 

Upper Floridan aquifer, and a hydrogeologic framework for 

the upper part of the Floridan aquifer system. This information included well data from throughout the study area and 

reflection seismic data collected along Hillsboro canal. 

Collection and Compilation of Well Data

Well data used in the analyses in the study and described 

or included in this report include data collected from previously drilled wells and from the Upper Floridan aquifer test 

corehole G–2984 (site 18, fig. 1). Previously collected data 

were compiled from well construction reports for aquifer 

system wells drilled and completed for a variety of purposes, 

including wastewater injection, water supply, ASR, and 

hydraulic testing. Information from 84 wells at 33 sites was 

used in this study (fig. 1; appendix table 1–1). Well identification, location, and construction information are stored in 

the USGS Groundwater Site Inventory (GWSI) database, 

and can be accessed using the USGS local well identifier 

(appendix table 1–1), or in well construction reports (appendix 

table 1–2). Data collected and compiled for sites in the study 

area include lithologic descriptions, borehole geophysical 

data and images, hydraulic properties, and water-quality data 

(appendix table 1–3). 

Test corehole G–2984 was continuously cored from 

land surface into the Upper Floridan aquifer to a total depth 

of 1,308 ft below land surface (bls) within the uppermost 

part of the Avon Park Formation. The core samples were 

examined for lithology, color, grain size, texture, porosity, 

depositional features, exposure surfaces, bedding thickness, and fossil content. Optical and acoustic images of the 

borehole were collected, and can be used to observe geologic 

or hydrologic features from sections of missing core, or can 

be used to calibrate depths of core and observed features. 

Lithostratigraphy and sequence stratigraphy were delineated 

using information from G–2984 core samples, optical borehole 

images (OBIs), and acoustic borehole images (ABIs). Other 

borehole geophysical data collected include: natural gammaray activity (GR), caliper, induction formation resistivity 

(rock plus groundwater), spontaneous potential, single point 

resistance, sonic, flowmeter, and borehole fluid conductivity 

and temperature. These geophysical data provide vertical logs 

or records of the rock or fluid properties or both within the 

borehole. Recognizable patterns in the borehole geophysical 

logs can be used to identify specific geologic or hydrogeologic 

units and contacts. Borehole sonic data record changes in 

interval sonic wave transit time (sonic Δt) and can provide 

information on relative porosity. Spinner flowmeter data are 

used to locate intervals (flow zones) in which groundwater is 

flowing into the borehole or borehole fluid is flowing out of 
6 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

the borehole. When combined with other borehole geophysical 

data, such as OBI images, it is possible to estimate the relative 

contribution of each flow zone to total borehole fluid discharge 

from a well.

Borehole geophysical data were also acquired as part 

of this study in three previously drilled wells (G–2939 and 

G–2940 at site 6 and G–2916 at site 2; fig. 1); these data 

include caliper, spinner flowmeter, borehole fluid conductivity 

and temperature, and induction resistivity logs; and optical 

borehole images. 

Borehole geophysical data from previously drilled wells, 

collected by commercial logging companies, were used to 

guide well-to-well correlation and identification of major 

water-bearing units. These data include gamma ray, caliper, 

spontaneous potential, dual-induction and shallow formation 

resistivity, sonic Δt, borehole fluid properties including 

temperature and conductivity, and spinner flowmeter measurements. In addition, existing borehole image data, also collected 

by commercial logging companies, including acoustic 

televiewer and formation microresistivity images, were used 

to assist in the identification of stratigraphic boundaries.

Additional lithologic data from wells in the study area 

were compiled from Florida Geological Survey reports 

(Florida Geological Survey, 2012), and SFWMD and consultants’ well-construction reports that are available online at the 

SFWMD hydrogeologic data archive website (http://mytest.

sfwmd.gov/dbhydroplsql/show_dbkey_info.main_menu) called 

DBHYDRO (appendix table 1–2). These data were reviewed 

on an individual well basis to determine if they provided 

sufficient detail and were used in this study only to help guide 

stratigraphic interpretations.

Salinity distribution in the Floridan aquifer system was 

characterized on the basis of analyses of existing waterquality data (appendix table 1–3). Most of these data were 

compiled from construction reports, and some data were 

collected as part of previous studies by the USGS. These 

data include specific conductance, and chloride, sulfate, and 

dissolved-solids concentration. 

Delineation of Lithostratigraphic, SequenceStratigraphic, and Hydrogeologic Frameworks 

The correlation of lithostratigraphic, 

sequence-stratigraphic and hydrogeologic frameworks across 

Broward County provides information needed to identify 

areas in the eastern part of the county that would be favorable 

for the development of a water supply from the Floridan 

aquifer system. The lithostratigraphic framework describes 

the 3-dimensional distribution of lithostratigraphic units, or 

boundaries between lithostratigraphic units, as identified by 

distinct and pervasive spatial changes in lithologic characteristics. Lithology is the description of rocks on the basis of 

such characteristics as texture, mineralogic composition, and 

grain size (Neuendorf and others, 2005). Lithostratigraphic 

boundaries in the upper part of the Upper Floridan aquifer 

were identified by distinct and pervasive vertical changes in 

lithology observed in core and cuttings samples collected 

in eastern Broward County—in test corehole G–2984, well 

PB–1766, and well G–2968 (fig. 1). For the intervals in the 

upper part of the Upper Floridan aquifer for which core was 

available, these lithostratigraphic boundaries correlate with 

characteristic patterns in borehole geophysical data, such 

as GR or sonic Δt logs, and the boundaries were delineated 

throughout the study area using these data. 

The lithostratigraphic framework was extended deeper 

in the Floridan aquifer system into a stratigraphic framework 

using geophysical-log marker horizons, and these marker 

horizons were also delineated throughout the study area. 

GR and sonic Δt data were used in well-to-well correlation. 

A major reason for the reliance on geophysical-log marker 

horizons is the limited vertical coverage of lithology based on 

core samples for the intermediate confining unit and Floridan 

aquifer system. Also, for many wells, existing descriptions 

of drill cuttings were not considered reliable or were of 

insufficient detail to be used as input into a lithostratigraphic 

framework. The geophysical-log marker horizons are the most 

robust element used in the delineation of the three frameworks 

throughout the study area. 

The sequence-stratigraphic framework describes the 

3-dimensional distribution of depositional cycles. In wells 

for which only 1-dimensional data are available, depositional 

cycles are identified by the vertical arrangement of varying 

lithologies (defined by sedimentary particle types, depositional 

textures, and bedding style), and are bound by upper and 

lower surfaces that represent an abrupt upward increase in 

paleo-water depth. In lithologic logs of wells, the depositional 

cycle is the fundamental and smallest set of vertical lithologic 

variation that occurs during a single cycle of relative sea-level 

rise and fall. Depositional cycles are classified from lower- to 

higher-order (larger to smaller in scale) (as in Kerans and 

Tinker, 1997, fig. 1.11). In general, lower order depositional 

cycles may correlate over a regional scale. Depositional cycles 

in the uppermost part of the Upper Floridan aquifer were 

identified by examination of core samples and borehole image 

data from the test corehole G–2984. A preliminary sequencestratigraphic framework was developed, and extended 

throughout the study area based primarily on correlation of 

geophysical-log marker horizons, but including, where available, lithologic descriptions, OBIs, ABIs, acoustic televiewer 

data, and formation microresistivity image data. 

The hydrogeologic framework describes the 

3-dimensional distribution of hydrogeologic units, notably 

aquifers and confining units, as identified by distinct and 

pervasive differences in hydrologic characteristics, such as 

permeability and porosity. Boundaries between hydrogeologic 

units in the Floridan aquifer system were delineated using 

borehole geophysical data—principally flowmeter measurements, and fluid-temperature and conductivity data, and 

borehole images. Other contributing data include hydraulic 

test data such as that from aquifer and packer tests, lithologic 

descriptions, drilling characteristics, and zone-specific 
Stratigraphic Framework 7

water-quality data (appendix table 1–3). Hydrogeologic 

units may comprise multiple flow zones. In many cases, flow 

zones can be identified by abrupt and substantial vertical 

changes in borehole fluid flow rates or fluid temperature and 

conductivity measurements, or both. Where hydraulic test 

data or borehole geophysical flowmeter and fluid properties 

data were not available, approximate determinations of 

hydrologic unit boundaries were made based on correlation 

of other data, including lithologic descriptions and other 

geophysical data that included formation resistivity, sonic Δt 

or density (both related to formation porosity), GR, caliper, 

and spontaneous potential data. 

Marine Seismic Acquisition, Processing, and 

Interpretation

In 2010, about 14 mi of digital, high-resolution, 

multichannel, marine seismic-reflection data were acquired 

(from a shallow-draft boat) by Walker Marine Geophysical 

Company along the Hillsboro Canal at the border between 

Broward and Palm Beach Counties (fig. 1).Water depths in 

the canal ranged from about 5 to 12 ft. The seismic-reflection 

survey was completed using a MARDAQ25 digital acquisition and processing system, an air-gun source array, and 

24-channel hydrophone streamer. Digital sampling rate was 

10 kilohertz (kHz), shot spacing between 19.7 and 26.2 ft, 

and range of the recording window from 0 to 1.0 second. 

Real-time navigational positions were collected with a 

Trimble differential global positioning system (DGPS). Data 

were recorded on a proprietary 24-bit parallel system in 

SEGY format. Post-cruise data processing was conducted by 

Velseis Pty. Ltd. and included true amplitude and migrated 

stacks to produce a seismic profile in SEGY format. 

Geophysical data, borehole images, and lithologic 

descriptions from the test corehole G–2984, and boreholes 

PB–1766 and PB–1775 (fig. 1) were used to link the seismic 

reflection stratigraphy on the seismic-reflection profile to 

lithostratigraphic and hydrogeologic units identified in the 

well data. Some of the depositional sequences identified in 

test corehole G–2984 were identified on the seismic profile. 

Preliminary description and interpretation of seismicreflection configuration patterns are based on comparison to 

examples in Mitchum and others (1977).

Stratigraphic Framework

The Floridan aquifer system in the study area is a 

thick sequence of predominantly carbonate rocks that 

includes, in ascending order, the upper part of the Cedar 

Keys Formation of Paleocene age, the Oldsmar Formation 

of early Eocene age, the Avon Park Formation of middle 

Eocene age, and the lower part of the Arcadia Formation of 

Oligocene or early Miocene age (Miller, 1986; Guertin and 

others, 2000) (fig. 2). Although carbonate rocks of Ocala 

Limestone and Suwannee Limestone are reported to be 

present in southeastern Florida (Miller, 1986; Reese, 1994; 

Reese and Memberg, 2000; Reese and Richardson, 2008), 

no evidence was observed to indicate the presence of the 

Ocala Limestone and Suwannee Limestone in the study area 

(fig. 2). Composing both the intermediate confining unit 

and the uppermost part of the Floridan aquifer system, the 

Hawthorn Group ranges in age from possibly late Oligocene 

to early Pliocene (Wingard and others, 1994; Guertin and 

others, 2000; Cunningham and others, 2001a; Cunningham 

and others, 2003) and contains the Arcadia and Peace River 

Formations (Scott, 1988).

Geologic Units and Lithology

Duncan and others (1994b, p. 30) describe the Avon Park 

Formation (fig. 2) in southeastern Florida as “characterized by 

white to yellowish-gray limestones ranging from packstone 

to mudstone interbedded with very light orange to grayishbrown dolostones that commonly contain organics.” The 

color of Avon Park Formation dolomite (Duncan and others 

[1994b, p. 30], referred to the sedimentary rock dolomite 

as “dolostone”, an obsolete word use) may be light brown, 

orange-brown, dark brown, or black and the texture may be 

sucrosic or dense and microcrystalline. The upper contact 

of the Avon Park Formation is marked in some places by 

light-brown, finely crystalline to fossiliferous, dolomitic 

limestone or dolomite that is thinly interbedded with limestone 

(Reese, 2004). This contact is defined by an unconformity in 

west-central peninsular Florida (Arthur and others, 2008), in 

the Broward County study area, and in all other areas of the 

peninsula where the Ocala Limestone is absent (Miller, 1986). 

Applin and Applin (1944) found the cone-shaped, larger 

benthic foraminifera Dictyoconus to be the most prevalent and 

consistent larger benthic foraminifera throughout the Avon 

Park Formation. Powell (2010) observed that this is also the 

case in core recovered from the upper Avon Park Formation 

in a test corehole in south-central Florida (Highlands County) 

north of the study area, which was earlier described by Ward 

and others (2003).

Total porosity is high (40 percent or greater) in the upper 

part of the Avon Park Formation (Reese, 2000) and common 

porosity types are interparticle, intraparticle, intercrystalline, 

and vuggy. Thick intervals containing mostly dolomite, but 

commonly interbedded with limestone, are present in the 

middle to lower part of the Avon Park Formation in southeastern Florida (Reese, 2004). Highly transmissive zones are 

common in these dolomite units, principally as a consequence 

of fracture, intercrystalline, and vuggy porosity. The thickness 

of the formation ranges from about 900 to nearly 1,100 ft in 

the study area (Miller, 1986, pl. 7).

Some well-construction reports in the study area (Camp, 

Dresser, and McKee, Inc., 1996; Montgomery Watson, 1996; 

CH2M HILL, 1999) identify a unit that lies between the Avon 

Park Formation and the Arcadia Formation as Suwannee 
8 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Limestone. However, the Suwannee Limestone was not 

identified within the boundaries of the study area described 

herein, based on lithologic data from the G–2984 test corehole 

and correlation of these data to other wells in the study. No 

core samples from G–2984 match the detailed core-sample 

descriptions of the Suwannee Limestone reported for the 

Florida Keys (Cunningham and others, 1998) or in central 

south Florida in Highlands County (Ward and others, 2003). 

Also, no Ocala Limestone was identified in the G–2984 

test corehole, as determined by comparison to the coresample descriptions for a test corehole in Highlands County 

(Ward and others, 2003).

The Arcadia Formation of the Hawthorn Group in 

southern Florida, as defined by Scott (1988, p. 56), consists 

“predominantly of limestone and dolostone containing varied 

amounts of quartz sand, clay, and phosphate grains. Thin beds 

of quartz sand and clay commonly are scattered throughout 

the section.” The characteristics that distinguish the Arcadia 

Formation from underlying units in southeastern Florida are 

(1) intervals of quartz sandstone or with common subordinate 

quartz grains; (2) calcareous mudstone intervals; (3) common 

green, olive-gray, or light gray rock colors; (4) intervals of 

high phosphate grain content relative to that in underlying 

units and in some cases having high GR log activity (100 to 

200 American Petroleum Institute standard units); and 

(5) intervals of dolosilt. Missimer (2002) identified 10 lithofacies that compose the Arcadia Formation in southwestern 

Florida, many of which are similar to lithofacies found in 

Broward County. These 10 lithofacies are (1) brecciated 

and laminated packstones (lower Arcadia); (2) laminated, 

sandy mudstone/wackestone (lower Arcadia); (3) laminated 

clay; (4) laminated, microsucrosic, dolomitic mudstone/

wackestone; (5) muddy, quartz sand and mollusks; (6) sandy, 

molluscan skeletal wackestone; (7) sandy, molluscan, echinoid, bryozoan, wackestone; (8) Hyotissa (genera) packstone 

(wackestone); (9) molluscan wackestone (low quartz sand 

content); and (10) bryozoan wackestone (minor quartz sand). 

The lithologies described by Missimer (2002) for the Arcadia 

Formation more closely resemble those present in the G–2984 

test corehole in Broward County than do the lithologies for 

the Arcadia Formation beneath the Florida Keys described 

by Cunningham and others (1998). The major difference is 

a much higher concentration of siliciclastics—quartz sand 

and silt, and terrigenous clay—in the core samples from 

Broward County.

In the Peace River Formation, quartz sand is 

predominant, but sediment and rock can include terrigenous 

mudstone and limestone. The quartz sands are characteristically clayey, calcareous to dolomitic, phosphatic, very fine to 

medium grained, and poorly consolidated (Scott, 1988, p. 79). 

Cunningham and others (2001a) recognized five lithofacies 

composing the Peace River Formation in the Florida Keys 

and southern peninsular Florida: diatomaceous mudstone, 

terrigenous mudstone, clay-rich quartz sand, quartz sand, and 

pelecypod-rich quartz sand and sandstone.

Geologic units that overlie the Hawthorn Group in 

southeastern Florida include (1) the Tamiami and Stock 

Island Formations of Pliocene age (Guertin and others, 2000); 

(2) Pleistocene-age units composed mainly of the Fort 

Thompson Formation, Anastasia Formation, Miami Limestone 

and Pamlico Sand; and (3) undifferentiated sediments of Holocene age (fig. 2). These units constitute the surficial aquifer 

system, which includes the Biscayne aquifer. In the western 

part of the study area, the Ochopee Limestone Member of the 

Tamiami Formation composes the gray limestone aquifer—a 

minor aquifer within the surficial aquifer system (Fish, 1988; 

Reese and Cunningham, 2000).

Stratigraphic Markers

The stratigraphic framework of eastern Broward County 

was mapped by identifying and correlating the stratigraphic 

and geophysical-log markers across the study area. A 

stratigraphic marker is a “an easily recognized stratigraphic 

feature having characteristics distinctive enough for it to 

serve as a reference or datum or to be traceable over long 

distances, especially in the subsurface, as in well drilling or in 

mine working, e.g., a stratigraphic unit readily identified by 

characteristics recognized on an electric log, or any recognizable rock surface such as an unconformity” (Neuendorf and 

others, 2005). A stratigraphic marker horizon is “a marker 

represented by a rock surface or stratigraphic level, such 

as a vertical or lateral boundary based on electric or other 

mechanically recorded logs, that may serve to delineate 

lithostratigraphic units” (Neuendorf and others, 2005). Two 

types of stratigraphic markers were used primarily in construction of the stratigraphic framework: (1) a geophysical-log 

marker delineated principally on the basis of correlation of 

geophysical data between boreholes and; (2) where available, lithostratigraphic boundaries, which are referred to as 

lithostratigraphic marker horizons. Three lithostratigraphic 

marker horizons and three geophysical-log marker horizons 

are identified in eastern Broward County, and they divide the 

Avon Park Formation and Arcadia Formation into six informal 

stratigraphic units (fig. 2, table 1). All six of these stratigraphic 

markers have characteristic patterns in borehole geophysical 

GR and sonic Δt data, but the three lithostratigraphic marker 

horizons also display distinct lithologic changes that are 

laterally persistent and recognizable (table 1). Both types 

of stratigraphic markers were delineated in the study area, 

primarily through correlation of borehole geophysical data 

between wells. 

 Stratigraphic marker horizon depths were determined in 

at least one well at each site in the study (appendix table 1–4). 

All or some of the geophysical-log marker horizons were not 

determined at each site because wells were not deep enough to 

penetrate them. The stratigraphic units defined by these marker 

horizons are illustrated in data plots for wells at five sites 

(figs. 3–8). Stratigraphic units are described below in order of 

decreasing depth. The lithologic distinctions associated with 
Stratigraphic Framework 9

the formation contacts and lithostratigraphic marker horizons, 

if evident, are based on lithologies described for this study, 

including those for test corehole G–2984, and lithologies 

described by others in the study area.

The geophysical-log marker horizon defining the upper 

surface of the lower Avon Park Formation is identified by 

correlation of characteristic borehole geophysical log patterns 

in southern and central Florida, where it has been previously 

referred to as the middle Avon Park marker horizon or 

MAP (Reese and Richardson, 2008). This marker horizon 

is identified in east-central Florida by the “B” gamma ray 

marker bed described by Duncan and others (1994a, p. 17), 

which separates the “more thinly-bedded strata of the upper 

Avon Park Formation from more thickly-bedded and massive 

units of the lower Avon Park Formation.” Duncan and others 

(1994b) demonstrated the continuity of this geophysical-log 

marker horizon between east-central and southeastern Florida 

using GR and sonic log curves. This marker horizon was 

previously identified in seven wells in Broward County in 

Reese and Richardson (2008) [sections D–D′ (fig. 17D), E–E′ 

(fig. 17E), and Y–Y′ (fig. 17H, pl. 4), section lines shown in 

fig. 1 of this study, and well BCN-I1]. A change in lithology 

across this marker horizon in the study area, if present, was 

not identified, perhaps because descriptions of cuttings 

samples from previous studies or well-construction reports 

lacked the resolution to indicate any such change.

The geophysical-log marker horizon defining the 

upper surface of the lower-middle Avon Park Formation 

was previously delineated in four wells in Broward County 

(Reese and Richardson, 2008, section Y–Y′, fig. 10D, pl. 4, 

UAP geophysical-log marker). No distinguishing lithologic 

characteristics for this marker horizon have been observed in 

the study area, possibly because cuttings sample descriptions 

lack sufficient detail. Sonic Δt data, however, indicate this 

horizon approximately coincides with the top of a vertical 

succession of variations in geophysical log character having 

overall lower sonic Δt than does the overlying upper-middle 

Avon Park Formation, and an increase in sonic Δt variations over very thin vertical intervals represented by high 

and low sonic Δt values that produce a spikey log pattern 

(figs. 4–7, pls. 1–3).

The geophysical-log marker horizon defining the top 

of the upper-middle Avon Park Formation is defined in the 

study area by (1) a slight downward increase in GR values 

to a background GR level for the Avon Park Formation, and 

(2) the base of thin (3 to 10 ft) zones of sharply alternating 

high and low sonic Δt values, producing a spikey log pattern 

(for example, figs. 5 and 6). A zone of lower GR values, and in 

many cases greater sonic Δt variability, usually extends about 

20 to 30 ft upward from this marker into the upper Avon Park 

Formation and can be correlated to all the sites in the study 

area (figs. 4–8; pls. 1–3). At or near the upper surface of the 

middle Avon Park Formation in G–2984 there is an upward 

increase in the thickness of dense, gray mudstone layers. 

These layers and other lithologic changes could indicate an 

overall shift toward a shallower marine environment.

 On the basis of observations of lithologies in the G–2984 

test corehole, the unconformity at the upper contact of the 

Avon Park Formation is overlain by a basal interval of the 

Arcadia Formation that is 10 ft thick or less and composed 

Table 1. Lithostratigraphic and geophysical-log units identified or defined in the study.

[UAP, Upper Avon Park]

Unit name Unit type Previous or original name of 

upper boundary for unit

Source of upper 

boundary

Upper boundary 

associated with 

lithologic change 

in study area

Upper Arcadia 

Formation Lithostratigraphic unit Top of Arcadia Formation Scott, 1988 Yes

Lower Arcadia 

Formation Lithostratigraphic unit Base of “lower Hawthorn marker unit.”

Reese, 2000, 2004; 

Reese and Memberg, 2000 Yes

Upper Avon Park 

Formation Lithostratigraphic unit Top of Avon Park Formation Applin and Applin, 1944; Ward and others, 2003 Yes

Upper-middle 

Avon Park 

Formation

Geophysical-log unit None This study Poorly defined in 

G-2984

Lower-middle 

Avon Park 

Formation

Geophysical-log unit Upper Avon Park marker 

horizon

Reese and Richardson, 2008, 

pls. 1–4. None identified

Lower Avon 

Park Formation Geophysical-log unit

Middle Avon Park marker 

horizon; “B” gamma ray 

marker bed in east-central 

Florida

Reese and Richardson, 2008, 

figs. 17A–17H, pls. 1–4; 

Duncan and others, 1994a

None identified
10 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Quartz 

sand

Quartz 

sandstone Siltstone

Dolomite

Shell bed

Conglomerate

Limestone Grainstone Packstone Wackestone Mudstone

Rudstone

Floatstone

Dolomitic Phosphatic Chert Crystals or 

crystalline

Calcareous

Fossils or 

fossiliferous Sandy Silty Clayey

No sample

Primary lithology

EXPLANATION

Accessory lithologic components or modifiers

No data

Clay or 

claystone

Marl

Moldic Vuggy

Chalky

Shells

Breccia

Dolosilt

High frequency depositional 

cycle characteristics 

Grain size fining upwards in cycle

Grain size coarsening upward in cycle

Fractures apparent in cycle

Laminae present in cycle

Grain size generally fining upwards in 

cycle–But has a reversal in grain size in 

a thin bed at the base 

No apparent grain size change within cycle

Depositional sequence 

characteristics and boundaries

Depth of top of the Avon Park Formation 

sequence 1 is less certain–Because borehole 

geophysical image log data were not collected 

in the well 

Depth of bottom of the Avon Park Formation 

sequence 1 is unknown

? 

Arcadia Formation sequence 4 

Arcadia Formation sequence 3 

Arcadia Formation sequence 2 

Arcadia Formation sequence 1 

Avon Park Formation sequence 2 

Avon Park Formation sequence 1 

Interpreted as prograding–Lower 

relative sea level 

Interpreted as transgressive–Higher 

relative sea level 

AR4 

AR3 

AR2 

AR1 

AP2 

AP1 

ND Not determined

ND Not determined

Figure 3. Explanation for figures 4 through 8, 14, 25 and 29.
Stratigraphic Framework 11

Flow zones evaluated in open hole intervals 

using borehole flowmeter and fluid properties 

geophysical data and shown in flow zone column

Open hole interval over which no flow zones 

were identified

Flow zone interpreted from borehole flowmeter and 

 fluid properties geophysical data

Interval not evaluated for flow

Deeper interval not evaluated for flow

Open hole 

interval over 

which flow 

was evaluated Open hole interval over which no flow zones 

were identified

Intermediate confining unit Middle semiconfining unit

Upper Floridan aquifer Avon Park permeable zone

Hydrogeologic unit

Upper Avon Park Formation

Upper-middle Avon Park Formation

Lower Arcadia Formation

Lithostratigraphic unit and 

corresponding upper boundaries

Lower-middle Avon Park Formation

Interval drilled in deeper test well at same site, and top of 

interval indicates total depth and base of open 

interval in monitoring well 

Packer test

Lower Avon Park Formation interval

Upper Arcadia Formation

Abbreviations for borehole geophysical log curves

Description

Abbreviation for

logging tool 

or device

Unit of measure Description

CAL(-5)1

GR (spliced)2

GAMM

RIL

Sonic DT

XCAL, YCAL 

Caliper

Gamma ray

Gamma ray

Resistivity from slim hole induction 

tool– 40 centimeter radius of investigation

Sonic interval transit time or 

delta T–Compensated

X-caliper and Y-caliper–Both on same tool 

and 90 degrees apart

In.

GAPI

CPS

ohm-m

μsec/ft

In. 

Inch

American Petroleum Institute 

standard unit

Counts per second

Ohm-meter

Microsecond per foot

Inch

Lower Floridan aquifer 

uppermost major permeable zone

Lower Floridan aquifer 

confining unit

1 Number indicates data collection interval number. 

2 (spliced) indicates more than one data collection interval is included. If intervals overlap, splicing was done at the greatest depth of the upper interval. 

Figure 3. Explanation for figures 4 through 8, 14, 25 and 29—Continued.
12 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 4. Borehole geophysical logs and lithologic data collected for well PB-1775 at site 16. Fluid resistivity, 

temperature and flowmeter data were collected under flowing and static conditions. The flowmeter rate was 

calculated by subtraction of static from flowing values, calibration in casing, and correction for borehole size 

using caliper log data. Depth, in feetbelow land surface

XCAL spliced, in inches

0 20

YCAL spliced, in inches

0 20

GRspliced, in GAPI

0 150

Lithology

Depositional 

sequences

Stratigraphic

unit

SonicDT, in μsec/ft

170 70

Fluidresistivity, in Ohm-m

1 2 Fluid temperature, in 

degrees Fahrenheit 73.5 72

Flowmeterrate, in 

0 gallons per minute 1,000

Percentof total flow

0 100

Flow zone

Hydrogeologic

unit

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

AR1 

and AR2

AR3 

and AR4 AP2 AP1

Lower Arcadia Upper Avon Park Upper-middle Avon Park

Upper 

Arcadia

120

Lower-middle Avon Park
Stratigraphic Framework 13

Figure 5. Borehole geophysical logs collected for well G-2938 at site 6. 

Expanded plots of one other well at this site are shown in figures 25 and 26. Depth, in feet below land surface

GR, in GAPI

0 150

Caliper, in inches

0 30

Depositional 

sequence

Stratigraphic

unit

SonicDT, in μsec/ft

170 70

Flowzone

Hydrogeologic

unit

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

AR3 

and AR4

AR1 

and AR2 AP2 AP1

Upper 

Arcadia Lower Arcadia Upper Avon Park Upper-middle Avon Park

120

Lower-middle Avon Park
14 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 6. Borehole geophysical logs collected for well CS-I2 at site 5. Data from this 

well are also shown in figure 29.

YCAL, in inches

0 50

XCAL, in inches

0 50

GR, in GAPI

0 150

Sonic DT, in μsec/ft

170 70

Flowzone

Packertest

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700 Depth, in feet below land surface

Depositional 

sequences

Stratigraphic

unit

AR3 

and AR4

AR1 

and AR2 AP2 AP1

Lower Arcadia Upper Avon Park Upper-middle Avon Park

120

Hydrogeologic

unit

Lower-middle Avon Park

? 

Zone of moderately saline water in the brackish-water zone (shown in figure 29)
Stratigraphic Framework 15

Figure 7. Borehole geophysical logs collected for well G-2945 at site 23. Depth, in feet below land surface

GR, in GAPI

0 150

CAL, in inches

0 20

SonicDT, in μsec/ft

170 70

Depositional 

sequence

Stratigraphic

unit

120

Flowzone

Packertest

Hydrogeologic

unit

* *

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

*Casing depth and flow zones above 1,300 feet are from well G-2989 and deeper flow zone is indicated 

 in well G-2946, both at the same site. Packer tests intervals are from well G-2944 at the same site. AR3 and AR4 AR1 and AR2 AP2 AP1

Upper 

Arcadia Lower Arcadia Upper Avon Park Upper-middle Avon Park Lower-middle Avon Park
16 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 8. Borehole geophysical logs, lithologic data, and depositional cycles and 

sequences for test corehole G-2984 at site 18. Data from this well are also shown in 

figures 14, 21, 22, and 24. Depth, in feet below land surface

CAL-5, in inches

0 6

GAMM-6, in CPS

0 400

CAL-6, in inches

0 6

RIL-6, in Ohm-m

0 30

Sonic DT-6, in μsec/ft

170 70

 900

 1,000

 1,100

 1,200

 1,300

Lithology

Depositional

cycle

Depositional

sequence

Sequence

name

Stratigraphic 

unit

Formation

Hydrogeologic

unit

AR4 AR3 AR2 AR1 AP2 AP1

Upper

Arcadia Lower Arcadia Upper Avon Park Upper-middle Avon Park

Arcadia Formation Avon Park Formation

120

ND ND ND
Stratigraphic Framework 17

of phosphate-grain-rich limestone, quartz sand, and quartz 

sandstone (fig. 8). The lithology of the uppermost Avon 

Park Formation just below this unconformity is markedly 

different in that it is a fine to very coarse grained, benthic 

foraminifer grainstone and packstone that does not contain 

phosphate or quartz grains. The limestone of the Avon Park 

Formation also contains conical, larger benthic foraminifera 

including Fallotella floridana (Jacqueline B. Powell, Paleo 

Solutions, LLC., oral comm., 2013). Fallotella floridana is 

absent throughout the Arcadia Formation. In the logs for most 

wells examined in this study, there is an abrupt increase in 

GR values on GR logs across the unconformity, with values 

in the Avon Park Formation notably lower than values in 

the lowermost part of the overlying Arcadia Formation. The 

fossil assemblage within the lowermost Arcadia Formation is 

commonly dominated by echinoids, pelecypods, and gastropods. Further, the dominant color of the limestone near and at 

the upper surface of the Avon Park Formation is a very pale 

orange (10YR 8/2), whereas the basal rocks and quartz sand 

of the Arcadia Formation most commonly are yellowish gray 

(5Y 8/1) (Geological Society of America, 1995).

The Arcadia Formation is informally divided into two 

lithostratigraphic units, the lower Arcadia Formation and the 

upper Arcadia Formation (figs. 2, 4–8). Observations noted in 

core samples and optical borehole images acquired from the 

G–2984 test corehole and GR geophysical values from the 

same test corehole provide the physical criteria for division 

of the two lithostratigraphic units, and a GR-log-based 

stratigraphic marker horizon provides a means of county-wide 

correlation of the upper contact of the lower Arcadia Formation. In core samples from the test corehole G–2984 (fig. 8), 

this marker horizon is identified as a drowning unconformity 

(a substantial change in sediment composition and distribution associated with marine submergence of a carbonate 

platform; Schlager, 2005) at the upper boundary of the lower 

Arcadia Formation (depth of 920.6 ft bls), whereas below 

the unconformity, a 1-ft thick interval of limestone is partly 

phosphatized and contains common phosphate grains. Petrographic observations of a thin section provide the evidence for 

the presence of phosphatized rock and phosphate grains. The 

phosphate produces relatively high GR values on the GR log 

from the G–2984 test corehole when compared to the GR log 

values above and below the phosphatized limestone (fig. 8). 

Overlying the unconformity at 920.6 ft bls in the G–2984 test 

corehole, the rock at the base of the upper Arcadia Formation 

is a calcareous mudstone to claystone. The upper contact of 

the lower Arcadia Formation corresponds to the base of a 

previously defined “lower Hawthorn marker unit” mapped in 

Lee, Hendry, and Collier Counties (Reese, 2000), Palm Beach 

County (Reese and Memberg, 2000), and Martin and St. Lucie 

Counties (Reese, 2004). The characteristic log pattern of GR 

values in this lower Hawthorn marker unit, which is the same 

as the lower part of the upper Arcadia Formation, is consistent 

over large parts of southern Florida.

The upper contact of the Arcadia Formation is usually 

well defined on GR logs as a pronounced peak produced by 

high GR values. In southeastern Florida, this contact is marked 

by an “increase in the abundance in large (GR) peaks in the 

Arcadia” as compared to the GR values in the overlying siliciclastics of the Peace River Formation (Scott, 1988, p. 125). 

The peak at the upper contact of the formation can be readily 

correlated between most wells in the study area and may be 

associated with a limestone layer containing concentrated 

phosphate grains or gravel that has been referred to as a “phosphatic rubble zone” (Scott, 1988, p. 58). This layer was found 

to be several feet thick in G–2984, and in the Florida Keys the 

uppermost limestone of the Arcadia Formation is phosphatized 

over a thin interval below the upper bounding surface of the 

formation (Cunningham and others, 1998). The formation 

contact bounding the upper surface of the Arcadia Formation 

represents either a major composite sequence boundary 

(Cunningham and others, 1998) or a depositional sequence 

boundary (Guertin and others, 2000; Missimer, 2002).

Structure and Thickness of Lithostratigraphic 

Units

In the study area, the altitude of the surface that forms 

the upper contact of the Avon Park Formation trends upward 

about 150 ft from west to east (fig. 9). The generally westward 

dipping structure at the upper contact of the Avon Park 

Formation in the study area has been mapped previously 

(Reese, 1994; Reese and Richardson, 2008). A structural low 

or basin extends north to south in central Broward and MiamiDade Counties, and relief of about 200 ft was mapped from 

the coast to central Miami-Dade County (Reese, 1994, fig. 6). 

The altitude of the upper contact of the Avon Park Formation 

ranges from 1,127 ft below NGVD 29 at well G–2989 in the 

southwestern part of the study area to 954 ft below NGVD 29 

at well G–2962 in the southeastern part. The altitude of the 

upper contact decreases across I–595 in the south-central part 

of the study area from south to north by 20 to 40 ft, indicating 

that a structural flexure or offset along a buried subsurface 

fault may be present in the vicinity of the highway (fig. 9). A 

structural low having as much as 50 ft of relief is indicated 

in the northeastern part of the study area, centered on well 

G–2942 (site 28, fig. 9). 

An isolated structural low at the upper contact of the 

Avon Park Formation was mapped around test corehole 

G–2984 (site 18, fig. 9), and based on the regional structural 

trend in the area, the altitude of the upper contact of the Avon 

Park Formation at this well is as much as 80 ft deeper than 

the projection of the regional structural trend across the well 

location. Corroborating evidence for the structural low at 

G–2984 is a comparison of the altitude of the upper contact 

and thickness of the upper Arcadia Formation at well G–2984 

to that at nearby well G–2968 (site 8, fig. 9). At G–2984, 

the thickness of the upper Arcadia Formation is 62 ft greater 

than at well G–2968 (appendix table 1–4, pl. 1). This greater 

thickness of the upper Arcadia Formation and the lower 

altitude of the upper contact of the upper Arcadia Formation 
18 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 9. Altitude of the upper contact surface of the Avon Park Formation.

–1,040

–1,000

–960

–1,080

–1,080

–1,040

–1,000

–960

–1,120

–1,040

–1,040

8

G-2968

–972

G-2887

–972

17

PB-1766

–1,053

PB-1775

–1,049

G-2970

–1,002

HAL-RO1

–955

G-2974

–960

HOL-RO1

G-2963 –989

–1,083

G-2945

–1,120

PBP-I1

–1,070

G-2989

–1,127

G-2962

–954

G-2966

–1,073

FTL-I4

–979

S-567

–1,000

18

G-2984

–1,053

G-2916

–968

G-2986

–994

D-365

–1,009

6

G-2938

–1,026

10

G-2917

–1,027

SUN-I3

–1,095

32

G-2981

–1,062

G-2983

–1,110

5

CS-I2

–1,067 28

G-2942

–1,050

BCN-I1

–1,020 21

MAR-I2

–1,039

G-2914

–1,090

G-2978

–1,050

G-2985

–1,031

G-2987

–1,040

PLT-I1

–1,066

G-2971

–1,033

PLT-ROI1

–1,089

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro

Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

EXPLANATION

10

G-2917

–1,027

–1,100

Well location and altitude—

 Site number 

 Well number 

 Altitude of the upper surface 

 of the Avon Park Formation, 

 in feet relative to NGVD 29

Seismic sag structure—

 Located along Hillsboro Canal

 marine seismic profile tract 

 (see fig. 1). Extent away from 

 seismic profile tract is 

 unknown

Line of equal altitude—Shows

 altitude of the upper surface 

 of the Avon Park Formation, 

 in feet relative to NGVD 29. 

 Contour interval is 40 feet. 

 Contours approximately 

 located. Hachures indicate 

 depression

Hillsboro Canal marine seismic 

 profile track

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’” and 

45 ̊30’ central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES
Stratigraphic Framework 19

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’

EXPLANATION

G-2916

148

NR

150 Line of equal thickness—

 Shows thickness of the 

 upper Avon Park formation, 

 in feet. Contour interval is 

 25 feet. Contours 

 approximately located

Well location and thickness— 

 Well number shown. 

 Thickness of the upper 

 Avon Park formation, 

 in feet

Not reached—Entire unit 

 not penetrated

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

5 MILES

150

125

150

150

125

G-2968

145

G-2986

123 G-2916

148

BCN-I1

131

G-2942

145

D365

NR

MAR-I2

CS-I2 153

145

PLT-I1

124

PLT-ROI1

127

PBP-I1

150

SUN-I3

137

G-2983

140

G-2914

125

G-2978

130

G-2938

125

G-2917

140

PB-1775

135

PB-1766

140 G-2984

151

G-2887

135

G-2985

122

G-2963

155

G-2989

153

G-2981

130

G-2966

148

G-2945

157

G-2971

127

G-2974

130

G-2962

122

G-2970

120

FTL-I4

115

G-2987

125

S-567

124

HAL-RO1

NR

HOL-RO1

128

75

95

595

1

441

Figure 10. Thickness of the upper Avon Park Formation.
20 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

at G–2984 compared to that at G–2968 indicate that G–2984 

is located in a paleo-low area that was filled in with sediments 

during deposition of the upper Arcadia Formation. Seismic 

data indicate that the isolated structural low at G–2984 is the 

result of a deeply buried, collapsed cave system. The structural 

low at well G–2942 could have a similar origin.

Generally, the upper Avon Park Formation is thickest 

in the northwestern, extreme northeastern, and southwestern 

parts of the study area and thins towards the central and 

southeastern parts, including areas along and north of I–595. 

The thickness of the upper Avon Park Formation ranges from 

115 ft at well FTL-I4 in the east-central part of the study area 

to 157 ft at well G–2945 in the southwestern part of the study 

area (fig. 10).

Generally, the thickness of the lower Arcadia Formation 

increases from south to north, with most of the thickening 

occurring to the north of I–595. The thickness of the lower 

Arcadia Formation in the study area ranges from 80 ft at well 

PBP-I1 in the southwestern part of the study area to 155 ft at 

well G–2942 in the northeastern part of the study area (fig. 11). 

Sequence-Stratigraphic Analysis

In sequence stratigraphy, depositional sequences are 

genetically-related strata that can be arranged in units that are 

bounded by surfaces of erosion, or nondeposition, or their 

correlative conformities (Van Wagoner and others, 1988). The 

emphasis in sequence stratigraphy on unconformity-bound 

depositional sequences differs from the simple lateral correlation of similar rock types between subsurface data points 

in more conventional lithostratigraphy. Because hydrologic 

properties commonly are physically associated with specific 

lithologies, and may be spatially associated with erosional 

or nondepositional surfaces, recognition of depositional 

sequences may improve correlation of hydrologic units and 

improve the accuracy of the hydrologic framework.

Prior to this study, borehole geophysical data correlations 

had been primarily used to develop conceptual geologic 

frameworks for Floridan aquifer system rocks in Broward 

County. Improvement of the spatial resolution of lithostratigraphy and cyclostratigraphy by using sequence stratigraphy 

for a part of the vertical range of Floridan aquifer system 

rocks has resulted in refinement of the Floridian aquifer 

system hydrogeologic framework. The preliminary sequence 

stratigraphy developed for the lower Arcadia Formation 

and an upper part of the Avon Park Formation in this study 

needs to be tested further and a robust geologic data base 

compiled to develop a more extensive and still more refined 

hydrogeologic framework. 

The terminology of sequence stratigraphy is complex, 

and its concepts are continually evolving (Catuneanu and 

others, 2009). The fundamental sequence-stratigraphic unit 

is the high-frequency cycle (HFC or parasequence), which is 

a depositional cycle defined by a distinct vertical lithofacies 

succession and bounded at the top and bottom by surfaces 

across which there is evidence for an abrupt, relative change 

in sea level (Kerans and Tinker, 1997). The cycle hierarchy 

used herein indicates two relative positions in the cycle 

hierarchy shown in table 2, in which the cycles are either of 

short duration (high order) or long duration (lower order). 

The short duration cycles are defined as HFCs and the long 

duration cycles are defined as depositional sequences. The 

depositional sequences would probably be equivalent to the 

third-order composite or depositional sequences delineated 

for depositional cycles of the Avon Park Formation by Ward 

and others (2003). No absolute time duration is implied for 

the HFCs and depositional sequences. This cycle terminology 

for Broward County is tentative and its refinement will require 

further testing.

Table 2. Nomenclature of stratigraphic cycle hierarchies and order of cyclicity. Modified from Kerans and Tinker (1997, fig. 1.11).

[<, less than the value; >, greater than the value]

Tectono-eustatic/

eustatic cycle order Sequence-stratigraphic unit Duration (million years)

Relative sea-level 

amplitude (meters)

Relative sea-level 

rise/fall rate 

(centimeters per 1,000 

years)

First Undefined >100 Undefined <1

Second Supersequence 10–100 50–100 1–3

Third Composite sequence/

Depositional sequence 1–10 50–100 1–10

Fourth High-frequency sequence/

High-frequency cycle set 0.1–1 1–150 40–500

Fifth High-frequency cycle 0.01–0.1 1–150 60–700
Stratigraphic Framework 21

PALM BEACH

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

MIAMI–DADE

BROWARD

C-9 Canal

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’

EXPLANATION

G-2916

150

NL No log

Well location and thickness— 

 Well number. Thickness of 

 the lower Arcadia Formation, 

 in feet

Line of equal thickness—

 Shows thickness of the lower 

 Arcadia Formation, in feet. 

 Contour interval is 25 feet. 

 Contours approximately 

 located

150

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

5 MILES

100

125

150

G-2986

142

G-2916

150

BCN-I1

139

G-2942

155

D365

139

MAR-I2

120

CS-I1

142

PLT-M1

106

PLT-ROI1

100

PBP-I1

80

SUN-I3

90

G-2983

95

G-2914

110

G-2978

NL

G-2938

118

G-2917

130

PB-1775

135

PB-1766

117 G-2984

143

G-2887

143

G-2985

88

G-2989

90

G-2981

90

G-2966

97

G-2945

93

G-2972

96

G-2974

90

G-2962

90

G-2970

100

FTL-I4

95

G-2987

100

S-567

NL

HAL-RO1

90

HOL-RO1

92

75

95

595

1

441

Figure 11. Thickness of the lower Arcadia Formation.
22 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Sequence Stratigraphy at Test Corehole G–2984

A preliminary sequence stratigraphy was delineated 

for the upper part of the upper-middle Avon Park Formation 

(1,309 to 1,210 ft bls), the upper Avon Park Formation 

(1,210 to 1,068 ft bls), and the lower Arcadia Formation 

(1,068 to 921 ft bls), on the basis of examination of core 

samples and borehole wall images acquired from test corehole 

G–2984 (fig. 8). In southeastern Florida, this well provided 

core samples from the thickest continuously cored interval to 

date of any part of the Avon Park Formation.

Six depositional sequences were identified between 

1,309 and 921 ft bls in the G–2984 test corehole (fig. 8). 

From deepest to shallowest, these sequences are Avon Park 

sequence 1 (AP1), Avon Park sequence 2 (AP2), and Arcadia 

sequences 1 through 4 (AR1–AR4). The upper bounding 

surface of each sequence generally is an unconformity, 

and in some instances, evidence in core samples suggests 

subaerial exposure. In some cases, the sequences boundaries 

can be correlated throughout the study area using borehole 

geophysical logs.

Upper-Middle to Upper Avon Park Formation

The AP1 and AP2 depositional sequences were delineated 

in test corehole G–2984 in the upper part of the upper-middle 

Avon Park Formation and the upper Avon Park Formation 

(pl. 1). The AP1 sequence extended from the base of the core 

samples at 1,309 ft and upward to 1,134 ft bls. Peritidal HFCs 

compose the AP1 and the AP1 is interpreted as a highstand 

and progradational phase of the southeastern Florida platform 

(fig. 8). The penetrated part of AP1 contains 39 HFCs, each 

of which is commonly 3 to 4 ft thick (fig. 8). The base of 

AP1 was not penetrated in G–2984, so the depth of the lower 

boundary of the sequence is unknown.

In the G–2984 test corehole, the HFCs in the lower part 

of the AP1 sequence in the upper-middle Avon Park Formation 

between depths of 1,309 and 1,210 ft bls (pl. 1) commonly 

consist of a benthic foraminiferal packstone to grainstone, 

intraclast floatstone, or echinoid floatstone in the lower part, 

with grain size fining upward to a thin layer of finely laminated, micrite-rich limestone, or a dense, hard, light gray, lime 

mudstone cycle cap, or both. This common arrangement of 

vertical lithofacies is representative of an upward-shallowing 

cycle from shallow-marine subtidal to tidal flat depositional 

settings. In the lower part of some HFCs, granule- to pebblesized, angular to rounded, gray limestone intraclasts are 

dispersed in a matrix of mostly sand-sized benthic foraminiferarich packstone or grainstone. Small (0.5-in. [inch] diameter), 

disk-shaped echinoids and cone-shaped larger benthic 

foraminiferal genera (for example, Fallotella) can be abundant 

in the lower to middle part of the HFCs. The thin layers of 

finely laminated sediments contain some organic matter and 

are referred to as stromatolite or laminite (algal tidal flat) facies 

(table 3), similar to those seen in the Avon Park Formation in 

south-central Florida (Ward and others, 2003). In many cases, 

the mudstone layers are at the top of HFCs and are usually less 

than 1 ft thick. The mudstone layers commonly include large 

vugs at or near their boundaries, and abundant and pervasive, 

subhorizontal to subvertical, irregular to tortuous small holes 

or marks (pinpoint-sized to 0.06-in. diameter) that in many 

cases appear to be rhizoliths, but also could be produced by 

burrowing. In some cases, these mudstone layers are brecciated and have an eroded upper surface; they were probably 

deposited in a mudflat environment with marked subaerial 

exposure. For some HFCs in the lower part of AP1, the 

mudstone layer is missing and the algal tidal-flat facies occurs 

below of the upper bounding surface of the cycles.

Although HFCs are also interpreted to be peritidal, some 

of the characteristics of the HFCs in the upper part of the AP1 

sequence in the upper Avon Park Formation, from 1,210 to 

1,134 ft bls in G–2984, differ from those in the lower part 

of the sequence, between 1,309 and 1,210 ft bls (fig. 8). In 

the upper part of the AP1 sequence, dense, gray, mudstone 

layers capping the cycles are thicker than those in the lower 

part of the sequence, the laminite layers are absent from the 

upper part of the HFCs, and intraclasts are absent from the 

lower part of the HFCs. The mudstone layers are commonly 

greater than 1 ft thick and as thick as 3 to 4 ft, and have in 

addition to the abundant, small pore spaces possibly related 

to burrowing or rhizoliths, small gastropod molds. In some 

of the HFCs that contain thick mudstone layers, pervasive, 

large (1- to 2-in. diameter), irregular, subvertical vugs are 

present in the mudstone that possibly formed by dissolution 

along preexisting large rhizoliths or burrows. These large 

vugs can extend several feet down into the HFC, with their 

width decreasing downward. Although grain size generally 

also fines upward within the HFCs in the upper AP1 sequence, 

some of the HFCs have a reversal in grain size near the base 

of the HFC, with a finer-grained 0.1- to 1-ft-thick bed of 

poorly cemented wackestone at the base of the HFC (fig. 8). 

These thin beds at the base of some cycles may have been 

deposited in a transitional environment, such as a lagoon, as 

opposed to a subtidal, shallow-marine environment of deposition prevalent in the lower parts of other HFCs. The AP1 

sequence is part of the Avon Park Formation, as evidenced 

by the common occurrence of repetitive, upward-fining, 

peritidal HFCs with common subaerial caps (compare with 

Ward and others, 2003), and the common occurrence of 

cone-shaped, larger benthic foraminifera, including Fallotella

(Powell, 2010).

The AP2 sequence extends from 1,134 up to 1,068 ft bls 

in the upper part of the upper Avon Park Formation (fig. 8), 

and is interpreted to be deposited mostly in a subtidal marine 

environment in which the water depth was greater than that 

during deposition of the AP1 sequence. This sequence is 

interpreted to be representative of a transgressive, backstepping phase of the southeastern Florida platform (fig. 8). 

The 10 HFCs in the AP2 sequence have a similar range in 

thickness as the HFCs in the AP1 sequence (fig. 8), except 

for the uppermost HFC, which is 29 ft thick. Subtidal HFCs 

compose the AP2 sequence. They commonly have a soft, 
Stratigraphic Framework 23

Table 3. Avon Park Formation lithofacies in well G-2984. Modified from Ward and others (2003, table 1).

Lithofacies Composition Interpretation

Benthic-foram wackestone/

mud-dominated packstone

Carbonate-muddy limestone dominated by benthic foraminifers, most commonly Fallotella floridana. Other common 

constituents: ostracodes, mollusks, pellets and peloids. 

Generally low and highly variable porosity: moldic, vuggy, 

microcrystalline, and intraskeletal.

Low-energy inner shelf. Shallow 

subtidal to intertidal.

Benthic foram grain-dominated 

packstone/grainstone

Grainy limestone dominated by benthic foraminifers, most 

commonly Fallotella floridana. Other common constituents: ostracodes, mollusks, algal rhodoliths, and intraclasts. 

Generally good porosity (10–25 percent estimated in thin 

section): intergranular, intraskeletal, moldic, and vuggy.

High-energy inner shelf. Shallow 

subtidal to intertidal.

Skeletal wackestone/

mud-dominated packstone

Carbonate-muddy limestone with echinoids, mollusks, and 

mixtures of benthic and planktic foraminifers. Generally 

low and highly variable porosity: moldic, vuggy, microcrystalline, and intraskeletal.

Low-energy open shelf. Shallow 

subtidal

Skeletal grain-dominated 

packstone/grainstone

Grainy limestone with benthic foraminifers, echinoids, mollusks, peloids, algal rhodoliths, and intraclasts. Generally 

good porosity (10–25 percent estimated in thin section): 

intergranular, intraskeletal, moldic, and vuggy.

High-energy open shelf. Shallow 

subtidal

Skeletal floatstone/rudstone Coarse-grained equivalent of skeletal wackestone/mud-dominated packstone and grain-dominated packstone/grainstone 

rich in gravel-size mollusks and/or echinoids. Variable porosity (low in echinoid-rich layers): intergranular, intraskeletal, moldic (especially in mollusk-rich layers), and vuggy.

Shallow subtidal

Stromatolite Wavy laminated carbonate mudstone, fine packstone, or 

fine grainstone with thin irregular organic-rich laminae. 

Constituents: pellets, ostracodes, and benthic foraminifers. 

Porosity highly variable, up to estimated 20 percent in 

grainy laminae: moldic, fenestral, vuggy, intergranular, and 

minor fracture.

Restricted inner shelf. Intertidal to 

supratidal.

Laminite Laminated carbonate mudstone and/or wackestone. Poorly 

fossiliferous. Ostracodes, benthic foraminifers, and pellets. 

Generally very low porosity: fenestral, fracture, and moldic.

Restricted inner shelf. Low-energy tidal 

flats.

Intraclastic floatstone/rudstone In situ carbonate conglomerate composed of gravel-size fragments of limestone and dolomite. Porosity highly variable 

depending on amount of matrix: intergranular, fracture, and 

moldic.

High-energy event

Collapse breccia Intraclast floatstone/rudstone composed of rounded to angular 

fragments of various limestone rock types.

Zones of post-depositional collapse 

breccia, mostly associated with large 

vugs. Others may be associated with 

dissolution of evaporites in tidal-flats.

Mudstone Carbonate mudstone with abundant, pervasive, small, irregular 

to tortuous pores and marks due to rhizoliths or borrowing. Poorly to non-fossiliferous. Very low porosity: fracture 

and vuggy. Commonly hard and dense, but also broken to 

brecciated.

Subaerial exposure
24 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

poorly-cemented, benthic foraminifer wackestone depositional 

texture in their lower part, and in most cases coarsen upward. 

The top of the HFCs are commonly defined by thin layers 

(0.1 to 0.5 ft thick) of irregularly cemented, medium- to coarsegrained, benthic-foraminifer packstone to grainstone having 

abundant pinpoint-sized interparticle porosity, and in some 

cases, large irregular vugs. The upper 0.6 ft of the uppermost 

HFC of AP2 is well cemented and karstic, and has large (0.25 to 

0.5 in.) semivertical vugs that may follow preexisting rhizoliths 

or burrows. The semivertical vugs in this HFC extend downward as much as 3 or 4 ft and are filled with fine, phosphatic, 

quartz sand that probably filled the vugs during transgression of 

the upper bounding surface of the AP2 sequence.

The AP2 sequence is part of the Avon Park Formation, 

with evidence including the similarity of the subtidal 

lithofacies present in both the AP1 and AP2 sequences and 

the abundant occurrence of cone-shaped, larger benthic 

foraminifera throughout (Fallotella; Powell, 2010). Discoid, 

larger benthic foraminifera characteristic of the Ocala Limestone (Powell, 2010) are not present. Additionally, the Ocala 

Limestone is interpreted to be deposited in a mid- to outerramp environment that is generally below normal wavebase, 

rather than in an inner-ramp environment with shallower water 

depths (Ward and others, 2003).

Lower Arcadia Formation

The lower Arcadia Formation in test corehole G–2984, 

which is 147 ft thick, contains four depositional sequences, 

AR1 through AR4, in ascending order (fig. 8, pl. 1). An 

erosional unconformity is present at the top of the AR3 and 

AR4 sequences. Additionally, phosphatization is present at the 

top of the AR3 and AR4 sequences. Some of these sequence 

boundaries may represent a long hiatus, and two or more of 

these sequences grouped together may represent a composite 

sequence (table 2). The HFCs in these sequences are much 

thicker than most of the HFCs in the sequences of the upper 

part of the Avon Park Formation. Only seven HFCs are present 

in all four sequences, and four of these HFCs are at least 20 ft 

thick and have coarsening upward grain size. In southwestern 

Florida, the lower Arcadia Formation (Supersequence A) 

of late Oligocene age was found to “consist of primarily 

shoaling-upward sediment packages deposited in shallow 

water” (Missimer, 2002, p. 150).

The limestone in the AR1 and AR2 sequences is 

molluscan rudstone and floatstone, packstone, and grainstone 

with common moldic porosity. The lithology of the 19-ft thick 

interval below 1,048 ft bls to the base of the AR1 sequence, 

however, is a quartz sandstone with a high proportion of phosphate grains (as much as 50 percent, fig. 8). Within the AR1 

sequence, the top of the lowest HFC, at a depth of 1,061 ft bls, 

is underlain by a firmground (a submarine depositional surface 

consisting of a firm substrate) and an associated a Glossifungites ichnofacies. This firmground surface may be a drowning 

unconformity that formed during a period of high relative sea 

level (Schlager, 2005). 

A unit lying between the Avon Park Formation and the 

Arcadia Formation is described as the Suwannee Limestone 

in construction reports for other wells in the study area 

(Camp, Dresser, and McKee, Inc., 1996; Montgomery 

Watson, 1996; CH2M HILL, 1999), and this unit is the same 

interval that includes both the AR1 and AR2 sequences in 

test corehole G–2984. Evidence herein indicates that these 

sequences are part of the Arcadia Formation because the 

rocks and sediment of AR1 and AR2 sequences have the 

following properties characteristic of the Arcadia Formation 

(Scott, 1988; Cunningham and others, 1998): (1) the common 

to abundant occurrence of quartz and phosphate sand, (2) the 

presence of sucrosic dolomite in some of the limestone and 

sandstone, (3) a heterozoan carbonate particle assemblage 

(James, 1997), and (4) the lack of thin, exposure-capped 

peritidal cycles. At the W–17156 test corehole in the Florida 

Keys, no phosphorite, quartz sand grains, or dolomite were 

observed in the Suwannee Limestone (Cunningham and 

others, 1998). The carbonate particle assemblage prevalent 

in the AR1 and AR2 sequences in G–2984 is heterozoan, 

which is similar to that found in the Arcadia Formation in 

the Florida Keys in the W–17156 test corehole, rather than a 

chlorozoan carbonate particle assemblage (James, 1997) found 

in the Suwannee Limestone in that test corehole (Cunningham 

and others, 1998).

The bottom 39 ft of sequence AR3 is quartzose sand 

or sandstone with high phosphate grain content (fig. 8), and 

within this interval, the top of the lowest HFC in the sequence, 

at 982.3 ft bls, is a possible firmground surface associated with 

a Glossifungites ichnofacies. The surface may be a transgressive surface followed by progradation in the overlying HFC. 

Based on the core and the OBI and ABI logs, in the upper part 

of the lower HFC in the AR3 sequence from a depth of 985 to 

982.3 ft bls, and from a depth of 965 to 961 ft bls in the upper 

HFC, thin (1–2 ft thick), well-cemented, dense, sandstone or 

limestone layers are interbedded with uncemented or poorly 

cemented sand, or possibly bedding plane vugs (fig. 8). The 

uncemented layers are indicated on the caliper log by thin, 

abrupt, borehole enlargements (fig. 8) and sediment is visible 

inside the “vugs” on the OBI log. In the upper HFC of the 

AR3 sequence, above a depth of 961 ft bls, sandy, phosphatic 

packstone, rudstone, and floatstone with moldic porosity is the 

dominant lithology.

The two thin HFCs present in the AR4 sequence are 

dominated by thick (4 to 7 ft) beds consisting of oyster shell 

rudstone (fig. 8). The oyster shells are large and thick, and 

may be whole shells that grew in place. The shell beds have a 

matrix composed of packstone with rock and shell fragments, 

or mudstone, or very fine sand- to silt-sized sucrosic dolomite. 

Correlation of Sequences Within the Study Area

On the basis of correlations between borehole 

geophysical log data and the lithology of core samples from 

the G–2984 test corehole, the upper surface of the AP1 

sequence was identified in wells at other sites in the study 

area. Using borehole image logs, this boundary was placed 

at the top of the uppermost HFC that appears to have an 
Stratigraphic Framework 25

upper bounding dense, lime mudstone layer. The depth of the 

upper boundary of the AP1 sequence ranges from 1,010 to 

1,248 ft bls in the study area (appendix table 1–4), and this 

boundary shallows in altitude from east to west in the study 

area (pls. 1 and 2). In addition, the thicknesses of HFCs in 

the AP2 sequence commonly increase above this boundary 

and generally lack cycles capped by lime mudstone. The 

boundary between the AP1 and AP2 sequences was identified 

on the basis of analysis of (1) optical borehole imagery in 

wells G–2916 and G–2940; (2) acoustic televiewer data in 

wells G–2946, G–2964, G–2982, G–2991, and PB–1775; and 

(3) formation microresistivity image data in well PB–1841. 

This boundary was determined with less certainty in additional wells in hydrogeologic sections A–A′, C–C′, and Z–Z′

(pls. 1–3) and well CS-I2 (fig. 6) using other types of borehole 

geophysical data, such as sonic, shallow-reading resistivity, 

and caliper data in combination with lithologic data. 

The AP2 sequence thickens from the northeast to the 

southwest, from 58 ft in well G–2916 (pl. 1) to 95 and 125 ft 

in wells G–2982 (pl. 2) and G–2945 (fig. 7) respectively. The 

AP2 sequence also thickens from east to west in the northern 

part of the study area, from G–2916 to PB–1766 (pl. 1).

The upper boundary of the AR2 sequence was correlated 

throughout the study area using GR log character and values 

and lithologic data. The depth of the boundary ranges from to 

900 to 1,060 ft bls (appendix table 1–4, pls. 1–3, figs. 4–8). 

The upper boundary of the AR2 sequence is usually defined by 

a large GR activity peak that is related to high phosphate grain 

content. The depth of the upper surface of the AR2 sequence 

in test corehole G–2984 is at a depth of 1,004 ft bls, and this 

sequence is overlain by phosphatic quartz sandstone (fig. 8). 

The combined thickness of the AR1 and AR2 sequences 

does not vary greatly in the study area, ranging from 52 ft in 

PB–1766 to 70 ft in CS-I2 and PB–1775 (pls. 1–3, figs. 4–8).

Seismic Stratigraphy and Structure

Approximately 14 mi of high-frequency, marine 

seismic-reflection data were acquired along the Hillsboro 

Canal in northeastern-most Broward County (fig. 12). 

These data yielded a single, 2-dimensional, high-resolution, 

seismic-reflection profile that was used to evaluate geologic 

structures and stratigraphic complexities that cannot be 

delineated using borehole data alone. The hydrogeologic cross 

section A–A′ parallels the seismic-reflection profile along the 

Hillsboro Canal between wells PB–1766 and G–2984 (pl. 1, 

fig. 1). Geologic, hydrogeologic, and geophysical data from 

wells PB–1766, PB–1775, and G–2984 (fig. 1, appendix 

tables 1–4 and 1–5) were used to correlate the dominant 

lithostratigraphic, sequence-stratigraphic, and hydrogeologic 

units identified in the boreholes to the seismic-reflection 

profile (fig. 13). The seismic profile was especially useful in 

identifying karst collapse structures, which could disrupt continuity of confining beds within the Floridan aquifer system. 

Karst features similar to those observed in the Hillsboro 

seismic-reflection profile are shown on seismic-reflection 

profiles in southern Florida presented by Cunningham and 

others (2001b, 2003) and Cunningham and Walker (2009). The 

integration of borehole datasets and seismic-reflection profiles 

enhanced delineation of well-to-well horizontal distribution 

and connectivity of hydrogeologic units.

The Hillsboro Canal seismic-reflection profile is 

displayed with two vertical scales, indicating two-way 

travel time and corresponding depth below canal stage 

level. The two-way travel times of the seismic-reflection 

profile were converted to depth by using average verticalinterval velocities assigned to three major divisions of the 

lithostratigraphic section imaged on the seismic-reflection 

profile: (1) an upper section consisting of mixed carbonates 

and siliciclastics from the canal bottom to the upper contact 

of the Arcadia Formation, (2) a middle section consisting of 

carbonate strata between the upper contact of the Arcadia 

Formation to the upper contact of the Avon Park Formation, 

and (3) a lower section consisting of carbonate strata from 

the upper contact of the Avon Park Formation to a lower part 

of the Avon Park Formation (fig. 13). The different average 

interval velocities (AIVs) shown on the west and east sides 

of figure 13 demonstrate their lateral variation across the 

seismic-reflection profile. For seismic reflections above the 

upper contact of the Arcadia Formation, an approximate depth 

scale was calculated based on the correlation of borehole 

data to the seismic-reflection profile. The thicknesses of the 

interval between the canal stage to the upper contact of the 

Arcadia Formation in the PB–1766 and G–2984 boreholes 

were divided by the one-way acoustic compressional wave 

travel times measured from the seismic-reflection profile 

for the intervals between time zero and the upper contact 

of the Arcadia Formation at the two wells. The average 

velocity for this interval is 5,569 feet per second (ft/s) in test 

borehole PB–1766 and 6,159 ft/s in test corehole G–2984. 

These AIVs are similar to interval velocities of 5,315 ft/s and 

5,578 ft/s used by Cunningham and others (2001b) for vertical 

lithostratigraphic intervals along the Caloosahatchee River 

and San Carlos Bay, respectively, in southwestern Florida. 

For seismic reflections below the upper contact of the Arcadia 

Formation to the upper contact of the Avon Park Formation, an 

approximate depth scale was created from the sonic logs run 

over this stratigraphic interval in test borehole PB–1766 and 

much of this interval in the G–2984 test corehole. The calculated average velocity from the upper contact of the Arcadia 

Formation to the upper contact of the Avon Park Formation is 

7,899 ft/s in test borehole PB–1766 and estimated at 6,508 ft/s 

in test corehole G–2984. Test borehole PB–1766 has the 

thickest interval of the Avon Park Formation that was logged 

with a sonic tool along the seismic-reflection profile. Thus, an 

AIV of the Avon Park Formation was produced from the Avon 

Park Formation sonic log values acquired in test borehole 

PB–1766 and used as the AIV of the Avon Park Formation 

across the seismic-reflection profile. The average velocity 

calculated for this thick interval of the Avon Park Formation 

is 10,030 ft/s. 
26 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida WEST EAST PB-1766 PB-1775 G-2984

0

200

Depth below canal water level, in feet

Depth below canal water level, in feet

400600800

1,0001,2001,400

0

100200300400500600700

1,6001,8002,0002,2002,4002,6002,8003,000

02004006008001,0001,2001,4001,6001,8002,0002,2002,4002,6002,800

Two-way traveltime, in milliseconds

0100200300400500600700

Two-way traveltime, in milliseconds

AIV=5,569 ft/s AIV=7,899 ft/s AIV=10,030 feet per second (ft/s)

AIV=6,159 ft/s AIV=6,508 ft/s AIV=10,030 feet per second (ft/s)

Shot point

41,100

41,000

40,900

40,800

20,400

20,300

20,200

20,100

20,000

500

400

300

200

0

100

30,800

30,700

30,600

30,500

30,400

30,300

30,200

30,100

10,300

10,200

10,100

10,000

30,000

20,500

Vertical scale greatly exaggerated

2 MILES 0

2 KILOMETERS 0

1

1

EXPLANATION

Average vertical-interval velocities shown on right and left sidesNoisy, low-amplitude vertical bands

—Probably caused by energy 

attenuation at or near the canal bottom

AIV White-line anomalies

—Most occur from top to bottom of the profile and 

were caused by acquisition during passage under bridges and pipelines. This can cause the onboard navigation system to lose connection to navigational satellites

Figure 12. Uninterpreted seismic-reflection profile acquired along the Hillsboro Canal and locations of wells PB-1766, PB-1775, and G-2984 projected onto the profile (fig. 1).
Stratigraphic Framework 27

No data

EAST

Depth below canal water level, in feet

02004006008001,0001,2001,4001,6001,8002,0002,2002,4002,6002,800

WEST

PB-1766

0

200

Depth below canal water level, in feet

400600800

1,0001,2001,400

0

100200300400500600700

1,6001,8002,0002,2002,4002,6002,8003,000

Two-way traveltime, in milliseconds

0100200300400500600700

Two-way traveltime, in milliseconds

AIV=5,569 ft/s AIV=7,899 ft/s AIV=10,030 feet per second (ft/s)

AIV = 6,159 ft/s AIV = 6,508 ft/s AIV = 10,030 ft/s Top lower Arcadia Formation

G-2984 PB-1775

Ochopee

Ochopee

Limestone

Limestone

Member

Island

Formation

Stock

Member Ochopee

Ochopee

Limestone

Limestone

Member

Member

Uppermost permeable

zone of Lower Floridan aquifer

Shot point

41,100

41,000

40,900

40,800

20,400

20,300

20,200

20,100

20,000

500

400

300

200

0

100

30,800

30,700

30,600

30,500

30,400

30,300

30,200

30,100

10,300

10,200

10,100

10,000

30,000

20,500

CS-4

CS-6

CS-7

CS-5

Top 

Pinecrest Sand

Member

Upper

Floridan

aquifer

Top Arcadia

Formation

Top 

Peace River

Formation

Avon Park

permeable

zone

Top AP1

sequence

CS-2

CS-1

CS-3

1

Island

Formation

Stock

Intermediate

confining unit

Middle

confining 

unit 1

Middle

confining 

unit 2

Unnamed 

sequence 

boundary

Top AR4

sequence

EXPLANATION 

Semi-vertical faults

—Common within the limits of the 

structural sags. Dashed where most uncertain

Average vertical-interval velocities shown on right and left sides Seismic-sag structure and numerationTruncation of reflections

—At the upper surface of the Arcadia Formation

AIV

CS-1

1 Stock Island Formation, after Cunningham and others, 1998.

Vertical scale greatly exaggerated

2 MILES 0

2 KILOMETERS 0

1

1

Figure 13. Seismic-reflection profile displayed in figure 12 showing interpreted lithostratigraphic and sequence-stratigraphic boundaries, hydrostratigraphy, and seven seismic-sag structures.
28 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

The Hillsboro Canal seismic-reflection profile 

(figs. 12 and 13) shows a continuous, thick, 2-dimensional 

profile of the major elements of the southeastern Florida 

middle Eocene to Pleistocene lithostratigraphic, sequence 

stratigraphic, and hydrogeologic record. Seismic reflections above the upper contact of the Arcadia Formation are 

continuous to discontinuous, with parallel to subparallel 

configurations that show prograding clinoform patterns 

having a maximum eastward apparent dip of 1.5 degrees. In 

the eastern part of the seismic-reflection profile, hummocky, 

clinoform seismic-reflection configurations are common 

above the Peace River Formation. Truncated reflections along 

a few narrow segments at the upper contact of the Arcadia 

Formation are indicative of karstic, erosional truncation, 

such as the two just west of shot point 20,200 (fig. 13, green 

arrows). Peace River Formation reflectors display an eastward 

downlap onto the upper surface contact of the Arcadia Formation across the entire profile. This downlapping relation and 

the truncation of reflections at the upper contact of the Arcadia 

Formation indicate the presence of a seismic-sequence 

boundary at the upper contact of the Arcadia Formation, and 

this seismic boundary corresponds to an unconformity and 

depositional sequence boundary observed in the G–2984 test 

corehole. The Arcadia Formation and upper and middle Avon 

Park Formation generally have parallel reflection configuration 

patterns, but also minor subparallel reflection configuration 

patterns and hummocky and wavy patterns. Because of the 

large contrast in the sonic velocity at the upper surface of the 

AP1 sequence, shown by the sonic Δt curve (inverse of sonic 

velocity) for G–2984 (fig. 8, pl. 1), this surface is traceable on 

the seismic-reflection profile as a strong amplitude reflection 

(fig. 13). Toward the bottom of the profile, areas of hummocky 

reflection configurations increase, as do chaotic reflection 

configurations, neither of which can be reliably interpreted.

Seven narrow segments within the seismic-reflection 

profile contain sagging reflections that stack vertically to 

form seismic-sag structural systems (Cunningham and 

Walker, 2009). These stacked reflection sags extend upward 

from within the Avon Park Formation to the upper contact 

of the Arcadia Formation and are labeled CS–1 through 

CS–7 in figure 13. In some cases, they terminate within the 

Peace River Formation or above it. The seven seismic-sag 

structural systems display vertically stacked, concave-upward 

arrangements of generally parallel seismic-reflection patterns 

that commonly display an upward decrease in sag angle. 

Cunningham and Walker (2009) defined two types of such 

structural systems – narrow and broad. The difference between 

the two is based on the differences in their inner sag width. 

The inner sag width is defined as “the distance between inflection points (that is, where the shape of the subsidence profile 

changes from concave to convex upward) on both sides of the 

structural trough” (McDonnell and others, 2007). Cunningham 

and Walker (2009) found that in southeastern Florida beneath 

Biscayne Bay and the nearby Atlantic Ocean, the inner sag 

width of the narrow seismic-sag structural systems ranged 

from about 548 ft to 2,405 ft, with a mean of 1,165 ft, and the 

inner sag width of the broad seismic-sag structural systems 

ranged from approximately 3,600 ft to 16,000 ft, with a mean 

of about 8,100 ft. Six of the seven seismic-sag structural 

systems along the Hillsboro Canal are classified as narrow 

systems (average inner sag diameter of 1,844 ft), and one 

is classified as a broad system (C–3, inner sag diameter of 

4,730 ft). Local offset of seismic reflections are observed 

along the flanks of all seven seismic-sag structural systems 

and are indicative of faults associated with the sags.

The seismic-sag structural systems appear to be related to 

downward deformation of overlying strata into collapsed deep 

cave systems, as suggested by Cunningham and Walker (2009) 

for similar structures in southeastern Florida. The reflections 

on the Hillsboro Canal seismic-reflection profile generally 

have a chaotic configuration below the traceable depth of the 

seismic-sag structural systems. Therefore, the exact depths of 

the collapsed cave systems are not known, but they are probably deeper than the uppermost permeable zone of the Lower 

Floridan aquifer (fig. 13). This would place the minimum 

depths of the collapsed systems within the Avon Park Formation. The range in stratigraphic position of the uppermost sag 

for each of the seven seismic-sag structural systems is between 

the upper contact of the Arcadia Formation to possibly just 

above the upper contact of the Ochopee Limestone Member 

of the Tamiami Formation (fig. 13). This range suggests that 

collapse into paleocave systems occurred during a period that 

includes the Miocene and Pliocene Epochs.

Test corehole G–2984 is located within a seismic-sag 

structural system (fig. 13, CS–5). As discussed previously, 

an isolated structural low at the level of the upper contact 

of the Avon Park Formation at G–2984 (fig. 9) was mapped 

using well control only. The upper contact of the Avon Park 

Formation at G–2984 is as much as 80 ft deeper than the 

regional trend for this mapped boundary. The reflection at the 

upper surface of the lower Arcadia Formation is about 50 ft 

deeper to the west of G–2984, where the maximum sag on 

reflections in sag CS–5 is observed (fig. 13). None of the other 

six seismic-sag structural systems identified along the seismicreflection profile are evident on maps constructed solely on 

basis of the 1-dimensional, sparse well control along the canal 

(fig. 9). This emphasizes the value of seismic-reflection data in 

delineating the presence of these structural systems. Faulting 

and fracturing associated with these systems could provide 

passageways for vertical fluid flow and lead to upconing of 

saline water at water-supply or ASR wells in the Floridan 

aquifer system.

Hydrogeologic Framework

In eastern Broward County, part of the Floridan aquifer 

system studied herein includes the Upper Floridan aquifer, 

the middle semiconfining unit 1, the Avon Park permeable 

zone, the middle semiconfining unit 2, and the uppermost 

permeable zone of the Lower Floridan aquifer. The Avon 
Hydrogeologic Framework 29

Park permeable zone was not recognized by Miller (1986); 

middle semiconfining unit 1 and most of middle semiconfining 

unit 2 correspond to Miller’s (1986) middle confining unit I. 

The Avon Park permeable zone also has been called the 

“middle Floridan aquifer” within the study area, as a unit 

within the Upper Floridan aquifer (Lukasiewicz, 2003). The 

hydrogeologic framework defined herein is consistent with 

that of Reese and Richardson (2008) for southern Florida. 

The hydrogeologic framework of the Floridan aquifer 

system in eastern Broward County, from the top of the 

Floridan aquifer system to the bottom of uppermost permeable 

zone of the Lower Floridan aquifer, was constructed on the 

basis of analyses of borehole geophysical data, flowmeter 

logs, and borehole images and lithologic data, where available (pls. 1–3). Data from wells in eastern Broward County 

indicate the Upper Floridan aquifer, Avon Park permeable 

zone, and uppermost permeable zone of the Lower Floridan 

aquifer are present beneath and extend across this part of the 

county (pls. 1–3).

Upper Floridan Aquifer

The Upper Floridan aquifer is confined above by 

the intermediate confining unit, and below by the middle 

semiconfining unit 1 (fig. 2). The upper surface of the Upper 

Floridan aquifer is typically identified by borehole geophysical 

data patterns similar to those observed at G–2984, which 

indicate: (1) a decrease in GR activity relative to an elevated 

GR activity in the overlying confining unit; (2) an increase 

in formation resistivity as a result of a change in mineralogic 

composition of the aquifer and fluid properties; (3) fluctuating 

caliper readings indicative of an increase in megaporosity; 

and (4) a decrease in fluid conductivity and temperature that 

accompanies the increase in hydraulic conductivity (fig. 14). 

It was noted that the upper surface of the Upper Floridan 

aquifer, which is present within the lower Arcadia Formation, 

is distinguished by a lithology that is predominantly limestone 

with interspersed quartzose sandstone. These rocks are 

overlain by lime mudstone with intervals of clays and marls 

of the intermediate confining unit. The altitude of the upper 

surface of the Upper Floridan aquifer in the study area lies 

between –900 and –1,050 ft NGVD 29 (fig. 15).

The bottom of Upper Floridan aquifer is distinguished 

in the study area from the underlying middle semiconfining 

unit 1 by a reduction in abundance and relative contribution 

of flow zones identified by flowmeter analysis (fig. 14). 

Where flowmeter data are not available, formation resistivity, 

caliper, and sonic Δt data were used to identify the bottom 

of the Upper Floridan aquifer. Caliper-reading fluctuations 

decrease toward the bottom of the Upper Floridan aquifer as 

enlargement of the borehole in high porosity zones decreases. 

Formation resistivity data collected in a few boreholes indicate 

a generally increasing resistivity with depth through the Upper 

Floridan aquifer. Sonic Δt values were used to qualitatively 

identify relative changes in porosity values. Sonic Δt values 

greater than 120 microseconds per foot (μsec/ft) are estimated 

to indicate values of porosity greater than 42 percent. Sonic 

Δt values generally decrease from the top to the bottom of the 

Upper Floridan aquifer, as porosity values decrease. Because 

the decrease in porosity values with depth is gradational, the 

base of the Upper Floridan aquifer has in some cases been 

defined as the level below which sonic Δt values do not exceed 

120 μsec/ft. The altitude to the bottom of the Upper Floridan 

aquifer in the study area lies between –1,040 and –1,270 ft. 

The thickness of Upper Floridan aquifer in the study area 

ranges from 40 ft at G–2985 (cross-section C–C’; pl. 2), to 

350 ft at G–2968 (cross sections A–A’ and Z–Z’; pls. 1 and 3) 

(fig. 16).

The Upper Floridan aquifer in the study area generally 

correlates with part of the lower Arcadia Formation, the upper 

Avon Park Formation, and the upper part of the upper-middle 

Avon Park Formation. In some cases, however, the Upper 

Floridan aquifer is restricted to the lower Arcadia Formation 

and upper Avon Park Formation (pls. 1–3). Throughout the 

study area, the upper surface of the Upper Floridan aquifer 

occurs within the lower Arcadia Formation, but in all cases 

below the upper surface of the lower Arcadia Formation 

(pls. 1–3). The bottom of the Upper Floridan aquifer generally occurs within the upper-middle Avon Park Formation, 

although it may correlate with the upper surface of the 

upper-middle Avon Park Formation or occurs within the upper 

Avon Park Formation in the southwestern part of the study 

area (cross section C–C’, pl. 2). At G–2984, the upper surface 

of the Upper Floridan aquifer occurs within the AR3 sequence 

of the lower Arcadia Formation, and the bottom of the Upper 

Floridan aquifer is positioned within the AP1 sequence of the 

upper-middle Avon Park Formation (fig. 14).

Transmissivity of the Upper Floridan aquifer generally 

increases from west to east across the study area (fig. 17), and 

ranges from 120 to 31,000 feet squared per day (ft2/d; appendix 

table 1–6). The anomalously low value at CS-I2 (120 ft2/d) may 

be the result of testing only two zones totaling 80 ft of the entire 

240 ft thickness of the Upper Floridan aquifer at that location. 

Flowmeter data were collected in most of the boreholes 

used to define the hydrogeologic framework in the study area. 

Generally, multiple flow zones are present in the Upper Floridan 

aquifer, and these zones are on the scale of 1 ft to tens of feet 

thick. Fifteen flow zones were identified in G–2984 using 

spinner flowmeter analysis and oscillations or changes in fluid 

conductivity and temperature values (fig. 14). A thin flow zone 

that contributes substantial flow into the borehole occurs at the 

upper surface of the Upper Floridan aquifer in G–2984. A group 

of four thin flow zones occurs within the middle of the Upper 

Floridan aquifer, and collectively contribute almost one third of 

the total flow from the aquifer into the borehole. This group of 

four flow zones occurs in the lower part of the upper Avon Park 

Formation and in the upper part of the AP1 sequence.

The occurrence and thicknesses of flow zones below 

the top of the AP1 sequence within the Upper Floridan 

aquifer decrease to the west (pls. 1 and 2; figs. 6 and 7). Flow 

zones within this interval are not indicated by flowmeter 
30 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 14. Borehole geophysical data including fluid properties and flowmeter logs, lithology, 

hydrogeologic units, and flow zones for test corehole G-2984.

CAL-6, in inches

0 6

GAMM-6, in CPS

0 400 Lithology

Lithostratigraphic

unit 5,100 6,100

Fluid temperature-6, in degrees Celsius

21.6 22.6 Flowmeterrate-6, in gallons per minute

0 147 SonicDT-6, in μsec/ft

170 70

Flow zone

Hydrogeologic

unit

900

1,000

1,100

1,200

1,300Depth, in feet below land surface

Depositional 

cycle

Depositional

sequence

Zones of lost

circulation

120

AR 4 AR3 AR2 AR1 AP2 AP1

Upper

Arcadia Lower Arcadia Upper Avon Park Upper-middle Avon Park

Backup curve with units

from 147 to 294

Fluid conductivity, in microsiemens 

per centimeter

ND ND
Hydrogeologic Framework 31

PALM BEACH

BROWARD

North New

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

MIAMI–DADE

BROWARD

C-9 Canal

River Canal

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’

EXPLANATION

G-2916

–933

Well location and altitude— 

 Well number 

 Altitude of the upper surface 

 of the Upper Floridan aquifer, 

 in feet relative to NGVD 29

Line of equal altitude—

 Shows altitude of the 

 upper surface of the 

 Upper Floridan aquifer, in 

 feet relative to NGVD 29. 

 Contour interval is 50 feet. 

 Contours approximately 

 located. Hachures indicate 

 depression

–980

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

5 MILES

–1,050

–1,000

–950

–950

–900

G-2986

–967

G-2916

–933

BCN-I1

–986

G-2942

–1,000

D365

–985 MAR-I2

–977

CS-I2

–1,007

PLT-I1

–1,005

PLT-ROI1

–1,032

PBP-I1

–1,040

G-2963

–1,043

SUN-I3

–1,042

G-2982

–1,040

G-2914

–1,025

G-2978

–990

G-2938

–966 G-2917

–967

PB-1775

–935

PB-1766

–973 G-2984

–948

G-2968

–908

G-2985

–993

G-2989

–1,087

G-2981

–1,002

G-2966

–1,015

G-2944

–1,057

G-2971

–975

G-2973

–891

G-2961

–914

G-2970

–942

FTL-I4

–944

G-2987

–985

S-567

–934

HAL-RO1

–917

HOL-RO1

–937

75

95

595

1

441

Figure 15. Altitude of the upper surface of the Upper Floridan aquifer.
32 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

PALM BEACH

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

MIAMI–DADE

BROWARD

C-9 Canal

EXPLANATION

G-2916

150

NR

Well location and thickness— 

 Well number 

 Thickness of the Upper 

 Floridan aquifer, in feet

Line of equal thickness—

 Shows thickness of the 

 Upper Floridan aquifer, in 

 feet. Contour interval is 

 100 feet. Contours 

 approximately located

320

Not reached, entire aquifer

 not penetrated

ND Not determined

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83 5 MILES

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’central meridian –83 ̊00’

300

200

300

100

200

300

200

G-2986

280

G-2916

NR

BCN-I1

240

G-2942

260

D365

260 MAR-I2

230

CS-I2

240

PLT-I1

215

PLT-ROI1

190

PBP-I1

290

G-2963

330

SUN-I3

190

G-2982

210

G-2914

235

G-2978

260

G-2938

225 G-2917

230

PB-1775

249

PB-1766

240

G-2984

294

G-2968

350

G-2985

40

G-2989

190

G-2981

190

G-2966

266

G-2944

170

G-2971

240

G-2973

330

G-2961

190

G-2970

190 FTL-I4

150

G-2987

180

S-567

ND

HAL-RO1

NR

HOL-RO1

180

75

95

595

1

441

Figure 16. Thickness of the Upper Floridan aquifer.
Hydrogeologic Framework 33

Figure 17. Distribution of transmissivity in the Upper Floridan aquifer.

10,000

20,000

20,000

10,000

30,000

G-2887

24,000

G-2970

ND

HAL-RO1

17,000

HOL-RO1

31,000

PBP-I2

2,700p

G-2989

3,700

G-2961

ND

G-2988

24,000

G-2966

ND

FLT-14

ND

S-567

ND

G-2984

ND

G-2889

29,000 G-2986

ND

D-365

ND

6

G-2940

16,000

10

G-2917

20,000

30

SUN-I3

ND

32

G-2981

1,300

31

G-2982

ND

5

CS-12

120p

G-2942

ND

BCN-I1

ND

17

PB-1765

8,100**

PB-1775

10,000

PB-1776

19,000**

21

MAR-I2

ND

33

G-2914

5,700**

G-2978

ND

G-2985

9,000*

G-2987

ND

PLT-I1

ND

G-2971

ND

PLT-ROI1

ND

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Canal

Hillsboro

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

EXPLANATION

Line of equal transmissivity—

 Shows transmissivity in the 

 Upper Floridan aquifer, in feet 

 squared per day. Contours 

 approximately located

20,000

 Well location and 

 transmissivity—

 Site number 

 Well number 

 Transmissivity in the Upper 

 Floridan aquifer, in feet 

 squared per day

Value may be higher than 

 ambient value. Value is 

 based on test after 

 production well was 

 acidized

Value estimated based on test 

 of interval including both 

 Upper Floridan aquifer and 

 Avon Park permeable zone, 

 and flowmeter log of same 

 interval 

Data collected during a 

 packer test. All other tests 

 are of constructed wells. 

 For CS-12, value is from the 

 combination of two packer 

 test results of separate

 intervals in the Upper 

 Floridan aquifer

ND No data

19,000**

9,000*

2,700p

32

G-2981

1,300

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES
34 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

measurements in some wells to the west, including SUN-I3, 

PLT-ROI1, and G–2985 (pl. 2), and only one or two thin 

(less than 10 ft) flow zones are indicated in three other wells 

(G–2981, pl. 2; CS-I2, fig. 6; G–2945, fig. 7). In contrast, 

to the east, below the top of the AP1 sequence in the Upper 

Floridan aquifer, seven flow zones with a combined thickness 

of 60 ft are indicated in G–2984 (fig. 14), and four flow zones, 

also with a combined thickness of 60 ft, are indicated by the 

flowmeter data in G–2968 (pl. 1). Although the overlying AP2 

sequence thickens to the west, there is only one thin flow zone, 

associated with the upper contact of the Avon Park Formation, 

present in some wells. 

Middle Semiconfining Unit 1

The middle semiconfining unit 1 separates the overlying 

Upper Floridan aquifer from the underlying Avon Park 

permeable zone. In the study area, the altitude of the top of the 

middle semiconfining unit 1 ranges from –1,040 ft to –1,270 ft 

NGVD 29, and the altitude at the bottom range from –1,350 ft 

to –1,630 ft NGVD 29. The thickness ranges across the study 

area from 150 ft to about 500 ft. Where hydraulic conductivity 

has been estimated, values range from 0.9 to 19 feet per 

day (ft/d) (table 4). Flow zones are indicated (by flowmeter 

measurements) in some wells in the study area (pls. 1–3), but 

these few flow zones typically contribute less to overall flow 

than the flow zones in the aquifer units of the Floridan aquifer 

system. 

Avon Park Permeable Zone

The Avon Park Permeable Zone is identified by an increase 

in the number and spatial density of flow zones relative to overlying and underlying confining units, as indicated by changes in 

vertical borehole fluid flow in flowmeter measurements and by 

zones of decreased and more pronounced fluctuations in sonic 

Δt values, which indicate zones of greater and lesser porosity 

(pls. 1–3). The top of this zone is estimated to range from 

–1,350 to –1,630 ft NGVD 29 (fig. 18) and the bottom from 

–1,500 to –1,710 ft NGVD 29 in the study area. The thickness 

is estimated to range from 35 to 210 ft (fig. 19). The Avon Park 

permeable zone generally occurs within the upper part of the 

lower-middle Avon Park Formation (pls. 1–3).

Estimated transmissivity of the Avon Park permeable 

zone in the study area ranges from 900 to 10,000 ft2/d (fig. 20, 

appendix table 1–6) for selected sites. The summed length of 

the tested interval for selected sites was generally greater than 

50 ft. Additionally, where tested intervals included both the 

Upper Floridan aquifer and Avon Park permeable zone an estimate of transmissivity for each zone was made. The estimated 

hydraulic conductivity of the Avon Park permeable zone in the 

study area ranges from about 1 to 170 ft/d (table 4).

Middle Semiconfining Unit 2

The middle semiconfining unit 2 separates the overlying 

Avon Park permeable zone from the underlying uppermost 

permeable zone of the Lower Floridan aquifer, and can 

be recognized by a lower density of flow zones and less 

pronounced fluctuations in sonic Δt values than in the 

overlying Avon Park permeable zone (pls. 1–3). The altitude 

of the top of middle semiconfining unit 2 ranges from about 

–1,500 ft to –1,710 ft NGVD 29, and the base from –1,970 ft 

to –2,250 ft NGVD 29 in the study area. The thickness varies 

across the study area from 340 ft to about 670 ft (appendix 

table 1–5). Estimated hydraulic conductivity values range 

from 0.02 to 66 ft/d (table 4). Productive flow zones are 

indicated by flowmeter measurements in some wells, for 

example wells G–2971 and BCN-I1 (pls. 2 and 3), but the unit 

is considered to be semiconfining. 

Uppermost Permeable Zone of the Lower 

Floridan Aquifer

The Lower Floridan aquifer is identified by the 

presence of an increased number and spatial density of flow 

zones relative to overlying middle semiconfining unit 2, as 

indicated by flowmeter data; by zones of decreased and more 

pronounced fluctuations in sonic Δt values, indicating zones 

of increased and decreased porosity (pls. 1–3); and by caliper 

curves with thin, abrupt, increases in borehole diameter 

values indicating zones of fracturing, or thin intervals of 

megaporosity. The altitude of the upper surface of uppermost 

permeable zone of the Lower Floridan aquifer is estimated 

to range from –1,970 to –2,250 ft NGVD 29 and the lower 

surface from –2,100 to –2,320 ft NGVD 29 in the study area 

(appendix table 1–5). The thickness is estimated to range 

from 50 to 190 ft. The uppermost permeable zone of the 

Lower Floridan aquifer corresponds to the lower Avon Park 

Formation (pls. 1–3). Transmissivity ranges from 61 to greater 

than 35,000 ft2/d (appendix table 1–6). Estimates of hydraulic 

conductivity range from 1.2 to 708 ft/d (table 4). Flowmeter 

analysis indicates the presence of one or more flow zones in 

the uppermost permeable zone of the Lower Floridan aquifer.

Table 4. Horizontal hydraulic conductivity values for major 

permeable zones and semiconfining units based on data from 

aquifer and packer tests in the study area.

[APPZ, Avon Park permeable zone; LF1, uppermost major permeable zone of 

the Lower Floridan aquifer; MC1, middle semiconfining unit; MC2, middle 

semiconfining unit 2; UFA, Upper Floridan aquifer]

Permeable 

zone or 

semi-confining unit

Minimum

value

(feet/day)

Maximum

value

(feet/day)

Median

(feet/day)

Number

of tests

UFA 1.4 200 80 20

MC1 0.9 19 3 6

APPZ 1 170 16 17

MC2 0.02 66 1 62

LF1 1.2 708 94 5
Hydrogeologic Framework 35

EXPLANATION

Line of equal altitude—Shows 

 altitude of the upper surface 

 of the Avon Park permeable 

 zone, in feet relative to 

 NGVD 29. Contour interval 

 is 100 feet. Contours 

 approximately located

–1,420

Not determined

Not reached

Well location and altitude—

 Well number in black 

 Altitude of the upper surface 

 of the Avon Park permeable 

 zone, in feet relative to 

 NGVD 29

ND

NR

G-2968

–1,408

–1,600

–1,500

–1,500

–1,400

–1,500

G-2968

–1,408

PB-1766

–1,503 PB-1775

–1,469

G-2970

–1,462

HAL-RO1

NR

G-2973

–1,381

HOL-RO1

NR G-2963

–1,617

G-2944

–1,637

PBP-I1

–1,570

G-2989

NR

G-2961

–1,344

G-2966

–1,441

FTL-I4

–1,434

S-567

ND

G-2984

NR

G-2916

NR

G-2986

NR

D-365

NR

G-2938

–1,478

G-2917

NR

SUN-I3

–1,622

G-2981

NR

G-2982

–1,610

CS-I2

–1,547

G-2942

–1,445

BCN-I1

MAR-I2 –1,526

–1,547

G-2914

NR

G-2978

–1,529

G-2985

–1,528

G-2987

NR

PLT-I1

–1,540

G-2971

–1,515

PLT-ROI1

–1,571

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian -83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES

Figure 18. Altitude of the upper boundary of the Avon Park permeable zone.
36 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

G-2968

170

PB-1766

195

PB-1775

145

G-2970

90

HAL-RO1

NR

G-2973

120

HOL-RO1

NR

G-2963

47

G-2944

70

PBP-I1

130

G-2989

NR

G-2961

150

G-2966

210

FTL-I4

80

S-567

ND

G-2984

NR

G-2916

NR

G-2986

NR

D-365

NR

G-2938

108

G-2917

NR

SUN-I3

60

G-2981

NR

G-2982

80

CS-I2

80 G-2942

185

BCN-I1

86

MAR-I2

100

G-2914

NR

G-2978

70

G-2985

35

G-2987

NR

PLT-I1

140

G-2971

70

PLT-ROI1

90

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

EXPLANATION

Line of equal thickness—Shows 

 thickness of the Avon Park 

 permeable zone, in feet. 

 Contour interval is 100 feet. 

 Contours approximately 

 located

100

Not determined

Not reached, entire zone 

 not penetrated

Well location and thickness—

 Well number

 Thickness of the Avon Park 

 permeable zone, in feet 

ND

NR

G-2968

170

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES

200

100

100

100

Figure 19. Thickness of the Avon Park permeable zone.
Hydrogeologic Framework 37

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TL

A

N

TIC

O

CEA

N

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’

EXPLANATION

8

G-2968

10,000

ND

NR

10,000p

9,000*

7,000**

[10,000]

Well—

 Site number

 Well number

Value estimated based on 

 combining transmissivity 

 values of two tests of 

 separate intervals in a well 

 or in two wells at a site

Value estimated based on test 

 of Upper Floridan aquifer and 

 flowmeter log of open interval 

 including both Upper Floridan 

 aquifer and Avon Park 

 permeable zone

Value estimated based on test 

 of interval including both 

 Upper Floridan aquifer and 

 Avon Park permeable zone, 

 and flowmeter log of same 

 interval

Data collected during packer 

 test, all other tests are of 

 constructed well intervals

Not reached, zone not 

 penetrated

No data or tested interval 

 of insufficient length

Transmissivity in Avon Park 

 permeable zone, in feet 

 squared per day

80°20' 80°10'

26°20'

26°10'

26°00'

0 2.5

0 2.5

5 KILOMETERS

5 MILES

G-2970

ND

G-2978

ND

G-2983

4,200

G-2982

9,000p

G-2942

ND

D-365

NR

8

G-2968 

[10,000p]

S-567

ND

CS-I2

ND

27

PLT-I1

PLT-I2

[6,500p]

PBP-I1

ND

G-2944

900p

G-2961

G-2975

ND

G-2917

NR

G-2914

NR

MAR-I2

ND

G-2916

NR

FTL-I4

ND

G-2939

9.400

BCN-I4

ND

G-2986

NR

16

PB-1775 

7,000**

PB-1766

ND

HOL-RO1

NR

HAL-RO1

NR

G-2966

ND

PLT-ROI1

>2,700p

G-2971

ND

G-2988

NR

G-2984 

NR

G-2987

NR

7

G-2985

9,000*

G-2963

ND

G-2973

ND

75

95

595

1

441

Figure 20. Distribution of transmissivity of the Avon Park permeable zone.
38 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Conceptualization of Groundwater Flow Within 

the Floridan Aquifer System

One goal for this study is to develop an improved 

understanding of geologic features that influence groundwater 

flow within the Floridan aquifer system in the study area. 

Theoretically, the lithologic attributes of the pore network can 

be characterized within the context of the cyclostratigraphic 

framework, and this provides valuable information on the 

heterogeneous distribution of porosity and permeability to 

inform groundwater management of the Floridan aquifer 

system. This report provides an integrated analysis of available 

borehole-geophysical, seismic-reflection, and lithologic data. 

Core samples from the G–2984 test corehole were macroscopically and microscopically examined to characterize the relation 

between rock depositional textures, associated pore networks, 

and borehole geophysical log data, especially digital optical 

and acoustic borehole images, and borehole flowmeter data. 

The result is a preliminary conceptual model of groundwater 

flow in the Floridan aquifer system in Broward County. 

Water-bearing carbonate rocks of the Floridan aquifer 

system exhibit considerable groundwater exchange 

between a matrix porosity and vuggy porosity (Martin and 

Screaton, 2001). The porosity of this system has been described 

as a dual-continuum, providing both diffuse and concentrated 

groundwater flow that is hydraulically interconnected (Vacher 

and Mylroie, 2002; Budd and Vacher, 2004; Screaton and 

others, 2004). Diffuse groundwater flow can occur in a 

carbonate rock within which the pore system consists mostly 

by interparticle, interparticle, intercrystalline, and separate-vug 

pore space. Concentrated groundwater flow likely occurs 

within carbonate rock with a pore system characterized by 

touching-vug pores. In the Floridan aquifer system, this type of 

vuggy pore space is mainly interconnected vuggy megapores 

(for example bedding-plane vugs), vertical fractures, tectonic 

faults, and extensional faults related to karst collapse. 

The Upper Floridan aquifer at the G–2984 test corehole 

corresponds to the lower Arcadia Formation, upper Avon Park 

Formation, and upper-middle Avon Park Formation in the 

depth interval from about 960 to 1,255 ft bls (figs. 8 and 14, 

and pl. 1), and contains both diffuse and concentrated groundwater flow zones. Different types of flow zones are indicated 

by core, thin section, flowmeter, and borehole-wall image data. 

The Upper Floridan aquifer is overlain by rocks of the upper 

part of the lower Arcadia Formation, which consist of lowpermeability floatstone and rudstone, and quartz sandstone.

The upper surface of the Upper Floridan aquifer in the 

G–2984 corehole is marked by a thin, approximately 2 ft-thick 

flow zone between about 960 and 964 ft bls. This flow zone 

is formed by two open bedding-plane vugs. Concentrated 

groundwater flow into the borehole through this zone is 

demonstrated by an abrupt vertical increase in borehole fluid 

flow that was detected by a spinner flowmeter (fig. 21). From 

about 955 to 962 ft bls, bryozoan floatstone composes the 

lower Arcadia Formation. 

Diffuse flow in the Upper Floridan aquifer is recognized 

in the interval from about 1,102 to 1,130 ft bls in the G–2984 

test corehole (interval shown is 1,102 to 1,115 bls; fig. 22). 

The rock of this flow zone is mostly a benthic foraminifera 

grain-dominated packstone. A benthic foraminifera, peloid, 

skeletal fragment, grain-dominated packstone and grainstone 

was observed in an acid-etched limestone core sample and 

accompanying thin section acquired from about 1,110 ft bls 

(fig. 23). The dominant pore type at this depth is interparticle 

porosity. Interparticle porosity of the 1,109.5 ft sample is 

between 20 and 35 percent, based on a visual estimate from 

the thin section. A gradual, rather than abrupt, upward increase 

in borehole fluid-flow velocity measured by the spinner flowmeter in the interval from 1,105 to 1,115 bls indicates diffuse 

groundwater flow, which is corroborated by the observed pore 

types in core samples and thin section. 

Both diffuse and concentrated groundwater flow occurs 

between approximately 1,166 and 1,177 ft bls in the G–2984 

test corehole as indicated by optical and acoustic images, 

spinner flowmeter, borehole-fluid temperature and conductivity data (fig. 24). The diffuse flow is associated with mostly 

interparticle and particle-moldic pore types in grain-dominated 

packstone and grainstone, whereas concentrated flow is associated with vuggy megaporosity in micrite-dominated limestone 

that is mainly mudstone and wackestone. Three flow zones are 

present within this 10 ft interval of the Avon Park Formation. 

The upper flow zone (at approximately 1,166–1,171 ft bls) has 

a depositional texture characterized by moldic, benthic foraminifera, mud- to grain-dominated packstone and grainstone. 

Moldic and interparticle porosity provide for diffuse groundwater flow within this grain-dominated limestone. Two lower 

flow zones (at approximately 1,171 to 1,174 ft bls and 1,175 to 

1,177 ft bls) were identified by the observation of vuggy 

megaporosity on borehole images, and the association of the 

megaporosity with increases in vertical borehole fluid flow 

velocities measured by a spinner flowmeter. These two flow 

zones have a depositional texture characterized by particlemoldic, benthic-foraminifera, mudstone and wackestone, and 

mud-dominated packstone. The vuggy megaporosity in these 

two zones is mostly semi-vertically oriented and centimeterscale in diameter.

Although core-sample data are not widely available for 

the flow zones identified with borehole geophysical data, 

inferences regarding the nature of groundwater flow into or 

out of other wells could be made on the basis of the flowmeter 

measurements. For example, a concentrated flow zone is 

inferred in the G–2940 test corehole (fig. 25) by comparing 

spinner flowmeter data to pore network types that were 

observed on digital optical images. The flow zone is present 

in the lower Arcadia Formation and is approximately 1 ft 

thick (from about 1,027 to 1,028 ft bls). Evidence indicates 

groundwater flow is into the borehole through a bedding-plane 

vug (fig. 26). A similar type of flow zone is observed in data 

from the PB–1775 well (from about 1,040 to 1,060 ft bls) in 

the lowermost part of the Arcadia Formation (fig. 4). Although 

these flow zones and a minor flow zone in G–2984 between 
Hydrogeologic Framework 39

Fluid conductivity, in microsiemens per centimeter

Fluid temperature, in degrees Celsius

Caliper, in inches

Flowmeter rate, in gallons per minute

Spinner flowmeter, in counts per second

960

965

0° 180° 270°

Optical borehole 

image

Acoustic borehole 

image (amplitude)

Oriented to magnetic

North

Oriented to magnetic

North

Depth, in feet below 

land surface

Flow zone

Circumference of 

borehole

12.6 inches 12.6 inches

Circumference of 

borehole

955

High frequency 

depositional cycles 

90° 0° 0° 90° 180° 270° 0°

4 8

5,100 6,100

22.4 22.6

0

0

100

161.7 147

Figure 21. Borehole geophysical log data for test corehole G-2984, from 955 to 968 feet below land surface (ft bls), 

including optical and acoustic images, flowmeter and fluid properties, flow zones, and relation to high frequency 

depositional cycles.
40 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Fluid conductivity, in microSiemens per centimeter

Fluid temperature, in degrees Celsius

Caliper, in inches

Flowmeter rate, in gallons per minute

Spinner flowmeter, in counts per second

1,105

1,110

Optical borehole

image 

Acoustic borehole

image (amplitude) 

Oriented to magnetic

North

Oriented to magnetic

North

Depth, in feet below

land surface 

Flow zone

Circumference of

borehole 

12.6 inches 12.6 inches

Circumference of

borehole 

1,115

Flow zone continues down to 1,130 ft

High frequency

depositional cycles 

Location of 

thin section 

shown in figure 23

0° 90° 180° 270° 0° 0° 90° 180° 270° 0°

4 8

5,100 6,100

22.3 22.4

0

0

100

147

Figure 22. Borehole geophysical log data for test corehole G-2984, from 1,102 to 1,115 feet below land surface 

(ft bls), including optical and acoustic images, flowmeter and fluid properties, flow zones, and relation to high 

frequency depositional cycles.
Hydrogeologic Framework 41

2 mm

2 mm

A

B

Figure 23. Microscopic images of G-2984 at 1,109.45 feet below land surface (ft bls). (A) Thin-section: 

depositional texture is a small benthic foraminifer, peloid, skeletal fragment grainstone and graindominated packstone with mainly interparticle porosity; (B) photograph of acid-etched, slabbed, core 

sample: depositional texture is a small benthic foraminifera, peloid, skeletal fragment grainstone and 

grain-dominated packstone with mainly interparticle porosity.
42 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

180°

Depth, in feet below 

land surface

0° 180°

1,170

1,175

High frequency 

depositional cycles

1,165

Optical borehole 

image

Acoustic borehole 

image (amplitude)

Circumference of 

borehole

12.6 inches 12.6 inches

Circumference of 

Flow zone

borehole

Vertical black 

streak that continues over 

almost the entire

depth interval 

shown probably

resulted from 

drilling mud cake

being packed in 

a grove worn in 

the borehole wall 

EXPLANATION

Possible full vertical extent of large, irregular, semi-vertical vugs—Shown by optical and acoustic image logs 

 in high frequency depositional cycle extending from 1,170.7 to 1,175 feet below land surface. Base is uncertain. 

 May extend further down as indicated by dashed line

Oriented to magnetic

North

Oriented to magnetic

North

Dark areas

indicated to be 

semi-vertical 

open vugs 

0° 90° 270° 0° 90° 270° 0°

Caliper, in inches

Fluid conductivity, in microSiemens per centimeter

Fluid temperature, in degrees Celsius

Spinner flowmeter, in counts per second

Flowmeter rate, in gallons per minute

4 6

5,100 5,500

22.1 22.5

0

0

40

70

Figure 24. Borehole geophysical log data for test corehole G-2984, from 1,165 to 1,178 feet below land surface (ft 

bls), including optical and acoustic image, flowmeter and fluid properties, flow zones, and relation to high frequency 

depositional cycles.
Hydrogeologic Framework 43

Figure 25. Borehole geophysical log data, including fluid properties and flowmeter log 

data, hydrogeologic units, and flow zones, for monitoring well G-2940 at site 6, from 900 to 

1,220 feet below land surface (ft bls). Flowmeter data were corrected for borehole size 

using caliper log data.

GR from G-2938, in GAPI

0 150

Caliper, in inches

0 12

Lithostratigraphic

unit

20.8 21.3

Fluid conductivity, in microsiemens 

11,100 per centimeter 11,900

Uncalibrated flowmeter rate

0 21.5

Flow zone

Hydrogeologic unit

900

1,000

1,100

1,200

(CPS x feet squared)

Depth, in feet below 

land surface

Lower Arcadia Upper Avon Park Upper-middle Avon Park Upper Arcadia

Backup curve with units from 21.5 to 43

Bottom of open hole during loggingof G-2940 

at depth of 1,157 feet below land surface

Bottom of reported constructed 

open-hole interval and total depth of 

G-2940 (1,200 feet below land surface)

Grout filling large vugs in borehole wall in this interval observed in optical borehole image data and may have reduced 

flow from flow zones during logging. Pressure grouting of casing set through this interval in a nearby well (G-2939) at 

the site may have caused intrusion of grout into the area of this well.

*

*

Fluid temperature, 

in degrees Celsius
44 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida Lower Arcadia Upper Avon Park

Caliper, in inches

Fluid conductivity, in microSiemens per centimeter

Fluid temperature, in degrees Celsius

Spinner flowmeter, in counts per second

Uncalibrated flowmeter rate

counts per second x feet-squared

1,025

1,030

1,035

Depth, in feet below 

land surface

Optical borehole 

image

Oriented to 

magnetic

North

25.1 inches

Circumference of 

borehole

Flow zone

Lithostratigraphic unit

6 12

11,000 11,500

21 21.4

0

0

65

21.5

0° 90° 180° 270° 0°

Figure 26. Borehole geophysical log data for well G-2940, from 1,024 to 1,038 feet below land 

surface (ft bls), including optical image, flowmeter and fluid properties, and flow zones.
Distribution of Salinity in the Upper Part of the Floridan Aquifer System 45

about 1,053 to 1,056 ft bls (fig. 14) are all in the lowermost 

part of the Arcadia Formation, the paucity of data leave 

unclear whether these flow zones are related.

This preliminary analysis of this part of the Floridan 

aquifer system pore system is limited by the availability of 

reliable and sufficient geologic data and flowmeter measurements across flow zones at most of the well locations in the 

study area. Flowmeter data, naturally, are valuable indicators 

of the presence of individual flow zones, their vertical extent, 

and heterogeneity in flow properties, and flowmeter data are 

available for several wells in the study area. These data alone, 

however, do not indicate the lateral extent of the flow zones 

or their lateral heterogeneity. The G–2984 core data provide 

information on the geologic settings that correspond to the 

different types of flow zones in the Upper Floridan aquifer. 

Geologic settings are commonly spatially extensive, and the 

location of deposits characteristic of specific settings can thus 

sometimes be correlated between wells. In the study area, 

only a small number of core samples are available for a few 

wells to correlate with the data from G–2984, or to provide 

lithologic information for hydrologic units below the Upper 

Floridan aquifer, such as the Avon Park permeable zone and 

the uppermost permeable zone of the Lower Floridan aquifer. 

Optical and acoustic borehole image data can indicate the 

presence of some types of megaporosity, but flowmeter data 

are required to show whether megaporosity features are 

associated with increased hydraulic conductivity. 

The dual nature of the porosity has implications for the 

evaluation of the suitability of the Floridan aquifer system for 

various water-resource management activities. Diffuse flow 

may be conducive for water storage, whereas concentrated 

flow may preclude containment. Thus, understanding the 

distribution of the types of flow is important in evaluation 

of the potential of a site for aquifer storage and recovery. 

For example, a relatively thick upper Floridan aquifer ASR 

production zone that contains subzones of diffuse-flow from 

matrix porosity and concentrated-flow from vuggy megaporosity could result in preferential movement of injected water 

into the megaporous zones and potential for movement beyond 

the estimated ASR capture volume. Furthermore, any type of 

predictive analyses (using analytical or numerical models), to 

access water-supply availability, would need to consider scaleappropriate heterogeneity of the types of flow, in both vertical 

and horizontal dimensions. The data presented here allow 

characterization of the scale of the vertical heterogeneity, but 

additional data would be needed to define the lateral extent, 

connectivity, and continuity of individual flow zones.

Distribution of Salinity in the Upper 

Part of the Floridan Aquifer System

The salinity distribution from the uppermost permeable 

zone of the Lower Floridan aquifer to the upper surface of the 

Floridan aquifer system in eastern Broward County can be 

characterized on the basis of analysis of direct measurements 

of water quality, for example dissolved-solids concentration, 

and indirect measurements of formation resistivity, which 

is used as a proxy for concentration of dissolved solids. 

Measured dissolved-solids concentration in groundwater 

samples are the most accurate measure of salinity, but data for 

the Floridan aquifer system in eastern Broward County may be 

difficult to compare between wells because sampling dates and 

borehole column intervals vary. Salinity may vary vertically 

over multiple contributing flow zones. Thus, a more discrete 

sample interval provides a more precise salinity measurement. 

Conversely, a large borehole column sampled interval is likely 

to be a composite salinity, which is more difficult to interpret. 

In any single well, sampled intervals within a specific hydrologic unit may produce water of varying salinity. For example, 

at site 17, well PB–1765, samples collected within a few days 

from two different intervals in the Upper Floridan aquifer 

show a greater than 2,000-mg/L difference in dissolved-solids 

concentration (appendix table 1–7; fig. 27). To assess temporal 

variability in salinity, multiple samples must be collected from 

depth-specific intervals. For example, at site 33, well G–2914, 

samples collected from the same depth interval (1,110 to 

1,270 ft bls) show a 1,500-mg/L difference in dissolved-solids 

concentration over 6 months (appendix table 1–7; fig. 27). 

Interpretations of the distribution of salinity in the Floridan 

aquifer system in eastern Broward County need to be considered in light of the variable sampling intervals and dates from 

the data set (appendix table 1–7).

A salinity classification scheme based on dissolved-solids 

concentration is used to describe the distribution of salinity 

in the Floridan aquifer system in this study. This scheme, 

modified from Fetter (1988), has three categories: (1) brackish 

water—dissolved-solids concentration ranges from 1,000 to 

10,000 mg/L, (2) moderately saline water—dissolved-solids 

concentration ranges from greater than 10,000 to 35,000 mg/L, 

and (3) saline water—dissolved-solids concentration greater 

than 35,000 mg/L.

In general, chemical analyses of water samples from the 

Upper Floridan aquifer indicate a trend in salinity from the 

highest values in the central part of the study area to lower 

values toward the north and south (fig. 27). Some samples from 

the west-central part of the study area, at sites 5 and 32, have 

concentrations of dissolved solids greater than 10,000 mg/L. 

In the Avon Park permeable zone, salinity tends to be highest 

close to the coast, with several samples exceeding 10,000 mg/L 

dissolved-solids concentration, and lower toward the western 

part of the study area (fig. 28). Although salinity generally 

increases with depth, in some locations salinity measurements 

from samples in the Upper Floridan aquifer are higher than 

those in the Avon Park permeable zone, for example, at sites 5, 

6, and 30 (figs. 27 and 28; appendix table 1–7). 

Borehole formation resistivity data can be used to 

estimate the vertical distribution of salinity at the time the data 

are collected. Deep induction and other types of resistivity 

data were collected in 33 boreholes at 24 sites (appendix 

table 1–8). The dual-induction and shallow-resistivity tool, 
46 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Figure 27. Distribution of salinity as dissolved-solids concentration in the Upper Floridan aquifer.

G-2887

PB-1765

PB-1775

PB-1776

G-2970

HAL-RO1*

HOL-RO1*

G-2988*

PBP-M1

19

ND

4

ND

FTL-M1

29

ND

G-2984

G-2889

G-2916 G-2986*

D-365

G-2940

G-2917*

G-2918

30

SUN-M1 32

G-2981

31

ND

28

ND

BCN-M2

MAR-M2*

G-2914

ND

G-2985

G-2987

27

ND

13

ND

25

ND

5

CS-I1*, CS-I2

CS-M2

17

8

21

1

12

11

7

23

15

26

24

16 18

9

2

3

33

6

10

14

20

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

G-2989

EXPLANATION

Well—

 Site number

 Well number for well(s) at 

 site with water-quality data

 collected from the Upper 

 Floridan aquifer

30

G-2889

Salinity ranges, as 

 dissolved-solids 

 concentration, from water 

 samples collected in the 

 Upper Floridan aquifer—

2,000 to 4,000 milligrams 

 per liter

4,000 to 6,000 milligrams 

 per liter

6,000 to 8,000 milligrams 

 per liter

8,000 to 10,000 milligrams 

 per liter

Greater than 

 10,000 milligrams 

 per liter

Sites with estimated 

dissolved-solids 

concentration of 10,000 

milligrams per liter or 

greater in the lower part of 

the Upper Floridan aquifer, 

or in the entire Upper 

Floridan aquifer (sites 5 

and 32). Not indicated to be 

present at all other sites 

shown. 

(See appendix table 1-8)

No water-quality data

 collected from the Upper 

 Floridan aquifer

G-2986*

ND

Salinity, as dissolved-solids 

 concentration, estimated 

 in the Upper Floridan aquifer 

 using borehole geophysical 

 resistivity data—

Estimated dissolved-solids 

 concentration in the Upper 

 Floridan aquifer–Calculated 

 from chloride concentration, 

 in milligrams per liter (see

 appendix table 1–7). All other 

 sites have measured 

 dissolved-solids 

 concentration

26

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES
Distribution of Salinity in the Upper Part of the Floridan Aquifer System 47

Figure 28. Distribution of salinity as dissolved-solids concentration in the Avon Park permeable zone.

G-2968

17

PB-1766

PB-1775

G-2973

G-2974

NR

ND

G-2963

G-2964

G-2944

G-2945

G-2961

G-2975

FTL-M2

NR

NR

NR

NR

6

G-2939

10

NR

30

SUN-M1

32

NR

31

G-2983

5

CS-M2

G-2942

G-2943

BCN-M4

21

MAR-M2*

33

NR

G-2979*

G-2985

NR

PLT-I1*

G-2980 PLT-M1

G-2972

PLT-ROI1

PLT-ROM1

19 4

ND

29

ND

28

27

13

25

8

1

12

11

7

23 15

26

24

16

18

9

2

3

14

20

ND

22

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

A

TLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

EXPLANATION

Well–

 Site number 

 Well number for well(s)

 at site with water-quality 

 data collected from the Avon 

 Park permeable zone

Salinity ranges, as dissolved-

 solids concentration, from 

 water samples collected 

 in the Avon Park 

 permeable zone

2,000 to 4,000 milligrams 

 per liter

4,000 to 6,000 milligrams 

 per liter

6,000 to 8,000 milligrams 

 per liter

8,000 to 10,000 milligrams 

 per liter

Greater than 

 10,000 milligrams 

 per liter

Not reached, zone not 

 penetrated 

No water-quality data 

 collected from the Avon 

 Park permeable zone 

ND

NR

Estimated dissolved-solids 

 concentration in the Avon 

 Park permeable zone-

 Calculated from chloride 

 concentration, in 

 milligrams per liter (see 

 appendix table 1–7). All 

 other sites have 

 measured dissolved-

 solids concentration

MAR-M2*

G-2968

8

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES
48 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

which includes the deep induction array, measures resistivity 

at three radial distances from the borehole into the formation: 

shallow, medium and deep (fig. 29), and data from this tool 

were available from 31 of the 33 boreholes. The deep-induction measurements were found to approximate true formation 

resistivity where there was an absence of saline drilling fluid 

(Reese, 1994), and these types of resistivity data were available for 32 of the 33 boreholes. The shallow and intermediate 

resistivity data can be used to determine whether excessive 

invasion into the formation by drilling fluids has occurred. 

Using the empirical Archie’s law (1942), and values for formation resistivity, porosity, cementation factor, and formation 

temperature for the upper part of the Floridan aquifer system 

in southeast Florida (Reese, 1994), groundwater salinity of 

10,000 mg/L dissolved solids was estimated to be represented 

by a formation resistivity of 4–6 ohm-meters. This value of 

formation resistivity is based on a porosity estimate of 30 to 

40 percent, a cementation factor of 1.8 to 2.1, and a formation 

temperature of 20 to 26 degrees Celsius.

Estimates of salinity from borehole resistivity data, 

supported by results of chemical analyses, were used to map 

the deepest occurrence of groundwater with concentrations 

of dissolved solids less than 10,000 mg/L (fig. 30: appendix 

table 1–8). The 10,000 mg/L dissolved solids threshold marks 

the greatest salinity allowable in an underground source of 

drinking water (USDW) (Florida Administrative Code, 2008). 

At depths greater than the USDW surface (fig. 30), no 

additional sources of drinking water are likely to be available. 

This surface generally becomes progressively deeper from 

the coast toward the west (fig. 30). Resistivity and waterquality data from several sites, however, indicate that above 

this surface, an interval of groundwater with salinity greater 

than 10,000 mg/L dissolved solids may occur in the Upper 

Floridan aquifer, for example at sites 5, 21, 26, 30, 31, and 32 

(figs. 27, 28 and 30; appendix table 1–8). These sites are in the 

west-central part of the study area, where the Upper Floridan 

aquifer generally deepens. A conceptual model developed 

from these data show the presence of a zone of moderately 

saline water perched above brackish water in the west-central 

part of the study area (fig. 31). The sites with highest directlymeasured salinity in the Upper Floridan aquifer also occur at 

the sites with the lowest estimated transmissivity (fig. 32). The 

occurrence of a zone of moderately-saline water in the Upper 

Floridan aquifer perched above less saline water in the Avon 

Park permeable zone may be the result of incompletely flushed 

connate water or intruded seawater, in structurally lower, less 

permeable parts of the Upper Floridan aquifer. 

Summary and Conclusions

 Concerns about water-level declines and saltwater 

intrusion in the Biscayne aquifer have prompted water 

managers in Broward County to examine the potential use of 

the Floridan aquifer system as an alternative water supply, 

either directly, by pumping from supply wells and treating 

the water, or indirectly, by aquifer storage and recovery 

(ASR). The ability to predict physical properties of the 

Floridan aquifer system conducive to its use as an alternative 

water supply or for ASR requires a refined hydrogeologic 

framework, and information about the distribution of salinity 

of the water. This report provides information that can be 

used to assist decisions about the management of the Floridan 

aquifer system by (1) identifying major permeable zones and 

semiconfining units of the Floridan aquifer system—from the 

upper flow zone of the Lower Floridan aquifer to the top of the 

Upper Floridan aquifer—and delineating their configuration, 

thickness, and extent; (2) providing estimated values and 

other information on hydraulic properties of these units; and 

(3) describing the distribution of salinity within these units.

The information used to refine the hydrogeologic 

framework includes lithologic data, borehole geophysical 

data, and reflection-seismic data. A test corehole, G–2984 was 

drilled from land surface into the uppermost permeable zone 

of the Lower Floridan aquifer, and was continuously cored 

from the top of the Upper Floridan aquifer to the bottom of 

the well. The core was analyzed for lithologic properties, 

depositional features, bedding thickness, and fossils. Optical 

and acoustic images of the borehole (OBIs and ABIs) were 

collected. Other borehole geophysical data collected include: 

natural gamma-ray activity (GR), caliper, induction formation 

resistivity (rock plus groundwater), spontaneous potential, 

single point resistance, sonic Δt, flowmeter, and borehole 

fluid conductivity and temperature. Borehole geophysical 

and lithologic data from other wells in the study area were 

compiled. Reflection-seismic data were collected along the 

Hillsboro Canal. These data were used to identify lithostratigraphic units and stratigraphic sequences, and to construct the 

hydrogeologic framework. Salinity distribution in the Floridan 

aquifer system was characterized using existing water-quality 

data, including specific conductance, formation resistivity, and 

chloride, sulfate, and dissolved-solids concentration.

Stratigraphic units identified in the study area include, in 

ascending order, the lower Avon Park Formation, the lowermiddle Avon Park Formation, the upper-middle Avon Park 

Formation, the upper Avon Park Formation, the lower Arcadia 

Formation, and the upper Arcadia Formation. The upper 

contact of the Avon Park Formation deepens from east to west 

across the study area. An isolated structural low is observed 

near G–2984, and is associated with faults and a paleocollapse feature identified on the Hillsboro seismic reflection 

profile. The upper Avon Park Formation is generally thinnest 

in the central and southeastern part of the study area, and 

thickens toward the north and southwest. The lower Arcadia 

Formation generally thickens from south to north across the 

study area.

Six depositional sequences were identified in the 

G–2984 test corehole, from deepest to shallowest: Avon Park 

sequence 1, Avon Park sequence 2, and Arcadia sequences 1 

through 4. The depositional sequences were identified and 

correlated with lithologic and borehole geophysical data, and 

used to map sequence surfaces and their thicknesses. 
Summary and Conclusions 49

Depth, in feet below land surface

Lower 

Arcadia

Formation

upper-middle 

Avon Park Formation

Upper Avon Park 

Formation

lower-middle 

Avon Park Formation

lower 

Avon Park Formation

Resistivity, in ohm-meters

Salinity zone

Stratigraphic 

unit

Completed and 

packer test 

intervals

Hydrogeologic 

unit

CS-I1

CS-M2

CS-M2

Deep 

induction, 

well CS-I2

Medium 

induction, 

well CS-I2

CS-I2

Shallowreading 

spherically 

focused log, 

well CS-I2

CS-I2

5,640

no data

6,550

11,500

5,400

9,370

5,800

10,700

2,330

4,430

15,100

no data

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

2,000

2,100

2,200

2,300

CS-I1

1 2 10 100

1 2 10 100

EXPLANATION

2,300

4,430

Brackish water–Dissolved-solids concentration range 

 from 1,000 to 10,000 milligrams per liter. Depth of base 

 of zone estimated by deep induction resistivity less

 than 6 ohm-meters

Moderately saline water, lower zone–Dissolved-solids 

 concentration range from 10,000 to 35,000 milligrams 

 per liter. Depth of base of zone estimated by deep 

 induction resistivity less than 2 ohm-meters 

Saline water–Dissolved-solids concentration of about 

 35,000 milligrams per liter or slightly higher 

Salinity ranges and definitions of zone boundaries in

 salinity zone column–

Moderately saline water, upper zone–Dissolved-solids 

 concentration range from 10,000 to 35,000 milligrams 

 per liter. Depth of base of zone estimated by deep 

 induction resistivity less than 4 ohm-meters

Packer test interval in well CS-I2

Completed interval in well

 CS-M2 or CS-I1

Bottom of logged interval

Salinity—Water samples collected from 

 completed intervals and packer test intervals. 

 Upper number is chloride concentration, and 

 lower number is dissolved-solids concentration. 

 Concentrations shown in milligrams per liter

Figure 29. Water-quality data, resistivity geophysical log data, salinity zones, and lithostratigraphic and 

hydrogeologic units for wells at site 5. The data shown are from wells CS-I1, CS-I2, and CS-M2 at the 

site. CS-I1 is 750 feet south of CS-I2. Modified from Reese (1994). Well CS-I2 is also shown in figure 6.
50 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

–2,000

–1,800

–1,600

–1,400

G-2968

G-2969

PB-1766

G-2970

G-2973

G-2963

G-2964

G-2944

G-2946

PBP-I2

G-2961

G-2966

FTL-I1

FTL-I4

S-567

G-2938

SUN-I3

SUN-M3 G-2982

G-2983

CS-I2

G-2942

BCN-I1

BCN-I6

G-2292

MAR-M2

G-2978

G-2979

G-2985

G-2980

G-2971

PLT-ROI1

5

17

8

21

1

28

6

13

29

12

11

7

4

23

15

19

30

31

25

27

26

22

24

Line of equal altitude—

 Shows estimated altitude of the 

 greatest depth of groundwater 

 of less than 10,000 milligrams 

 per liter dissolved-solids 

 concentration, in feet relative 

 to NGVD 29. Contour interval 

 is 200 feet. Approximately 

 located. Indicated by 

 water-quality and borehole 

 geophysical log data (see 

 appendix table 1–8)

G-2968

–1,600

Well—

 Site number 

 Well number for well(s) used 

 in determining the greatest 

 depth of groundwater of less 

 than 10,000 milligrams per 

 liter dissolved-solids 

 concentration (see appendix

 table 1–8)

Sites with a zone of 

 estimated 

 dissolved-solids 

 concentration of 

 10,000 milligrams 

 per liter or greater at 

 shallower depths 

 than the greatest depth 

 of groundwater of less 

 than 10,000 milligrams 

 per liter dissolved-solids 

 concentration—

Indicated by water-quality or 

borehole geophysical resistivity

data or both (see appendix 

tables 1–7 and 1–8)

8

26

EXPLANATION

75

95

595

1

441

PALM BEACH

BROWARD

MIAMI–DADE

BROWARD

North New

River Canal

Hillsboro Canal

C-13 Canal

C-12 Canal

C-11 Canal

C-10 Canal

C-9 Canal

C-14 Canal

ATLANTIC

OCEAN

SAWGRASS EXPRESSWAY

FLORIDA’S 

TURNPIKE

80°20' 80°10'

26°20'

26°10'

26°00'

Base from U.S. Geological Survey digital data, 1:24,000, datum NAD83

Albers Equal Area Conic Projection, Standard parallels 29 ̊30’ and 

45 ̊30’ central meridian –83 ̊00’ 0 2.5

0 2.5

5 KILOMETERS

5 MILES

Figure 30. Greatest depth of groundwater with dissolved solids concentration of less than or 

equal to 10,000 milligrams per liter.
Summary and Conclusions 51

Figure 31. Schematic diagram showing perched zone of elevated salinity in the Upper 

Floridan aquifer in the west central part of the study area.

Figure 32. Relation between transmissivity and salinity in the Upper Floridan aquifer.

WEST

Depth

EAST

NOT TO SCALE

Upper Floridan aquifer

Middle semiconfining unit (MC1)

Middle semiconfining unit (MC2)

Avon Park Permeable Zone

EXPLANATION

Dissolved-solids concentration 

 (no pattern) range from 1,000 

 to less than 10,000 milligrams 

 per liter 

Dissolved-solids concentration 

 range from 10,000 to 35,000 

 milligrams per liter 

Salinity range

Dissolved-solids concentration 

 greater than 35,000 milligrams 

 per liter or higher 

G-2981

CS-I2 and 

CS-M2

G-2940 G-2917 and 

G-2918

HAL-RO1

G-2989

PBP-I2 and 

PBP-M1

PB-1765

G-2985

G-2914

PB-1775

G-2988

G-2887

G-2889

HOL-RO1

Transmissivity of the Upper Floridan aquifer, in feet-squared per day

Salinity of the Upper Floridan aquifer as 

dissolved-solids concentration, in milligrams per liter

32

5

6 10

33

7 15 20

20

16

24

23

8

2

17

12,000

14,000

10,000

8,000

6,000

4,000

0

2,000

5,000 10,000 15,000 20,000 25,000 30,000 35,000

0

EXPLANATION

Data point—

Data point and range in salinity—

 Shows range in salinity at sites 

 with more than one sample from 

 the Upper Floridan aquifer. In 

 some cases samples were 

 collected from multiple wells at 

 a single site

G-2914

33

Well number(s). If more than one 

well number is shown, first well 

is source of transmissivity value 

at the site and second well is 

source of salinity value

Site number
52 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

The seismic-reflection data acquired along the Hillsboro 

Canal were correlated with geologic, hydrogeologic, and 

geophysical data from proximal wells, and show a continuous, 

thick, 2-dimensional profile of the major lithostratigraphic, 

sequence stratigraphic and hydrogeologic units across the 

study area. The Arcadia Formation and upper and middle 

Avon Park Formation generally show parallel to subparallel, 

flat to wavy or hummocky reflection configuration patterns. 

Seven narrow segments were identified that contain seismicsag structural systems. These seismic-sag systems extend 

upward from the Avon Park Formation to the upper contact 

of the Arcadia Formation and are interpreted as downward 

deformation of overlying strata into collapsed deep cave 

systems. Faulting and fracturing associated with these systems 

could provide passageways for vertical fluid flow and cause 

upconing of saline water at water-supply or ASR wells in the 

Floridan aquifer system. 

The hydrogeologic framework of the Floridan aquifer 

system in eastern Broward County, from the top of the 

Floridan aquifer system to the bottom of the uppermost permeable zone of the Lower Floridan aquifer, was constructed 

using borehole geophysical data, flowmeter analyses, and 

borehole images and lithologic data. The Upper Floridan 

aquifer in the study area generally correlates with part of the 

lower Arcadia Formation, the upper Avon Park Formation, 

and the upper part of the upper-middle Avon Park Formation. 

Throughout the study area, the upper surface of the Upper 

Floridan aquifer occurs within the lower Arcadia Formation, 

below the upper surface of the lower Arcadia Formation. The 

bottom of the Upper Floridan aquifer generally occurs within 

the upper-middle Avon Park Formation, although it may 

correlate with the upper surface of the upper-middle Avon 

Park Formation or occurs within the upper Avon Park Formation in the southwestern part of the study area. Transmissivity 

of the Upper Floridan aquifer generally increases from west to 

east across the study area. The occurrence and thicknesses of 

flow zones below the top of the Avon Park sequence 1 within 

the Upper Floridan aquifer decrease to the west. Although 

the Avon Park sequence 2 thickens to the west, only one thin 

flow zone occurs in some locations, associated with the upper 

contact of the Avon Park Formation.

Beneath the middle semiconfining unit 1, the Avon Park 

permeable zone is identified by an increase in the number and 

spatial density of flow zones relative to overlying and underlying semi-confining units. The Avon Park permeable zone 

generally occurs within the upper part of the lower-middle 

Avon Park Formation. Transmissivity values of the Avon Park 

permeable zone are generally lower than for the Floridan 

aquifer system, but vary over a similar range of orders of 

magnitude. The overlying middle semiconfining zone 1 and 

underlying middle semiconfining zone 2 are each hundreds of 

feet thick, and estimated hydraulic conductivity values of the 

semi-confining units are one to several orders of magnitude 

lower than for the Avon Park permeable zone. The Lower 

Floridan 1 is identified by the presence of an increased number 

and spatial density of flow zones relative to the overlying 

middle semiconfining unit 2, and the hydraulic properties 

are comparable to the Upper Floridan aquifer and Avon Park 

permeable zone.

Core samples, optical and acoustic borehole images, 

flowmeter data, and other borehole geophysical data from 

the G–2984 test corehole were examined to characterize the 

relationship between rock depositional textures, associated 

pore networks, and flow zones. A thin flow zone, contributing 

substantial and concentrated flow into the borehole, is formed 

by two open bedding-plane vugs at the upper surface of 

the Floridan aquifer system. A thicker zone of diffuse flow 

deeper in the aquifer system was identified, with interparticle 

porosity as the dominant pore type. Still deeper in the Upper 

Floridan aquifer, a zone containing both diffuse flow and 

concentrated flow was identified. The diffuse flow is associated with mostly interparticle and moldic-particle pore types, 

whereas concentrated groundwater flow is associated with 

vuggy megaporosity.

Using flowmeter data and optical images, flow zones in 

two additional boreholes (G–2940 and PB–1775) were also 

characterized. In both boreholes, concentrated flow zones in 

the lower Arcadia Formation are associated with thin beddingplane vugs. It is unclear if these flow zones are related.

These data support a conceptual model of groundwater 

flow in the Floridan aquifer system in Broward County 

wherein concentrated flow occurs in discrete, thin, bedding 

plane vugs or zones of vuggy megaporosity, and diffuse flow 

tends to occur through interparticle or moldic-particle porosity 

in matrix-dominated lithologies. Considerable groundwater 

exchange may occur between such zones of different type 

porosity. The dual nature of the porosity is an important 

consideration in the suitability of the Floridan aquifer system 

for various water-resource management activities: zones of 

diffuse flow may be more conducive for storage of water, 

whereas zones of concentrated flow may prohibit containment. For example, a relatively thick ASR production zone 

in the Upper Floridan aquifer that contains subzones of 

diffuse-flow from matrix porosity and concentrated-flow from 

vuggy megaporosity could result in preferential movement of 

injected water through the megaporous zones and migration 

outside of the ASR capture volume. Furthermore, any type of 

predictive analyses would need to consider scale-appropriate 

heterogeneity of the types of flow, in both vertical and 

horizontal dimensions.

Existing water-quality data were used to characterize 

the distribution of salinity in the Floridan aquifer system in 

eastern Broward County. In general, higher salinity values 

are observed in the central part of the study area, and lower 

salinity values are observed toward the north and south. 

Although salinity generally increases with depth, in the 

west-central part of the study area a zone of relatively more 

saline water in the Upper Floridan aquifer is perched above 

less saline water in the underlying Avon Park permeable zone. 

The areas with the highest salinity are also those with the 

lowest estimated transmissivity, indicating that the occurrence 

of perched saline water in the Upper Floridan aquifer may 

be a consequence of incompletely flushed connate water or 

intruded seawater.
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District: South Florida Water Management District Technical Publication 84–1, 235 p., plus apps.

Sprinkle, C.L., 1989, Geochemistry of the Floridan aquifer 

system in Florida and in parts of Georgia, South Carolina, 

and Alabama: U.S. Geological Survey Professional Paper 

1403–I, 105 p., 9 pls.

Vacher, H. L., and J. Mylroie (2002), Eogenetic karst from the 

perspective of an equivalent porous medium, Carbonates 

Evaporites, 17(2), 182–196.

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Rahmanian, V.D., 1990, Siliciclastic sequence stratigraphy in well logs, cores and outcrops; concepts for highresolution correlation of time and facies: American Association of Petroleum Geologists Methods in Exploration 

Series, no. 7, 55 p.

Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., and 

others, 1988, An overview of the fundamentals of sequence 

stratigraphy and key definitions, in C. K. Wilgus and others, 

eds., Sea-level changes—An integrated approach: Society 

of Economic Paleontologists and Mineralogists Special 

Publication no. 42, p. 39–45.

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and Carlson, J.I., 2003, Sequence-stratigraphic analysis of 

the Regional Observation Monitoring Program (ROMP) 

29A test corehole and its relation to carbonate porosity and 

regional transmissivity in the Floridan aquifer system, Highlands County, Florida: U.S. Geological Survey Open-File 

Report 03–201, 34 p., plus apps.

Weedman, S.D., Scott, T.M., Edwards, L.E., and others, 1995, 

Preliminary analysis of integrated stratigraphic data from 

the Phred #1 corehole, Indian River County, Florida: U.S. 

Geological Survey Open-File Report 95–824, 63 p.

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Appendix 1
58 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Hydraulic Test Data

Hydraulic test data, including data derived from aquifer 

performance tests, packer tests, step-drawdown, and specific 

capacity tests are listed in appendix table 1–6. The references 

for the reports from which these test data were taken are 

provided in appendix table 1–2. Values included in appendix 

table 1–6 include those for transmissivity, hydraulic conductivity, storativity, leakance, and specific capacity. Generally, 

data only for those tests conducted at about the depth of the 

uppermost permeable zone of the Lower Floridan aquifer or 

shallower in the Floridan aquifer system are included. Most 

of the packer tests were conducted during the drilling of deep 

injection well systems for the purpose of determining the 

degree of confinement of the tested interval, and pumping for 

these tests was at a constant rate for a short period of time, 

usually 3 to 4 hours. In contrast, the constant rate aquifer 

performance tests in completed wells were commonly pumped 

for much longer periods, such as 24 or 72 hours.

The transmissivity values reported in appendix 

table 1–6 for many of the tests are based on water-level data 

(drawdown) in production or monitoring wells collected during constant rate pumping or recovery. Methods of analysis 

for tests reported in appendix table 1–6 include those of Theis 

(1935) and Cooper and Jacob (1946) for “confined aquifers” 

and Hantush and Jacob (1955), Hantush (1960), Moench 

(1985), and Walton (1962) for “leaky confined aquifers.” For 

some tests, no analytical method was reported, only that the 

analysis was made on drawdown or recovery data. Presumably, the method used for these tests was one for a confined 

aquifer. Horizontal hydraulic conductivity values were calculated from aquifer and packer tests using transmissivity results 

and the thicknesses of the open intervals tested.

Transmissivity is reported for some packer tests; 

however, these values are representative only of short intervals 

(commonly about 20 to 50 feet [ft] thick; appendix table 1–6). 

Some limitations on the reliability of transmissivity estimates 

determined from packer test data include partial penetration 

of an aquifer, low pumping rates, short pumping periods, the 

possibility of borehole wall skin effects due to incomplete 

development, and high friction losses as fluid flows up the 

small diameter of drill pipe compared to the diameter of casing 

in constructed wells. The conventional procedure for conducting packer tests is to pump the well prior to the test for a specified period or a period long enough to produce formation fluid 

of a constant salinity, although some wellbore damage may 

still remain after the development period. The packer test data 

were used to help identify contact boundaries of major permeable zones and semiconfining units and to provide insight to 

the magnitude of horizontal hydraulic conductivity.

 The specific capacity of a well, determined by pumping 

the well at a constant rate until the water level stabilizes, 

is equal to the pumping rate divided by the feet of drawdown, and is reported in units of gallons per minute per foot 

(gal/min/ft). Transmissivity is proportional to specific capacity 

in large-diameter water-supply wells.

References Cited in Appendix Table 1–2

AECOM, 2010, Engineering report on the construction and 

testing of test production well TPW-1 for the Town of 

Davie: Prepared for the Town of Davie, p. 1–1 to 5–2, 

plus apps.

Bennett, M.W., Linton, P.F., and Rectenwald, E.E., 2001, 

Completion report for the exploratory well EXW-1, western 

Hillsboro basin site, Palm Beach County: South Florida 

Water Management District hydrogeologic investigation of 

the Floridan aquifer system, 34 p., 7 apps.

Black, Crow, and Eidsness Inc., 1974, Results of drilling and 

testing of monitoring and deep disposal wells at Margate, 

Florida: Engineering report prepared for the City of Margate 

Utilities Authority and LAH Associates, Limited, Fla., 31 p.

Camp, Dresser, and McKee, Inc., 1987, City of Plantation 

deep injection well—number 1: Final well completion 

report, p. 1–1 to 5–1, plus apps.

Camp, Dresser, and McKee, Inc., 1991a, City of Plantation 

Central District Water Treatment Facility R.O. reject disposal well – no. 1: Well completion report v. 1. 

Camp, Dresser, and McKee, Inc., 1991b, City of Plantation 

Regional Wastewater Treatment Plant effluent injection well 

– no. 2: Well completion report v. 1, p. 1–0 to 6–1. 

Camp, Dresser, and McKee, Inc., 1993a, Floridan aquifer 

test/production well and monitor well: Completion report 

prepared for the City of Deerfield Beach, Florida, and South 

Florida Water Management District, 29 p.

Camp, Dresser, and McKee, Inc., 1993b, Wastewater Treatment Plant III well completion report dual zone monitor 

well 1A: Engineering report prepared for City of Sunrise, 

Fla., p. 1–0 to 5–2, plus apps.

Camp, Dresser, and McKee, Inc., 1993c, Wastewater Treatment Plant III well completion report dual zone monitor 

well 2: Engineering report prepared for City of Sunrise, 

Fla., p. 1–0 to 5–2, plus apps.

Camp, Dresser, and McKee, Inc., 1996, Engineering report 

supporting operational testing of IW-3 at Sunrise, Florida: 

Engineering report prepared for City of Sunrise, Fla., v. 1, 

p. 1–1 to 8–3, plus apps.

Camp, Dresser, and McKee, Inc., 2008, City of Deerfield 

Beach West Water Treatment Plant concentrate injection 

well system: Well completion report, v. 1, p. 1–1 to 7–1, 

plus apps.

Camp, Dresser, and McKee, Inc., 2010, City of Deerfield 

Beach West Water Treatment Plant Floridan aquifer well 

no. 2 final completion depth proposal: Memorandum to the 

South Floridan Water Management District, 6 p.
Appendix 1 59

CH2M HILL, 1984, Engineering report on drilling and testing 

of the deep injection and monitoring wells at the City of 

Margate Wastewater Treatment Plant: Prepared for the City 

of Margate Department of Utilities Margate, Florida, p. 1–1 

to 4–4, plus apps.

CH2M HILL, 1985, Engineering report on the drilling and 

testing of the City of Sunrise injection and monitoring 

wells: Prepared for the City of Sunrise, Broward County, 

Florida, p. 1–1 to 5–1, plus apps.

CH2M HILL, 1994, Report on the modification to monitor 

well MW-2: Prepared for the City of Margate Department 

of Environmental and Engineering Services, 7 p. 1–1 to 

1–9, attachments. 

CH2M HILL, 1995, Rehabilitation of monitor well MW-1 and 

construction and testing of monitor well MW-2 and regional 

monitor well RMW-1 at the G.T. Lohmeyer Wastewater Treatment Plant: Engineering report prepared for the City of Fort 

Lauderdale, Broward County, Fla., p. 1–1 to 6–2, plus apps.

CH2M HILL, 1996, Construction and testing of monitor well 

MW-3 at the G.T. Lohmeyer Wastewater Treatment Plant: 

Engineering report prepared for the City of Fort Lauderdale, 

Broward County, Fla., p. 1–1 to 6–1, plus apps.

CH2M HILL, 1997, Construction and testing of the aquifer 

storage and recovery (ASR) system at the BCOES 2A Water 

Treatment Plant: Engineering report prepared for the Broward County Office of Environmental Services and Montgomery Watson, p. 1–1 to 6–3, 13 apps.

CH2M HILL, 1999, Construction and testing of injection well 

IW-4 at the City of Fort Lauderdale G.T. Lohmeyer Wastewater Treatment Plant: Engineering report prepared for the 

City of Fort Lauderdale, v. I, p. 1–1 to 6–1, plus apps.

Geraghty and Miller, Inc., 1984, Construction and testing of 

disposal wells 1, 2 and 3 at the George T. Lohmeyer Plant 

Fort Lauderdale, Florida: Report prepared for Broward 

County, v. I, 39 p., plus apps. 

Geraghty and Miller, Inc., 1986, Construction and testing of 

an injection well at the Coral Springs Improvement District: 

Report prepared for Broward County, Fla., 30 p., plus apps. 

Geraghty and Miller, Inc., 1990a, Construction and testing of 

injection wells #1 and #2 with associated deep monitor well 

#1, Broward County North District Regional Wastewater 

Treatment Plant: Report prepared for James M. Montgomery, Consulting Engineers, Inc. in association with Hazen 

and Sawyer, P.C, Engineers, 30 p., plus apps.

Geraghty and Miller, Inc., 1990b, Construction and testing of 

injection well system #2 at the Coral Springs Improvement 

District Wastewater Treatment Plant: Report prepared for 

the City of Coral Springs, Fla., 31 p., plus apps. 

Geraghty and Miller, Inc., 1991, Construction and testing of 

injection wells #3 and #4 with associated deep monitor well 

#2, Broward County North District Regional Wastewater 

Treatment Plant: Report prepared for James M. Montgomery, Consulting Engineers, Inc. in association with Hazen 

and Sawyer, P.C, Engineers, 32 p., plus apps.

Geraghty and Miller, Inc., 1995, Construction and testing of 

injection well #2 at the Pembroke Pines Wastewater Treatment Plant: Report prepared for the City of Pembroke Pines, 

Fla., 23 p., plus apps.

Hazen and Sawyer, 1989, Completion report for the City of 

Hallandale Floridan aquifer test well: City of Hallandale, Fla.

Hazen and Sawyer, 1996, City of Miramar, Florida Utilities 

Department Wastewater Reclamation Facility injection well 

construction: Well construction report prepared for the technical advisory committee members, p. 1–1 to 4–4, plus apps.

Hazen and Sawyer, P.C., 1999, North Regional Wastewater 

Treatment Plant monitor well 4 construction completion 

report: Prepared for Broward County Office of Environmental Services, p. 1–1 to 4–1, plus apps.

Hazen and Sawyer, P.C., 2000, Injection wells 5 and 6 construction completion report, North Regional Wastewater 

Treatment Plant: Prepared for Broward County Office of 

Environmental Services, p. 1–1 to 5–4, plus apps.

Hazen and Sawyer, 2001, Injection well no. 1 construction 

completion report —Water/Wastewater Treatment Plant: 

Prepared for Cooper City Utility Department, p. 1–1 to 5–5, 

plus apps.

Hazen and Sawyer, P.C., 2002a, Engineering well completion 

report concentrate disposal system: Prepared for the City 

of Pompano Beach in association with Water Technology 

Associates, Inc., p. 1–1 to 5–5, plus apps. 

Hazen and Sawyer, P.C., 2002b, Underground Injection 

Control application, aquifer storage and recovery Class 

V injection well system at the Broward County 2A Water 

Treatment Plant Site: 4 p., plus apps.

Hazen and Sawyer, P.C., 2003, Engineering well completion 

report, Hollywood Southern Regional WWTP injection well 

effluent disposal system: Prepared for the City of Hollywood in association with Water Technologies Associates, 

Inc., p. 1–1 to 5–5, plus apps.

Hazen and Sawyer, P.C., 2006, Engineering well completion 

report, —Peele-Dixie Water Treatment Plant concentrate 

disposal well: Prepared for City of Fort Lauderdale, p. 1–1 

to 5–5, plus apps.

Hazen and Sawyer, P.C., 2007, Engineering well completion 

report Hallandale Beach WTP concentrate disposal well: 

Prepared for the City of Hallandale Beach, p. 1–1 to 5–5, 

plus apps.
60 Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System of Broward County, Florida

Hazen and Sawyer, P.C., 2008, City of Plantation Regional 

Wastewater Treatment Plant engineering well completion 

report for dual zone monitoring well: Prepared for City of 

Plantation, p. 1–1 to 4–3, plus apps.

Hazen and Sawyer, P.C. and Geraghty and Miller, Inc., 1981, 

Construction and testing of the test injection well, City 

of Fort Lauderdale, Florida: Final report prepared for 

EPA project C-120474-220 city project 7089, 61 p., 

plus apps.

Lukasiewicz, John, 2003, Floridan aquifer system test well 

program, C-13 Canal, Oakland Park, Florida: South Florida 

Water Management District Technical Publication WS-16, 

49 p., plus apps.

Malcolm Pirnie, Inc., 1990, City of Hollywood Water Treatment 

Plant Floridan aquifer test well: p. 1–1 to 7–1, plus apps.

Malcolm Pirnie, Inc., 2009, Technical memorandum detailing installation of test production wells F1 and F2: City of 

Miramar, Fla., p. 1–1 to 5–1, plus apps.

Metcalf and Eddy, Inc., and Missimer International, Inc., 

2000, City of Plantation East Water Treatment Plant 

concentrate injection well no. 1 completion report, v. 1: Prepared for City of Plantation Utilities, Plantation, Fla., 81 p., 

plus apps.

Missimer and Assoc., Inc., 1992, Technical memorandum on 

the construction and testing of well F-2, City of Hollywood, 

Florida: Prepared for Metcalf & Eddy, Inc., 32 p., plus apps.

Montgomery Watson, 1996, City of Miramar Western Water 

Treatment Plant Injection Well System, Injection Wells 

IW-1 and IW-2 and Monitor Well DZMW-1: Prepared for 

the City of Miramar, Florida, 2 reports plus apps.

Montgomery Watson, 1997, Modification of monitor well 

MW-1A at the Sawgrass Wastewater Treatment Plant: 

Report prepared for the City of Sunrise, Fla., plus apps.

Montgomery Watson, 1998a, Springtree Water Treatment 

Plant aquifer storage and recovery system well construction 

report: Prepared for the City of Sunrise, Florida, p. 1–1 to 

5–1, 13 apps.

Montgomery Watson, 1998b, Fiveash Water Treatment Plant 

aquifer storage and recovery system well construction 

report: Prepared for the City of Fort Lauderdale, Florida, 

p. 1–1 to 6–1, 14 apps.

Montgomery Watson Americas, Inc., 1999, Sawgrass Water 

Treatment Plant concentrate disposal system report and 

appendix I: Prepared for City of Sunrise, Florida, p. E-2 to 

6–14, plus apps.

Montgomery Watson Americas, Inc., 2007, Sawgrass Water 

Treatment Plant Floridan Blending Test Well: Sunrise Project no. 06–005 final report, 24 p., plus apps.

Palm Beach County Water Utilities Department, 2003, Eastern 

Hillsboro Canal Water Treatment Plant #9 aquifer storage 

and recovery well: Well construction report and operational 

testing request, p. 1–1 to 4–1, 16 apps.

Post, Buckley, Schuh and Jernigan, Inc., 1987, Engineering 

report for deep test/injection well and deep monitor well: 

Prepared for the City of Pembroke Pines, Broward County, 

Fla., p. 1–1 to 11–4, plus apps. 

References Cited in Headnote to 

Appendix Table 1–6

Cooper, H.H., Jr., and Jacob, C.E., 1946, A generalized graphical method for evaluating formation constants and summarizing well-field history: American Geophysical Union 

Transactions, v. 27, no. 4, p. 526–534.

Hantush, M.S., 1960, Modifications of the theory of leaky 

aquifers: Journal of Geophysical Research, v. 65, no. 11, 

p. 3713–3725.

Hantush, M.S., and Jacob, C.E., 1955, Nonsteady radial flow 

in an infinite leaky aquifer: American Geophysical Union 

Transactions, v. 36, no. 1, p. 95–100.

Moench, A.F., 1985, Transient flow to a large-diameter well 

in an aquifer with storative semiconfining layers: Water 

Resources Research, v. 21, no. 8, p. 1121–1131. 

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: American Geophysical Union Transactions, v. 16, p. 519–524.

Walton, W.C., 1962, Selected analytical methods for well and 

aquifer evaluation: Illinois State Water Survey Bulletin 

no. 49, 81 p.
Manuscript approved January 6, 2014

Prepared by the Raleigh Publishing Service Center

Mike Deacon, Editor

Kimberly Swidarski, Illustrations and layout

For more information about this publication, contact:

Director 

U.S. Geological Survey

Florida Water Science Center

4446 Pet Lane, Suite 108

Lutz, FL 33559

(813) 498-5000

or visit our Web site at

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Reese and Cunningham—Hydrogeologic Framework and Salinity Distribution of the Floridan Aquifer System—Scientific Investigations Report 2014–5029

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20145029