U.S. Gulf Coast Petroleum Systems Project

Assessment of Undiscovered Oil and Gas Resources in 

the South Florida Basin, 2016

Introduction

The U.S. Geological Survey (USGS) recently completed a 

geology-based assessment of technically recoverable continuous 

(unconventional) and conventional resources in the South 

Florida basin (fig. 1). The South Florida basin is located on the 

Florida platform, a carbonate platform that can be more than 

350 miles wide (Hine and others, 2001; Scott, 2001). 

The basin has a maximum sediment thickness of 

15,000–17,000 feet (ft) and a center that is located 

offshore, west of the southwest coast of the 

peninsula (Pressler, 1947; Halley, 1985). The 

onshore part of the South Florida basin, an emergent 

segment of the Florida platform, and the Florida 

State waters represent about half of the entire 

basin area (Applegate and Pontigo, 1984).

During the Middle Jurassic through to about 

the middle Oligocene, shallow-water marine 

deposition was dominant in the South Florida 

basin, and sequences of carbonate and evaporite 

rocks were deposited in water typically less than 

300 ft deep (Halley, 1985; Scott, 2001). Organic-rich 

carbonate mud also accumulated during the 

intermittent occurrence of salinity-stratified 

interior lagoons (Halley, 1985).

At least two geochemically distinct composite 

total petroleum systems are recognized in the 

South Florida basin that are separated by the 

wedge-like, regionally persistent Punta Gorda 

Anhydrite of the Glades Group (fig. 2); this 

anhydrite unit varies in thickness from 200 to 

2,100 ft (Applin and Applin, 1965). The rocks 

underlying the Punta Gorda Anhydrite are Upper 

Jurassic(?)–Lower Cretaceous and consist of the 

Wood River, Bone Island, and Pumpkin Bay 

Formations, as well as the Lehigh Acres Formation 

of the Glades Group (fig. 2). The Upper Jurassic(?) 

Wood River Formation consists of carbonate-rich 

deposits; however, the basal 100–150 ft of the 

formation contains approximately 100 ft of shale 

and arkosic sandstone (Braunstein and others, 

1988; Pollastro and others, 2001). The overlying 

Lower Cretaceous Bone Island and Pumpkin Bay 

Formations are carbonate and evaporite strata with variable 

porosity (Pollastro and others, 2001). The Lehigh Acres 

Formation overlies these formations and is divided from 

oldest to youngest into the West Felda Shale, Twelve Mile, 

and Able Members. The West Felda Shale Member is a 

Tampa

Miami

Key West

Sarasota

FLORIDA

THE

BAHAMAS

GULF OF MEXICO

ATLANTIC OCEAN

 LAKE

OKEECHOBEE

−84° −83° −82° −81° −80° −79°

28°

27°

26°

25°

24°

0 50 100 KILOMETERS

0 50 100 MILES

Base map from U.S. Department of the Interior National Park Service

FLORIDA

ALABAMA GEORGIA

Map area

GULF OF

MEXICO

ATLANTIC

OCEAN

THE

BAHAMAS

Pre-Punta Gorda Conventional Oil AU

South Florida Basin Province

 boundary (part)

Post-Punta Gorda Conventional Oil AU

County boundary

EXPLANATION

Figure 1. Map of the South Florida basin, showing the assessment unit (AU) 

boundaries for the conventional oil AUs.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3074

February 2019

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered, technically recoverable

resources of 49 million barrels of oil and 18 billion cubic feet of gas in the onshore and State waters part of the South Florida basin.
regionally persistent calcareous shale that is typically less 

than 100 ft thick in the South Florida basin (Applegate 

and others, 1981). The Twelve Mile Member is a skeletal 

limestone (Winston, 1987) and contains the informal Brown 

Dolomite Zone (Applegate, 1987; Pollastro and others, 

2001). The Able Member consists primarily of anhydritic 

and argillaceous limestone. Rocks overlying the Punta Gorda 

Anhydrite are Lower Cretaceous and consist of the Ocean 

Reef Group (Sunniland, Lake Trafford, and Rattlesnake 

Hammock Formations) and Big Cypress Group (Marco 

Junction, Gordon Pass, and Dollar Bay Formations) (fig. 2). 

This entire section of several thousand feet of rock consists 

of repetitive evaporite-carbonate cycles with anhydrite, limestone, and dolomite lithologies. The Sunniland Formation, 

consisting of a lower micritic dark carbonate zone source 

rock and an overlying porous grainstone, contains the only 

discovered commercial oil accumulations in south Florida 

with a total of 14 existing or depleted oil fields (Palacas, 

1978; Palacas and others, 1981; Applegate and Pontigo, 1984; 

Applegate, 1987; Winston, 1987; Lloyd, 1997; Pollastro and 

others, 2001). The discovered oil accumulations are in isolated bioclastic-debris mounds and shoals from rudistid reefs. 

Low-gravity oil shows have been reported from the Dollar 

Bay Formation, but commercial production has not been 

established. Isolated oil shows have also been reported 

from the Lake Trafford Formation; however, similar to 

the Dollar Bay Formation, no commercial production has 

been established.

Isolith, isopach, and porosity maps were created and used 

in conjunction with production data to guide the geologic 

definition of the assessment units in this study. New information 

on source-rock characteristics for Upper Jurassic(?)–Lower 

Cretaceous formations underlying the Punta Gorda Anhydrite 

and the Lower Cretaceous Sunniland and Dollar Bay Formations 

were derived from programmed pyrolysis and other geochemical and petrographic approaches and were used to outline 

petroleum system properties.

Four assessment units (AU) were defined in the South 

Florida basin: two were quantitatively assessed, and two were 

not. Three of the AUs are contained within the Post-Punta Gorda 

Composite Total Petroleum System (TPS), and one AU is within 

the Pre-Punta Gorda Composite TPS. Input data for the two 

conventional oil AUs are summarized in table 1.

Most of the petroleum exploration and (or) production wells 

that are drilled and tested within the South Florida basin are 

located along a feature known as the Sunniland trend. The 

Sunniland trend is where the greatest thickness (up to 150 ft) 

of lower Sunniland source rock coincides with the location of 

overlying, highest porosity Sunniland grainstones (Applegate 

and Pontigo, 1984). Generation of low-maturity, high-sulfur, 

heavy oil is interpreted to have begun at approximately 

40 mega-annum (Pollastro and others, 2001), followed by 

short-distance migration (hundreds of feet) along natural 

fractures to the overlying high-porosity grainstone shoal 

reservoirs. Trapping of oils on structural highs formed from 

rudistid debris occurs with updip permeability barriers 

against adjoining micrite and anhydrite layers.

?

Corkscrew Swamp

Formation

Rookery Bay

Formation

Panther Camp

Formation

Dollar Bay

Formation

Gordon Pass

Formation

Marco Junction

Formation

Rattlesnake Hammock

Formation

Lake Trafford

Formation

Sunniland Formation

Punta Gorda Anhydrite

West Felda

Shale Member

Pumpkin Bay Formation

Bone Island Formation

Glades Group

Lehigh Acres

Formation

Big Cypress Group Group Ocean Reef Group

Twelve Mile

Member

Naples Bay

Able Member

Washitan–

Fredericksburgian

Trinitian

Nuevoleonian

Durangoan

LaCastian Wood River Formation

Zuloagan

Comanchean

Marquesas Supergroup

Unnamed volcanic complex (part)

Series Stratigraphic unit Lower Cretaceous

Provincial

series/stage

Upper

Jurassic

Coahuilan

EXPLANATION

Post-Punta Gorda Conventional Oil AU

Pre-Punta Gorda Conventional Oil AU

Figure 2. Stratigraphic column for the South Florida basin, 

showing stratigraphic units included in conventional oil 

assessment units (AUs), from Roberts-Ashby and others (2015).
The boundaries for the Pre-Punta Gorda Conventional 

Oil AU are defined by the State water boundaries; the presence 

of porous reservoir rock of significant thickness within the 

formations underlying the Punta Gorda Anhydrite, as indicated 

by porosity maps created from geophysical well logs; and the 

Tampa-Sarasota Arch. Boundaries for the Post-Punta Gorda 

Conventional Oil AU are defined based on the documented 

presence of source rock in the lower Sunniland, dark-carbonate 

zone; overlying porous limestone reservoirs; locations of 

documented oil shows; and State water boundaries.

Boundaries for the Sunniland Unconventional Oil AU are 

defined based on the greater than 70-ft isopach thickness of dark 

carbonate (Applegate and Pontigo, 1984), whereas boundaries 

for the Dollar Bay Unconventional Oil AU used the 0–25 percent 

dark-carbonate facies boundary of Winston (1971). Additionally, 

both unconventional oil AUs were dependent upon State water 

boundaries. The unconventional oil AUs are defined but not assessed 

because of insufficient data and the absence of unconventional 

hydrocarbon production in south Florida at the time of this assessment.

Undiscovered Resources Summary

 The USGS assessed technically recoverable, conventional 

resources for two AUs within the South Florida basin; two continuous AUs were not quantitatively assessed (table 2). For the conventional oil resources, estimated means totals are 49 million barrels of 

oil (MMBO) with an F95–F5 range from 0 to 147 MMBO; 18 

billion cubic feet of gas (BCFG) with an F95–F5 range from 0 to 62 

BCFG; and 1 million barrels of natural gas liquids (MMBNGL) 

with an F95–F5 range from 0 to 2 MMBNGL. For the Pre-Punta 

Gorda Conventional Oil AU, the estimated mean resources are 34 

MMBO with an F95–F5 range from 0 to 115 MMBO; 17 BCFG 

with an F95–F5 range from 0 to 59 BCFG; and 1 MMBNGL with 

an F95–F5 range from 0 to 2 MMBNGL. For the Post-Punta Gorda 

Conventional Oil AU, the estimated means are 15 MMBO with an 

F95–F5 range from 0 to 32 MMBO and 1 BCFG with an F95–F5 

range from 0 to 3 BCFG. More than half (69 percent) of the total 

assessed mean oil resources and a majority of the total assessed gas 

(94 percent) and natural gas liquids (100 percent) are in the 

Pre-Punta Gorda Conventional Oil AU.

Table 1. Key input data for two conventional assessment units (AUs) in the South Florida basin.

[AU, assessment unit; MMBO, million barrels of oil. Shading indicates not applicable] 

Assessment input data—

Conventional AUs

Post-Punta Gorda Conventional Oil AU Pre-Punta Gorda Conventional Oil AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Number of oil fields 1 10 40 11.0 1 5 25 5.7

Size of oil fields (MMBO) 0.5 1 20 1.5 0.5 4 200 8.4

AU probability 0.9 0.7

Table 2. Results for two conventional assessment units (AUs) in the South Florida basin. 

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids; AU, assessment unit. 

Results shown are fully risked estimates. For gas accumulations, all liquids are included in the NGL category. F95 represents a 95-percent chance of at least the amount 

tabulated; other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. Shading indicates not applicable]

Total petroleum systems and 

assessment units (AUs)

AU 

probability

Accumulation 

type

Total undiscovered resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Post-Punta Gorda Composite Total Petroleum System

Dollar Bay Unconventional Oil AU Not quantitatively assessed

Sunniland Unconventional Oil AU Not quantitatively assessed

Post-Punta Gorda Composite Total Petroleum System

Post-Punta Gorda Conventional Oil AU 0.9 Oil 0 13 32 15 0 1 3 1 0 0 0 0

Pre-Punta Gorda Composite Total Petroleum System

Pre-Punta Gorda Conventional Oil AU 0.7 Oil 0 22 115 34 0 11 59 17 0 0 2 1

Total undiscovered

 conventional resources 0 35 147 49 0 12 62 18 0 0 2 1
References Cited 

Applegate, A.V., 1987, The Brown Dolomite zone of the 

Lehigh Acres Formation (Aptian) in the South Florida 

Basin—A potentially prolific producing horizon offshore, 

part II: Florida Geological Survey Information Circular 

No. 104, p. 46–66.

Applegate, A.V., and Pontigo, F.A., 1984, Stratigraphy and oil 

potential of the Lower Cretaceous Sunniland Formation in 

south Florida: Florida Geological Survey Report of Investigations No. 89, 40 p.

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, 

Subdivision and regional stratigraphy of the pre-Punta Gorda 

rocks (lowermost Cretaceous–Jurassic?) in south Florida: 

Gulf Coast Association of Geological Societies Transactions, 

v. 31, p. 447–453.

Applin, P.L., and Applin, E.R., 1965, The Comanche Series and 

associated rocks in the subsurface in central and south Florida: 

U.S. Geological Survey Professional Paper 447, 84 p.

Braunstein, J., Huddlestun, P.F., and Biel, R., 1988, Gulf 

Coast Region, Correlation of stratigraphic units of North 

America (COSUNA) Project: Tulsa, Okla., American Association of Petroleum Geologists, Correlation Chart series.

Halley, R.B., 1985, Setting and geologic summary of the Lower 

Cretaceous, Sunniland field, southern Florida, in Roehl, P.O., 

Choquette, P.W., ed., Carbonate petroleum reservoirs: New 

York, Springer-Verlag, p. 443–454.

Hine, A.C., Brooks, G.R., Davis, R.A., Jr., Doyle, L.J., Gelfenbaum, G., Locker, S.D., Twichell, D.C., and Weisberg, R.H., 

2001, A summary of findings of the West-Central Florida 

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and exploration: Florida Geological Survey, Information 

Circular No. 111, 62 p.

Palacas, J.G., 1978, Distribution of organic carbon and petroleum 

source rock potential of Cretaceous and lower Tertiary 

carbonates, South Florida Basin—Preliminary results: U.S. 

Geological Survey Open-File Report 78–140, 46 p.

Palacas, J.G., Daws, T.A., and Applegate, A.V., 1981, Preliminary 

petroleum source-rock assessment of pre-Punta Gorda rocks 

(lowermost Cretaceous–Jurassic?) in south Florida: Gulf 

Coast Association of Geological Societies Transactions, 

v. 31, p. 369–376.

Pollastro, R.M., Schenk, C.J., and Charpentier, R.R., 2001, 

Assessment of undiscovered oil and gas in the onshore and 

State waters portion of the South Florida Basin, Florida—

USGS Province 50, chap. 1 of Pollastro, R.M., and Schenk, 

C.J., comps., National assessment of oil and gas project—

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U.S. Geological Survey Digital Data Series 69–A, 70 p.

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American Association of Petroleum Geologists Bulletin, 

v. 31, p. 1851–1862.

Roberts-Ashby, T.L., Brennan, S.T., Merrill, M.D., Blondes, 

M.S., Freeman, P.A., Cahan, S.M., DeVera, C.A., and Lohr, 

C.D., 2015, Geologic framework for the national assessment 

of carbon dioxide storage resources—South Florida Basin, 

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framework for the national assessment of carbon dioxide 

storage resources: U.S. Geological Survey Open-File Report 

2012–1024–L, 22 p., https://doi.org/10.3133/ofr20121024L.

Scott, T.M., 2001, Text to accompany the geologic map of 

Florida: Florida Geological Survey Open-File Report 80, 28 p.

Winston, G.O., 1971, The Dollar Bay Formation of Lower 

Cretaceous (Fredericksburg) age in south Florida—Its 

stratigraphy and petroleum possibilities: Florida Bureau of 

Geology Special Publication No. 15, 99 p.

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stratigraphy of the pre-Punta Gorda rocks in south Florida, 

p. 225–229, in Maurrasse, F.J.-M.R., ed., Miami Geological 

Society Memoir 3, Symposium on south Florida geology, 

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Coral Gables, Fla., Miami Geological Society, 233 p.

South Florida Basin Assessment Team

Tina L. Roberts-Ashby, Paul C. Hackley, Celeste D. Lohr, Christopher J. Schenk, Tracey J. Mercier, 

Katherine J. Whidden, Phuong A. Le, Marilyn E. Tennyson, Stephanie B. Gaswirth, Cheryl A. Woodall, 

Michael E. Brownfield, Heidi M. Leathers-Miller, Kristen R. Marra, and Thomas M. Finn

For More Information 

Assessment results are also available at the USGS Energy Resources Program website at https://energy.usgs.gov.

ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20183074