Proceedings of the 1988 

U.S. Geological Survey 

Workshop on the Geology 

and Geohydrology of the 

Atlantic Coastal Plain 

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Proceedings of the 1988 

U.S. Geological Survey 

Workshop on the Geology 

and Geohydrology of the 

Atlantic Coastal Plain 

Edited by GREGORY S. GOHN 

A collection of short scientific papers that 

discuss research presented at the workshop held 

September 28-29, 1988, in Reston, Va. 

U.S. GEOLOGICAL SURVEY CIRCULAR 1059 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary 

U.S. GEOLOGICAL SURVEY 

DALLAS l. PECK, Director 

Any use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 

Free on application to 

Book and Open-File Report Sales 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

U.S. Geological Survey Workshop on the Geology and Geohydrology of the 

Atlantic Coastal Plain (1988 : Reston, Va.) 

Proceedings of the 1988 U.S. Geological Survey Workshop on the Geology 

and Geohydrology of the Atlantic Coastal Plain I edited by Gregory S. Gohn. 

p. em. - (U.S. Geological Survey circular ; 1059) 

Includes bibliographical references. 

1. Geology-Atlantic Coast (U.S.)-Congresses. 2. Geology-Middle Atlantic States-Congresses. 3. Hydrogeology-Atlantic Coast (U.S.)-Congresses. 4. Hydrogeology--Middle Atlantic States (U.S.)- Congresses. 

I. Gohn, Gregory S. II. Geological Survey (U.S.). Ill. Title. IV. Series. 

QE78.3.U2 1988 

557.4-dc20 91-11200 

CIP 
PREFACE 

This Circular records the proceedings of a workshop sponsored by the U.S. 

Geological Survey (USGS) on the geology and hydrology of the U.S. Atlantic Coastal 

Plain. The workshop was held on September 28-29, 1988, in the U.S. Geological 

Survey's National Center in Reston, Va., and was attended by more than 80 State and 

federal scientists and scientific managers. Geological surveys and water-resource 

agencies from seven Coastal Plain States were represented, as were the Geologic 

Division and Water Resources Division of the USGS. The goal of the workshop was 

to provide a forum in which Atlantic Coastal Plain researchers representing a variety 

of agencies, geologic disciplines, and geographic areas could meet and exchange 

scientific and programmatic information. An abridged version of the workshop agenda 

is given in the following section. 

Scientific presentations at the workshop were grouped into three technical 

sessions for oral presentations and one poster session. The technical sessions were 

grouped along geographic lines; the opening session featured results of an ongoing 

cooperative research effort in New Jersey between the New Jersey Geological Survey 

and the USGS. The subsequent session concentrated on the northern part of the U.S. 

Atlantic Coastal Plain exclusive of New Jersey, and a following session concentrated 

on the southern part of the Atlantic Coastal Plain as well as the eastern Gulf of 

Mexico Coastal Plain. Seventeen posters on a variety of topics were exhibited at the 

poster session. In addition to the technical sessions, a panel and audience discussion 

and three regional discussion groups were organized to discuss existing programs and 

new directions in Atlantic Coastal Plain research. 

All individuals in attendance at the workshop were invited to contribute to this 

proceedings volume. Twenty-six papers were submitted in response to that invitation. 

These reports are presented in two following sections: one section is devoted to the 

deliberations of the workshop's regional discussion groups plus one related article on 

research directions and needs, and the other section is devoted to technical articles. 

Collectively, these 26 articles represent much of the spectrum of ongoing research in 

the U.S. Atlantic Coastal Plain and suggest future research directions that will become 

increasingly important in the coming decade. 

Gregory S. Gohn 

Editor 

PrEface Ill 
WORKSHOP AGENDA (ABRIDGED) 

WEDNESDAY, SEPTEMBER 28, 1988 

8:00a.m. 

8:30a.m. 

8:40a.m. 

9:00a.m. 

1:30 p.m. 

6:30p.m. 

Registration 

Introduction and welcome 

Opening remarks 

John Dragonetti, USGS 

Assistant Director for Intergovernmental Affairs 

Session 1: New Jersey Coastal Plain 

Richard Dalton, New Jersey Geological Survey, Presiding 

Session 2: Northern Atlantic Coastal Plain Exclusive of New Jersey 

Lucy McCartan, USGS, Presiding 

Session 3: Poster session 

David Soller, USGS. Coordinator 

THURSDAY, SEPTEMBER 29, 1988 

9:00a.m. 

10:50 a.m. 

1:00 p.m. 

IV Workshop Agenda 

Session 4: Southern Atlantic Coastal Plain and Eastern Gulf of 

Mexico Coastal Plain 

Henry Trapp, USGS, Presiding 

Session 5: Atlantic Coastal Plain Research-Panel and Audience 

Discussion on Existing Programs and New Directions in Atlantic 

Coastal Plain Research 

Juergen Reinhardt, USGS. Presiding 

Session 5-Continued 
CONTENTS 

Preface, by Gregory S. Gohn III 

Workshop Agenda (abridged) IV 

REVIEWS OF REGIONAL RESEARCH GOALS 

1. Regional Discussion Group 1-The Northern Atlantic Coastal Plain in New Jersey, 

Pennsylvania, Delaware, and New York 

Compiled by James P. Owens and Peter J. Sugarman 1 

2. Regional Discussion Group 2-Summary of Research Directions in the Central 

Atlantic Coastal Plain in the Salisbury Embayment and North Carolina 

Compiled by C. Wylie Poag and Robert Shedlock 3 

3. Regional Discussion Group 3-Research Needs and Areas for Cooperative Programs 

in the Southern Carbonate Province 

Compiled by Irwin H. Kantrowitz and Henry Trapp, Jr. 4 

4. Existing Programs and New Directions in Hydrogeologic Research in the Atlantic 

Coastal Plain-The West-Central Florida Perspective 

By Thomas H. Yorke 7 

TECHNICAL PAPERS 

New jersey Coastal Plain 

5. Calcareous Nannofossils-Their Use in Interpreting Paleocene and Eocene Geologic 

Events in the New Jersey Coastal Plain 

By Laurel M. Bybell 9 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian 

Sections of the New Jersey Coastal Plain 

By Gregory S. Gohn 15 

7. Paleohydrology of Four Watersheds in the New Jersey Coastal Plain 

By Wayne L. Newell and John S. Wyckoff 23 

8. Geochemical Variation in Pore-Water Samples from the Freehold, New Jersey, Core 

By Amleto A. Pucci, Jr., and James P. Owens 29 

9. Geologic Controls on Aquifer Distribution in the Coastal Plain of Northern New 

Jersey 

By Peter J. Sugarman 35 

10. Silcrete near Woodstown, New Jersey 

By John S. Wyckoff and Wayne L. Newell 39 

11. Hydrogeologic units in the Coastal Plain of New Jersey and their Delineation by 

Borehole Geophysical Methods 

By Otto S. Zapecza 45 

Cor•ents V 
VI Contents 

Central Atlantic Coastal Plain 

12. A Summary of the Geological Evolution of Chesapeake Bay, Eastern United States 

By Steven M. Colman, Jeffrey P. Halka, and C.H. Hobbs III 53 

13. Dynamics of Upper Paleocene Deposits in the Salisbury Embayment, Virginia and 

Maryland 

By Lucy E. Edwards 57 

14. Late Pleistocene and Holocene Development of Delaware Bay 

By Harley J. Knebel 61 

15. Nature and Timing of Deformation of Upper Mesozoic and Cenozoic Deposits in the 

Inner Atlantic Coastal Plain, Virginia and Maryland 

By R.B. Mixon, D.S. Powars, and D.L. Daniels 65 

16. National Water-Quality Assessment Program Activities on the Delmarva Peninsula in 

Parts of Delaware, Maryland, and Virginia 

By Patrick J. Phillips, Robert J. Shedlock, and Pixie A. Hamilton 75 

17. Campanian to Quaternary Depositional Sequences in the Baltimore Canyon Trough 

and Their Relations to Deposits Underlying the Middle U.S. Atlantic Coastal Plain 

By C. Wylie Poag 79 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of 

Virginia 

By D.S. Powars, R.B. Mixon, and Scott Bruce 85 

19. Stratigraphic and Structural Controls on Ground-Water Flow in the Coastal Plain 

Aquifers, North-Central Charles County, Maryland 

By John M. Wilson, William B. Fleck, Lucy McCartan, Laurel M. Bybell, 

George W. Andrews, and Gilbert J. Brenner 103 

Southeastern Coastal Plains 

20. Lithologic Changes in Fluvial to Marine Depositional Systems in Paleogene Strata of 

Georgia and Alabama 

By Thomas G. Gibson 109 

21. Correlation, Age, and Depositional Framework of Subsurface Upper Santonian and 

Campanian Sediments in East-Central South Carolina 

By Gregory S. Gohn 115 

22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern 

Florida 

By Lucy McCartan, A.D. Duerr, and R.M. Hawkins 121 

23. Celestine (SrSO 4) in Hardee and De So to Counties, Florida 

By Lucy McCartan, L.N. Plummer, J.W. Hosterman, E. Busenberg, E.J. Dwornik, 

A.D. Duerr, R.L. Miller, and J.L. Kiesler 129 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Florida 

By Lucy McCartan, J.T. Trommer, J.P. Owens, and R.M. Hawkins 139 

25. Ion-Exchange Control of Radium-226 Activities in Ground Water of Sarasota 

County, Florida 

By Ronald L. Miller 149 

26. Sedimentary Cycles and Sequence Stratigraphy in the Eastern Gulf of Mexico Coastal 

Plain 

By Juergen Reinhardt 153 

FIGURES 

3.1. Map showing the location of the southern carbonate province, which is approximately coincident with the areal extent of the Floridan aquifer system 5 
5.1. Map showing locations of New Jersey wells yielding samples that were 

examined for calcareous nannofossils 10 

5.2. Correlation chart of New Jersey Paleocene and Eocene stratigraphic units 11 

6.1. Map showing county boundaries on the New Jersey Coastal Plain and locations 

of drill holes mentioned in this report 15 

6.2. Correlation chart for the Campanian and Maastrichtian cycles of the New Jersey 

Coastal Plain 16 

6.3. Electric log for the Campanian and Maastrichtian sections in the Howell 

Township corehole 5 17 

6.4. Chart showing stratigraphic positions of the intervals studied from the four coreholes used in this report 17 

6.5. Chart showing distribution of selected ostracode species in the subsurface stratigraphic cycles used in this report 18 

7 .1. Locations of the four studied watersheds plotted on an isopach map of the 

Kirkwood-Cohansey aquifer system in New Jersey 23 

7 .2. Map showing sediment yield in New Jersey 24 

7.3. Map showing surficial deposits and geomorphology in part of the Newtonville 

quadrangle, New Jersey 25 

7 .4. Map showing surficial deposits and geomorphology in the Atsion quadrangle, 

New Jersey 26 

7. 5. Photograph showing a frost wedge within the Bridgeton Formation near 

Hammonton, N.J. 27 

7 .6. Photograph showing an involution in the Bridgeton Formation near Hammonton, 

N.J. 27 

8.1. Map showing location of the test corehole near Freehold, N.J. 29 

8.2. Logs showing geologic units, lithology, and mineralogy in the core from near 

Freehold, N.J. 30 

8. 3. Graphs showing variation of selected chemical constituents with depth in the core 

from near Freehold, N.J. 32 

9 .1. Map showing locations of studied core holes and the four quadrangles composing 

the study area in the northern New Jersey Coastal Plain 35 

9.2. Cross section based on five wells from Marlboro to Allaire, N.J. 36 

10. 1. Map showing distribution of the Kirkwood Formation and the associated silcrete 

boulders near Woodstown, N.J. 39 

10.2. Line drawing of a ground-penetrating radar trace along a traverse just north of 

Mannington, N.J. 40 

10. 3. Photograph of a silcrete boulder showing peds and clay skins 40 

10.4. Photomicrograph of silcrete in plane-polarized light showing floating fabric and 

two generations of cement 41 

10.5. Photomicrograph of a pyrite-rich zone within silcrete in plane-polarized light 41 

10.6. Photograph of a slabbed silcrete boulder containing unoxidized pyrite 41 

10.7. Photomicrograph of an argillan in plane-polarized light 42 

10.8. Ternary plot of genetic compositional fields for silcrete 42 

11.1. Map of the New Jersey Coastal Plain showing lines of hydrogeologic sections 

shown in figures 11.2, 11.3, and 11.4 45 

11.2. Hydrogeologic section A-A' from Quinton Township, Salem County, N.J., to 

Red Bank, Monmouth County, based on gamma-ray logs 48 

11.3. Hydrogeologic section B-B' from Berkeley Township, Ocean County, N.J., to 

Avon-by-the-Sea, Monmouth County, based on electric logs 49 

Cont,~nts VII 
VIII Contents 

11.4. Hydrogeologic section C-C' from Hightstown, Mercer County, N.J., to Dover 

Township, Ocean County, based on electric and gamma-ray logs 50 

12.1. Map showing modern tidal channels in the Chesapeake Bay and the three ancient 

channel systems of the Susquehanna River 54 

13. 1. Maps showing data on the Aquia Formation and Marlboro Clay from eight coreholes in the Salisbury embayment, Maryland and Virginia 58 

14.1. Maps of Delaware Bay showing tracklines along which seismic-reflection profiles 

were collected, thalweg locations of ancestral drainage systems of the Delaware 

River, and paleogeography and sedimentary environments of the ancestral 

estuary 62 

15 .1. Map showing alignment of the Stafford and Brandywine fault systems, early 

Mesozoic basins, and geophysical lineaments 67 

15.2. Structure-contour map of the top of Paleocene beds in the area of the Skinkers 

Neck anticline and Port Royal fault, northeastern Virginia and southwestern 

Mary land Coastal Plain 68 

15.3. Isopach map of lower Eocene beds (Nanjemoy Formation) in the area of the 

Skinkers Neck anticline and Port Royal fault. northeastern Virginia 69 

15.4. Detailed gravity map of the Virginia-Maryland Coastal Plain along the trend of 

buried western border faults of the early Mesozoic Taylorsville basin 70 

15.5. Geologic cross section of the Skinkers Neck anticline and Port Royal fault, 

Bowling Green area, northeastern Virginia Coastal Plain 71 

16.1. Map showing the network of wells in the surficial aquifer planned for the 

Delmarva pilot project 76 

17. 1. Map showing locations of principal physiographic and geologic features, selected 

boreholes, and tracklines along which multichannel seismic-reflection profiles 

were collected in the Baltimore Canyon trough 80 

17.2. Map of selected principal depocenters of the Baltimore Canyon trough and 

northern Hatteras basin during the Campanian to Quaternary 81 

18 .1. Map showing structure contours on the top of pre-Cretaceous basement in the 

Virginia Coastal Plain 86 

18.2. Map showing principal basins and arches of the U.S. Atlantic Coastal Plain 87 

18.3. Diagrammatic geologic cross section to basement, Outer Coastal Plain of 

Virginia 88 

18.4. Uppermost Mesozoic and Cenozoic geologic cross section, Outer Coastal Plain of 

Virginia 89 

18.5. Lithic and gamma-ray logs of the Fentress corehole 90 

18.6. Lithic and gamma-ray logs of the Dismal Swamp corehole 92 

18.7. Lithic and gamma-ray logs of the Exmore corehole 96 

19.1. Map showing the trace of a major reverse fault within the Brandywine fault 

system in Prince Georges and Charles Counties, Md. 103 

19.2. Cross section showing stratigraphic relations among the formations, aquifers, and 

confining units in the Waldorf area of Charles County, Md. 104 

19.3. Graph comparing model-calculated water levels and hydrograph from well 

CH Be 43, which is screened in the Magothy aquifer 106 
20 .1. Map of the Chattahoochee River valley and surrounding study area in 

Alabama and Georgia 110 

20.2. Correlation chart of Paleocene to middle Eocene formations and proposed 

shoreline elevations in the Chattahoochee River valley 111 

21.1. Map showing locations of drill holes in east-central South Carolina mentioned in 

this report 116 

21.2. Gamma log for the studied section in USGS-Clubhouse Crossroads 1, Dorchester 

County, S.C. 118 

21.3. Gamma and electrical resistivity logs for the studied section in USGS-St. 

George 1, Dorchester County. S.C. 118 

21.4. Cross section from USGS-Clubhouse Crossroads 1 to the Morgan Point well 

showing distribution of facies in unit 4 119 

22.1. Map showing locations of the ROMP 17 corehole and the Dees well, De Soto 

County, Fla. 121 

22.2. Chart showing stratigraphic nomenclature for the upper Eocene-Miocene series 

in southwestern Florida 122 

22.3. Chart showing lithologic, gamma-ray, and resistivity logs and stratigraphy of the 

ROMP 17 corehole 123 

22.4. X-ray diffractograms of minerals in lightly crushed samples from the ROMP 17 

core 124 

22.5. X-ray diffractograms of minerals in the clay-sized fraction (less than 2 ~m) of 

cuttings from the Dees well 125 

23.1. Map showing locations of three Florida drill holes in which celestine has been 

found 129 

23.2. Stratigraphic columns showing depths at which celestine was found in the Dees 

and Newbern Grove wells 130 

23.3. X-ray diffractogram of celestine in cuttings from a depth of 1,083 ft, Newbern 

Grove well. Hardee County. Fla. 131 

23 .4. Scanning electron micrograph of celestine grains in cuttings from a depth of 

1,083 ft, Newbern Grove well, Hardee County, Fla. 131 

23.5. Map showing concentration of Sr2+ in ground water in Hardee and De Soto 

Counties, Fla. 132 

23.6. Geologic cross section southward from Polk City, Fla .. along ground-water flow 

path 134 

23.7. Graph showing concentrations of so;- and Sr2+ and saturation indices of 

gypsum and celestine for wells shown in figure 23.6 134 

24.1. Map of part of a sinkhole complex in the study area, Pinellas County, Fla., 

showing topography, locations of drill holes, and the line of stratigraphic section 

A-A' 140 

24.2. Structure contour map of base of surficial sands in part of the northeast corner of 

the Dunedin 7 .5-minute quadrangle 141 

24.3. Logs showing lithology and mineralogy of drill holes WP and FL3, Pinellas 

County, Fla. 142 

24.4. Logs showing lithology and mineralogy of drill holes T3 and T2, Pinellas 

County, Fla. 143 

24.5. Chart showing stratigraphic nomenclature for Oligocene to Pleistocene units in 

Pinellas County, Fla. 145 

24.6. Section A-A' showing stratigraphy and distribution of vermiculite 146 
X Contents 

25 .1. Graph comparing radium-226 activity and specific-conductance data for Sarasota 

County, Fla., and an inland phosphate mine 150 

25.2. Graph showing release of radium-226 from three solid-phase samples 150 

26.1. Generalized geologic map of the Cretaceous units in the Chattahoochee River 

valley region on the northeastern margin of the Gulf of Mexico Coastal 

Plain 154 

26.2. Chart relating the Upper Cretaceous depositional cycles in the Chattahoochee 

River valley to the model of coastal onlap and eustatic sea-level curves of Haq 

and others (1987) 155 

TABLES 

6.1. Selected ostracode species from the studied New Jersey cores 19 

11.1. Geologic and hydrogeologic units in the Coastal Plain of New Jersey 47 

15.1. Age, thickness, and generalized lithology of rock units in the Inner Coastal Plain 

of Virginia 66 

21.1. Upper Santonian, Campanian, and lower Maastrichtian datums in the 

USGS-Clubhouse Crossroads 1 and USGS-St. George 1 wells, 

South Carolina 117 

23 .1. Concentration of strontium in ground water in Hardee and De Soto Counties, 

Fla. 133 

23.2. Some chemical and mineralogical characteristics of south-central Florida and 

three other gypsum-bearing localities 135 

24.1. Mineralogy of selected lithologic samples from the Pinellas County, Fla., sinkhole complex 144 

24.2. Selected mineralogical characteristics of stratigraphic units in the Pinellas County, 

Fla., sinkhole complex 147 
CONVERSION FACTORS 

Multiply 

inch (in.) 

foot (ft) 

mile (mi) 

nautical mi (nmi) 

angstrom (A) 

millimeter (mm) 

centimeter (m) 

meter (m) 

kilometer (km) 

square mile (me) 

cubic foot (ft3

) 

liter (L) 

cubic centimeter (cm3

) 

ton (2,000 pounds) 

gram (g) 

pound-force per square inch 

(lbf/in. 2

) 

square foot per day (ft2/d) 

cubic foot per second (fe/s) 

milligal (mGal) 

picocurie (pCi) 

By 

Length 

25.4 

0.3048 

1.609 

1.852 

1010 

0.03937 

0.3937 

3.28 

0.6214 

0.5400 

Area 

2.590 

Volume 

0.02832 

1.057 

0.061 

Mass 

0.9072 

28.35 

Pressure 

6,895 

Transmissivity 

0.0929 

Flow 

0.02832 

Acceleration 

0.00001 

Radioactivity 

0.037 

To obtain 

millimeter ( mm) 

meter (m) 

kilometer (km) 

kilometer (km) 

meter (m) 

inch (in.) 

inch (in.) 

foot (ft) 

mile (mi) 

nautical mile (nmi) 

square kilometer (km2

) 

cubic meter (m3

) 

quart (qt) 

cubic inch (in. 3

) 

metric ton (1,000 kg) 

ounce avoirdupois ( ozavdp) 

pascal (Pa) 

square meter per day (m2

/d) 

cubic meter per second (m3

/s) 

meter per second squared (rnls2

) 

becquerel (Bq) = 1 disintegration per 

second 

Temperature.-Temperatures can be converted as follows: 

degree Fahrenheit (°F) = 1. 8 degree Celsius (°C) + 32 

degree Celsius = (degree Fahrenheit - 32)/1.8 

Age designations. -The time of a geologic event and the age of an epoch boundary 

are expressed as Ma (mega-annum), and intervals of time are expressed as m.y. (million 

years). Both terms mean 1,000,000 years, or years X 106 . For example, sediments were 

deposited at 85 Ma (85X 106 years before 1950 A.D.), and the deposition continued for 

the next 2 m.y. 

Conversion Factors XI 

Proceedings of the 1988 U.S. Geological Survey 

Workshop on the Geology and Geohydrology of the 

Atlantic Coastal Plain 

Edited by Gregory S. Gohn 

REVIEWS OF REGIONAL RESEARCH GOALS 

1. Regional Discussion Group 1 -The Northern Atlantic Coastal Plain in New Jersey, 

Pennsylvania, Delaware, and New York 

Compiled by james P. Owens1 and Peter j. Sugarman2 

The regional discussion group for the northern Atlantic Coastal Plain consisted primarily of scientists from the 

New Jersey Geological Survey, the Pennsylvania Geological Survey, and the Trenton, N.J., and Reston, Va., offices 

of the U.S. Geological Survey. The group focused on new 

research directions in the New Jersey Coastal Plain but also 

discussed stratigraphic and hydrologic relations among 

Coastal Plain units of New Jersey, Long Island, Pennsylvania, and Delaware. The following topics were suggested 

by group members for possible future research programs 

and cooperative studies. 

Salnvater intrusion. -Studies of saltwater intrusion 

into Coastal Plain aquifers are essential because of the threat 

this phenomenon poses to ground-water resources. Measurements of saltwater heads are particularly important 

because only limited information is presently available. 

Suggested studies related to this topic include the following: 

1. Establishment of a regional monitoring-well network 

for identifying coastal areas where saltwater intrudes and 

for better understanding the hydrology of saltwater 

intrusion. 

2. Studies of saltwater intrusion into the Potomac-RaritanMagothy aquifer systems along Delaware Bay. This 

work would probably require a cooperative, multi-State 

effort. 

Manuscript approved for publication January 28, 1991. 1

U.S. Geological Survey. Reston, VA 22092. 2

New Jersey Geological Survey, Trenton, NJ 08625. 

3. Studies of saltwater intrusion into the Potomac-RaritanMagothy aquifer system along Raritan Bay. This investigation could also include study of the move'llent of 

lead and cadmium into the aquifer system along with the 

saline water. 

4. Hydrogeochemical studies (including core squeezing) of 

confining units that contain brackish or salin~ water. 

Saltwater intrusion is believed to change the physical 

properties of confining beds. 

Middle Tertiary aquifers.-Relations between the 

stratigraphy and hydrology of middle Tertiary units in 

southern New Jersey and northern Delaware need study. 

The emphasis of this study would be on Eocene, Oligocene, 

and Miocene aquifers and their stratigraphic and hydrologic 

relations across Delaware Bay. 

Offshore geology of Monmouth and Ocean Counties, 

N.J.-An obvious data gap highlighted by the conference is 

the lack of information regarding the transition of geologic 

and hydrogeologic units from the Coastal Plair to the 

adjacent offshore areas. In the northern New Jersey Coastal 

Plain and adjacent offshore areas, a study of the Kirkwood 

Formation, the Cohansey Sand, and overlying Ple.istocene 

formations could incorporate stratigraphic, isotopic (radiocarbon), mineralogic, and geomorphic investigations. A 

second study could focus on the deeper aquifer units and 

their continuation into the offshore area. 

Geochemical map of Nelt.' Jersey.- A geochemical 

map of New Jersey would present water-chemistry data for 

the numerous subsurface formations in the Coastal Plain. 

It could utilize existing water-quality data and NURE 

1. Regional Discussion Group 1-The Northern Atlantic Coastal P~11in 
(National Uranium Resource Evaluation) data. This map 

would be useful in regulating underground storage tanks 

where ground-water corrosion affects tank life. 

Geology of impermeable materials. -A project on 

impermeable materials would involve varied studies of clay 

and silt in the Coastal Plain. Geologic studies would involve 

field mapping to produce a resource map and the use of 

facies models to predict clay occurrences. Hydrologic 

studies would include measurements of permeability and 

other properties of clay and silt layers and their geochemical 

characteristics as confining units. 

Raritan Formation in the northern New Jersey 

Coastal Plain.-The Woodbridge Clay Member of the 

Raritan Formation defines the boundary between the upper 

and middle aquifer systems in the northern New Jersey 

Coastal Plain. Its surface and subsurface distribution and 

its physical properties are important for the understanding 

of these major aquifer systems. This study could involve 

core drilling, palynologic studies, and seismic-reflection 

surveys. 

Amboy trough between Trenton and New Brunswick, 

N.J. -Geologic studies of the Amboy trough would require 

integrated investigations of the stratigraphy and geomorphology of the Cretaceous and Pleistocene sections in that 

area and structural implications derived fro"'l these data. 

Scattered evidence in the trough suggests som~ tectonism in 

this region. Detailed mapping of the surficial sediments in 

the trough would define the extent and tining of these 

structural movements. 

Pennsylvania Coastal Plain. -Relativdy few investigations have been conducted in the Pennsylvania Coastal 

Plain during the past decade. Consequently, if studies were 

to be initiated, they should be fundamental studies of the 

stratigraphic framework. The need for geologic studies 

related to pollution of Coastal Plain units in the Delaware 

Valley could provide a focus for such work. 

2 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
2. Regional Discussion Group 2-Summary of Research Directions in the Central Atlantic 

Coastal Plain in the Salisbury Embayment and North Carolina 

Compiled by C. Wylie Poag 1 and Robert Shedlock2 

Members of the regional discussion group concerned 

with research needs in the Salisbury embayment and North 

Carolina segment of the U.S. Atlantic Coastal Plain 

included representatives from the Geologic Division (GD) 

and Water Resources Division (WRD) of the U.S. Geological Survey (USGS) and from the Maryland Geological 

Survey (MGS), the Delaware Geological Survey (DGS), 

the Virginia Water Control Board (VWCB), and the North 

Carolina Department of Natural Resources-Groundwater 

(NC-DNR-G). Active participants included Emory Cleaves 

(MGS), Kelvin Ramsey (DGS}, Scott Bruce (VWCB), Ted 

Mew (NC-DNR-G), Norm Sohl (GD), Wylie Poag (GD), 

Bob Mixon (GD), Dave Prowell (GD), Lucy Edwards 

(GO), Norm Fredericksen (GD), Steve Colman (GD), Ron 

Litwin (GD), Dave Powars (GD), Helaine Markewich 

(GO), Bob Shedlock (WRD), and Steve Hiortdahl (WRD). 

Although the charge of this discussion group was to 

agree on new research initiatives for this area, the limited 

time did not permit the group to develop a consensus on any 

detailed new initiatives. Instead, the group focused on three 

general and fundamental targets for further investigation. 

1. Nomenclature and Correlation of 

Depositional Units 

Everyone agreed that more communication is needed 

among geologists and hydrogeologists, especially to iron 

out problems of stratigraphic nomenclature, complex facies 

changes, and biostratigraphy of noncalcareous units. Multi1

U.S. Geological Survey, Woods Hole, MA 02543. 2 U.S. Geological Survey, Towson, MD 21204. 

discipline research teams and interdisciplinary workshops, 

such as the present one, are fruitful means of im"Jroving 

this communication and providing more comprehensive 

research efforts. 

2. Centralized Field-Data Library 

The group expressed a widely felt need tC' assess 

currently available field data, such as core collectbns and 

libraries of borehole logs, which are held by various 

institutions represented in this group. These data are not 

readily accessible to all because they reside in the files of 

different agencies, which have somewhat different missions. Ron Litwin volunteered to compile a directory of 

such data and asked that workers from each ag~ncy or 

division send him brief descriptions of their geo1ogic or 

hydrogeologic data. Dave Powars agreed to co~pile a 

summary of drilling capabilities and resources now supported by different institutions. 

3. Geologic Data on the Nearshore Regior of 

the Continental Shelf 

The most clearly articulated research direction was to 

carry out more nearshore test drilling. This dr~lling is 

essential to refine conceptual models of geolo'l:ic and 

hydrogeologic units, to establish a detailed structural and 

depositional framework, and to examine the relatio'lship of 

Coastal Plain deposits to downdip facies in the Bllltimore 

Canyon trough. Such work would also have economic 

significance as it would provide important inkrmation 

relevant to the intrusion of saline waters into the water 

supplies of coastal cities. An interagency effort was suggested, but time did not permit discussion of a plan of 

action. 

2. Regional Discussion Group 2-The Central Atlantic Coastal p•;,jn 3 
3. Regional Discussion Group 3-Research Needs and Areas For Cooperative Pro~rams in 

the Southern Carbonate Province 

Compiled by Irwin H. Kantrowitz1 and Henry Trapp, jr.2 

INTRODUCTION 

Members of the regional discussion group concerned 

with research needs in the southern carbonate province 

(Florida and parts of Alabama, Georgia, and South Carolina) represented the Geologic Division (GD) and Water 

Resources Division (WRD) of the U.S. Geological Survey 

(USGS) and the Florida Geological Survey (FGS). The 

discussion emphasized areas of overlapping or complementary interests among scientists of these groups. Present for 

the discussion were Jonathan Arthur (FGS), Paulette Bond 

(FGS), Irwin Kantrowitz (WRD), Harley Knebel (GD), 

Lucy McCartan (GD), Ronald Miller (WRD), Peter Popenoe (GD), Juergen Reinhardt (GD), Walter Schmidt (FGS), 

Henry Trapp, Jr. (WRD), and Thomas Yorke (WRD). 

Irwin Kantrowitz served as moderator and prepared the first 

draft of this report; Henry Trapp served as recorder of the 

discussion. All members of the group were given an 

opportunity to review and revise the draft, as was James 

Miller (WRD), who was unable to attend the workshop. 

This report summarizes the cumulative thinking of the 

group regarding fruitful areas of geologic research in the 

southern carbonate province. It was beyond the scope of 

this report to document existing literature, active research, 

and available data; however, this body of knowledge is 

considerable and would provide the starting point for any 

future research. 

The major area of needed research identified by the 

group involves a better description and delineation of 

aquifers and confining beds in the Tertiary sediments 

comprising and overlying the Floridan aquifer system. In 

particular, detailed three-dimensional mapping of the material between the surface and a depth of 200 ft is necessary 

in order to characterize the nature of ground-water recharge 

and to map shallow aquifers, which commonly are discontinuous. The areal extent of the Floridan aquifer system is 

approximately coincident with the southern carbonate province (fig. 3.1). Because of the heavy use made of the 

1

U.S. Geological Survey, Tallahassee, FL 32301. 2

U.S. Geological Survey, West Trenton, NJ 08628. 

Floridan and overlying aquifers for water supply and 

because of the relatively large number of agencies at the 

Federal, State, and local levels having active programs in 

hydrogeology (geology and ground-water hyd1"ology), prospects for cooperative efforts are favorable. Within the broad 

category of hydrogeology, detailed lithostratigraphy, biostratigraphy, geophysical studies, and min~ralogy were 

thought to be the most promising subjects for cooperative 

programs. Other broad research topics identified were the 

distribution of radon-producing sediments and vertebrate 

paleontology. 

HYDROGEOLOGY 

The major controlling factor in obtaining a better 

understanding of the geology, and, cons~quently, the 

hydrogeology, of the southern carbonate province is the 

flatness of its surface, which restricts exposure of the rocks. 

Additional geologic understanding will have to come from 

the interpretation of subsurface data obtained either directly 

through cores and drill cuttings or indirectly through the use 

of geophysical methods. 

High-resolution seismic-reflection prC'filing, combined with core drilling, was suggested as a possible means 

of collecting data in some areas. Offshore seismic lines 

have been run by oil companies as well as by the Minerals 

Management Service (U.S. Department of the Interior). 

Although many of these data may be proprietary, some may 

be available for purchase or inspection. In addition, some 

new acoustic profiles should be collected, pmicularly to 

correlate the offshore data (commonly obtcined beyond 

State jurisdiction) with data from nearshore and estuarine 

areas. Onshore Vibroseis exploration ani, possibly, 

ground-penetrating radar offer a means of extending these 

correlations into areas underlain by aquifers containing 

freshwater. 

Another possible method of obtaining data inland 

would be to conduct seismic surveys along some rivers or 

canals. However, applying seismic techniq'Ies to these 

narrow, water-covered areas poses a sizable challenge. 

4 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
IW 

34' 

""" \ 

\ 

. \ 

82' 

·---... \ SOUT!'! CAROLINA 

i 

i 

i 

i 

i 

i '- ; '/G'EOAG,IA ·, 1 -. " 

')('':\ ~ J\ ~, s'4~1'f.~ 

h , T' - \ • ~ - ·, 

1 I I \ _. ~ I ·, ~~ I \ } 11l''< ' 

28' 

26' 

i 

i 

i 

50 100 MILES 

50 100 KILOMETERS 

.•' . ..ol.J ..... 

•b:>"""" ··" 

Figure 3.1. Location of the southern carbonate province, which is approximately 

coincident with the areal extent of the Floridan aquifer system. Modified from Miller 

(1986). 

Difficult acoustic conditions are expected to be caused by 

(1) extreme shallow water (ringing), (2) hard carbonate 

rocks (poor signal penetration), (3) irregular karst environments (signal attenuation and sidescattering), and (4) gas in 

the sediments (poor signal penetration). The data from these 

environments must be acquired digitally in order to take 

advantage of processing techniques such as deconvolution, 

frequency-wave-number filtering, and statics corrections 

that enhance signal and attenuate noise. In addition, a 

feasibility study would need to be conducted to determine 

which equipment could best be used in these environments. 

This feasibility study would involve using different sound 

sources (such as water guns, air guns, and Uniboom), 

different streamers (single channel and multichannel), and 

different source-streamer offsets. With this suite of comparative data, one could choose and arrange the field 

equipment in order to obtain the best reflection records. 

Geophysical logs run in coreholes are another means 

of areally extending geologic knowledge of the subsurface. 

Many water wells have gamma-ray logs, even if little or no 

other geologic information has been collected. Comparison 

of these relatively abundant logs with the logs run in 

3. Regional Discussion Group 3-The Southern Carbonate Province 5 
carefully studied coreholes, which, in turn, are tied to 

seismic lines, may permit the correlation of detailed point 

data over broad areas. Additional coreholes to act as 

stratigraphic tie points may be needed to verify regional 

geologic interpretations. 

In addition to enhancing the areal interpretation of 

structure and stratigraphy based on geophysical lines and 

downhole logs, coreholes could provide material for the 

detailed study of mineralogy and biostratigraphy. Detailed 

mineralogic study of core material may prove useful in 

explaining and predicting the chemical quality of ground 

water as well as the ability of confining beds to retard the 

movement of some ions. 

Biostratigraphic studies of cores may prove useful in 

correlating key marker beds, thus permitting the subsurface 

mapping of hydrogeologic units and the identification of 

geologic structures affecting ground-water movement. Fossil assemblages, as well as lithology and mineralogy, 

provide information on depositional environments and the 

geologic history of the rocks subsequent to deposition. 

Mapping of depositional lithofacies is essential to accurate 

prediction of trends in rock permeability. Although recrystallization of the carbonate rocks may have obscured the 

fossil content, other methods, such as study of insoluble 

residues and stable isotopes, may prove useful. 

RADON 

The presence of radon in enclosed areas as a result of 

outgassing from radon-producing sediments is an emerging 

national issue. Uranium, the radon parent material, is 

commonly found in association with phosphate. Radon 

health hazards may be a particular problem in Florida 

because of the occurrence of the phosphate-rich Hawthorn 

Formation throughout much of the State. The FGS has an 

advisory role in the State's efforts to deal with the radon 

problem, but it is not yet clear whether there will be 

research opportunities-that is, geologically oriented problems warranting future study. Elsewhere, however, high 

radon concentrations have been associated with faults and 

fissures that have not been previously mapped. Therefore, 

in addition to providing baseline information on a potential 

health hazard, radon surveys may provide clues about local 

stratigraphy and structural geology. 

VERTEBRATE PALEONTOLOGY 

The Tertiary deposits of Florida contain a rich vertebrate fauna, and the Florida State Museum has the ability to 

protect fossiliferous areas for study prior to development. 

The FGS has no program in vertebrate paleontology and the 

USGS program is extremely limited. Therefore, despite the 

opportunities, there is little likelihood of research in the 

near future. 

SUMMARY AND CONCLUSIONS 

If acquisition and processing problems can be overcome, then seismic profiles can be combined with geophysical logs interpreted on the basis of drill-hole cores and 

cuttings to augment knowledge of the extent, distribution, 

and characteristics of aquifers and confining beds within the 

southern carbonate province. Because the USGS (both the 

Water Resources and Geologic Divisions) and the FGS have 

mutual interests and complementary abilities in the broad 

research field of hydrogeology, prospects for cooperative 

research appear favorable. 

To enhance any formal research efforts, an inventory 

of available data, including offshore and onshore seismic 

lines and geophysical logs, needs to be assembled. Other 

actions, such as requesting access to data from the shallow 

part of oil or injection wells drilled in the future, can greatly 

add to our knowledge of the subsurface at a relatively 

modest cost. 

REFERENCE CITED 

Miller, J.A., 1986, Hydrogeologic framework of the Floridan 

aquifer system in Florida and in parts of Georgia, Alabama, 

and South Carolina: U.S. Geological Survey Professional 

Paper 1403-B, 91 p. 

6 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
4. Existing Programs and New Directions in Hydrogeologic Research in the Atlantic Coastal 

Plain-The West-Central Florida Perspective 

By Thomas H. Yorke1 

This report on existing programs and new directions 

in Atlantic Coastal Plain research is presented from the 

perspective of the Florida water managers and is based on 

day-to-day dealings with many State and local officials. The 

Tampa Subdistrict office of the Water Resources Division, 

U.S. Geological Survey (USGS), has a cooperative program with 15 local jurisdictions, including city, county, and 

State agencies and the Southwest Florida Water Management District. These agencies are responsible for providing 

an adequate supply of potable water to the ever-increasing 

population of west -central Florida or are responsible for 

protecting the water resources. 

Numerous discussions among members of the USGS 

and representatives of these agencies have focused on five 

major areas of concern about ground water in west-central 

Florida. These concerns are summarized by the following 

questions: (1) What are the hydraulic and physical characteristics of water-bearing and confining units that control 

the horizontal and vertical movement of saltwater into 

freshwater zones? (2) What are the rate and direction of 

water movement between the water-bearing units of the 

intermediate aquifer system (interbedded clays and limestones between the surficial materials and the Upper Floridan aquifer) and the Upper Floridan aquifer, and how will 

additional pumping affect the rate and direction of movement? (3) What is the effect of ground-water withdrawals 

on the quantity and quality of water in streams, lakes, and 

estuaries? ( 4) What is the potential for contamination of the 

Floridan aquifer system by toxic agricultural and industrial 

chemicals? (5) What changes occur in the chemical character of ground water as it moves through and between 

different aquifer and confining units? 

The Tampa Subdistrict and Florida District offices 

of the Water Resources Division are addressing most of 

these issues as part of a jointly funded investigative program 

with the Florida Department of Environmental Regulation, Florida Water Management Districts, counties, and 

municipalities. Several studies are underway to define the 

1 U.S. Geological Survey. Reston, VA 22092. 

saltwater-freshwater interface and the potential for S"'ltwater 

intrusion along the west coast of Florida. The purpose of 

one study is to locate and sample wells on or near the 

interface; the purpose of another study is to investigate the 

areal and temporal variation in the quantity and quality of 

discharges of major springs on the coast in Herna1do and 

Citrus Counties. Digital models are being used to simulate 

the transport of salt and other chemically cons~rvative 

constituents in ground water as part of three separate 

investigations. 

Other projects are investigations of the migration of 

water between different water-bearing units of the intermediate and Floridan aquifer systems. Two studies include 

analyses of hydraulic characteristics and chemical constituents to determine directions and rates of water ffi')Vement 

and changes in the chemical quality of the water. A third 

study is an assessment of the potential for contamination of 

the Floridan aquifer; concentrations in water of tritium, 

oxygen isotopes, and other indicators of relative age are 

used to evaluate ease of recharge. 

Stochastic and deterministic models are being used in 

several current studies to evaluate the relation between 

ground water and surface water. Statistical relations have 

been developed to estimate changes in streamflow and lake 

levels that would result from additional pumr1ng and 

concomitant declines in ground-water levels. Grou1d-water 

flow models are being used to estimate changes in spring 

and stream discharges due to declines in ground-water 

levels caused by droughts and by increased withdrawals for 

irrigation and municipal supplies. Both statist:~al and 

numerical models are being used to evaluate potential water 

quality and biological changes in estuarine enviro1ments. 

Although many of the concerns of water ma"'agers in 

west-central Florida are being addressed by curre'1t investigations, additional hydrogeologic research is n~eded in 

several areas. Answers to many of the questions d~pend on 

a better understanding of secondary porosity in the carbonate rocks that form the intermediate and Floridan aquifer 

systems. The approach being taken by many of t"'e Water 

Management Districts is to obtain core, geophysical, and 

aquifer test information from a dense network of observa4. Hydrogeologic Research-The West-Central Florida Perspe~tive 7 
tion wells and boreholes. Although this information is 

invaluable, it is site specific and very expensive. Some of 

this effort could be redirected toward identifying lineations 

on aerial photographs, acquiring borehole televiewer 

images, and using surface geophysical techniques to 

improve our capability for defining fractures, solution 

features, and flow patterns. 

The mineralogy and quality of the pore water in the 

clay beds of the intermediate and Floridan aquifer systems 

are among the least understood characteristics of hydrogeology in west-central Florida. This information is important 

for predicting changes in water quality that would result 

from vertical migration of water induced by additional 

pumping. These characteristics also are important for evaluating the migration of contaminants from the surface or 

deep waste-injection zones to the potable-water zones. The 

mineralogy of the clays will influence how long the confining units will retard the movement of contaminants and 

whether there will be differential sorption of o~rtain types of 

toxic compounds. 

Another topic for geologic research is th~ distribution 

of sediments in tidal rivers and estuaries. Water managers in 

west-central Florida and all coastal States a~e faced with 

multibillion-dollar decisions on alternatives for restoring 

and maintaining the quality and productivity of these water 

bodies. The mechanisms affecting the distrib'Ition of sediments within the affected water bodies and th~ interchange 

of nutrients and contaminants between the s~diments and 

overlying water must be determined. Researc'l on both the 

historical depositional patterns of sediments ir the estuaries 

and the current sediment transport characteristics will be 

useful in assessing alternatives for improving the quality of 

our estuaries. Ultimately, the research must lead to analytical tools such as digital models for predicting how various 

land and water development activities will affect the sediment balance, water quality, and biological interactions of 

tidal rivers and estuaries. 

8 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
TECHNICAL PAPERS 

New jersey Coastal Plain 

5. Calcareous Nannofossils-Their Use in Interpreting Paleocene and Eocene Geologi~ 

Events in the New Jersey Coastal Plain 

By Laurel M. Bybell1 

INTRODUCTION 

Since 1985, as part of a cooperative project between 

the New Jersey Geological Survey (NJGS) and the U.S. 

Geological Survey (USGS), I have examined Paleogene 

samples from 19 wells in the New Jersey Coastal Plain for 

their calcareous nannofossil content (fig. 5.1). Calcareous 

nannofossils are now being used to accurately date many 

marine sediments in New Jersey. This information provides 

a data base that is currently being used to develop a model 

for interpreting the geologic history of this area; unconformities and other features dated by nannofossils aid in modeling the timing of tectonism, eustatic sea-level changes, and 

depocenter shifts. 

Acknowledgments 

I thank James P. Owens (USGS) and Peter J. Sugarman (NJGS) for providing all the well samples, for constant 

cooperation, and for helpful suggestions, without which this 

paper would not have been possible. I thank Jean Self-Trail 

(USGS) for processing many of the samples and drafting the 

figures. I appreciate the thoughtful reviews of James P. 

Owens and Wayne L. Newell (USGS). 

METHODS 

Samples for this study are from cores, cuttings, and 

sidewall cores and even from old wells drilled by percussion 

tools. Because many of the samples were not from recent 

coreholes, and it was impossible to determine what precautions, if any, originally had been taken to avoid contamination, I had to be constantly aware of the possibility of 

1

U.S. Geological Survey, Reston, VA 22092. 

downhole contamination, reworking, and drilling-mud contamination. Where necessary, I even performed species 

counts to ensure the utmost accuracy of the paleontological 

results. 

I used the calcareous nannofossil zones of Martini 

(1971). No one well contained the entire Paleo~ene and 

Eocene sequence from Zone NP 1 to the middle of Zone NP 

21, but data from the 19 wells could be pieced together to 

produce a complete section. In producing the c'lmposite 

section, I was careful to consider geographic location, 

facies changes, and updip-downdip relations. Ths report 

focuses on Paleocene through upper middle Eoc~ne sediments (Zones NP 1-16, fig. 5.2), although upper Eocene, 

lower Oligocene, and upper Oligocene sediment~ are also 

present in the subsurface of the New Jersey Coastal Plain. 

The ACGS-4 core, which contains the most detailed 

information from the subsurface of New Jer~'ey, was 

described by Owens and others (1988) and P1ore and 

Bybell (1988). 

Once samples from all the wells were examined and 

each sample was placed within a nannofossil zone, I 

measured the thickness of each NP zone in each hole. Zones 

NP 1-13 each represent about 1 m. y. , and Zones 1 1

P 14-16 

each represent about 3-4 m.y. according to the time scale of 

Berggren and others ( 1985). For a nannofossil zone at the 

top or bottom of a well or next to a barren interval, I assume 

that only a minimum thickness is represented. However, a 

barren interval could also indicate changing de.,ositional 

conditions or a transition zone into the next nannofossil 

zone, and if it did, little sediment might be missjng. 

In addition to being used to compile a complete 

vertical section, the nannofossil data were also us1'!d to map 

variations in sediment thickness across the Nr.w Jersey 

Coastal Plain at a particular time represented by one 

calcareous nannofossil zone. The first step was to take the 

surface elevation of each well and correct it to sea level. 

The base of each nannofossil zone was plotted and corrected 

5. Calcareous Nannofossils, New Jersey Coastal Plain 9 
NEW JERSEY 

N 

1 

25 50 75 MILES 

25 50 75 100 KILOMETERS 

Figure 5.1. Locations of New Jersey wells yielding samples 

that were examined for calcareous nannofossils. Contour 

lines indicate feet below present sea level for base of Zone 

NP 12. Shading indicates the Camden-Trenton band, an 

area that may have been tectonically active during the 

Paleocene and Eocene. 

to feet below and above current sea level. For each NP 

zone, contour lines of equal depth were plotted relative to 

sea level. The contour lines that were plotted across the 

approximately 40-mi-wide New Jersey Coastal Plain that 

makes up the study area are at 0, 500, 1 ,000, and 1,500 ft 

below present sea level; as an example, figure 5.1 shows the 

contours for the base of the lower Eocene Zone NP 12. 

These sediments dip seaward at about 35 ft/mi, and this 

amount of dip implies that tectonic tilting has probably 

taken place since deposition. In this report, however, the 

direction, not the amount, of dip is what is most significant 

in determining variations in sediment thickness, and thus 

the positions of depocenters, in the New Jrrsey Coastal 

Plain. 

RESULTS 

In the simplified passive-margin model proposed in 

this report for the New Jersey Coastal Plah during the 

Paleocene and early to middle Eocene, indivirlual calcareous nannofossil zones are represented by thn layers of 

sediment that generally become somewhat thi~ker, but not 

significantly so, downdip to the southeast. There is no 

evidence for the South New Jersey high or the Raritan 

embayment or any other significant persistent topographic 

feature in the New Jersey Coastal Plain durirg the Paleocene or Eocene. The variation in thickness witl'in each zone 

is minor (usually less than 50 ft) in comprrison to the 

current dip of these deposits to the southeast (I ,500 ft in 40 

mi). However, these data on thickness variation, used in 

conjunction with lithologic studies, are invalual:>le for determining local geologic processes. Using calcareous nannofossil data, I plotted the varying patterns through time that 

are the result of changes in sedimentation rrte, shifts in 

depocenters, tectonism, and eustatic sea-leve1 changes. I 

discuss below what appears to have been happening in New 

Jersey during the time of deposition of each nannofossil 

zone from the base of the Paleocene up through the early 

middle Eocene. 

Paleocene, Zones NP 1-9 

As is described below, the Paleocene strata on the 

New Jersey Coastal Plain record repeated eust2tic sea-level 

changes, as well as complex lateral and verti-:-al shifts in 

depocenters. Local basinal forces appear to have acted 

separately north and south of the region betwren Camden 

and Trenton and the present shoreline. This region (shaded 

in fig. 5.1) appears to have been tectonicar:r active at 

various times during the Paleocene. It is called the CamdenTrenton band in this report. 

Zone NP 1, 66.4-66.0 Ma. -Zone NP 1 is the oldest 

NP Zone in the Paleocene, and it is not present in any of the 

19 holes examined to date in New Jersey. Thus, the 

unconformity at the Cretaceous-Tertiary boundary in New 

Jersey represents a minimum of 500,000 yr accc·ding to the 

time scale of Berggren and others ( 1985). 

Hornerstown Sand, Zones NP 2-4 (Lower Paleocene) 

Zone NP 2, 66.0-65.0 Ma. -Zone NP 2 was identified only in core ASP 1 (fig. 5.1). For most of the New 

Jersey Coastal Plain, therefore, the unconfornity at the 

Cretaceous-Tertiary boundary is indicated by the absence 

of Zone NP 2, as well as Zone NP 1 , and represents about 

1.4 m.y. 

10 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Age 

in 

Ma 

37 

39 

41 

43 

45 

47 

49 

51 

53 

55 

57 

59 

61 

63 

65 

w 

z 

w 

u 

0 

w 

w 

z 

w 

u 

0 

w 

...J 

<( 

a... 

Series 

UPPER 

MIDDLE 

LOWER 

UPPER 

LOWER 

Stratigraphic 

unit 

SHARK 

RIVER 

FORMATION 

MANASQUAN 

FORMATION 

Sediments 

present in 

northern 

New Jersey 

Sediments 

present in 

southern 

New Jersey 

Calcareous 

nannofossil Age 

zones of in 

Martini (1971) Ma 

NP 19/20 

1-----~- 37.8 

NP18 

1-----~- 40.0 

NP 17 

~----+- 42.2 

NP16 

1-----~- 45.4 

NP15 

1-----~- A8.0 

NP14 

t---N-P-1-3--+- 52.6 

1-----~- 53.7 

NP12 

Figure 5.2. New jersey Paleocene and Eocene stratigraphic units. Diagonal stripes show major unconformiti~s in 

the regions north and south of the Camden-Trenton band. Time scale is from Berggren and others (1985). 

Zones NP 3-4, 65.0-62.0 Ma.-Both outcrop and 

subsurface sediments of the Homerstown from Zones NP 3 

and NP 4 are preserved only in updip locations (GL and 

ASP holes, fig. 5.1). The absence of this material from 

downdip localities may be a result of erosion of the 

Homerstown during the subsequent, less extensive transgression recorded in the upper part of Zone NP 5. Zones NP 

3 and NP 4 are each about 5-10 ft thick, and th~ contour 

lines for these two zones indicate that the sediments dip 

relatively uniformly to the southeast. These sediments 

represent a widespread lower Paleocene transgre::sion that 

occurred not only in New Jersey, but also in Virginia and 

Maryland, and that probably resulted from a global sealevel rise at about 65 Ma. 

5. Calcareous Nannofossils, New Jersey Coastal rrain 11 
Vincentown Formation, Zone NP S-Lower Part of Zone 

NP 9 (Upper Paleocene) 

Zone NP 5, 62.0-61.6 Ma.-As mentioned above, 

there is an unconformity at the Hornerstown-Vincentown 

boundary, which is marked by the absence of the lower part 

of Zone NP 5, and probably the upper part of Zone NP 4. 

The thickness of Zone NP 5 sediments increases somewhat 

downdip to the southeast from about 5 ft in the GL cores to 

about 20 ft at Island Beach (fig. 5.1). The widespread 

presence of this zone in wells in New Jersey, as well as in 

Maryland and Virginia, probably indicates that this again 

was a time of global sea-level rise. The sediments dip to the 

southeast. 

Zone NP 6, 61.6-60.4 Ma. -During deposition of 

Zone NP 6, the depocenter in New Jersey appears to have 

shifted to the north, where the units indicate a significant 

increase in the sedimentation rate. At localities B-4 and 

B-5 (fig. 5.1), the sediments are 60 ft thick (these are the 

thickest deposits observed for any one zone in this study); 

they thin to the south to 10ft at Butler Place (fig. 5.1) and 

are completely absent south of the Camden-Trenton band. 

This distribution could be explained by downward tectonic 

movement to the north or upward tectonic movement in 

southern New Jersey, or both, or an increase in sediments 

being poured into the area to the north. 

Zone NP 7, 60.4-59.9 Ma. -Sediments representing 

Zone NP 7 are found only south of the Camden-Trenton 

band in updip areas, and the depocenter appears to have 

shifted again, this time to the south. There is no downdip 

information because none of the wells I have examined to 

date in this part of the State were drilled deeply enough to 

reach this zone. Sediments of this age are 5-10 ft thick. 

There appears to have been a reversal at this time of the 

conditions found during Zone NP 6 time, and the region 

north of the Camden-Trenton band was higher than the 

region south of the band. 

Zone NP 8, 59.9-59.1 Ma. -Zone NP 8 thickens 

downdip toward the southeast from 5-10 ft thick at the GL 

cores to approximately 40 ft thick at Island Beach. The 

presence of this zone both north and south of Camden 

indicates a significant transgression, which may have 

masked the effects of any local basin warping. A corresponding transgression in Virginia and Maryland indicates 

that we are seeing the effects of a worldwide rise in sea level 

around 59 Ma. 

Lower part of Zone NP 9, 59.1-57.8 Ma.-Zone NP 

9 is missing north of the Camden-Trenton band. The 

thickness of the lower part of Zone 9 ranges from 10 to 30 

ft in southern New Jersey, but there is no apparent downdip 

thickening. Local basin forces again dominated during Zone 

NP 9 time. and the northern part of the coastal plain 

apparently was high relative to the southern part. 

Upper Paleocene Part of the Manasquan Form~tion, Upper 

Part of Zone N P 9 

Upper part of Zone NP 9.-The upper part of Zone 

NP 9 occurs in the Manasquan Formation only in the GL 

wells (fig. 5.1). This part of the Manasquan has not been 

found anywhere else to date in New Jersey. 

Eocene, Zone NP 1 0-Lower Part of Zone NP 21 

The lower and middle Eocene deposits differ significantly from the Paleocene in New Jersey and appear to 

indicate more stable conditions. There are i 1dications of 

small shifts in the depocenter during the Eoc ~ne, again in 

relation to the Camden-Trenton band, but they are of much 

smaller magnitude than those in the Paleocere. However, 

the late Eocene may have been a time of renewed tectonism 

in New Jersey. 

Lower Eocene Part of the Manasquan Formatio..,_, Zones 

NP 10-14 

Zone NP 10, 57.8-56.7 Ma. -Zone ~TP 10 is the 

oldest Eocene zone. The Paleocene-Eocere boundary 

occurs within the Manasquan, and, at the GL localities, 

deposition appears to have been continuous across this 

boundary. New Jersey may well have the most complete 

marine Paleocene-Eocene boundary section in the world. 

Zone NP 10 is present both north and S')uth of the 

Camden-Trenton band. However, this zone is absent at 

Butler Place within the band. This distributhn could be 

explained if the Camden-Trenton band was up slightly 

during deposition of Zone NP 10; there also is a possibility 

that this thin zone was not sampled at B·ltler Place. 

Additional data are needed from the Camden-Trenton band 

to show whether Zone NP 10 is present there. The sediments in Zone NP 10 thicken down dip to the so·1theast from 

5-10ft in the GL cores to 35 ft at Island Beach. 

ZoneNP 11,56.7-55.3 Ma.-ZoneNP 11 is missing 

from updip locations (GL cores, New Brooklyr Park, B-4, 

B-5, and Bog Creek, fig. 5.1). In fact, the upcip locations 

have no marine Eocene deposits preserved from zones 

younger than Zone NP 10. This absence may rroresent less 

extensive transgressions, or, more likely, thes~ sediments 

may have been eroded during a widespread Miocene transgression. The thickest Zone NP 11 sediments in the study 

area occur in the Camden-Trenton band (40 and 46 ft, 

respectively, for Butler Place and Island Beach, in contrast 

to 6ft at ASP 2). The Camden-Trenton band may have been 

slightly lower than the northern and southern parts of the 

New Jersey Coastal Plain during deposition of Zone NP 11. 

Zone NP 12, 55.3-53.7 Ma. -Zone NP 12 is thickest 

north and south of the Camden-Trenton brnd, which 

appears to have been uplifted after Zone NP 11 time. The 

sediments dip to the southeast. 

12 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Zones NP 13/14, 53.7-48.0 Ma.-Zones NP 14 

through NP 16 each represent 3--4 m. y. Zones NP 13 and 14 

could not be clearly delineated in many of the wells 

examined to date, and so they have been combined for this 

report. The thickness range from approximately 15-20 ft 

updip to approximately 50 ft downdip at ACGS-4 does not 

appear to indicate an increase in sedimentation rate. The 

contours show that sediments dip to the southeast; they 

thicken downdip and possibly to the south. 

Shark River Formation, Zone NP 14-Middle Part of Zone 

NP 18 (Middle Eocene to Lower Upper Eocene), and 

Younger Zones 

Although the upper part of Zone NP 14 at ACGS-4 is 

in the Shark River Formation, this zone is not clearly 

delineated in most of the New Jersey wells, as mentioned 

above, and the Manasquan and Shark River parts are not 

discussed separately. 

Zones NP 15/16, 48.0-42.2 Ma.-Zones NP 15 and 

16 could be differentiated in only a few wells in the study 

area, and so they are combined in this report. The lack of an 

obvious pattern in the thickness variations of these zones 

probably is a result of the erosion of each zone's upper part 

before deposition of the overlying unit. In more updip areas 

particularly, these sediments are overlain by Miocene sediments. The dip is to the southeast. We have evidence for an 

unconformity in Zone NP 15 and possibly in Zone NP 14 

(Poore and Bybell, 1988). 

Zone NP 17-lower part of Zone NP 21.-After Zone 

NP 16 time, the conditions in New Jersey changed again. 

For example, parts of Zones NP 17 through 21 are present 

only in the most downdip holes (ACGS-4, Island Beach, 

Atlantic City, Anchor Dickinson), and this distribution 

suggests some tectonism in New Jersey at this time. 

However, Zones NP 17-21 are currently too poorl~· represented in wells examined in the study area to be di "CUssed 

in this report. 

CONCLUSIONS 

During the Paleocene through early middle Eocene, 

New Jersey had nearly continuous marine sedime'ltation. 

Although the sediments are thin and of nearly uniform 

thickness, detailed calcareous nannofossil data were used to 

(1) map variations in sediment thickness across the New 

Jersey Coastal Plain at any one time, as well as through 

time, (2) locate shifting of depocenters that may have been 

due to local tectonism, and (3) identify global eustatic 

sea-level changes. As additional wells are examin~d, data 

will be added to this New Jersey model and will be 

compared with data collected in Virginia and M~~land. 

REFERENCES CITED 

Berggren, W.A .. Kent, D.V., Flynn, J.J., and Van Couvering, 

J .A., 1985, Cenozoic geochronology: Geological S0ciety of 

America Bulletin, v. 96, no. 11, p. 1407-1418. 

Martini, Erlend, 1971, Standard Tertiary and Quaternary calcareous nannoplankton zonation, in Farinacci, Anna, ed., Proceedings of the II Planktonic Conference, Roma, 1970: 

Rome, Edizioni Tecnoscienza. v. 2, p. 739-785. 

Owens, J.P., Bybell, L.M., Paulachok, Gary, Ager, T.A., 

Gonzalez, V.M., and Sugarman, P.J., 1988, Stratigraphy of 

the Tertiary sediments in a 945-foot-deep corehole near Mays 

Landing in the southeastern New Jersey Coastal Pl"in: U.S. 

Geological Survey Professional Paper 1484, 39 p. 

Poore, R.Z., and Bybell, L.M., 1988, Eocene to Miocene 

biostratigraphy of New Jersey core ACGS 4-lrn'Jlications 

for regional stratigraphy: U.S. Geological Survey Bulletin 

1829, 22 p. 

5. Calcareous Nannofossils, New jersey Coastal rlain 13 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian 

Sections of the New Jersey Coastal Plain 1 

By Gregory S. Gohn2 

INTRODUCTION 

Ostracodes have rarely been considered in stratigraphic investigations of the Cretaceous section of the New 

Jersey Coastal Plain. Although ostracodes have proven to 

be of considerable stratigraphic utility in studying Cretaceous sections elsewhere in the Atlantic and Gulf of Mexico 

Coastal Plains (Alexander, 1929; Brown, 1957; Hazel and 

Paulson, 1964; Crane, 1965; Brouwers and Hazel, 1978; 

Hazel and Brouwers, 1982), only the early paper by 

Jennings (1936) and the unpublished thesis by Nine (1954) 

comprehensively treat Cretaceous ostracode faunas of the 

New Jersey Coastal Plain. Probably the most extensive 

stratigraphic use of ostracodes in New Jersey was by Brown 

and others (1972), who used a relatively few marker species 

to identify their regional chronostratigraphic units. Brouwers and Hazel ( 1978) gave partial lists of species from four 

outcrop samples from northern New Jersey as part of their 

study of Maastrichtian ostracodes in Maryland. Adams 

(1960) listed 26 species from the Red Bank Formation of 

New Jersey. 

This report is intended to illustrate that stratigraphically important Campanian and Maastrichtian ostracode 

faunas are common in New Jersey and that they hold 

considerable promise for biostratigraphic zonation of that 

section. A short discussion of the relationships between 

subsurface lithostratigraphic units used in this study and the 

well-known outcrop units of the Campanian and Maastrichtian Stages in New Jersey also is included. 

For this report, ostracode faunas were studied from 

Campanian and Maastrichtian sections in four coreholes in 

the New Jersey Coastal Plain (fig. 6.1). Two of these 

coreholes, USGS-Clayton 1 in Gloucester County and 

USGS-Freehold 1 in Monmouth County, were drilled in 

recent years by the U.S. Geological Survey (USGS) in 

cooperation with the New Jersey Geological Survey. Both 

of these holes were continuously cored. Prepared ostracode 

1

Prepared in cooperation with the New Jersey Geological Survey. 2

U.S. Geological Survey, Reston, VA 22092. 

40" 

30 MILES 

10 20 30 KILOMETERS 

Figure 6.1. County boundaries on the New Jersey Coastal 

Plain; Monmouth, Ocean, and Gloucester Counties are 

labeled. Locations of drill holes mentioned in this report 

are also shown. 

slides (5- to 10-ft sample interval) also were available from 

a 150-ft-thick cored interval at the base ofthe Ocean County 

Water Department corehole 6, drilled at Mantoloking in the 

1950's. In addition, a few short cores were available from 

the Howell Township corehole 5, southeastern Monmouth 

County, of which three were productive. In all, 73 ostracode slides were examined from the four core holes. 

Although not reported herein, about 30 slides were also 

examined from other localities including the Woodstown, 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian Sections, New Jersey Coastal P'•tin 15 
Outcrop Section: Nomenclature of 

Traditional nomenclature subsurface cycles: and sediment cycles of this report Owens and Sohl (1969) 

Tinton Sand 6 S6 

Red Bank Formation 

5 S5 Navesink Formation 

Mount Laurel Sand 

Wenonah Formation 4 S4 

Marshalltown Formation 

Englishtown Formation S3 

? 

Woodbury Clay 3 S2 

? 

Merchantville Formation S1 

Figure 6.2. Correlation chart for the Campanian and Maastrichtian cycles of the New Jersey Coastal Plain. 

Berlin, Mantua, Clayton, Island Beach, and Poricy Brook 

areas in New Jersey and the Chesapeake and Delaware 

Canal in Delaware. 

Acknowledgments 

I am indebted to Joseph E. Hazel (Louisiana State 

University) for his patience and endurance during the initial 

stages of my ostracode studies. Samples from the Mantoloking and USGS-Island Beach drill holes were originally 

prepared and examined by J.E. Hazel. The manuscript 

benefited greatly from reviews by N.F. Sohl (USGS) and 

J.E. Hazel. 

LITHOSTRATIGRAPHY 

Stratigraphic nomenclature for the outcropping Campanian and Maastrichtian sections of the New Jersey 

Coastal Plain has remained almost unchanged since publication of the stratigraphic report by Owens and Sohl (1969). 

In their report and in nearly all subsequent reports, nine 

formations are recognized between the Santonian Magothy 

Formation and the Tertiary section (fig. 6.2: see Olsson. 

1964, and Olsson and others, 1988. for an alternative 

stratigraphy for the Navesink and Red Bank Formations). 

Owens and Sohl ( 1969) also recognized the strongly cyclic 

nature of the New Jersey Cretaceous section and assigned 

the Campanian and Maastrichtian formations to their cycles 

3, 4. 5, and 6 (fig. 6. 2). Each cycle consists of a basal 

glauconite sand (Merchantville, Marshalltown, and Navesink Formations), a middle clay-silt unit (Woodbury Clay, 

Wenonah Formation, and lower part of the Red Bank 

Formation). and an upper quartz sand (Englishtown Formation, Mount Laurel Sand, and upper part of the Red Bank 

Formation). The Tinton Sand is a lithologically and areally 

restricted cycle that may be erosionally truncated. The cycle 

boundaries are sharp and disconformable, w'lereas formation contacts within the cycles are gradation2l. 

The formation nomenclature used for the outcrop 

section is also used in the subsurface of Ne•v Jersey (for 

example, see Petters, 1976, 1977; Zapecza, 1989, this 

volume). This usage implies that the four CampanianMaastrichtian cycles of Owens and Sohl (1969) are also 

present in the subsurface. However, the drill-hole sections 

studied for this report suggest a more complex stratigraphy. 

The thickest Campanian-Maastrichtian sections in 

New Jersey occur along the coast in southeastern Monmouth and eastern Ocean Counties (Brown and others, 

1972; Perry and others, 1975; Zapecza, 1989, this volume). 

These sections thin from this area northwestward toward the 

Fall Line and also southwestward along strike toward the 

Delmarva Peninsula (Owens and others, 19Ti; Olsson and 

others, 1988). Much of the southwestwar~ thinning is 

accomplished through the thinning or loss of the quartzsand units at the tops of cycles 3 and 5 of Owens and Sohl. 

Data from the deep drill holes in the Ocean CountyMonmouth County area of thick Campanian-J.faastrichtian 

sediments indicate that five sedimentary cycles (fig. 6.2, 

cycles S1 to S5) are present in that area. The Tinton Sand is 

absent (eroded?) from most of this area although it is 

present in the subsurface further updip in the Freehold 

corehole, where it represents cycle S6. In contrast, cycles 

S4 and S5 are readily correlated from the How~ll Township 

corehole (fig. 6.3) and the frequently studied Toms River 

Chemical Company well (Perry and others, 1975; Petters, 

1976; Zapecza, 1989, this volume) northward to the updip 

Freehold corehole and the outcrop belt. where t'ley correlate 

with outcrop cycles 4 and 5. 

The thick sand of cycle S3 in the Howell Township 

corehole (fig. 6.3, 525-410 ft) is also readily correlated 

with a similar section in the Freehold corehole, and this unit 

is equivalent to the outcropping Englishtown P<:lrmation of 

the northern New Jersey Coastal Plain. However, the 

thinner sands at the tops of cycles S 1 and S2 at Howell 

Township are not present updip at Freehold, where S1 and 

S2 consist only of micaceous clay-silts and glauconite 

sands. Apparently, the upper parts of cycles S 1 and S2 are 

truncated in the updip direction. As a result. a marine 

section that consists of the amalgamated fine-grained parts 

of cycles S 1 and S2 and the lower part of S3 in the Freehold 

corehole probably is equivalent to the Merchantville Formation and Woodbury Clay of the outcrop belt. 

Similar trends occur to the southwest. where the 

Clayton core hole (fig. 6.1) and nearby wells in southern 

New Jersey Jack sands correlative with the sand" at the tops 

of cycles S 1, S2, and S3 in the Toms River, Howell 

Township, and other nearby drill holes. In SO'.lthern New 

16 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Top of 

cycle 

S5 

spontaneous 

potential 

Top of 

cycle 

S4 

Top of 

cycle 

S3 

Top of 

cycle 

S2 

Top of 

cycle 

S1 

Top of 

Magothy 

Formation L__j L__j 

20 millivolts 20 ohm-m 

FEET 

resistivity 

300 

400 

600 

700 

Figure 6.3. Electric log for the Campanian and Maastrichtian sections in the Howell Township corehole 5. Boundaries for the subsurface cycles of this report are indicated. 

Jersey, the amalgamated fine-grained marine secfons of 

cycles S 1, S2, and S3 are also assigned to the Merchantville 

and Woodbury, as well as to an atypically fine-grained 

Englishtown Formation, in the outcrop (Minard, 1965) and 

the subsurface (Zapecza, 1989, this volume). 

OSTRACODE BIOSTRATIGRAPHY 

Species selected for inclusion in this report were 

restricted to forms having relatively simple (or comr1ex but 

stable) synonymies that have been discussed and (or) 

illustrated in recent years. Most of these species have-been 

re-illustrated by Hazel and Brouwers (1982). The species 

list was further restricted to include primarily species 

having well-established ranges and known stratigraphic 

utility, principally species used in the zonation of Hrzel and 

Brouwers (1982). Many of the included species were 

defined or discussed in papers by Hazel and Paulson ( 1964) 

and Brouwers and Hazel ( 1978), and concepts of most of 

these species have changed little since publication of those 

reports. My concepts of the species included in this report 

are drawn in large part from these three article~. Two 

species, "Cythereis'' n. sp. 1 (=Cythereis magnifica of 

Nine, 1954) and Planileberis? pulchra, described only by 

Jennings (1936) and Nine (1954, unpublished thesis), also 

are included, as is one distinctive undescribed species 

(Veenia? n. sp. 1, which is a large, thick-valved species that 

may be assignable to Veenia Butler and Jones, 1957). The 

stratigraphic positions of the studied sections in the four 

cores are shown in figure 6.4. 

Cycles Stratigraphic ranges of studied sectio"1s 

S6 Not studied 

S5 J .... 

S4 

"'0 

r o..a 

f--------f---___.--0 ----£i -------------i ..c:: c:: c:: 

0 

S3 > co 

u 

S2 

~ 3: \ ~ { \ ~-----~r;~------~ 

1""'11 

S1 

Figure 6.4. Stratigraphic positions of the intervals studied 

from the four coreholes used in this report. 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian Sections, New Jersey Coastal Pl<rin 17 
CYCLE OSTRACODE SPECIES ZONES 

S6 Barren Not 

Zoned 

Barren 2521 3 10 5 17 15 2614 

-------------------------------r- --------------- - - --------- S5 "Cythereis" 

I I /ixu/a 

I _________________ e~r:.r?D _________ - ----------- - - - ___ _r~ot Zoned I Tr EscharaS4 Maastrichtian Stage cytheridea 

pinochii 

Campanian I i . Stage Limburgina 

? verricula 

S3 

I 

: : 

' 

Ascetoleberis 

? plummeri 

S2 

I i I I 

I Alatacythere 

cheethami 

-?- S1 - ------- --- - - - - - -·- -·- - - -·-- - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - -

Barren Not 

zoned 

13 9 1 22 31 8 2412 2827 7 1118 30 20 4 2 6 1916 23 29 

Figure 6.5. Distribution of selected ostracode species in 

the subsurface stratigraphic cycles used in this report. 

Identifying numbers for individual species are from table 

6.1. The ranges shown on the figure are composites of the 

ranges seen in the four studied coreholes. Ranges of 

The ranges shown for the species found in the New 

Jersey cores (fig. 6.5, table 6.1) are augmented by the 

ranges given for those species by Hazel and Brouwers 

(1982) in their provincewide study of Coniacian through 

Maastrichtian ostracodes of the Atlantic and Gulf of Mexico 

Coastal Plains. Many New Jersey ranges are shorter than 

those given by Hazel and Brouwers. These truncated ranges 

may simply be an artifact of the relatively modest number of 

samples used in this report. However, they may also result, 

in part, from the cyclic nature of the studied sedimentary 

section. Ostracodes are predominantly a benthic group 

whose distribution is controlled by a variety of ecologic 

factors. It is likely, therefore, that the factors that produced 

the cyclic lithofacies changes, such as water depth, sedimentation rate, energy regime, and sediment type, also 

produced shifts in the distribution of biofacies. Certain 

species in New Jersey are shown by heavy lines; dotted 

lines are extended ranges of species given l'~' Hazel and 

Brouwers (1982). Zones are the ostracode interval zones of 

Hazel and Brouwers (1982). 

species may, therefore, be absent from a part:·~ular formation or facies for paleoenvironmental reasons. Finally, the 

shorter New Jersey ranges could result from the erosional 

truncation of cycles discussed above. In this case, parts of 

species ranges could be encompassed within the disconformities between cycles. 

Cycle Sl 

Ostracodes are relatively sparse in S 1, and all the 

species found in this unit also occur in cycle ~2 (fig. 6.5). 

Alatacythere cheethami is the stratigraphically most important species in unit S 1. Its total range in the lower 

Campanian (upper Austinian) sections of the western Gulf 

of Mexico Coastal Plain is nearly coincident with the 

Alatacythere cheethami Interval Zone of Hazel and Brouw18 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 6.1. Selected ostracode species from the studied 

New Jersey cores 

[Numbers are used in figure 6.5] 

1. Alatacythere cheetharni (Hazel and Paulson, 1964) 

2. Antibythocypris fabaformis (Berry, 1925) 

3. Antibythocypris gooberi Jennings, 1936 

4. Antibythocypris min uta (Berry, 1925) 

5. Anticythereis reticulata (Jennings, 1936) 

6. Ascetoleberis rugosissima (Alexander, 1929) 

7. Brachycythere acuminata Hazel and Paulson, 1964 

8. Brachycythere crenulata Crane, 1965 

9. Brachycythere pyriforma Hazel and Paulson, 1964 

10. Curfsina communis (lsraelsky, 1929) 

11. "Cythereis" bicornis Israelsky, 1929 

12. "Cythereis" hannai Israel sky, 1929 

13. "Cythereis" veclitella Crane, 1965 

14. "Cythereis" n. sp. 1 

15. Escharacytheridea pinochii (Jennings, 1936) 

16. Fissocarinocythere gapensis (Alexander, 1929) 

17. Fissocarinocythere huntensis (Alexander, 1929) 

18. Fissocarinocythere pittensis (Swain and Brown, 1964) 

19. Haplocytheridea insolita (Alexander and Alexander, 

1933) 

20. Haplocytheridea plwnmeri (Alexander, 1929) 

21. Limburgina verricula (Butler and Jones, 1957) 

22. Mosaleberis? reesidei (Swain, 1948) 

23. Phacorhabdotus cf. P. texan us Howe and Laurencich, 

1958 

24. Physocythere annulospinata (Hazel and Paulson, 1964) 

25. Planileberis? costatana (Israelsky, 1929) 

26. Planileberis? pulchra (Jennings, 1936) 

27. Schizoptocythere? compressa (Hazel and Paulson, 

1964) 

28. Schuleridea pan•asulcata (Swain, 1948) 

29. Veenia ponderosana (lsraelsky, 1929), late form of 

Hazel and Brouwers, 1982 

30. Veenia spoori (Israelsky, 1929) 

31. Veenia? n. sp. 1 

ers (1982). The lowest occurrence of this species in the 

western Gulf Coast sections is in the short interval between 

the first occurrence of Globotruncanita elevata and the last 

occurrence of Dicarinella concavata (Hazel and Brouwers, 

1982; Bryant, 1984; J.E. Hazel, written commun., 1988). 

Therefore, the lowest occurrence of A. clzeethami is just 

slightly higher than the Santonian-Campanian Stage boundary as defined by the first appearance of G. elevata. 

Because the lower part of S 1 is barren of ostracodes, the 

lowest occurrence of A. cheethami is not sufficient to 

indicate whether that unit is of Santonian and Campanian, 

or just Campanian, age. Petters (1976, 1977) and Olsson 

and Sikora ( 1989) previously have recognized marine Santonian beds (Merchantville lithology) above the M ::tgothy 

Formation in New Jersey. The Santonian age was based, 

however, on the presence of D. concavata, part of whose 

range is placed in the Campanian by some authors. It is 

likely that cycle S 1 of this report is largely equivalert to the 

Santonian sequence of Olsson and Sikora (1989). 

Cycle S2 

Ostracodes are relatively abundant in cycle S2. Alatacythere cheethami occurs in the lower part of S2 alo"'g with 

Brachycythere acuminata and numerous other species 

including Brachycythere pyriforma and "Cythereis'' bicornis. On the basis of the observed species, the lower part of 

S2 is assignable to the Alatacythere cheethami Interval 

Zone of Hazel and Brouwers (1982). The upper par of S2, 

which contains the highest occurrences of the genm Schuleridea, is assignable to the lower part of the oYerlying 

Ascetoleberis plummeri Interval Zone of those r11thors. 

These zonal assignments indicate an early Campanian age 

for S2 and probable equivalence to the lower Campanian 

sequence of Olsson and Sikora (1989). In additio~ to its 

occurrence in the Clayton, Freehold, and Howell Tcwnship 

coreholes, Alatacythere cheethami also occurs at 1 ,f16 ft in 

the USGS-Island Beach drill hole. 

Cycle S3 

Stratigraphically, Fissocarinocythere gapensis, Haplocytheridea insolita, and Ascetoleberis rugosissima are the 

most important species in S3, which contains locally sparse 

to common ostracodes. To date, A. rugosissima is known 

only from the Ascetoleberis plummeri Interval Zone of 

Hazel and Brouwers (1982), whereas the highest occurrences of F. gapensis and H. insolita are in the ov~rlying 

Limburgina verricula Interval Zone of those autho~s. It is 

likely that both zones are represented in cycle S3 and that 

this unit is of middle to late Campanian age. Cycle S3 

probably equates with the middle Campanian sequence of 

Olsson and Sikora (1989). 

Cycle S4 

Cycle S4 is characterized by the presence of Planileberis? costatana with Limburgina verricula, Fissocarinocythere huntensis, and Anticythereis reticulata. Although 

Hazel and Brouwers ( 1982) showed a much longer range for 

P.? costatana, I have not observed it outside of cycle S4 in 

New Jersey. The presence of specimens that may be 

Phacorhabdotus texanus suggests that the lower pa'i of S4 

(Marshalltown Formation) may be of latest Campanian age 

(Hazel and Brouwers, 1982); this age is compatible with the 

presence of Globotruncanita calcarata in the Marsralltown 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian Sections, New Jersey Coastal Pla~n 19 
as reported by Petters (1977) and Olsson and Sikora (1989). 

Slightly higher in S4, the lowest occurrences of F. huntensis and A. reticulata approximate the CampanianMaastrichtian Stage boundary. The presence of F. huntensis 

in cycle S4, and the presence of L. verricula with Escharacytheridea pinochii in the lower part of cycle S5 (see next 

section) require assignment of most of cycle S4 to the 

Escharacytheridea pinochii Interval Zone of Hazel and 

Brouwers (1982). Coarse quartz sands of the upper part of 

the Mount Laurel Sand are barren of ostracodes although 

clayey, finer grained sands of the lower part of the formation contain abundant specimens. Ostracodes are common 

in the Wenonah Formation and sparse to common in the 

Marshalltown. 

Cycle S5 

Ostracodes are abundant in the Navesink Formation 

and the lower part of the Red Bank Formation but are absent 

from the sands of the upper part of the Red Bank (and from 

the Tinton Sand). Characteristic species of cycle S5 include 

"Cythereis" n. sp. 1 (=Cythereis magnifica of Nine, 1954) 

in the Navesink and Red Bank and Planileberis? pulchra, 

which is restricted to the Navesink. Limburgina verricula 

last appears within the lower part of the Navesink. 

The presence of Limburgina verricula with Escharacytheridea pinochii in the lower part of the Navesink places 

this section within the Escharacytheridea pinochii Interval 

Zone of Hazel and Brouwers ( 1982). Cretaceous sediments 

above the last appearance of L. verricula are necessarily 

within the chronozone of the ''Cythereis" lixula Interval 

Zone of Hazel and Brouwers (1982). The lowest occurrence 

of Planileberis? pulchra and "Cythereis'' n. sp. 1 in the 

lower part of the Navesink serve as local markers for the 

cycle S4-cycle S5 (Mount Laurel-Navesink) boundary in 

New Jersey. 

SUMMARY 

In summary, it is apparent that ostracode faunas can 

be used successfully to provide local correlations within the 

New Jersey Campanian and Maastrichtian sections. These 

faunas can be related to the regional zonation of Hazel and 

Brouwers (1982), and they can be used to relate the 

chronozones of certain planktic Foraminifera to wells in 

which planktic faunas are unstudied or lacking. Several 

ostracode datums, among others, that appear to be of 

stratigraphic utility include the following: 

1. The highest occurrence of Planileberis? pulchra near the 

Navesink-Red Bank contact (within cycle S5). 

2. The highest occurrence of Limburgina verricula in the 

lower part of the Navesink Formation (cycle S5). 

3. The restriction in New Jersey of Planileberis? costatana 

to cycle S4. 

4. The lowest occurrence of Fissocarinocyt/tere huntensis 

and Anticythereis reticulata near the CampanianMaastrichtian boundary (within cycle S4). 

5. The highest occurrence of Fissocarinocyihere gapensis 

and Haplocytheridea insolita near the tor of cycle S3. 

6. The highest occurrence of Brachycythere pyriforma and 

species of Schuleridea at the top of cycle S2. 

7. The highest occurrence of Alatacythere cheethami in the 

lower part of cycle S2. 

REFERENCES CITED 

Adams, J.K., 1960, Note on lower Tertiary and Upper Cretaceous 

Ostracoda from New Jersey: Journal of Paleontology, v. 34, 

no. 2, p. 371-372. 

Alexander, C.l., 1929, Ostracoda of the Creta~eous of north 

Texas: University of Texas Bulletin 2907, 137 p. 

Brouwers, E.M .. and HazeL J.E., 1978, Ostracoia and correlation of the Severn Formation (Navarroan; Maestrichtian) of 

Maryland: Society of Economic Paleontolog:~sts and Mineralogists Paleontological Monograph 1 (Journal of Paleontology, v. 52, no. 6, suppl. ), 52 p. 

Brown, P.M .. 1957, Upper Cretaceous Ostracoda from North 

Carolina: North Carolina Department of Conservation and 

Development, Division of Mineral Resources Bulletin 70, 

28 p. 

Brown, P.M., Miller, J.A., and Swain. F.M., 1972, Structural 

and stratigraphic framework and spatial distribution of permeability of the Atlantic Coastal Plain, North Carolina to 

New York: U.S. Geological Survey Professional Paper 796, 

79 p. 

Bryant, W.A., 1984, Occurrence of the foraminitl~ral SantonianCampanian boundary within the type Austin Group of Texas 

and implications for Western Interior correlations [ abs.]: 

Geological Society of America Abstracts v·ith Programs, 

v. 16, no. 6, p. 457. 

Crane. M. J. . 1965, Upper Cretaceous ostracodes of the Gulf Coast 

area: Micropaleontology, v. 11. no. 2, p. 191-254. 

Hazel, J.E., and Brouwers, E.M., 1982, Biostratigraphic and 

chronostratigraphic distribution of ostracodes in the 

Coniacian-Maastrichtian (Austinian-Navarroan) in the Atlantic and Gulf coastal province. in Maddocks. R.F., ed., Texas 

Ostracoda, Guidebook of excursions and relrted papers for 

the Eighth International Symposium on Ostracoda: Houston, 

Tex., University of Houston, Department of Geosciences, 

p. 166-198. 

Hazel. J.E .. and Paulson. O.L.. Jr., 1964, Some new ostracode 

species from the Austinian and Tayloran (Coniacian and 

Campanian) rocks of the East Texas embaym~nt: Journal of 

Paleontology, v. 38, no. 6, p. 1047-1064. 

Jennings. P.H., 1936, A microfauna from the Monmouth and 

basal Rancocas Groups of New Jersey: Bulletin: of American 

Paleontology. v. 23, no. 78, p. 161-234. 

Minard. J.P .. 1965, Geologic map of the Woodstown quadrangle, 

Gloucester and Salem Counties, New Jersey: U.S. Geological Survey Geologic Quadrangle Map G')--404, scale 

1:24,000. 

20 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Nine, O.W., Jr., 1954, A microfauna from the Upper Cretaceous 

Navesink Formation in New Jersey: New Brunswick, N.J., 

Rutgers University, M.S. thesis, 259 p. 

Olsson, R.K., 1964, Late Cretaceous planktonic Foraminifera 

from New Jersey and Delaware: Micropaleontology, v. 10, 

no. 2, p. 157-188. 

Olsson, R.K., Gibson, T.G., Hansen, H.J., and Owens, J.P., 

1988, Geology of the northern Atlantic Coastal Plain-Long 

Island to Virginia, in Sheridan, R.E., and Grow, J.A., eds., 

The Atlantic continental margin-U.S., v. 1-2 of The geology of North America: Boulder, Colo., Geological Society of 

America, p. 87-105. 

Olsson, R.K., and Sikora, P.J., 1989, Cretaceous depositional 

sequences of the New Jersey continental margin [abs.]: 

Geological Society of America Abstracts with Programs, 

v. 21, no. 2, p. 56. 

Owens, J.P., and Sohl, N.F .. 1969, Shelf and deltaic paleoenvironments in the Cretaceous-Tertiary formations of the New 

Jersey Coastal Plain, Field Trip 2 in Subitzky, Seymour, ed., 

Geology of selected areas in New Jersey and eastern Pennsylvania and guidebook of excursions: New Brunswick, N.J., 

Rutgers University Press, p. 235-278. 

Owens, J.P., Sohl, N.F .. and Minard, J.P., 1977, A field guide to 

Cretaceous and lower Tertiary beds of the Raritan and 

Salisbury embayments, New Jersey, Delaware, ani Maryland: Washington, D.C. , American Association of Petroleum 

Geologists and Society of Economic Paleontologists and 

Mineralogists, 113 p. 

Perry, W.J., Jr., Minard, J.P., Weed, E.G.A., Robbins, E.l., and 

Rhodehamel, E.C., 1975, Stratigraphy of Atlantic coastal 

margin of United States north of Cape Hattera"-Brief 

survey: American Association of Petroleum Geologists Bulletin, v. 59, no. 9, p. 1529-1548. 

Petters, S.W., 1976, Upper Cretaceous subsurface stratigraphy of 

Atlantic Coastal Plain of New Jersey: American Association 

of Petroleum Geologists Bulletin, v. 60, no. 1, p. 87-107. 

---1977, Upper Cretaceous planktonic Foraminifera from the 

subsurface of the Atlantic Coastal Plain of New Jersey: 

Journal of Foraminiferal Research, v. 7, no. 3, p. 165-187. 

Zapecza, O.S., 1989, Hydrogeologic framework of the New 

Jersey Coastal Plain: U.S. Geological Survey Prof'~ssional 

Paper 1404-B, 49 p., 24 pis. 

6. Preliminary Ostracode Biostratigraphy of Subsurface Campanian and Maastrichtian Sections, New Jersey Coastal Pl"in 21 

7. Paleohydrology of Four Watersheds in the New Jersey Coastal Plain1 

By Wayne L. NeweUZ and john S. Wyckoff2 

INTRODUCTION 

We studied four watersheds of the southern New 

Jersey Coastal Plain (fig. 7 .1): the Maurice, Great Egg 

Harbor, Mullica, and Rancocas watersheds. The Maurice 

River enters Delaware Bay after flowing south across the 

dip slope of surficial and bedrock deposits, which include 

the Kirkwood Formation (early Miocene), Cohansey Sand 

(middle Miocene), and Bridgeton Formation (late Miocene). The Great Egg Harbor and Mullica Rivers flow 

southeastward into the Atlantic Ocean. Rancocas Creek and 

its branches flow westward into the Delaware River; they 

are entrenched into the Cohansey and Kirkwood and also 

drain across successively older formations of early Tertiary 

and Late Cretaceous age. All four watersheds contain thick 

extensive surficial deposits that cannot be produced under 

present-day hydrologic conditions. In this report, we 

describe the present hydrogeology of the southern New 

Jersey Coastal Plain and evidence for former hydrologic 

conditions that were capable of eroding the landscape and 

producing a cover of surficial deposits. 

PHYSICAL GEOGRAPHY 

The uplands of the southern New Jersey Coastal Plain 

form a plateau that dips gently seaward; the altitude ranges 

from more than 200 ft on the hills in the west in and around 

Berlin to 30 ft on the plains in the southeast around 

Woodbine. Broad drainage basins within the area descend 

to the Atlantic Ocean and Delaware Bay. The valley 

bottoms commonly are 30-100 ft below the upland surfaces, are l-2 mi wide , and have gently sloping , swampy 

surfaces. 

The upland surfaces are gently rolling. Locally subdued linear ridges are the surface expression of gravel bars 

within the underlying Bridgeton Formation. Along the 

western margin of the uplands, windblown sand and silt 

from the nearby Delaware Valley cover topographic irreg-

'Prepared in cooperation with the New Jersey Geological Survey. 2

U.S. Geological Survey, Reston , VA 22092. 

ularities. Farms and hardwood forests exist where the 

upland soils retain water. 

The uplands south of the Mullica River are underlain 

by the Bridgeton Formation , which is deeply weathered, 

arkosic sand and gravel. The uplands are generally well 

drained except where locally discontinuous clay beds cause 

a perched water table. Thick stands of white cedar and 

swamp maple grow in the poorly drained areas. The 

Bridgeton Formation ranges from lO to 65 ft in thickness. 

Underlying the Bridgeton Formation is the Cohansey 

Sand, which is typically a well-sorted, orthoquartzitic, 

marine-shelf sand. Locally, the Cohansey includes a full 

range of nearshore marine and deltaic facies. Although 

these facies include some laterally continuous clay beds, the 

fTimOUTCROP LIMIT OF 

\ THE KIRK't00D FORMATION 

-·-LINE OF EQUAL THICKNESS 

..., -APPROXIMATE UPDIP LIMIT OF 

eGAGING STAT IONS 

18 MILES + 39"00' 

74"30' 

+39"30' 

74"00' 

Figure 7.1. Locations of the four studied watersheds plotted on an isopach map of the Kirkwood-Cohansey aquifer 

system in New jersey. lsopachs in feet. Modified from 

Zapecza (1989). 

7. Paleohydrology of Four Watersheds in the New Jersey Coastal Plain 23 
Cohansey and the surficial deposits and soils overlying it 

where the Bridgeton is not present are generally excessively 

well drained. Vegetation on these deposits is characterized 

by scrub pines and scattered oak trees. 

The Kirkwood Formation underlies the Cohansey and 

crops out along the western slopes of the scarp separating 

the uplands from the Delaware River valley bottom (fig. 

7 .1). In outcrop, it is a very fine, well-sorted, micaceous, 

quartzitic, marine-shelf sand. In the subsurface, changes in 

facies occur, and the Kirkwood becomes progressively 

darker and finer grained, and it is locally fossiliferous. 

Most of the entrenched Holocene fluvial systems 

draining the uplands dissect the Bridgeton Formation and 

flow along broad valley bottoms floored with the Cohansey 

Sand. Surficial deposits in the valley bottoms are a combination of reworked Cohansey and Bridgeton sediments. 

Locally, blankets of windblown Cohansey Sand occur in the 

valley bottoms and on the downwind valley slopes. These 

deposits have the same range of permeability characteristics 

as their parent materials. 

HYDROLOGIC CHARACTER OF FOUR NEW 

JERSEY COASTAL PLAIN WATERSHEDS 

The present southern New Jersey climate is humid 

temperate and is moderated by Delaware Bay and the 

Atlantic Ocean. The average annual precipitation is 40-44 

in., and temperature extremes are 5 and 100 °F (Powley, 

1978). 

Four gauged rivers that drain the surficial and bedrock deposits of the New Jersey Coastal Plain were chosen 

to characterize the hydrologic response of their watersheds 

to present climatic conditions. These watersheds are the 

North Fork of Rancocas Creek, the Batsto River (tributary 

to the Mullica), the Great Egg Harbor River, and the 

Maurice River (fig. 7 .1). The basins of Rancocas Creek and 

the Mullica share a common divide. Rancocas Creek flows 

westward across the strike of the bedrock formations into 

the Delaware River, whereas the Mullica River flows 

southeastward down the dip slope of the Cohansey Sand 

into the Atlantic. The Great Egg Harbor River is also a 

dip-slope-draining river discharging to the Atlantic. The 

Maurice River flows obliquely down the dip of the Cohansey and into Delaware Bay. 

Continuous discharge records (U.S. Geological Survey , 1979-86) from the four watersheds for 7 yr, from 1979 

to 1986, were examined, and their base flows and maximum flood peaks were compared. The normalized base 

flows for the Maurice River and Great Egg Harbor River are 

each just less than 1 cubic foot per second per square mile 

((ft3

/s)/mi 2). The Batsto River's base flow is about 

1.3 (fe/s)/mi2 , and the Rancocas basin contributes about 

0. 75 (fe/s)/mi2 to base flow. The large base flow for the 

Batsto River reflects the contribution of the southeastdipping surficial aquifer, which produces discharge collected not only from the Batsto watershed but also poached 

from the headwaters of the Rancocas watershed. The 

surficial aquifer is the zone containing permeable sediments 

at or near the surface that contribute discharge to the surface 

hydrology (that is, lakes, streams, and ponds) or receive 

recharge from it. Base flow for each of the rivers is similar 

through the seasons, and this uniformity indicates major 

continuous ground-water discharge into the surface-water 

system. 

The largest storm during the recording period generated a discharge less than 1,310 ft3

/s for the Batsto River. 

Examination of slopes, flood plains, and channel sediments 

indicates that sediment stripping, transportation, and deposition are minimal. During the most extreme precipitation 

events, when inches fell per hour, there was no surface 

runoff. All the water infiltrated into the surface aquifer. 

Stream discharge levels rose as a combination of (1) direct 

input into the channel and adjacent swamps and (2) rising 

Sed•ment y•eld. 

in tons per square mile 

0 10-40 

- 25-100 

! i 1 75-500 

- Vanable 

Figure 7.2. Sediment yield in New jersey. Modified from 

U.S. Geological Survey (1968). 

24 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
74.52'30. 

39.35 

EXPlANATION 

Holocene swamp deposits 

I '\o... '-....I Pleistocene fan deposits 

Q Miocene upland deposits 

1 MIL[ 

74.45' 

Figure 7.3. Surficial deposits and geomorphology in the Great Egg Harbor River valley in part of 

the Newtonville quadrangle, New Jersey. Large alluvial fans grade from an upland underlain by 

the Bridgeton Formation indicated by the scarp shown by the hachured line. Directions of 

sediment transport are shown by arrows. 

ground-water discharge. Sediment yield from the watersheds studied is probably less than 10 tons/mi2

, and the 

yield for the whole region averages 10--40 tons/mi 2 (fig . 

7. 2). Such small sediment yields suggest that present fluvial 

processes are ineffective in modifying the southern New 

Jersey landscape. 

GEOMORPHOLOGY AND SURFICIAL 

GEOLOGY 

The broad bottomlands of the Great Egg Harbor, 

Maurice, and Mullica River valleys are bordered by low, 

gently sloping terraces that are parallel to the valley 

bottoms. Locally, they merge almost imperceptibly with 

very low gradient valley side slopes. Exposures indicate 

that the low terraces are underlain by a layer of alluvium 

3-6 ft thick. The side slopes are covered with an equally 

thin but extensive cover of colluvium. A thin layer of 

windblown sand has a variable thickness and commonly 

obscures the transition from slope deposits to valley bottom 

deposits. Where exposed, the terrace deposits commonly 

are thin-bedded sheets of very fine to coarse sand containing 

sparse gravel. Stone lines mark the unconformable contacts. 

Holocene channel and flood-plain alluvium, by comparison, is a complex of point-bar deposits and trough crossbeds, which have abundant plant fragments and local 

deposits of woody peat. The thin colluvium is separated 

from underlying materials by a stone line that truncates 

older bedforms and weathering profiles. The material above 

the unconformity is homogenized and massive. Typically, 

weathered, rounded quartz and chert pebbles and ironstone 

clasts are observed randomly floating in a sandy matrix. 

Sparse ventifacts are present in the stone line and the 

colluvium. Young , thin, chromic soil profiles are common 

in such deposits. 

The windblown sand consists of very well rounded, 

frosted or polished fine to medium grains of quartz and 

heavy minerals in structureless sheets. Locally, low dunes 

(6-9 ft high) enclose depressions. Ventifact pavements 

present at the bases of some dunes indicate a period of 

deflation prior to deposition of the overlying blanket of 

windblown sand. 

Extensive debris fans debouch from tributaries into 

the main valleys, especially in the middle reaches of the 

Great Egg Harbor River (fig. 7.3). The fans merge with the 

7. Paleohydrology of Four Watersheds in the New Jersey Coastal Plain 25 
EXPLANATION 

IB Holocene alluvium and swamp deposits 

~ Pleistocene braided-channel deposits 

1 MILE 

39'37'30' '--------------------------------------------' 

Figure 7.4. Surficial deposits and geomorphology in the Atsion quadrangle, New Jersey. Holocene drainage is 

incised into the braided-stream fabric that resulted from permafrost meltout cycles. 

alluvial terraces at some localities and include the same 

extensive veneer of thin-bedded deposits. 

The Mullica River arises in a broad plain that is also 

drained by the Batsto River, Sleeper Branch, and Nescochague Creek. Each of these streams is entrenched 6-9 ft 

below the plain and has a small, swampy flood plain and 

tightly meandering narrow channel that is scaled to present 

discharge from each subbasin. The intervening low, sloping 

26 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Figure 7.5. Frost wedge within the Bridgeton 

Formation near Hammonton , N.j .. Note the 

vertical alignment of the coarse clasts and the 

chaotic fabric within the wedge and the color 

transition between the adjacent sediments 

and the wedge . A thin layer of congeliturbate 

can be seen at the top of the profile; it is 

homogenized , poorly sorted, coarse to fine 

sand containing scattered pebbles and floating fine gravel. Shovel is 2.0 ft long. 

plains that parallel the dip slope of the Cohansey Sand are 

etched with an intricate pattern of braided, small-scale 

stream channels (fig. 7 .4). Each channel is about 10ft wide 

and 3ft deep. Excavations during dry spells indicate that the 

low sloping plain and channel complex is underlain by 

complex sets of festoon crossbeds (Farrell, 1983). The 

deposits themselves are entirely indigenous to the Cohansey 

Sand within the watershed; no distinctive Delaware Valley 

provenance clasts or sediments (notably , glauconite sands) 

have been found . This lack of exotic material indicates that 

there was no great debouching of the Delaware River across 

the New Jersey Coastal Plain uplands to deposit sediments 

along the outer edge of the Coastal Plain of New Jersey. 

PALEOCLIMATE-SIGNATURE OF FROZEN 

GROUND 

In the shallow subsurface across the uplands, on low 

terraces, and on marine terraces, almost all exposures reveal 

evidence of a frozen landscape (figs. 7.5 and 7.6). This 

Figure 7.6. An involution in the Bridgeton Formation near 

Hammonton, N.j. , displaying characteristic alignment of 

clasts indicative of deformation and reorientation of 

clasts. 

evidence includes intersecting patterns of fossil frost 

wedges, involutions, congeliturbated layers containing vertically aligned clasts, closed depressions underlain by involutions, and debris flows overlying formerly frozen sand 

dunes. Throughout much of the area, topmost horizons of 

old, deeply weathered soils have been destroyed by congeliturbation in the active layer (the top 3-6 ft). At some 

localities, frost-wedge structures and weathering profiles 

suggest multiple periods of frost activity separated by 

periods of weathering and erosion without freeze-thaw 

events. A general picture emerges that during maximum 

glacial climatic events, southern New Jersey was a high 

plateau 300 ft or more above the sea level at that time; the 

shoreline then was approximately 100 mi east of the present 

shoreline . These conditions prevailed as far south as the 

latitude of Washington, D.C. (E.J. Ciolkosz, Pennsylvania 

State University, oral commun., Nov. 1987). 

PALEOHYDROLOGY 

During glacial events, the combination of frozen 

surface horizons and steeper channel gradients out onto the 

exposed continental shelf would have caused rates and 

volumes of water movement through the fluvial system to 

be drastically different from present conditions. If modern 

permafrost environments are a guide, then melting of the 

top 3 ft during summer would have provided a saturated 

active layer capable of large-scale sediment movement on 

very low gradient slopes. Hydrographs of streams draining 

thawed Arctic Coastal Plain watersheds indicated that 

summer rainstorms can provide an overprint of catastrophic 

erosional and depositional events (Brown and others, 

1968). The impermeable boundary of frozen sediments 

restricts erosion and sediment transport to the thawed, thin 

surficial layer. Conversely, recharge of the surface aquifer 

7. Paleohydrology of Four Watersheds in the New Jersey Coastal Plain 27 
is minimized. Under such conditions, overland flow and the 

entrainment of sediment in the fluvial system was possible 

in sediments that presently constitute a super-permeable 

medium. Such erosion and deposition, coupled with widespread downslope creep and debris flows, resulted in the 

surficial deposits that exist today. 

The broad plain where the Mullica River arises is the 

one locality where the surficial deposits and underlying 

Cohansey Sand have not displayed any of the frozen-ground 

characteristics common to all the other upland areas. The 

braided channels and festoon crossbeds of the deposits 

suggest massive discharge events. Peak discharges for these 

streams currently run in the hundreds of cubic feet per 

second. An order of magnitude increase in discharge (to 

thousands of cubic feet per second) could have been 

generated by thawing and dewatering of the top 3 ft of the 

regolith. Large storms may have further overloaded the 

Mullica watershed. The melting event would have moved 

one last mass of debris to the mouths of tributaries. The 

braided channels are in the area of converging flow where 

discharge accumulates exponentially. Downstream, major 

erosion cut the channels deeper and a final veneer of alluvial 

debris was shed out on the exposed continental shelf. These 

deposits are now found under Holocene swamp, bay, and 

beach deposits along the coast (Ferland, 1981). Following 

warming and melting of permafrost, the surface aquifer and 

present hydrologic conditions were established. 

! 

REFERENCES CITED 

Brown, Jerry, Dingman, S., Lawrence, Lewellen, and Robert, I., 

1968, Hydrology of a drainage basin on the Alaskan Coastal 

Plain: U.S. Army Cold Regions Research and Engineering 

Laboratory Research Report 240, 17 p. 

Farrell, Stewart, 1983, Pleistocene braided stream deposits in the 

Atsion quadrangle area, northeastern Atlantic County, New 

Jersey [-Guidebook]: New Brunswick, N.J., New Jersey 

Geological Society. 

Ferland, M.A., 1981, Stratigraphy and evolution of the southern 

New Jersey backbarrier region: New Brunswick, N.J., Rutgers University, Department of Geology, M.S. thesis, 

205 p. 

Powley, V.R., 1978, Soil survey of Cumberland County, New 

Jersey: Washington, D.C., U.S. Soil Conservation Service, 

69 p., 43 pis. 

U.S. Geological Survey, 1968, Water resources investigations in 

New Jersey: Washington, D.C., U.S. Geological Survey, 

New Jersey Department of Conservation and Economic 

Development, New Jersey Department of Health, and New 

Jersey Department of Agriculture, 1 pl. 

---1979-86, Water resources data for New Jersey, water year 

1979-86. Volume 1, Atlantic Slope Basins, Hudson River to 

Cape May; Volume 2, Delaware River Basin and tributaries 

to Delaware Bay: U.S. Geological Survey Water Data Report 

NJ-79-1,2 to NJ-86-1,2. 

Zapecza, O.S., 1989, Hydrogeologic framework of the New 

Jersey Coastal Plain: U.S. Geological Survey Professional 

Paper 1404-B, 49 p., 24 pis. 

28 Proceedings, 1988 USGS Workshop on the Geology and Geo~ydrology of the Atlantic Coastal Plain 
8. Geochemical Variation in Pore-Water Samples from the Freehold, New jersey, Core 

By Amleto A. Pucci, Jr.,1 and James P. Owens 2 

INTRODUCTION 

The pore water of confining units can be shown to 

significantly affect the solute chemistry in an aquifer, 

although few field studies have directly collected hydrochemical data on pore water from confining units (Back, 

1985). This report describes the geology and solute chemistry from core samples of confining-unit and aquifer 

sediments at a test corehole (25-566) drilled near Freehold, 

Monmouth County, N.J. (fig. 8.1), and identifies several 

geochemical variations. The test corehole was cored continuously to bedrock (1 ,320 ft) and penetrated seven aquifers and eight confining units. Nearly total core recovery 

was achieved for silts and clays; recovery of sands was 

more difficult. Therefore, it was possible to sample pore 

water within confining units, where the geochemical controls are different from those in aquifers. 

Acknowledgments 

The authors thank the New Jersey Geological Survey, 

which supported the drilling, and Frank Manheim, U.S. 

Geological Survey, who provided the core-squeezing equipment and advice on the sampling methods. 

GEOLOGY AND MINERALOGY 

The corehole is in the northern part of the New Jersey 

Coastal Plain, which is underlain by a wedge-shaped body 

of unconsolidated sediments that contains scattered, thin 

indurated units. These sediments range in age from Cretaceous to Holocene. Cretaceous and Tertiary sediments 

generally strike northeast and dip southeast (Owens and 

Minard, 1975). 

The core provided samples of Tertiary and Cretaceous strata and samples of crystalline basement rock (fig. 

8.2). The Tertiary formations in the upper 95 ft of the core 

1

U.S. Geological Survey, West Trenton, NJ 08628. 2

U.S. Geological Survey, Reston, VA 22092. 

are mainly intensively weathered marine shelf deposits that 

include glauconitic sand but consist mostly of quartz sands 

or silty sands (fig. 8.2). 

Cretaceous marine sediments were found at depths 

ranging from 95 to 625 ft. These sediments, which include 

significant amounts of glauconite, calcium carbonate shell 

10 20 30 MILES 

10 20 30 KILOMETfRS 

Figure 8.1. Location of the test corehole (25-5~6) near 

Freehold, N.J. County boundaries in New Jersey are 

shown. 

8. Geochemical Variation in Pore-Water Samples from the Freehold, New Jersey, Core 29 
w 

0 

""C' 

a 

~ 

a. 

:r 

ere 

~ 

... 

I.C 

= = c 

fll 

C1 

fll 

~ ~ 

:r "' 

0 

"C 

0 

:s 

;. 

I!> 

C1 

~ 

0 

~ 

Q,l 

:s 

c. 

C1 

~ :r 

'< 

c. 

a 

0 

~ 

0 

...... 

;. 

I!> 

~ r;i' 

a 

r;· 

~ 

0 

~ e!.. 

""C' 

r;i' 

:r 

Depth 

below 

land 

surface, 

feet L'th 1 Geologic unit 1 o ogy 

100 

200 

Kirkwood Formation 

Vincentown Formation ~Hornerstown Sand ~Tinton Sand 

Red Bank Sand 

Navesink Formation 

~Mount Laurel Sand 

~Wenonah Formation 

3 0 0 . ··- M a r s h a lito w n Form at ion 

Englishtown Formation 

400 I' 'IWoodbury Clay 

soo~ 

Merchantville Formation 

600 

700 Magothy Formation 

800 

900 Raritan Formation 

1000 

1100 

Potomac Formation 

1200 

Bedrock 

EXPLANATION 

CONTACTS 

~ 

Tertiary 

rl) 

:s 

0 

Ql 

f,J 

«S 

Qj 

... 

u 

1:>:::::1 Sand b-_-_j Clay 

I I Gradational 

~~i"J Slit 1:::-::::.1 Glauconite a Dlsconformable 

Clay mineralogy 

Glauconite 

and 1/S 

5096 

Illite 

5096 

Kaolinite 

5096 

---~ 

=-=-:=-=~ _____ .... .., -:-_-_-_-_-...7 

~-----.J 

----7 :_-_-_7 

:_-_-/ 

-:::.....--:.!_ __ 

-:---~---~ 

----7' :.....-_-_-...{ 

:_-_-_-_, 

-:-_-_-_-_4 

~-----_--\ 

~-:=--=:-=-:=-1 -::-~-==-~~ 

~~~~~ -:-_-_-_-_-_-_-....:~ 

=-~-----=---~ 

--~-----------=-i 

=-=-=-=-=-~~ -:-_-_-_-_-_-_--::_, 

-------"7' 

-=---==-=-==-=~J ------~ 

~~~~~~ ·--~~--~ 

Sand mineralogy 

5096 

iJf~~~f .;:::) 

(J,. 

.:;::·.:\ 

1111;, 

"~~\ 

·';F 

~::) 

50 

1 

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,ii( 

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Specific gravity 

greater than 2.85 

50 

.:.:; ... :::} 

·:-:1 

:I 

:l 

.=l 

~I 

·I 

I 

:1 

50 

\ 

,., 

::~ 

r 

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5096 

,;,;l 

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Specific gravity 

less than 2.85 

HEG =Hornblende, epidote, and garnet 

ZTR =Zircon, tourmaline, and rutile 

SSK =Staurolite, sillimanite, and k yanite 

Figure 8.2. Geologic units, lithology, and mineralogy in the core from near Freehold, N.j. Clay and sand mineralogies are reported in weight percentages 

of the total clay or sand fraction, respectively. 1/S, illite/smectite. 
material, siderite, and pyrite and minor amounts of goethite, show little evidence of subaerial oxidation. The 

marine sediments in this section are cyclic deposits, which 

form thick and regionally continuous confining units and 

aquifers (Zapecza, 1989). 

Fluviodeltaic and marine Cretaceous sediments were 

found at depths of 625 to 1 ,277 ft. The fluviodeltaic 

sediments are complexly interfingered clastic sands and 

silty clays. Most of the clays and silts in the interval are red, 

white, or yellow~ their colors indicate that they are highly 

oxidized. As is typical of fluviodeltaic deposits, lithofacies 

changes are rapid and less predictable than those in the 

overlying marine section. 

In the clay-mineral fraction (fig. 8.2), the content of 

glauconite and mixed-layer illite-smectite (I/S) generally 

varies inversely with kaolinite content in the core. 1/S is 

most abundant in the marine and marginal-marine sediments in the upper core (depth interval 160 to 800 ft), 

whereas kaolinite is most abundant in the fluviodeltaic 

sediments in the lower part of the core (depth interval 800 

to 1,277 ft). Illite, which is less abundant than either I/S or 

kaolinite in the clay fraction, makes up 10 to 20 percent of 

the clay fraction throughout most of the core. 

Sand minerals were separated into two groups: heavy 

(specific gravity greater than 2. 85) and light (specific 

gravity less than 2.85) (fig. 8.2). Heavy minerals, which 

typically compose less than 1 percent of the sand fraction, 

have been divided into three groups: (1) hornblende, epidote, and garnet (HEG); (2) zircon, tourmaline, and rutile 

(ZTR)~ and (3) staurolite, sillimanite, and kyanite (SSK). 

The HEG group is relatively the most abundant, and it 

generally increases in proportion from the bottom to the top 

of the core, mainly because of increases in hornblende. The 

proportion of the ZTR group is relatively constant over the 

core length. The SSK group is most abundant in the base of 

the core and generally decreases in proportion from the 

bottom to the top of the core. 

In the light-sand group, quartz is the most abundant 

mineral (greater than 50 percent) throughout the core. Rock 

fragments, principally mica gneiss or nonfeldspathic rocks, 

constitute the second most abundant fraction of this group 

throughout the core; the maximum amount is found in the 

Magothy Formation. Feldspars, mostly potassium feldspar 

(microcline ), compose less than 10 percent of the light-sand 

group throughout most of the core. The low feldspar and 

high quartz contents of the light-sand group in the lower 

core indicate that these formations consist mainly of mature 

sands. 

GEOHYDROLOGY 

Regional ground-water movement generally is to the 

east and southeast. The aquifers are recharged by infiltration in outcrop areas northwest of Freehold and by vertical 

leakage through overlying confining units beneatr topographically high areas. A topographic high at the drill site 

suggests that the local flow could be downward. Simulated 

predevelopment flow (Martin, in press) had a dov'llward 

Darcy velocity of approximately 1.0 in. per year i1to the 

Wenonah-Mount Laurel aquifer (depth interval, 228 to 298 

ft). Downward vertical velocities into lower aquifers from 

confining units are progressively smaller with depth, ranging from 0.5 in. per year into the Englishtown aquifer 

system (depth interval, 331 to 416ft), to less than 0.1 in. 

per year into the lower aquifer (depth interval, 1,042 to 

1,110 ft) of the underlying Potomac-Raritan-Magotry aquifer system. Winograd and Farlekas (1974) conduced that 

cross-formational flow downward from a confining unit was 

a major source of dissolved constituents in the upper aquifer 

of the Potomac-Raritan-Magothy aquifer system rear the 

site of the present study. 

METHOD OF PORE-WATER SAMPLING AND 

ANALYSIS 

Pore-water samples were obtained by using the methods and the stainless-steel hydraulic squeezer desctibed by 

Lusczynski (1961) and Trapp and others (1984). Some 

central core material (approximately 100 mL volume) was 

removed immediately after recovery to lessen the po~sibility 

of contamination from drilling fluid. The core material was 

placed in plastic containers, chilled, and stored for several 

days before squeezing. Pore water was squeezed from the 

core samples by pressures of 4,000-6,000 pou11ds per 

square inch~ it was collected in a plastic tube, and the tube 

was sealed and chilled. The volume of pore water extracted 

from each of the samples ranged from 5 to 10 rnL, and the 

extraction time ranged from several minutes to several 

hours. Ion chromatography was used to determine concentrations of major anions, and inductively coupled e'llissionspectra analysis was used to determine concentratio'ls of the 

major cations and silica. In all, 26 samples, including three 

split-spoon samples, were obtained at various depths. 

Because sample volumes were limited, alkalinity, pH, and 

aluminum content were not determined for most samples. 

Manheim ( 1966) reported that the composition of extracted 

pore water is not appreciably affected when the m~chanical 

squeezer is used properly. The possibility that the extraction 

procedure significantly influenced the water chemistry of 

sediments seemed minimal (Bischoff and others, 1970; 

Troup and others, 1974; Patterson and others, 1978). 

RESULTS AND DISCUSSION 

For purposes of discussion, the core is divided into 

three intervals (fig. 8.3): the shallow, weathered interval 

(Interval I); the intermediate-depth, unweathere1 marine 

8. Geochemical Variation in Pore-Water Samples from the Freehold, New Jersey, Core 31 
w 

t,J 

., 

a 

~ 

II) 

a. 

s· 

CJC 

~ 

.... 

\l) 

= = 

c: 

tl'l 

C1 

tl'l 

~ ~ 

'll 

:r 

0 

"C 

0 

::s 

..... 

:r 

II) 

C1 

~ 

0 

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Ill 

::s 

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~ r;i" 

a 

r;· 

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0 

Ill 

:a. 

e!.. 

., 

r;i" 

s· 

ca+2 and so; 2 

CONCENTRATIONS, 

FeTotal and Mn Total 

CONCENTRATIONS, 

IN LOGARITHM OF 

Mg+2 and Cl 

CONCENTRATIONS, 

IN MILLIEQUIV A LENTS 

PER LITER IN MILLIEQUIVALENTS PER LITER MILLJEQUIVALENTS PER LITER 

CORE HYDROGEOLOGIC 

INTERVAL UNIT 0 

INTERVAL I Confining unit 1 

INTERVAL~:::::::: II 

~ 

MerchantvilleWoodbury 

confining unit 

l 

il Confining 

unit 4 

::.. 

INTERVAL I; Ill ~I Confining 

unit 5 

·~ 

~ 

e 

0 

o I Q. unit 6 

EXPLANATION 

aq.:aquifer 

c.u. =confining unit= [J 

GEOLOGIC UNIT 

Confining unit 1 =Kirkwood Formation Confining unit 4 = } Raritan Formation Confining unit 5 = 

Na+, K+, and s.o2 CONCENTRATIONS, 

IN MILLIEQUIVALENTS PER LITER 

Confining unit 2 = Hornerstown Sand-Tinton Sand 

Confining unit 3 =Navesink Formation Confining unit6 = Undifferentiated sediments within the Potomac Formation 

Figure 8.3. Variation of selected chemical constituents with depth in the core from near Freehold, N.j. 

::r 

100 

200 

300 1-

UJ 

400 UJ 

u. 

~ 

500 ui 

() 

Lf 

cc 600 :::) 

rJ'J 

0 

z 700 c( 

...J 

!!: 

0 

...J 

UJ 

co 

J: 900 1-

Q. 

UJ 

0 

1000 
interval (Interval II); and the deepest fluviodeltaic-silicate 

interval (Interval Ill). These intervals are based on porewater chemistry as well as lithology and depositional 

environments of the sediments. 

Interval I, the weathered interval, is the uppermost 

interval in the core, ranging from 0 to 95 ft below the land 

surface. It consists of sediments of the Kirkwood and 

Vincentown Formations and the Homerstown Sand. The 

most abundant minerals are quartz, glauconite, illite, and 

kaolinite. This interval also contains calcite, siderite, and 

small amounts of pyrite (mainly in the lowest part of the 

section). Iron staining (red) and ferric-iron concretions were 

found in this core interval. 

All three pore-water samples from this interval were 

collected at depths of 81 to 86 ft (near the contact between 

the Vincentown Formation and the Homers town Sand). For 

these samples, sodium (Na+) and potassium (K+) are the 

dominant cations, and chloride (Cl-) is a dominant anion, 

although all concentrations are low. Elevated sodium concentrations in Coastal Plain sediments probably are caused 

by ion exchange of sodium for divalent calcium and 

magnesium ions on exchangeable minerals such as glauconite or liS (Foster, 1950). Dissolved potassium can be 

formed from degradation of organic material and (or) from 

glauconite weathering, which was visible in the core 

(Wolff, 1967). Iron concentrations are higher than those in 

the underlying Interval II. 

Interval II, the unweathered marine intervaL is the 

intermediate part of the core from 95 to 625 ft below the 

land surface. This interval consists of massive beds of 

unweathered marine deposits from the Tinton Sand through 

the Merchantville Formation. Glauconite, pyrite, and 

organic silt are distributed through the interval. Siderite 

deposits were found primarily in the confining units. 

In Interval II, the pore-water chemistry of the confining units differs from that of the aquifers in several ways: 

( 1) maximum concentrations of magnesium (5 milliequivalents per liter (meq/L)), calcium (greater than 30 meq/L), 

and sulfate (greater than 30 meq/L) occur in the confining 

units and minimum concentrations occur in the aquifers; 

(2) maximum concentrations of sodium (5.25 meq/L) are 

present in aquifers; (3) total ion concentrations are greater in 

the confining units than in the aquifers; (4) solute concentrations do not appear to be related to proportions of 

minerals in the light- or heavy-sand fractions (fig. 8.2) and 

probably relate to less abundant, but more reactive, solid 

phases; (5) concentration gradients between the hydrogeologic units are large. 

The confining-unit pore water in Interval II is a 

calcium-magnesium-sulfate type. The distributions of calcium, magnesium, and sulfate in all the confining units are 

very similar and suggest that a coupled mechanism is 

occurring. Dissolution of gypsum (CaS04 ·2H20) cannot be 

one of the mechanisms because it was not found anywhere 

in the core, nor were these sediments deposited in an 

evaporite environment. 

Aquifer pore water in Interval II ranges from a 

calcium-sulfate type to a sodium-potassium-carbonate type. 

The aquifer pore-water samples from this interYal had 

higher sodium concentrations than samples from the confining units and lower calcium and magnesium corr.entrations. Exchange minerals, such as glauconite and I/S, are 

abundant in this core interval and can generate dissolved 

sodium by ion exchange. Sodium-rich minerals such as 

albite, which can supply sodium by dissolution, are not 

found in this core interval. Sulfate concentrations in aquifer 

pore water are significant (as much as 6.5 meq/L) but are 

much less than those in the confining units. 

Interval III, the fluviodeltaic-silicate interval, is the 

deepest core interval; it extends from 625 to 1 ,277 ft. The 

interval consists of sediments from the Magothy, P.aritan, 

and Potomac Formations. The sediments are fluviodeltaic 

and marginal marine in origin. They are interfingered quartz 

sands and clays (mainly kaolinite). Pyrite and lig:1ite are 

found in all three formations. Some glauconite and much 

siderite are found at the very base of the Potomac Fo'J:llation 

and in the upper part of the Raritan Formation. 

Sodium is the dominant cation in the pore-water 

samples and represents more than 70 percent of t'--e total 

cations for the three aquifer samples from the PotomacRaritan-Magothy aquifer system. Maximum sodium concentrations for the core (6.9 meq/L) are in the pore-water 

samples from the upper aquifer of the Potomac-RaritanMagothy aquifer system (fig. 8.3). No single anion was 

dominant in the samples from Interval III. 

Lower concentrations of dissolved solids l'"!low a 

depth of 800 ft indicate little interaction between seiiments 

and pore water. The three deepest pore-water s~mples, 

which are all from the confining units of the PotomacRaritan-Magothy aquifer system (depths of 1,050, 1, 190, 

and 1,266 ft), are a sodium-bicarbonate-chloride type. The 

shallower samples, at depths of 834ft (within the urper part 

of the Raritan Formation) and 950 ft (in the middle Raritan 

Formation, near the contact with the middle aquifer of the 

Potomac-Raritan-Magothy aquifer system), are le~"> chloride rich than the deepest samples. 

SUMMARY AND CONCLUSIONS 

The pore-water chemistry in the corehole is consistent 

with the following observations: 

1. The pore-water constituents and the observed diagenesis 

in the core define three distinct intervals in the core: 

the weathered marine sediments (Interval I), the unweathered marine sediments (Interval II), and the 

fluviodeltaic-silicate sediments (Interval Ill). 

2. In the unweathered marine intervaL the chemistry of 

pore water in the confining units is very different from 

8. Geochemical Variation in Pore-Water Samples from the Freehold, New Jersey, Co .. e 33 
that in the aquifers, and large vertical gradients for 

concentrations of chemical constituents may prevail 

between hydrogeologic units. 

Additional investigation of pore-water chemistry and 

the dynamics within the pores is needed to understand the 

geochemical interactions between aquifers and confining 

units in this region of the Coastal Plain. 

REFERENCES CITED 

Back, William, 1985, Geochemical significance of aquitards, in 

Hydrogeology of rocks of low permeability: International 

Association of Hydrogeologists Memoire, v. 17, p. 358-369. 

Bischoff, J.L., Greer, R.E., and Luistro, A.O., 1970, Composition of interstitial waters of marine sedimentsTemperature of squeezing effect: Science, v. 167, no. 3922, 

p. 1245-1246. 

Foster, M.D., 1950, The origin of high sodium bicarbonate waters 

in the Atlantic and Gulf Coastal Plains: Geochimica et 

Cosmochimica Acta, v. 1. p. 33-48. 

Lusczynski, N.J., 1961, Filter-press method of extracting water 

samples for chloride analysis: U.S. Geological Survey WaterSupply Paper 1544-A, 8 p. 

Manheim, F.T., 1966, A hydraulic squeezer for obtaining interstitial water from consolidated and unconsolidated sediments: U.S. Geological Survey Professional Paper 550-C, 

p. C256-C261. 

Martin, Mary, in press, Ground-water flow in the New Jersey 

Coastal Plain: U.S. Geological Survey Prcfessional Paper 

1404-H. 

Owens, J.P., and Minard, J.P., 1975, Geologic map of the 

surficial deposits in the Trenton area, New Jersey and 

Pennsylvania: U.S. Geological Survey Misrellaneous Geologic Investigations Series Map 1-884, scale 1:48,000. 

Patterson, R.J., Frape, S.K., Dykes, L.S., and McLeod, R.A., 

1978, A coring and squeezing technique for fre detailed study 

of subsurface water chemistry: Canadian Journal of Earth 

Sciences, v. 15, p. 162-169. 

Trapp. Henry, Jr., Knobel, L.L., Meisler, Harcld, and Leahy, 

P.P., 1984, Test well DO-CE 88 at Cambridge, Dorchester 

County, Maryland: U.S. Geological Survey Water-Supply 

Paper 2229, 48 p. 

Troup, B.N., Bricker, O.P., and Bray, J.T., 1974. Oxidation 

effect on the analysis of iron in the interstitial water of recent 

anoxic sediments: Nature, v. 249, no. 5454, p. 237-239. 

Winograd, I.J., and Farlekas, G.M., 1974, Problems in 14C dating 

of water from aquifers of deltaic origin-Ar example from 

the New Jersey Coastal Plain: International Atomic Energy 

Agency [Vienna] Proceedings Series, no. STIIPUB/373, v. 2 

(Isotope techniques in groundwater hydrolog:r), p. 69-93. 

Wolff, R. G. , 1967, X-ray and chemical study of weathering 

glauconite: American Mineralogist, v. 52, p. 1129-1138. 

Zapecza, O.S., 1989. Hydrogeologic framework of the New 

Jersey Coastal Plain: U.S. Geological Survey Professional 

Paper 1404-B, 49 p. 

34 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
9. Geologic Controls on Aquifer Distribution in the Coastal Plain of Northern New Jersey 

By Peter J. Sugarman 1 

INTRODUCTION 

Since 1983, the New Jersey Geological Survey and 

the U.S. Geological Survey (USGS) have been working on 

a cooperative project to produce a new geologic map of the 

State of New Jersey. Work in the Coastal Plain has 

concentrated on detailed outcrop and subsurface mapping to 

produce a three-dimensional map integrating lithostratigraphy, biostratigraphy, sedimentary facies analysis, and subsurface geophysical logs. Use of this basin-analysis methodology also has shed significant light on the distribution 

and stratigraphic framework of some of the aquifer systems 

in the New Jersey Coastal Plain. This paper gives some 

examples from Monmouth County that highlight geologic 

differences between major and minor aquifer systems determined on the basis of interpretive models derived from 

previous and current regional geologic studies. 

METHODS 

Detailed geologic mapping was conducted in the 

Farmingdale, Adelphia, Freehold, and Marlboro 7.5-

minute quadrangles (fig. 9.1). Downdip subsurface control 

was obtained in five wells (fig. 9.1): Marlboro MUA (split 

spoon), USGS Freehold (continuous core), Farmingdale 

Boro (cable tool), USGS Allaire State Park C (split spoon), 

and New Jersey Geological Survey Allaire 2 (continuous 

core). 

Stratigraphic sections were constructed by defining 

lithologic assemblages as part of a time-stratigraphic framework. This process enables horizontal facies changes to be 

recognized and allows these lithologic changes to be understood from a paleogeographic perspective. Cross sections 

constructed by using this approach elucidate the distribution 

and correlation of aquifer sands and their relations to 

geologic controls including source, type, and volume of 

sediment; environment of deposition; and facies relations. 

1

New Jersey Geological Survey. Trenton, NJ 08625. 

SEDIMENTARY MODELS 

Aquifers in the Coastal Plain can be classified as 

major and minor. Major aquifers are capable of yielding 

large quantities of water; minor ones are used locally and 

may yield small to moderate quantities of water. Tre cross 

sections highlighted two basic geologic differences tetween 

the major and minor aquifers: 

1. The major aquifers in the Potomac, Raritan, Magothy, 

and Englishtown Formations are parts of large Cretaceous delta systems and display characteristics and 

styles of deltaic sedimentation. Their sedime'lts are 

predominantly nonmarine or marginal marine in origin 

and include upper-delta-plain, lower-delta-plain, and 

delta-front facies. The aquifers are commonly of uniform thickness and extend long distances downrlip. 

FREEHOLDtE MARLBORO QUA~RANGLE Q~ADRANGLE 

ADELPHIA FARMINGDALE 

QUADRANGLE QUADRANGLE 

NEW JERSEY 

MARLBORO QU.ADRANGLE 

e MARLBORC MUA 

FREEHOLD 

eCOREHOLE 

FARMINGDALE 

QUADRANGLE 

FARMINGDALE 

BOR'J 

• 

ALLAIRE 

STATE PARKe 

1&11 

Figure 9.1. Locations of studied coreholes and the four 

quadrangles composing the study area in the northern 

New Jersey Coastal Plain. Allaire State Park I, U.S. Geological Survey Allaire State Park C; Allaire State Park II, 

New Jersey Geological Survey Allaire 2. 

9. Geologic Controls on Aquifer Distribution in the Coastal Plain of Northern New jers"'y 35 
MARLBORO MUA 

ELEV 118' 

I 

I I 

4 MILES 

I 

2 4 KILOMETERS 

FREEHOLD 

ELEV 205' 

FARMINGDALE 

BORO 

E~EV 80' 

ALLAIRE 

1&11 

ELEV 1=95' 

II= 110' 200 

100 

0 

-100 

-200 

-300 

-400 

-500 

-600 

m 

rm 

< 

~ 

0 

z 

Cil 

~ c:· 

CD 

6' 

3 

CD 

Ql 

::I 

Ill 

CD 

Ql 

iD 

< 

~ 

::;· 

iil' 

; 

Figure 9.2. Cross section based on five wells from Marlboro to Allaire, N.J. Allaire I, U.S. Geological Survey Allaire State 

Park C; Allaire II, New Jersey Geological Survey Allaire 2. 

2. The minor aquifers in the Vincentown Formation. Red 

Bank Sand, and Mount Laurel Sand are the products of 

nondeltaic or interdeltaic deposition (Owens and Gohn, 

1985). Sand bodies consist typically of medium-grained 

quartz, are thick bedded to massive, are slightly glauconitic, and contain marine invertebrate fossils. They 

were deposited on a shallow shelf near the strandline. 

Sand aquifers in these units are discontinuous and form 

localized cells, or depocenters, which pinch out downdip because of facies changes. 

A cross section from Marlboro to Allaire is shown in 

figure 9. 2. The transitions from outcrop to the shallow 

subsurface are summarized below for three minor aquifers 

and one major aquifer. The Magothy, Raritan, and Potomac 

Formations (not shown on the cross section) are discussed 

only from the USGS Freehold corehole. They do not crop 

out in the study area and were sampled only in this well. 

VINCENTOWN FORMATION 

The Vincentown Formation is a minor aquifer in the 

study area. Wells tapping it yield 10 to 15 gallons per 

minute (gpm) (Jablonski, 1968). Its maximum thickness of 

135 ft is present just northeast of Farmingdale. In outcrop 

along the Manasquan River, the Vincentowr is an olivebrown to gray, massive, medium to coarse., glauconitic 

quartz sand containing broken shells, bryozoans, and 

sponge spicules. In the Farmingdale Boro well, about 1 mi 

downdip from the outcrop belt, the Vincentown remains 

predominantly a glauconitic quartz sand, but it is finer 

grained (fine to medium sand) and has com1derable silt. 

The formation thickness remains relatively uriform at 130 

ft. At the Allaire State Park well sites, the Vincentown is 

only 75 to 80ft thick and is predominantly a noncalcareous 

micaceous clay-silt to silt. The aquifer sands terminate 12 

36 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
mi downdip from the outcrop at a facies change (fig. 9.2). 

This type of facies model is consistent with a nearshore gulf 

(Shepard and Moore, 1955) or delta-marginal plain as 

defined by Friedman and Sanders (1978, p. 293). In the 

second scenario, sand deposition is marginal to a large delta 

primarily depositing fine-grained sediment. The sands represent thin strandline deposits transported and reworked by 

waves and longshore currents. 

RED BANK SAND 

The Red Bank Sand is another local aquifer in 

Monmouth County and typically produces 3-30 gpm (Jablonski, 1968). It contains two members: the lower Sandy 

Hook Member consists of dark-gray, glauconitic, micaceous, silty, fine quartz sand, and the upper Shrewsbury 

Member consists of micaceous, fine to medium quartz sand, 

which is slightly glauconitic. The Red Bank Sand is 

conformable with the underlying Navesink Formation, 

which is a dark-gray, clayey, glauconitic sand. These two 

formations are an excellent example of a coarsening-upward 

sedimentary sequence, in which the aquifer sand (Shrewsbury Member) represents the regressive, progradational part 

of the cycle. 

In outcrop in the northwest section of the Marlboro 

quadrangle, the cyclic package is about 150 ft thick, of 

which the upper 80 ft is the Shrewsbury aquifer sand. In the 

Freehold corehole, approximately 5 mi downdip from the 

area of maximum outcrop thickness, the Shrewsbury Member is thinner (approximately 60 ft), and the underlying 

Sandy Hook Member is indistinguishable from the Navesink; both are glauconitic sands. At the Farmingdale Boro 

well, the Shrewsbury Member is absent, and the Navesink 

and Red Bank constitute an undifferentiated glauconitic 

sand sequence. 

The environment of deposition for the Red Bank is 

believed to be similar to models discussed for the Vincentown. However, the transition from inner to middle shelf is 

more evident for the Red Bank, as its quartz sand facies 

(Shrewsbury Member) pinches out downdip and is replaced 

by a glauconitic sand. 

MOUNT LAUREL SAND 

The Mount Laurel Sand is a minor aquifer in the 

study area, where it is typically combined with the 

Wenonah Formation into a single aquifer. In this paper, the 

Mount Laurel Sand is considered as a separate mappable 

unit. 

The Mount Laurel Sand is variable in thickness. In 

outcrop, as in the subsurface, it may be as much as 60 ft 

thick. It is predominantly a thin-bedded, fine to rredium, 

glauconitic quartz sand containing thin-bedded day-silt 

layers. The sand beds are generally very micaceous and 

contain lignite. Large Callianassa burrows are present. The 

upper part of the formation is commonly a massive, pebbly, 

coarse quartz sand. 

The cross section (fig. 9.2) shows that its thic1

mess is 

10ft at the Freehold corehole, 40ft at Farmingdal~~ Boro, 

and 60 ft at the Allaire State Park wells. In the Marlboro 

quadrangle, thicknesses range from 5 to 60 ft. 

The environment of deposition for the Mount Laurel 

corresponds closely to the chenier plain model discussed by 

Kraft (1978). Deposition was centered along the strandline 

distant from the main deltaic lobe and was dominl\ted by 

fine-grained sediments. However, instead of one massive 

nearshore sand body (like those in the Vincentown Formation and Red Bank Sand), a sequence of thin nearshore sand 

bodies surrounded by silt-clay layers is present. THs sand 

distribution suggests more short-term fluctuations of sea 

level or more variation in the energy regime durin~ deposition of the Mount Laurel than during deposition of the Red 

Bank and Vincentown sands. 

ENGLISHTOWN FORMATION AND MAGOTHY 

FORMATION 

In the Coastal Plain of northern New Jersey, the 

Englishtown is a major aquifer. In outcrop, it consists of a 

gray, fine to medium quartz sand interstratified with darkgray and brown, carbonaceous clayey silt. The sand is 

typically crossbedded, micaceous, lignitic, and slightly 

feldspathic. The formation thickness is consistently 90 to 

100ft in the study area. Nichols (1976) found that Englishtown lithologies in the shallow subsurface strong!~· resembled those of its outcrop belt. According to Zapecza ( 1989), 

the Englishtown thickens in southernmost Monmouth 

County (Point Pleasant) to 200 ft and can be recognized into 

Ocean County. 

The Englishtown Sand exhibits depositional facies 

common to a major delta system, including delta-f-ont and 

lower-delta-plain facies. These facies include n~arshore 

sand deposits, such as barrier-shoreface and channelmouth-bar facies, and marginal-marine deposits including 

distributary-channel and levee sediments. 

The Magothy Formation is a subsurface unit in the 

study area; it is more than 200ft thick in the USGS Freehold 

corehole. It typically contains intercalated dark, carbonaceous, clayey silts and light-colored sands; thick, laminated 

carbonaceous clays; and thick, crossbedded lignitic sands 

(Owens and Gohn, 1985). These facies are consistent with 

its interpretation as delta-front and prodelta deposits. The 

Magothy is the equivalent of the upper aquife.. in the 

Potomac-Raritan-Magothy aquifer system (Zapecza, 1989). 

9. Geologic Controls on Aquifer Distribution in the Coastal Plain of Northern New jer~~y 37 
RARITAN FORMATION 

The Raritan Formation is more than 100ft thick in the 

USGS Freehold corehole and unconformably underlies the 

Magothy. In Monmouth County, the Raritan contains the 

Farrington aquifer (Farrington Sand Member of the Raritan 

Formation) and is considered to be the equivalent of the 

middle aquifer of the Potomac-Raritan-Magothy aquifer 

system (Zapecza, 1989). 

The Raritan is an excellent example of an 

unconformity-bounded sequence, which is nonmarine at its 

base but marine from the middle to the top (Sugarman and 

Owens, 1989). It represents a fining-upward transgressive 

sedimentary package reflecting a transition from upperdelta-plain to lower-delta-plain to delta-front and, finally, to 

shelf deposits. 

POTOMAC FORMATION 

Approximately 300 ft of sediments of the Potomac 

Formation underlie the Raritan and overlie the basement 

saprolite in the USGS Freehold corehole. Lithologies 

include fine to coarse sands, interbedded fine sands and 

clays with abundant lignite in many of the clays, and poorly 

sorted mixtures of gravel, sand, silt, and clay. The Potomac 

Formation in the study area is entirely continental and is 

characterized by upper-delta-plain and lower-delta-plain 

facies. 

REFERENCES CITED 

Friedman, G.M., and Sanders, J.E., 1978, Principles of sedimentology: New York, John Wiley, 792 p. 

Jablonski, L.A., 1968, Ground-water resources of Monmouth 

County, New Jersey: New Jersey Division of Water Policy 

and Supply Special Report 23, 117 p. 

Kraft, J.C.. 1978, Coastal stratigraphic sequences, in Davis, 

R.A., Jr., ed., Coastal sedimentary environments: New 

York, Springer-Verlag, p. 361-383. 

Nichols, W.D., 1976, Geohydrology of the Englishtown Formation in the northern Coastal Plain of NeVT Jersey: U.S. 

Geological Survey Water-Resources Investigations Report 

76-123, 62 p. 

Owens, J.P., and Gohn G.S .. 1985, Depositional history of the 

Cretaceous Series in the U.S. Atlantic Coastal Plain-Stratigraphy, paleoenvironments, and tectonic contr,.)ls of sedimentation, in Poag C.W., ed., Geologic evolutio1 of the United 

States Atlantic margin: New York, Van Nostrand Reinhold, 

p. 25-86. 

Shepard, F.P., and Moore, D.G., 1955, Central Texas coast 

sedimentation-Characteristics of sedimentar:r environment, 

recent history, and diagenesis: American Association of 

Petroleum Geologists Bulletin, v. 39, no. 8, p. 1463-1593. 

Sugarman. P.J., and Owens, J.P., 1989, Styles of Cretaceous 

cycles in the New Jersey Coastal Plain, surface and subsurface [abs.]: Geological Society of America Abstracts with 

Programs, v. 21, no. 2, p. 70. 

Zapecza, O.S., 1989, Hydrogeologic frameworJ'" of the New 

Jersey Coastal Plain: U.S. Geological Surve.y Professional 

Paper 1404-B, 49 p. 

38 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
10. Silcrete near Woodstown, New Jersey 1 

By John S. Wyckoff and Wayne L. Newell2 

INTRODUCTION 

Silcrete boulders occur in a belt that extends northeast 

from Mannington to just north of Swedesboro, N.J. (fig. 

10.1). They litter gentle slopes and flat surfaces near 40-50 

ft in altitude. Summerfield (1983a) characterized silcrete 

as a highly siliceous, indurated sand formed within the 

shallow subsurface as a result of weathering of bedrock or 

surficial deposits and later cemented at low temperatures 

and pressures. 

Quartzite boulders were previously noted in the New 

Jersey Coastal Plain by Cook (1855), Knapp and Salisbury 

(1917), Friedman (1954), Minard (1965), and J.P. Owens 

(U.S. Geological Survey, oral commun., 1988). Many 

previous workers did not distinguish among the various 

occurrences of quartzite having different origins, and previous studies reflect uncertainty concerning silcrete formation and characteristics. Often the silicrete boulders found 

near Woodstown have been dismissed as remnants of the 

"Fairton Quartzite" or as derivatives of Paleozoic quartzites 

from the Valley and Ridge Province. Knapp and Salisbury 

(1917) suggested that the boulders in the Woodstown area 

originated from a Miocene sandstone that once covered the 

Coastal Plain and was locally cemented by silica into a 

quartzite. Friedman (1954) described what he thought was a 

similar silica-cemented deposit cropping out along Cohansey Creek in Fairton , N.J., south of the boulder belt. 

Minard (1965) mapped the Woodstown quadrangle and 

noted the presence of quartzite boulders; however, he did 

not speculate on their origin (J.P. Owens, oral commun., 

1988). The boulders that Minard described (plus others 

nearby) are the subject of this study. 

We examined the macromorphological and micromorphological characteristics of the silcrete near Woodstown, and, in this paper, we suggest a mode of origin. The 

methods used in this study are similar to those used in other 

silcrete studies by Langford-Smith (1978), Wopfner (1978), 

and Summerfield (1982, 1983a, b, 1984). 

'Prepared in cooperation with the New Jersey Geological Survey. 2

U.S. Geological Survey, Reston, VA 22092. 

Acknowledgments 

John Evans and Elaine McGee, both of the U.S. 

Geological Survey (USGS), are acknowledged for their 

helpful and generous assistance with the scanning electron 

microscope and photographic work. We thank Robert 

Johnson (USGS), who performed the X-ray spectrometry 

and chemical analyses. We also thank and acknowledge 

Phil Schafer, Jim Owens, Lucy McCartan, and Milan 

Pavich, all of the USGS, for their excellent comments and 

reviews of this manuscript. 

FIELD OCCURRENCE AND 

MACROMORPHOLOG I CAL FEATURES 

The silcrete boulders occur in a belt that extends 

northeast from Mannington to just north of Swedesboro 

N 

\ 

EXPLANATION 

El Kirkwood Formation 

• Silcrete 

• Village 

4 MilES 

0 4 KilOMETERS 

Figure 1 0.1. Distribution of the Kirkwood Formation and 

the associated silcrete boulders near Woodstown, in 

southwestern New jersey. 

10. Silcrete near Woodstown, New jersey 39 
APPROXIMATE 

DEPTH OF PENETRATION 

6 FEET 

f------ ------------ LENGTH OF TRAVERSE 50 FEET ----- -------- -----1 

Figure 1 0.2. A ground-penetrating radar trace along a traverse just north of Mannington. Hyperbolic reflectors indicate 

point objects, which are silcrete boulders. 

(fig. 10.1). The boulders (1.5-3 ft in diameter) litter the 

landscape and occur along scarps and terraces near 40-50 ft 

in altitude. Locally, boulders can be seen eroding out of the 

gently sloping scarps. They have been a perennial nuisance 

to farmers, who often place them in piles at the edges of 

their fields or along driveways. They were used in the oldest 

colonial house foundations and were also used as source 

material for projectile points by aborigines. Groundpenetrating radar surveys indicate that the boulders are 

closely packed and occur locally at depths of 40 in. or less 

(fig. 10.2). 

Silcrete boulders are typically composed of well 

indurated quartz sand ranging from yellowish gray (5Y 7/2; 

color designations are from the Munsell Color Company, 

1975) to grayish orange (lOYR 7/4) with pinkish-gray (5YR 

8/1) and light-gray (N7) mottles. Some silcrete boulders 

display soil-like structures and pedogenic fabrics (fig. 

10.3). Such features include prisms, clay caps, and root 

casts. Morphologically , the boulders are quite variable, 

having both faceted and mammillary surface textures. The 

morphologic variability is the result of wind abrasion , 

dissolution, and reprecipitation. The variable nature of the 

boulders reflects their complex history of formation and 

subsequent destruction. 

The present geographic distribution of the boulders 

coincides with the outcrop of the lower Miocene Kirkwood 

Formation. The morphologies and boulder distribution indicate that the silcrete formed in the shallow subsurface, 

above the Alloway Clay Member and within the Grenloch 

Sand Member of the Kirkwood Formation. Isphording and 

Lodding (1968) documented weathering within the Alloway 

Clay Member near Woodstown. They suggested that the 

kaolinization of the illite-rich Alloway Clay produced large 

kaolinite crystals. The alteration of illite to kaolinite liberated silica. The Alloway Clay may also be important 

hydrologically as an aquiclude creating a perched water 

table within the overlying Grenloch Sand. The Grenloch 

Figure 1 0.3. A silcrete boulder showing peds and clay 

skins. The globular feature in the center of the photograph is interpreted to be aped. Surrounding the ped is a 

clay skin-a light-tan fine-grained matrix, which actually 

coats the exterior surfaces of the ped and the adjacent 

peds. Dime is for scale. 

Sand was indurated by precipitation of the liberated silica. 

The detrital mineralogy of the silcrete matches the mineralogy of the Grenloch Sand; both consist of mature, 

multicyclic orthoquartzite. 

MICROMORPHOLOGICAL FEATURES 

Petrographic and scanning electron microscope techniques reveal the complex texture and fabric of the silcrete. 

Petrographically, the silcrete ranges from a cementsupported to a grain-supported fabric . The framework 

quartz grains are very angular to subrounded and display 

embayed and corroded grain boundaries (fig. 10.4). Ilmenite is the second most abundant detrital mineral. Pyrite is 

only locally abundant (fig. 10.5) and is not volumetrically 

significant. However, the presence of pyrite within the 

40 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Figure 1 0.4. Photomicrograph of the silcrete in planepolarized light. The white grains are quartz. Note the 

floating fabric and two generations of cement. The first 

phase is a darker cement, which initially coated most of 

the framework quartz grains and reduced primary porosity. The second phase, a lighter colored cement, filled the 

remaining voids. In the upper right corner of the photograph is a colloform feature. Field of photograph is 1.0 mm 

by 1.5 mm. 

silcrete is unique , and no other silcrete studies have documented the association of pyrite and silcrete. We think that 

the pyrite may reflect the initial geological conditions prior 

to silcrete formation. Under reflected light and in thin 

section, authigenic pyrite can be seen rimming the ilmenite 

grains. In some samples, the pyrite coating surrounds 

adjacent quartz grains. Quartz grains surrounded by pyrite 

are not corroded, whereas quartz grains adjacent to silica 

cement are etched (fig. 10.5). The relation between the 

nature of the contact and the encompassing authigenic 

pyrite suggests a sequence of events in which the ilmenite 

weathered and produced iron oxides. The iron later reacted 

with bacteria-produced sulfides, under reducing conditions, 

to form pyrite. After formation of the pyrite, the framework 

quartz grains were corroded and had etched and embayed 

grain contacts. We suggest that, during the later dissolution 

events, much of the pyrite was also oxidized. In only a few 

instances, the pyrite was preserved as a result of rapid 

silicification , which enclosed the pyrite, protecting it from 

further destruction (fig. 10.6). 

Thin sections of the silcrete display several generations of a variety of silica (quartz) cements. Microcrystalline quartz (crystals having an average length of 0.001-0.01 

mm) cement is the most abundant, and macrocrystalline 

quartz (crystals that are discernible without a microscope) 

cement is the next most abundant. The least abundant 

cement consists of cryptocrystalline quartz (crystals too 

small to be observed with a microscope). The microcrystalline quartz cement occurs throughout, whereas macrocrystalline quartz is associated with root traces and voids. 

Cryptocrystalline quartz usually occurs in voids between 

Figure 1 0.5. Photomicrograph of pyrite-rich zone within 

the silcrete in plane-polarized light. The quartz grain in 

the center of the photograph is not corroded where it is in 

contact with the pyrite (opaque material); however, the 

opposite boundary, where the quartz is in contact with the 

silica cement, shows some corrosion. Note the other 

corroded and noncorroded boundaries of the quartz 

grains. Field of view is 1.00 mm by 1.5 mm. 

Figure 10.6. Slabbed silcrete boulder. The white zones are 

the result of what were once roots. The arrow indicates 

the mottling in the upper left part of the boulder, which is 

the light-gray (N7) zone where pyrite is present and 

unoxidized. Dime indicates scale. 

previously cemented framework quartz grains. Cryptocrystalline quartz cement appears as argillans or colloform 

features. These structures are thought to be the result of 

periodic precipitation of quartz cement from a vertically 

fluctuating ground-water table (Frankel and Kent, 1938; 

Summerfield, 1983b). The reduction in primary porosity 

and permeability resulting from cementation would cause 

enrichment of interstitial water with silica, thus enhancing 

formation of colloform and argillan features (fig. 10.7). 

10. Silcrete near Woodstown, New Jersey 41 
Figure 10.7. Photomicrograph of an argillan in 

plane-polarized light. Note the banding and 

the differences in the coarseness of the filling 

silica cement. Field of view is 0.20 mm by 0.31 

mm. 

PRELIMINARY CHEMICAL ANALYSIS 

Preliminary chemical analysis using X-ray fluorescence spectrometry described by Johnson and King (1987) 

shows that the silcrete contains about 97 percent silica, 2.5 

percent titanium, and less than 0.5 percent iron, aluminum, 

and other elements. Previous studies of other silcretes have 

shown similar values for silica and titanium (Summerfield, 

1983b). The absence of authigenic titanium-bearing minerals indicates that titanium was not mobilized and reprecipitated. The high titanium value reflects the abundance 

of detrital ilmenite. The abundance of ilmenite may have 

increased relative to that of other minerals as a result 

of selective weathering of more labile minerals lacking 

titanium. 

Figure 10.8 shows the three analyses plotted on a 

ternary diagram modified from Summerfield (1983b). The 

analyses do not plot within either of Summerfield's two 

genetic compositional fields (weathering profile or nonweathering profile) for silcrete from Africa. Thus, the fields 

described by Summerfield ( 1983b) are inappropriate for 

silcrete in New Jersey. The parent material and (or) the 

processes producing the New Jersey silcrete must have been 

% Ti02 

Figure 10.8. Ternary plot modified from Summerfield's 

(1983b) diagram of genetic compositional fields for silcrete 

from Africa. Results of three preliminary chemical analyses 

of the Woodstown, N.j., silcrete are plotted as black dots. 

different from those producing the silcretes studied by 

Summerfield (1983b). 

DISCUSSION AND SUMMARY 

The formation of silcrete in New Jersey was controlled by the outcrop pattern of the members within the 

Kirkwood Formation and the paleogeomorphic setting, 

which influenced movement and chemical character of the 

ground water. Our model suggests that the silcrete formed 

within the shallow subsurface of a broad, vegetated valley 

bottom at the contact between the Grenloch Sand Member 

and the underlying Alloway Clay Member of the Kirkwood 

Formation (lower Miocene). The geomorphic setting was 

characterized by Owens and Minard (1979) as a northeasttrending valley with fluvial deposition during the late 

Miocene and early Pliocene. The silcrete probably formed 

during subtropical to warm-temperate climatic conditions 

characterized by ample precipitation and leaching. Wolfe 

and Poore (1982) reported that the Miocene was the 

warmest epoch in the Neogene whereas alternating warm 

and cool intervals prevailed during the Pliocene. Overall, 

Miocene and Pliocene temperatures were warmer than 

present temperatures in the northeastern U.S. Atlantic 

Coastal Plain (Wolfe and Poore, 1982). L.W. Ward (oral 

comrnun., 1988) uses benthic mollusks to infer subtropical 

to warm temperate, shallow marine conditions during the 

late Pliocene in Maryland and Virginia. Because the late 

Miocene and early Pliocene were warmer than any period in 

the Quaternary and because of the geologic and geomorphic 

settings that existed, we suggest that the silcrete was 

cemented during the Pliocene. 

42 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
The formation of the silcrete was influenced by the 

difference in lithologies of the Grenloch Sand and the 

underlying Alloway Clay. Isphording (1970) noted extensive alteration of the Alloway Clay near Woodstown. 

Alteration resulted in the enrichment of kaolinite at the 

expense of illite and montmorillonite. Isphording and Lodding (1968) suggested that upward leaching by ground 

water caused the transformation of the various clay minerals 

to kaolinite and the concomitant release of silica. We, 

however, suggest that ground water moving both laterally 

and vertically altered the upper part of the Alloway Clay. 

Then, the silica-enriched water from the underlying weathered Alloway Clay precipitated and cemented the overlying 

Grenloch Sand. Another possible source of silica is the 

dissolution of the framework quartz grains prior to silicification. However, if this were a major factor, silcrete would 

probably be far more abundant in the siliciclastic sediments 

of the New Jersey Coastal Plain than it is. 

The pyrite formed before dissolution and silicification. Reducing conditions prevailed during the formation 

of the pyrite. Subsequently, oxidizing conditions prevailed. 

During oxidizing conditions, etching and silicification 

occurred in an episodic manner. The silcrete formed in 

the shallow subsurface beneath a broad, level, vegetated 

valley bottom. Ground-water levels probably were at or 

close to the surface, as in a swamp. Then dissection of 

the stable surface produced a fluctuating ground-water 

table. Under oxidizing conditions and during continued 

movement of large quantities of water through the profile 

both laterally and vertically, the sediment was silicified. 

Rapid local silicification preserved pyrite from oxidation. 

Continued downcutting and dissection of the paleovalley 

bottom produced a scarp between the low terraces of the 

valley and the Coastal Plain uplands to the east. As the 

scarp backwasted, the scarp surface became armored with 

boulders, which slowed the rate of retreat and preserved the 

adjacent bottomland surface beneath which the silcrete is 

found. Today the silcrete does not exist as a continuous 

layer because the layer was subjected to a variety of 

physical and chemical processes, which have been active 

since the middle Pliocene. These include continued dissolution, freezing and thawing, and various slope processes. 

Freeze-thaw processes, which are known to have taken 

place during the Pleistocene, could have significantly contributed to the breakup of the layer and would explain its 

discontinuity. 

REFERENCES CITED 

Cook, G.H., 1855, Report on the geology of the southern division 

of the State: New Jersey Geological Survey Annual Report 2, 

p. 55-108. 

FrankeL J.J., and Kent. L.E., 1938, Grahamstown surface quartzites (silcretes): Geological Society of South Africa ':"'ransactions, v. 40, p. 1--42. 

Friedman, Melvin, 1954, Miocene orthoquartzite fro'll New 

Jersey: Journal of Sedimentary Petrology, v. 24, no. 4, 

p. 235-241. 

Isphording, W.C., 1970, Petrology, stratigraphy, and redefinition of the Kirkwood Formation (Miocene) of New 

Jersey: Journal of Sedimentary Petrology, v. 40, no. 3, 

p. 986-997. 

Isphording, W. C. , and Lodding, William, 1968, Origin of the 

Woodstown, New Jersey, macro-kaolinite: Clays and Clay 

Minerals, v. 16, no. 3, p. 257-264. 

Johnson, R.G., and King, B-S.L., 1987, Energy-dispersive X-ray 

fluorescence spectrometry, in Baedecker, P .A., ed., Methods 

for geochemical analysis: U.S. Geological Survey Bulletin 

1770, p. F1-F5. 

Knapp, G.N., and Salisbury, R.D., 1917, The Quaternary formations of southern New Jersey: New Jersey Geological Survey 

Final Report Series of the State Geologist 8, 218 p. 

Langford-Smith, Trevor, 1978, A select review of silcrete 

research in Australia, in Langford-Smith, Trevor, ed., Silcrete in Australia: Armidale, New South Wales, P ustralia, 

University of New England, Department of Ge")graphy, 

p. 1-13. 

Minard, J.P., 1965, Geologic map of the Woodstown quadrangle, 

Gloucester and Salem Counties, New Jersey: U.S. Geological Survey Geologic Quadrangle Map GQ--401., scale 

1:24,000. 

Munsell Color Company, 1975, Munsell soil color charts: Baltimore, Md., 18 p. 

Owens, J.P., and Minard, J.P., 1979, Upper Cenozoic sP-diments 

of the lower Delaware Valley and the northern Delmarva 

Peninsula, New Jersey, Pennsylvania, Delaware, and Maryland: U.S. Geological Survey Professional Paper 1067-D, 

47 p. 

Summerfield, M.A., 1982, Distribution, nature, and probable 

genesis of silcrete in arid and semi-arid southern Africa, in 

Yaalon, D.H., ed., Aridic soils and geomorphic processesProceedings of the International Conference of the International Society of Soil Science, Jerusalem, 1981: Catena 

Supplement, v. 1, p. 37-65. 

---1983a, Petrography and diagenesis of silcrete from the 

Kalahari Basin and Cape Coastal Zone, southern Africa: 

Journal of Sedimentary Petrology, v. 53, no. 3, p. 895-909. 

---1983b, Silcrete as a paleoclimatic indicator-Evidence 

from southern Africa: Palaeogeography, Palaeoclimatology, 

Palaeoecology. v. 41, p. 65-79. 

---1984, lsovolumetric weathering and silcrete formation, 

southern Cape Province, South Africa: Earth Surface Processes and Landforms, v. 9, p. 135-141. 

Wolfe, J.A., and Poore, R.Z., 1982, Tertiary marine and nonmarine climatic trends, in U.S. National Research Council, 

Geophysics Study Committee, Climate in Earth history: 

Washington, D.C., National Academy Press, p. 154-158. 

Wopfner, Helmut, 1978, Silcretes of northern South Australia and 

adjacent regions, in Langford-Smith, Trevor, ed., Silcrete in 

Australia: Armidale, New South Wales, Australia, University 

of New England, Department of Geography, p. 93-142. 

1 0. Silcrete near Woodstown, New Jersey 43 

11. Hydrogeologic Units in the Coastal Plain of New Jersey and their Delineation by 

Borehole Geophysical Methods 

By Otto S. Zapecza 1 

INTRODUCTION 

An essential element of any ground-water investigation is the development of a working hydrogeologic framework. As part of the U.S. Geological Survey's Regional 

Aquifer-System Analysis (RASA) study of the northern 

Atlantic Coastal Plain, a regional hydrogeologic framework 

was developed for the Coastal Plain of New Jersey. The 

definition of hydrogeologic units (aquifers and confining 

units) within this framework is based on the hydraulic 

properties of the sediments and their correlation with 

established rock-stratigraphic units. This paper describes 

the hydrogeologic units in the Coastal Plain of New Jersey 

and how they can be delineated by using borehole geophysical techniques. 

Within the Coastal Plain of New Jersey (fig. 11.1), 

most regional subsurface mapping is based on formal 

geologic (rock-stratigraphic) and chronologie (timestratigraphic) units that are defined by lithologic and biostratigraphic correlations determined by analysis of borehole samples. An understanding and description of the 

regional ground-water flow system require a determination 

of the hydrogeologic framework. Many hydrogeologic-unit 

boundaries differ from boundaries of time- and rockstratigraphic units. For example, a geologic formation may 

contain more than one aquifer, a formation may function as 

an aquifer in one area and as a confining unit in another, or 

an aquifer or confining unit may be composed of several 

geologic formations. 

The characteristics of the ground-water system of the 

Coastal Plain are related directly to the geology. Waterbearing properties are a function of the lithology, thickness, 

and lateral extent of the various geologic formations. 

Therefore, knowledge of the depositional and postdepositional history of the geologic units is essential to the 

determination of hydrogeologic-unit boundaries and to an 

understanding of the ground-water flow system. 

1

U.S. Geological Survey, West Trenton, NJ 08628. 

The New Jersey Coastal Plain is a seaward-dipping 

wedge of unconsolidated sediments of Cretaceous to Quaternary age. These sediments, for the most part, consist of 

clay, silt, sand, and gravel and are of continental, coastal, 

or marine origin. The Coastal Plain sediments thicken 

seaward from a featheredge at the Fall Line to grerter than 

6,500 ft at the southern tip of Cape May County (fig. 11.1). 

4 

...J 

w 

0 

EXPLANATION 

10 

I I I 

0 10 20 

7 4° 

20 30 MII.ES 

jl I 

30 K ILOMETE"lS 

z 

~ 

I.LI 

(.) 

0 

Figure 11.1. New Jersey Coastal Plain and lines of hydrogeologic sections shown in figures 11.2, 11.3, and 11.4. 

11. Hydrogeologic Units in the Coastal Plain of New Jersey and their Delineation by Borehole Geophysical Metlr~ds 45 
This sedimentary wedge forms a complex ground-water 

system in which the sands and gravels function as aquifers 

and the silt and clay function as confining units. 

DESCRIPTION OF GEOLOGIC AND 

HYDROGEOLOGIC UNITS 

A stratigraphic column of geologic units and associated hydrogeologic units in the Coastal Plain of New Jersey 

is shown in table 11.1. The lowermost deposits of the 

Potomac Group and a large part of the Raritan Formation 

are fluvial or fluviodeltaic in origin and contain discontinuous lenses of gravel, sand, silt, and clay. 

Cretaceous and most Tertiary sediments overlying the 

Raritan Formation were deposited in various shelf and 

beach environments during cyclic marine transgressions and 

regressions. Glauconite, common in this part of the geologic section, is indicative of middle to outer shelf deposition (Owens and Sohl. 1969, p. 259). Large concentrations 

of glauconite in association with fine-grained sediments are 

indicative of transgressive deposits, which formed during 

major incursions of the sea. Such units include the Merchantville, Marshalltown, and Navesink Formations, the 

Hornerstown Sand, and the Manasquan Formation. Sedimentary sequences that coarsen upward and overlie the 

major glauconitic units are termed regressive deposits. 

These deposits accumulated in inner shelf, nearshore, and 

beach areas during the slow retreat of the sea. Such units 

include the Englishtown Formation, Wenonah Formation, 

Mount Laurel Sand, Red Bank Sand, Vincentown Formation, Kirkwood Formation, and Cohansey Sand. Generally, 

transgressive deposits form confining units within the 

Coastal Plain and regressive deposits form aquifers. 

Continental deposition returned to the Coastal Plain 

during late Tertiary and Quaternary times. The Beacon Hill 

Gravel and Bridgeton, Pensauken, and Cape May Formations are composed primarily of fluvial sand and gravel 

(Owens and Minard, 1979, p. Dl). 

The principal aquifers of the New Jersey Coastal 

Plain are the Kirkwood-Cohansey aquifer system, the 

Atlantic City 800-foot sand of the Kirkwood Formation, the 

Wenonah-Mount Laurel aquifer, the Englishtown aquifer 

system, and the Potomac-Raritan-Magothy aquifer system. 

Minor aquifers include the Rio Grande water-bearing zone 

of the Kirkwood Formation, the Piney Point aquifer, the 

Vincentown aquifer, and the Red Bank Sand. 

The Kirkwood-Cohansey aquifer system is the major 

unconfined aquifer. It consists of hydraulically connected 

sediments of the Kirkwood Formation, Cohansey Sand, and 

overlying surficial deposits. The Cohansey Sand is confined 

by clays within the Cape May Formation in the peninsular 

part of Cape May County. The Kirkwood Formation contains thick, silty clay units and two confined aquifers along 

the New Jersey Coast. The upper confined aquifer-the Rio 

Grande water-bearing zone-is used mainly in Cape May 

County. The principal aquifer-the Atlantic City 800-foot 

sand-is the lower aquifer. 

The predominantly fine grained, lo¥'-permeability 

geologic units between the aquifers of the Kirkwood Formation and the Wenonah-Mount Laurel aquif~r are grouped 

together as one composite confining unit. However, parts of 

the Red Bank Sand, Vincentown Formation, Shark River 

Formation, and Piney Point Formation are us~d locally as a 

source of water. 

The Cretaceous sediments of New Jersey contain a 

major aquifer and two major aquifer systems. The 

Wenonah-Mount Laurel aquifer consists of the coarsegrained upper part of the Wenonah Formation and the 

Mount Laurel Sand. The fine-grained lowe~ part of the 

Wenonah Formation and the Marshalltown Formation form 

a relatively thin, leaky, confining unit between the 

Wenonah-Mount Laurel aquifer and the Englishtown aquifer system. The Englishtown aquifer system consists of 

upper and lower sand facies in southeasten1 Monmouth 

County and northeastern Ocean County. Silt and clay of the 

Merchantville Formation and Woodbury Clay form the 

most extensive confining unit in the New Jersey Coastal 

Plain. This confining unit separates the Englist·~own aquifer 

system from the Potomac-Raritan-Magothy aq·.1ifer system. 

The Potomac-Raritan-Magothy aquifer system contains five 

mappable hydrogeologic units of variable extent. The five 

units include three aquifers, designated the uroer, middle, 

and lower aquifers on the basis of stratigraphic position 

within the system, and two confining units that lie between 

the aquifers. A more detailed description of the individual 

hydrogeologic units within the New Jersey Coastal Plain, 

including structure-contour and thickness m"'ps, is presented in a report by Zapecza ( 1989). 

DELINEATION OF HYDROGEOLOGIC UNITS 

The primary goal in developing a hyr:lrogeologic 

framework is to define and delineate areas of permeable and 

relatively impermeable rock. This goal is achieved by 

mapping on the basis of lithology. In the Coa ~tal Plain of 

New Jersey, the cyclic deposition of fine-grained sediments 

(clay and silt) that alternate with coarser grained sediments 

(sand and gravel) makes the use of borehole geophysical 

logs ideal for lithologic correlation. Geophysi~al logs are 

made by lowering sensors in boreholes or wells and 

recording the corresponding measurements at the surface. 

Borehole geophysical logs-primarily natural gamma-ray 

and electric logs-provide continuous objective records of 

the lithologies penetrated by the borehole or w~ll. Correlation of geophysical logs with detailed geologic and paleontologic data from numerous coreholes has show"' that many 

geologic formations or parts of formations have the same or 

similar geophysical characteristics throughout their areal 

46 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 11.1. Geologic and hydrogeologic units in the Coastal Plain of New Jersey 

[Modified from Zapecza, 1989, table 2] 

SYSTEM SERIES GEOLOGIC LITHOLOGY HYDROGEOLOGIC HYDROLOGIC CHARACTERISTICS 

UNIT UNIT 

Alluvial Sand, silt, and black nud. deposits 

Holocene Surficial material, comnonly hydraulically 

Beach sand s:~~=-r~~l~~ht·colored, mediUR· to coarse· Undifferen· connected to underlying aquifers. 

Quaternary and gravel tiated Locally some units may act as confining units. Thicker sands are capable of yielding large quantities 

Pleistocene Cape May of water. 

Formation 

Pensauken ~~ey;~~[y~ ight-colored, heterogeneous, Formation 

Bridgeton 

Formation 

Kirkwood· A major aquifer system. 

Beacon Hill Cohansey Ground water occurs generally 

Gravel, quartz, light· colored, sandy. aquifer under water·table conditions. 

Gravel system In Cape May County, the Cohansey Sand is under artesian conditions. Cohansey Sand :~~ne:.-~l~!g~~~~l~[~·~~:UR· to coarse· 

Miocene 

Tertiary Confining unit 

Kirkwood Sand, quartz, gray and tan, very fine to Thick diatomaceous clay bed occurs 

Formation mediun-grained, m1caceous, and dark· R1o Grande. a I ong coast and for a short 

colored diatomaceous clay. water-bearing distance inland. A thin water· zone bearing sand is present in the middle of this unit. Confining unit 

Atlantic City 800·foot sand A IIIBjor aquifer along the coast. 

Poorly permeable sediments. 

Oligocene 

Piney Point 

z Sand, quartz and glauconite, fine- to Piney Point Yields moderate quantities of water. coarse-grained. § aquifer 

Eocene er 

on 

Manasquan Clay, silty and sandy, glauconitic, green, Poorly permeable sediments. Fonnation gray, and brown; contains fine·gra1ned quartz sand. 

Sandne:r.artz, gray and green, fine· to coarse· ~ Vincentown § Vincentown Yields small to moderate quantities Formation ¥~:!ili~e~~~l~~On~~ ~ndown~~~F· very aquifer of water in and near its outcrop Paleocene calcarenite. area. 

Homers town Sand, clayey, glauconitic, dark·green, fine- Sand to coarse·grained. Poorly permeable sediments. 

Tinton Sand .. Sand, quartz and glauconite, brown and gray, I fine· to coarse·grained, clayey, micaceous. 

Red Bank Sand Red Bank Yields small guantities of water Sand in and near its outcrop area. 

Navesink ~r:~. c~un- s;~ t~O&~!:~~l~: green and Poorly permeable sediments. Formation 

Mount Laurel Sand, quartz, brown and gray, fine· to Wenonah· Sand coarse·grained, slightly glauconitic. Mount Laurel A major aquifer. aquifer 

Wenonah 

Formation ~:n. v:rrt~!":ti~~tr~";i~~~c~ray and Marshall town· Wenonah A leaky confining unit. confining unit Marshall town Clay, silty, darlt·greenish·gray; contains Formation glauconitic quartz sand. 

Upper Englishtown :~:..:;-r~81 t~~a~~~y, fine· to mediUII· English town Cretaceous Formation aquifer A major aquifer. Two sand units in system Monnouth and Ocean Counties. 

Woodbury clay Clay, gray and black, and micaceous silt. 

Cretaceous Merchantville· \J:j~~r~~~~llle~~~t~:;a!!~ contain 

Clay~ glauconitic, micaceous, gray and Woodbury a thin water·bearing Merchantville confining unit sand. Formation ~~~~i~oc~nrcv:~f!~ ~~:!:::.quartz 

Magothy :~~~r~~al i ~~g~;Y dr!~":;a~0 

Formation 1 ~~~m~ Upper clay. Includes Old Bridge Sand Member. aquifer 

i~ mn:- A major aquifer system. In the 

Raritan :~ner.~:t,l~:~~~~k~1~; ~~~i~~ ~::s:hite, fining northem Coastal Plain, the upper 

L.:l f-Y!!iL- aquifer is equivalent to the Formation and variegated clay. Includes Farrington ~ilil Old Bridge aquifer and the middle 

Sand Member. Middle aquifer is equivalent to the 

-~t; aquifer Farrington aquifer. In the Delaware 

~~~ mn--- River Valley, three aquifers are recognized. In the deeper sub· fining surface, units below the upper 

Lower Potomac Alternating clay, silt, sand, and gravel. f-Y!!iL- aquifer are undifferentiated. 

Cretaceous Group Lower 

aquifer 

Pre· Cretaceous Bedrock Precambrian and lower Paleozic crystalline Bedrock No wells obtain water from rocks, metamorphic schist, and gneiss; locally these consolidated rocks, Triassic sandstone and shale and Jurassic confining unit except along Fall Line. diabase are present. 

1 Of Olsson and others, 1980. 

11. Hydrogeologic Units in the Coastal Plain of New jersey and their Delineation by Borehole Geophysical Meth~ds 47 
,f:o, 

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Ocean County 

A' FEET 

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Monmouth County Monmouth County 

REO BANK SAND 

SEA --~S:a:le:m~C~o=u:n~ty~----~----------~~~~==~~~~~~~~~~~;;~~======~::~~~~~~~---=~~~~=RE=D~B~A~N~KiS~A~ND~~~~~~~~===:~~~~~~---r LEVEL SEA LEVEL 

-200 

-400 

-600 

-800 HORIZONTAL SCALE 

0 4 8 MILES 

0 4 8 KILOMETERS 

POT Oil! A C-RARITANMAGOTHy AQUIFER 

SYSTEM 

SYSTEM 

MERCHANTVILLE-WOODBURY 

CONFINING UNIT 

-200 

-400 

-600 

-800 

-1,000j_--------------------------------------------------------------------------------------------------------------------------------~V~ER;,T~IC;A~L~E~XA~G~G~E;,RA~T~IO~N~1~04;:1~-l,OOO DATUM IS SEA LEVEL 

Figure 11.2. Hydrogeologic section A-A' from Quinton Township, Salem County, N.j., to Red Bank, Monmouth County, based on gamma-ray logs. The 

line of section is shown in figure 11.1. From Zapecza (1989, pl. 4). 
8 8' 

FEET 

100 

SEA 

LEVEL 

Berkeley Township, 

Ocean County 

Brick Township, 

Ocean County 

FEET 

100 

SEA 

LEVEL 

-200 

-400 

-600 

-800 

-1,000 

-1,200 

-1,400 T POTOMAC-

-1,600 RARITAN-MAGOTHY 

-1,800 AQUIFER SYSTEM 

-2,000 

KIRKWOOD-COHANSEY 

AQUIFER SYSTEM 

coMPOS liE 

CONFINING UNIT 

/ 

/ 

/ 

/ 

/ 

WOODBURY MERCHANiVILLECONFINING UNii 

UPPER AQUIFER 

HORIZONTAL SCALE 

0 2 4 MILES 

0 4 KILOMETERS 

-200 

-400 

-600 

-800 

-1,000 

-1,200 

-1,400 

-1,600 

·-1,800 

·-2,000 

-2,200 / ~----~~----------~----------------------------------------------------------L·-2200 

DATUM IS SEA LEVEL VERTICAL EXAGGERATION 52:1 ' 

Figure 11.3. Hydrogeologic section 8-B' from Berkeley Township, Ocean County, N.J., to Avon-by-the-Sea, Monmouth 

County, based on electric logs. The line of section is shown in figure 11.1. From Zapecza (1989, pl. 5). 

extent. Distinctive "signatures" and characteristic patterns 

on natural gamma-ray logs and electric logs can mark 

contacts between aquifers and confining units more reliably 

than can drillers· logs or geological descriptions of drill 

cuttings. 

Natural gamma-ray logs are graphical plots of the rate 

of emission of gamma rays from the formations penetrated 

by the borehole. In general, silt and clay have much higher 

natural gamma activity than do clean quartz sands and 

carbonates because clays concentrate radioactive elements 

through ion exchange and adsorption. Feldspars and micas, 

which decompose readily into clay, also contain small 

amounts of the gamma-emitting radioisotope potassium-40 

(Keys and MacCary. 1971. p. 65). Gamma radiation 

increases to the right on the gamma-ray log. Therefore, 

permeable sediments such as sand and gravel, which 

generally have low radioactivity, are indicated by log 

deflections toward the left. whereas silt and clay, which 

generally contain radioisotopes. are indicated by log deflections toward the right. 

Figures 11.2, 11.3, and 11.4 are hydrogeologic 

sections showing correlations made on the basis of b'Jrehole 

geophysical logs. Section A-A' (fig. 11.2) is a series of 

natural gamma-ray logs of hydrogeologic units tha+ extend 

approximately 90 mi along strike from Salem County to 

Monmouth County. 

Correlation of natural gamma-ray logs in section 

A-A' (fig. 11.2) shows the lateral continuity of some major 

hydrogeologic units. Of note is the uniformity of chrracteristic gamma-log signatures for the Merchantville-Woodbury 

confining unit and the Navesink Formation and Homerstown Sand. The Merchantville-Woodbury confining unit 

has a consistent thickness of about 200ft along the section. 

In contrast. the Englishtown aquifer system thins markedly 

to the southwest. From Burlington County north, th~ typical 

signature of the Navesink Formation and Homers town Sand 

11. Hydrogeologic Units in the Coastal Plain of New Jersey and their Delineation by Borehole Geophysical Metho-4s 49 
1.11 

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-200 

-400 

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-800 

-1,000 

-1,200 

-1,400 

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c 

Hightstown, 

Mercer County 

E 

East Windsor Township, 

Mercer County 

G 

EXPLANATION 

E Electric log 

G Gamma-ray log 

HORIZONTAL SCALE 

0 2 4 MILES 

0 2 4 KILOMETERS 

Jackson Township, 

Ocean County Lakewood Township, 

Jackson Township, Ocean County Brick Township, 

Ocean County Ocean County E E 

G 

C' 

Dover Township, 

Ocean County 

FEET 

200 

SEA 

LEVEL 

-200 

-400 

-600 

-800 

-1,000 

-1,200 

-1,400 

-1,600 

-1,800 ..... ~ 

DATUM IS SEA LEVEL VERTICAL EXAGGERATION 1,800 52:1 

Figure 11.4. Hydrogeologic section C-C' from Hightstown, Mercer County, N.j., to Dover Township, Ocean County, based on electric and gamma-ray 

logs. The line of section is shown in figure 11.1. From Zapecza (1989, pl. 3). 
shows a progressively increasing separation between highradiation deflections. This is caused by the northeastward 

thickening wedge of the Upper Cretaceous Red Bank and 

Tinton Sands. 

Section B-B' (fig. 11.3) shows the correlation of 

hydrogeologic units by use of three electric logs. The 

electric logs in figure 11.3 are dual-track logs that consist of 

the spontaneous-potential curve on the left-hand track and a 

conventional single-point resistance curve on the right-hand 

track. 

The spontaneous-potential curve is a record of small 

changes in voltage caused by electrochemical reactions 

between the borehole fluid and the surrounding formation 

materials. In general, sands cause deflections to the left and 

clays cause deflections to the right. 

The single-point resistance curve is a record of 

electrical resistance of formation materials penetrated by the 

borehole. Most sands and gravels are more resistant to the 

flow of electric current than are silts and clays. Sands and 

gravels are indicated by sharp deflections to the right on the 

electric log; silts and clays are indicated by deflections to 

the left. 

Section B-B' (fig. 11.3), from northeastern Ocean 

County to southeastern Monmouth County, shows the 

characteristic electric-log patterns for several major aquifers 

and confining units. Simply, the aquifers are identified by 

the divergence of the two curves, whereas the confining 

units are identified by the convergence of the curves. 

Section C-C' (fig. 11.4), from eastern Mercer 

County to northeastern Ocean County, shows the downdip 

correlation of hydrogeologic units made by using electric 

and natural gamma-ray logs. Similarities in geophysical 

characteristics of the units, as shown on the logs, permit 

simple and accurate correlation of the principal aquifers and 

confining units. 

In addition to correlation of geophysical logs with 

geologic and paleontologic data from cores, the interpretation of hydrogeologic units discussed herein is substantiated 

by ( 1) long-term water-level measurements of the principal 

aquifers and their response to ground-water withirawals 

(Walker, 1983; Eckel and Walker, 1986; Zapecza and 

others, 1987) and (2) the vertical location of s~reened 

intervals in major supply wells. 

REFERENCES CITED 

Eckel. J.A., and Walker, R.L., 1986, Water levels in major 

artesian aquifers ofthe New Jersey Coastal Plain, 19?3: U.S. 

Geological Survey Water-Resources Investigatiom Report 

8~028, 62 p .. 7 pis., scale 1:250,000. 

Keys, W.S., and MacCary, L.M., 1971, Application of borehole 

geophysics to water-resources investigations: U.S. Geological Survey Techniques of Water-Resources Invesfgations, 

book 2, chapter E1, 126 p. 

Olsson, R.K., Miller, K.G., and Ungrady, T.E., 1980, Late 

Oligocene transgression of middle Atlantic Coastal Plain: 

Geology, v. 8, no. 11, p. 549-554. 

Owens, J.P., and Minard, J.P., 1979, Upper Cenozoic sediments 

of the lower Delaware Valley and the northern L'~lmarva 

Peninsula, New Jersey, Pennsylvania, Delaware, ard Maryland: U.S. Geological Survey Professional Paper 1067-D, 

47 p. 

Owens, J.P., and Sohl. N.F., 1969, Shelf and deltaic paleoenvironments in the Cretaceous-Tertiary formations of the New 

Jersey Coastal Plain, Field Trip 2, in Subitzky, ~·eymour, 

ed., Geology of selected areas in New Jersey and eastern 

Pennsylvania and guidebook of excursions: New Brmswick, 

N.J., Rutgers University Press, p. 235-278. 

Walker, R.L., 1983, Evaluation of water levels in maJor aquifers 

of the New Jersey Coastal Plain, 1978: U.S. G~ological 

Survey Water-Resources Investigations Report 82-4077, 

62 p., 5 pls., scale 1:250,000. 

Zapecza, O.S., 1989, Hydrogeologic framework of the New 

Jersey Coastal Plain: U.S. Geological Survey Professional 

Paper 1404-B, 49 p., 24 pls. 

Zapecza, 0. S., Voronin, L. M., and Martin, Mary, 1987, Groundwater withdrawal and water-level data used to simulate 

regional flow in the major Coastal Plain aquifers of New 

Jersey: U.S. Geological Survey Water-Resources hvestigations Report 87-4038, 120 p., 10 pis. 

11. Hydrogeologic Units in the Coastal Plain of New Jersey and their Delineation by Borehole Geophysical Methc~s 51 

Central Atlantic Coastal Plain 

12. A Summary of the Geological Evolution of Chesapeake Bay, Eastern United States 1 

By Steven M. Colman/ jeffrey P. Halka/ and C.H. Hobbs 1114 

INTRODUCTION 

The seaward margin of the U.S. Atlantic Coastal 

Plain has fluctuated through time, from near the Fall Line to 

near the edge of the present Outer Continental Shelf, owing 

to changes in relative sea level. The strata that underlie the 

Coastal Plain were deposited in environments that ranged 

from fully terrestrial to fully marine. Estuarine environments are critical components of the Coastal Plain; they 

represent the interface, otherwise known as the shoreline, 

between the marine and terrestrial depositional systems. 

The Quaternary evolution of estuaries has important implications for both documenting the history of sea-level 

changes and interpreting ancient coastal-plain strata. 

In this paper, we briefly summarize the Quaternary 

history of the Chesapeake Bay, the largest of the many 

Coastal Plain estuaries on the Atlantic coast. This summary 

is based on recent syntheses of a wide variety of data 

(Colman and others, 1988, 1990; Colman and Mixon, 

1988) on the history and evolution of the bay. 

DATA AND METHODS 

The Quaternary stratigraphic record in the Chesapeake Bay and the Delmarva Peninsula area is interpreted 

primarily from three basic types of data: (1) almost 1 ,600 

mi of shallow-penetration, high-resolution, seismicreflection profiles collected in the main part of the Chesapeake Bay (fig. 12.1); (2) onshore geologic mapping; and 

(3) boreholes drilled both onshore and in the bay for 

engineering work, water wells, and stratigraphic studies. 

The seismic-reflection data were collected by using 

both boomer-type systems and 3.5- to 5-kHz systems 

1

Virginia Institute of Marine Science Contribution Number 1493. 2

U.S. Geological Survey, Woods Hole, MA 02543. 3

Maryland Geological Survey, Baltimore, MD 21218. 4

Virginia Institute of Marine Science, Gloucester Point, VA 23062. 

(Colman and Hobbs, 1987, 1988; Colman and Halka, 

1989a, b). The seismic signals were filtered betw~en 300 

Hz and 5 kHz and were recorded at a 0.25-s swe~p rate. 

Loran-e was used for navigation during the seismicreflection surveys. 

Results of recent detailed surficial geologic mapping 

and descriptions of boreholes for the southern D~lmarva 

Peninsula have been published by Mixon (1985). Additional unpublished core data were used to refine ide"'s about 

the locations and depths of the ancient channels of the 

Susquehanna River beneath the Delmarva Peninsula (Colman and Mixon, 1988). Boreholes in the bay itself are 

concentrated along the bridge and tunnel crossings (Ryan, 

1953; Hack, 1957; Harrison and others, 1965) and near the 

bay mouth (Meisburger, 1972; Colman and Hobbs, 1987). 

PALEOCHANNELS OF THE SUSQUEHANNA 

RIVER 

The Quaternary stratigraphy beneath the Chesapeake 

Bay is dominated by paleochannels cut into the urderlying 

Tertiary marine deposits by the Susquehanna River and its 

tributaries and by the sediments that fill those chan~els. We 

have identified three distinct generations of the~e paleochannel systems, which we informally call the Cape 

Charles, the Eastville, and the Exmore paleocha~nels, in 

order of increasing age (fig. 12.1). All three chanrels cross 

beneath the southern Delmarva Peninsula, and each is 

named for a geographic feature on the peninsula. 

Seismic-reflection and borehole stratigraphic data 

clearly show that the three paleochannel systems are of 

different ages and that the sediments that fill them are 

separated by significant unconformities. The courses of the 

paleochannels are rarely coincident, although tr~y commonly intersect. Their relative ages can be determined by 

map patterns and by crosscutting relationships seen on 

seismic-reflection profiles. The three paleochanne1 systems 

have been mapped throughout the bay; their courses projected from the seismic-reflection data in the bay coincide 

exactly with their known positions onshore (fig. 12.1). 

12. A Summary of the Geological Evolution of Chesapeake Bay, Eastern United States 53 
0 20 KILOMETERS 

••• •• MODERN TIDAL CHANNELS 

---- CAPE CHARLES CHANNEL SYSTEM 

- EASTVILLE CHANNEL SYSTEM 

-· -· EXMORE CHANNEL SYSTEM 

10 nmi 

Figure 12.1. Modern tidal channels in the Chesapeake 

Bay and the three ancient channel systems of the 

Susquehanna River. The channel systems are listed in 

order of increasing age; see text. The Cape Charles 

paleochannel crosses beneath Fishermans Island at the 

southern tip of the Delmarva Peninsula. The light grid 

shows tracklines along which seismic-reflection profiles 

were collected. n mi, nautical miles. 

The paleochannel-fill sequences have been divided 

into two units, whose seismic-reflection attr:l:>utes are distinctly different. The lower unit of each fill iE characterized 

by relatively strong, irregular, discontinuous reflections, 

whereas the upper unit of each fill is characterized by 

relatively weak, long, smooth, continuous, gently dipping 

reflections. These seismic characteristics, together with 

lithologic and paleontologic data from relatively deep boreholes (Harrison and others, 1965; Mixon, 1985), indicate 

that the lower channel-fill unit of each pale':lchannel is a 

fluvial deposit, typically consisting of coarse sand and fine 

gravel. The upper unit of each paleochannel ffl, in contrast, 

was deposited either in restricted river-estuar:l to open-bay 

environments or in nearshore-marine environments at the 

bay mouth. The lithologies of the upper units of the 

paleochannels are commonly complex, consisting of interbedded muddy sand, silt, and peat. The upp~r. estuarine, 

units are finer grained than the lower, fluvial, units, and the 

estuarine units become finer grained both t'nsection and 

upbay. 

Where the paleochannels underlie prese'lt land areas, 

their internal structure and fill lithology are known from 

well logs and stratigraphic boreholes. The E2stville paleochannel is especially well documented where it crosses 

beneath the Delmarva Peninsula. Mixon ( 198~) divided the 

channel fill into several units and showed that, on the 

Delmarva Peninsula, the paleochannel is o~'erlain by a 

barrier-spit complex. Both the channel geomet)' and the fill 

stratigraphy derived from the borehole data are remarkably 

similar to those derived from the seismic-refler~tion profiles 

of channels beneath the bay. 

The geometry and stratigraphy of the paleochannel 

systems indicate that the channels were fotned during 

periods of low sea level, when the mouth of the Susquehanna River was far out on the present continental shelf. 

The geometries of the paleochannel systems are similar. 

The main trunk channel of each system is about 1 to 2. 5 mi 

wide and about 100 to 160ft deep. Longitudin1l profiles of 

the paleochannels are irregular, and the overall gradients of 

the trunk channels within the bay are unexp~ctedly low. 

During the last major low sea-level stand, abo'lt 18,000 yr 

ago, sea level was perhaps 280ft below present sea level on 

the mid-Atlantic Continental Shelf (Dillon and Oldale, 

1978). Near the eastern margin of the bay, the bases of the 

channels are about 200±20 ft below present s~a level, and 

they presumably grade to the deeper lowstand shorelines on 

the Outer Continental Shelf. 

The channel systems show progressively less relation 

to the present configuration of the Chesapeal-e Bay with 

increasing age (fig. 12.1). The channels are relatively close 

together in the northern part of the Chesapeake Bay, but 

they diverge significantly toward the southea~t; all three 

cross beneath the present Delmarva Peninsula. Where they 

cross the peninsula, the major paleochannels are progressively younger toward the south. 

54 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
The primary reason for this systematic divergence 

and southward age progression is the southward progradation of the Delmarva Peninsula during major interglacial 

high sea-level stands (Colman and Mixon, 1988). The latest 

episode of this progradation process is evident in the late 

Holocene history of the bay mouth, where the axial channel 

of the bay has been displaced as much as 7.5 mi in the last 

few thousand years (Colman and others, 1988). This 

progradation of the peninsula and the southward migration 

of the mouth of the bay were episodic, occurring only 

during the highest of interglacial high sea-level stands 

(Colman and Mixon, 1988). As sea level fell following a 

major interglaciation, the displaced estuarine channel 

became the new fluvial channel. the previous generation of 

the fluvial channel and its fill were preserved, and the 

course of the Susquehanna River was altered. 

AGES OF THE PALEOCHANNELS AND 

CHANNEL-FILL SEQUENCES 

Evidence for the ages of the paleochannels comes 

from a variety of chronometric and stratigraphic data. The 

ages of the Cape Charles paleochannel and its fill are 

relatively well known because they represent the most 

recent sea-level cycle and because radiocarbon ages are 

available for the channel fill. The paleochannel is correlated 

with marine oxygen-isotope stage 2 (Colman and Mixon, 

1988), the peak of which occurred about 18,000 yr ago 

(Imbrie and others, 1984). The Cape Charles paleochannel 

has been only partly filled by the Holocene transgression, 

and the channel itself is clearly related to the low sea-level 

stand associated with the last major glaciation, the late 

Wisconsinan. Radiocarbon ages from the channel fill range 

from about 8,000 to 15,000 yr before present (Harrison and 

others, 1965; Meisburger, 1972). 

Each of the older paleochannels is assumed to correlate with an interval of low sea level of about the same 

magnitude as that of the late Wisconsinan glaciation and 

oxygen-isotope stage 2. Each of the older paleochannels is 

filled with estuarine sediments and overlain by barrier-spit 

deposits on the Delmarva Peninsula, and no major unconformities exist within these sequences (Colman and Mixon, 

1988). Therefore, each of the paleochannels is inferred to 

correlate with a major glaciation immediately followed by a 

major interglaciation. These major glacial-interglacial transitions have been called terminations (Broecker and van 

Donk, 1970); the Cape Charles paleochannel and its Holocene fill represent termination I (Colman and Mixon, 1988). 

The barrier-spit deposits that overlie the paleochannels on 

the Delmarva Peninsula represent the last events of 

previous terminations and thus constrain the ages of the 

paleochannels. 

Uranium-series, uranium-trend, and amino add age 

estimates exist for the two ancient barrier systems on the 

Delmarva Peninsula; the ages of these and nearby d~posits 

have been the subject of considerable discussion and argument, which have been reviewed in relation to the hiftory of 

the bay by Colman and Mixon (1988). Uranium-series and 

amino acid age estimates are incompatible for some deposits; ages estimated by both methods conflict with stratigraphic interpretations of other deposits; and some of the 

uranium-series age estimates do not closely correspond to 

known times of high sea level. Nevertheless, the banier spit 

that overlies the Eastville paleochannel appears to correlate 

with the last major (Sangamon) interglaciation ard with 

oxygen-isotope stage 5. Accordingly, the Eastville paleochannel presumably dates from oxygen-isotope st:age 6, 

about 150,000 yr ago (Colman and Mixon, 1988). ~he age 

of the barrier spit that overlies the Exmore paleochannel is 

more problematic, but Colman and Mixon (198r) have 

suggested that these deposits may correlate with oxygenisotope stage 7 (about 200,000 yr ago) or with s+age 11 

(about 400,000 yr ago). The Exmore paleochannel likely 

correlates with the next older stage (stage 8, about 270,000 

yr ago, or stage 12, about 430,000 yr ago). 

EVOLUTION OF THE CHESAPEAKE BAY 

The Quaternary evolution of Chesapeake Bay is 

intimately related to major eustatic sea-level changes. The 

record of these changes in the Chesapeake Bay area consists 

of three generations of paleochannels of the Susq'Iehanna 

River system, representing low sea levels, and three generations of barrier-spit and channel-fill deposits, representing high sea levels. This unusual record contains features 

related to both maximum and minimum sea level 'l, along 

with nearly complete sedimentary records of three major 

transgressions. The record has a climax aspect, preserving 

mainly evidence of the highest and lowest sea levels. On the 

basis of available age information, the sea-level changes 

recorded in the Chesapeake Bay area appear to correlate 

well with the marine oxygen-isotope record and to represent 

the last few hundred thousand years of sea-level history. 

The present Chesapeake Bay is only the latest in a 

series of at least three generations of the bay, eacl' configured differently. During each period of the bay's existence, 

progradation of the Delmarva Peninsula caused southward 

migration of the bay mouth. As sea level fell following each 

estuarine episode, the bay drained and the fluvial chmnel of 

the Susquehanna River incised in a new location, s0uth and 

west of its former position. As a result, the stratigraphy and 

morphology of the bay generally became younger toward 

the south and west. The evolution of Chesape::-ke Bay 

shows that coastal-plain estuarine environments can be 

geologically dynamic, on both short and long tim~ scales. 

12. A Summary of the Geological Evolution of Chesapeake Bay, Eastern United States 55 
REFERENCES CITED 

Broecker, W. S. , and van Donk, Jan, 1970, Insolation changes, ice 

volumes, and the 180 record in deep-sea cores: Reviews of 

Geophysics and Space Physics, v. 8, p. 169-198. 

Colman, S.M., Berquist, C.R., Jr., and Hobbs, C.H., III, 1988, 

Structure, age, and origin of the bay-mouth shoal deposits, 

Chesapeake Bay, Virginia: Marine Geology, v. 83, 

p. 95-113. 

Colman, S.M., and Halka, J.P. 1989a, Maps showing Quaternary 

geology of the southern Maryland part of the Chesapeake 

Bay: U.S. Geological Survey Miscellaneous Field Studies 

Map MF-1948-C, 3 sheets, scale 1:125,000. 

---1989b, Maps showing Quaternary geology of the northern 

Maryland part of the Chesapeake Bay: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1948-D, 

3 sheets, scale 1:125,000. 

Colman, S.M., Halka, J.P., Hobbs, C.H., III. Mixon, R.B., and 

Foster, D. S. , 1990, Ancient channels of the Susquehanna 

River beneath Chesapeake Bay and the Delmarva Peninsula: 

Geological Society of America Bulletin, v. 102, p. 

1268-1279. 

Colman, S.M., and Hobbs, C.H., III, 1987, Quaternary geology 

of the southern Virginia part of the Chesapeake Bay: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1948-A, 2 sheets, scale 1:125,000. 

---1988, Maps showing Quaternary geology of the northern 

Virginia part of the Chesapeake Bay: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1948-B, 3 sheets, 

scale 1:125,000. 

Colman, S.M., and Mixon, R.B .. 1988, The record of major 

Quaternary sea-level fluctuations in a larg1~ Coastal Plain 

estuary, Chesapeake Bay, Eastern United States: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 68, p. 99-116. 

Dillon, W.P., and Oldale, R.N., 1978, Late Quat~rnary sea-level 

curve-Reinterpretation based on glaciotectonic influence: 

Geology, v. 6, p. 56--60. 

Hack, J.T., 1957, Submerged river system of C'1esapeake Bay: 

Geological Society of America Bulletin, v. 68, no. 7, 

p. 817-830. 

Harrison, W .. Malloy, R.J .. Rusnak, G.A., and Terasmae, J., 

1965, Possible late Pleistocene uplift, Chesapeake Bay 

entrance: Journal of Geology, v. 73, no. 2, p. 201-229. 

Imbrie, John, Hays, J.D., Martinson, D.G., Mcintyre, A., Mix, 

A.C., Morley, J.J., Pisias, N.G., Prell, W.L., and Shackleton, N.J., 1984, The orbital theory of Pleisto-:-ene climateSupport from a revised chronology of the marine 180 record, 

in Berger, A.L., and others, eds., Milankovitch and climate, 

Part 1: Boston, Mass., D. Reidel, p. 269-30~. 

Meisburger, E.P., 1972, Geomorphology and seiiments of the 

Chesapeake Bay entrance: U.S. Army, Corps of Engineers, 

Coastal Engineering Research Center Techn;cal Memorandum No. 38, 61 p. 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of 

uppermost Cenozoic deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological Survey 

Professional Paper 1067-G, 53 p. 

Ryan, J.D., 1953, The sediments of Chesapeake Bay: Maryland 

Department of Geology, Mines, and Water Re.sources Bulletin 12, 120 p. 

56 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
13. Dynamics of Upper Paleocene Deposits in the Salisbury Embayment, Virginia and 

Maryland 

By lucy E. Edwards 1 

The Paleogene sedimentary record in the Salisbury 

embayment reflects the combined influences of depositional, erosional, tectonic, eustatic, and paleogeographic 

factors. Eight cores from the Coastal Plain of Virginia 

and Maryland provide insight into the history of the 

embayment. 

Graphic correlation provides a means for separating 

various components of the depositional history of an area. 

The technique, introduced by Shaw (1964), uses two-axis 

graphs as a means of expressing time-equivalency between 

stratigraphic sections. The aspect of the technique to be 

emphasized here is that the line of correlation (LOC) 

between any section and the composite standard for the area 

can be used to compare relative rates of sediment accumulation, relative differences in times of onset of deposition, 

and relative differences in the extent of nondeposition and 

erosion. Relative age can be expressed in terms of composite standard unit values. Relative rates can be expressed in 

terms of the slopes of the individual LOC's. Details and 

applications of the method were provided by Shaw ( 1964), 

Miller (1977), Sweet (1979), Edwards (1984, 1989), and 

Dowsett (1988). 

The lower part of the Paleogene section in the 

Salisbury embayment consists of the lower Paleocene 

Brightseat Formation (not present everywhere), the upper 

Paleocene Aquia Formation, the upper Paleocene or lower 

Eocene Marlboro Clay (not present everywhere), arid the 

lower Eocene Nanjemoy Formation. The first and last 

appearance datums of dinocyst taxa in eight coreholes were 

used in the graphic correlation procedure. The dinocyst data 

are unpublished data of the author, some of which were 

summarized in Edwards and others (1984), and data from 

Witmer (1987). This report presents only the results from 

the Aquia Formation and Marlboro Clay. 

Figure 13. lA shows a simplified thickness map for 

the Aquia Formation and Marlboro Clay in the study area. 

The thinnest accumulation (at the Carters Corner corehole) 

is assigned a value of one; contour lines represent multipli1 U.S. Geological Survey. Reston. VA 22092. 

ers of this value. These sediments are thinnest in a narrow 

north-northeast-trending zone in the western part of the 

study area (at the Carters Corner and Lake Jefferson 

coreholes) and thickest in the eastern part (particdarly in 

the northeastern part where these units are 2.5 times as thick 

at the Solomons corehole as they are at the Carterf Corner 

corehole). Steep gradients occur near the area of thinning. 

The graphic correlation technique is used to explore the 

components of this pattern. 

For the eight sections studied, the Office Har section 

was chosen as the reference section because it was well 

sampled and centrally located. The Lake Jeffersor section 

was correlated to it to produce an initial composite section; 

then the Carters Corner section was correlated to this 

composite to produce a revised composite secthn. The 

other cores were added in the same fashion in tr~ order: 

Ashton, Oak Grove, Fort McLean, Haynesville, and 

Solomons. As might be expected for coastal-plain deposits, 

bends occurred in several of the LOC's (bends indicate 

changes in relative sediment accumulation rates). 

Because of the rather consistent locations of bends in 

the LOC's, the upper Paleocene sediments are disr.ussed in 

terms of two units, here labeled UP-I and UP-II. Although 

UP-I is roughly (but not exactly) equivalent to th~ Piscataway Member of the Aquia Formation and UP-II is roughly 

(but not exactly) equivalent to the Paspotansa Member of 

the Aquia Formation and the Marlboro Clay, it is important 

to note that these are not lithostratigraphic units, b'lt rather, 

depositional packages recognized by the graphic correlation 

procedure. 

One variable that contributes to the pattern of thicknesses is the difference in the timing of the onset of 

deposition. The relative position of the base of t'le Aquia 

Formation in each core can be noted with respr.ct to the 

oldest composite unit value found in any core. Onr. can then 

compute the amount of time (in composite units) for which 

deposits are missing at the base of UP-I in each core. The 

percentage of UP-I time for which deposits are missing 

from each core is contoured in figure 13 .1B (0 percent 

missing from the Oak Grove core). This figure shows a 

preexisting structural low centered around Oak Grove, 

13. Dynamics of Upper Paleocene Deposits in the Salisbury Embayment, Virginia and Maryland 57 
Figure 13.1. Data on the Aquia Formation and Marlboro 

Clay from eight coreholes in the Salisbury embayment, 

Maryland and Virginia. A, Simplified thickness for the 

Aquia Formation and Marlboro Clay in the study area. The 

thinnest value (at the Carters Corner corehole) is 1; 

contours represent multipliers of this thickness. B, The 

timing of the onset of deposition of UP-I. Values plotted 

are the percentage of UP-I time for which deposits are 

which was gradually filled during UP-I time. The exact 

alignment of this low is poorly defined. 

Another interesting facet of the basin history is the 

relative rate of deposition during the time deposition 

occurred and for which sediment remains. This rate is found 

from the slope of the individual LOC's. Periods of time 

without deposition and periods of time represented by 

sediments that have since been eroded are not incorporated 

into this rate. Figure 13.1C shows contours of this rate for 

UP-I time. This figure has been scaled to give the lowest 

observed rate (at the Carters Comer section) a value of 1, 

and contours represent multipliers of this value. The rate at 

the Solomons section is greater than nine times the rate at 

the Carters Comer section. The pattern appears to represent 

20 40 MILES 

II II 

30 60 KILOMETERS 

missing because of nondeposition in each co .. e. The Oak 

Grove section has 0 percent nondeposition. C, Relative 

rates of deposition during UP-I time. Lowe5t observed 

value (at the Carters Corner corehole) is 1; contours 

represent multipliers of this rate. D, Relative rates of 

deposition during UP-II time. Lowest observ~~d value (at 

the Solomons corehole) is 1; contours represent multipliers of this rate. 

mainly differences in sediment supply; there i0 little influence of the preexisting structure shown in figure 13.1B. 

The relatively low rate in the vicinity of Carters Comer, 

Office Hall, and Lake Jefferson may represen+ differential 

subsidence or slow deposition over an emerging structural 

high. 

Figure 13 .lD shows the changing picture of relative 

accumulation during UP-II time. Here also, the lowest rate 

(at the Solomons section) is given a value of 1, and contours 

represent multipliers of this rate. The range of variation is 

less than that during UP-I time; the highest rrte in UP-II 

time is less than four times the lowest rate. B~cause there 

are relatively few dinocyst datums late in UP-II time, 

calculated rates may not accurately account fo .. periods of 

58 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
erosion, but the general picture is probably good. Again, 

the pattern reflects differences in subsidence or sediment 

supply. During UP-II time, the section at Haynesville 

received a lot of sediment while the section at Solomons 

received relatively little. 

Figures 13.1B-D show some of the factors that 

combined to produce the record shown in figure 13. lA. 

Thus, we see relatively thin Aquia Formation and Marlboro 

Clay deposits at Lake Jefferson and Carters Comer, slightly 

thicker deposits at Office Hall, and still thicker deposits at 

Ashton, Fort McLean, Oak Grove, and Haynesville. The 

thickest deposits are at Solomons. The thinnest deposits 

result from a fairly late onset of deposition coupled with 

relatively low rates of deposition during the remainder of 

Paleocene time. The somewhat thicker Office Hall and Oak 

Grove sections result from an early onset of deposition 

combined with relatively low to moderate depositional 

rates. The deposits at Ashton, Fort McLean, and Haynesville have thicknesses similar to those at Oak Grove but are 

the response to different factors: late onset of deposition but 

somewhat higher depositional rates. The thickest deposits 

result from a very high rate during the latter part of UP-I 

time. This rate overwhelmed the effects of late onset of 

deposition and a slowing rate during UP-II time. 

Thus, the Aquia Formation and Marlboro Clay in the 

Salisbury embayment reflect a complex interplay of many 

factors. Preexisting and emerging structures combined 

with major changes in sediment supply to produce varying 

thicknesses of deposits and varying depositional rates. 

Acknowledgments 

I thank R.B. Mixon and T.G. Gibson for drilling and 

for collaborative research on the cores. 

REFERENCES CITED 

Dowsett, H.J., 1988, Diachrony of late Neogene microfossils 

in the southwest Pacific Ocean-Application of the graphic 

correlation method: Paleoceanography, v. 3, no. 2, 

p. 209-222. 

Edwards, L.E., 1984, Insights on why graphic correlation 

(Shaw's method) works: Journal of Geology, v. 92, no. 5, 

p. 583-597. 

---1989, Supplemented graphic correlation-A powerful tool 

for paleontologists and nonpaleontologists: Palaios, v. 4, 

no. 2, p. 127-143. 

Edwards, L.E., Goodman, D.K., and Witmer, R.J., 1984, Lower 

Tertiary (Pamunkey Group) dinoflagellate biostratigraphy, 

Potomac River area, Virginia and Maryland, in Fred~riksen, 

N.O., and Krafft, Kathleen, eds., Cretaceous and Tertiary 

stratigraphy, paleontology, and structure, soutl,western 

Maryland and northeastern Virginia; Field trip volr'lle and 

guidebook [for field trip held Oct. 17, 1984]: Reston, V a. , 

American Association of Stratigraphic Palyn,logists, 

p. 137-152. 

Miller, F. X., 1977, The graphic correlation method in biostratigraphy, in Kauffman, E.G., and Hazel, J.E., eds., Concepts 

and methods of biostratigraphy: Stroudsburg, Pa., Dowden, 

Hutchinson, and Ross, p. 165-186. 

Shaw, A.B., 1964, Time in stratigraphy: New York, :t-tfcGrawHill, 365 p. 

Sweet, W. C., 1979, Late Ordovician conodonts and bio,tratigraphy of the western Midcontinent province: Brigham Young 

University Geology Studies, v. 26, pt. 3, p. 45-85. 

Witmer, R.J., 1987, Tertiary dinoflagellate, acritarch, and chlorophyte assemblages from the Oak Grove core, Virginia 

Coastal Plain: Blacksburg, Va., Virginia Polytech1ic Institute and State University, unpub. Ph.D. dissertation, 693 p. 

13. Dynamics of Upper Paleocene Deposits in the Salisbury Embayment, Virginia and Maryland 59 

14. Late Pleistocene and Holocene Development of Delaware Bay 

By Harley J. Knebel1 

INTRODUCTION 

The geologic evolution of Delaware Bay since late 

Pleistocene time has been outlined in two recent papers by 

Knebel and Circe (1988) and Knebel and others (1988). In 

these reports, the primary data are medium-penetration 

seismic-reflection profiles collected along 282 nmi of tracklines in the lower Delaware Bay (fig. 14.1A). Interpretations of these subbottom profiles used previously published 

core and drill-hole data, as well as information on modem 

sedimentary environments within and around the study 

area. 

In the following discussion, I summarize the major 

aspects of the development of Delaware Bay from the two 

papers cited above. The reader should consult the full text 

of these papers for appropriate supporting references and for 

a more definitive treatment of the data. 

LATE PLEISTOCENE AND HOLOCENE 

GEOLOGIC HISTORY 

Two ancestral drainage systems of the Delaware 

River traversed the lower Delaware Bay during late Pleistocene time (fig. 14.1B). One system can be traced southeastward beneath the northern half of the survey area to 

where it intersects the shoreline about 3 nmi north of the tip 

of Cape May. The trunk valley of this system has relief of 

59 to 105 ft and axial depths of 125 to 154 ft below present 

sea level, which deepen eastward down the bay. The width 

of this valley ranges from 2 to 4 nmi; the average width 

exceeds 3 nmi. 

The trunk valley of the northern drainage system 

connects with a large filled paleovalley that runs beneath 

Cape May (fig. 14.1B) and extends onto the modem 

continental shelf. Drill-hole data from Cape May indicate 

that the bay-peninsula valley system was eroded into the 

Cohansey Sand (Miocene age) when sea level fell to at least 

-210 ft, probably during the late Illinoian glacial maximum. Subsequently, the valley was filled with transgressive 

1

U.S. Geological Survey, Woods Hole, MA 02543. 

strata as sea level rose during Sangamonian time. The 

transgressive sequence reached more than 98 ft in thickness 

beneath the lower bay area, and it consisted of basal fluvial 

sands and gravels overlain by heterogeneous estuarine fine 

sands and muds. 

At the height of the Sangamonian sea-level transgression, littoral and nearshore processes built the Cape May 

peninsula southward over the buried northern drainage 

system. Coastal deposition at this time also created a 

contiguous southwest-trending submarine ridge that 

extended part way across the present bay-mouth area and 

formed the nucleus of a modem bay-mouth bathymetric sill. 

The growth of the peninsula and the formation of the 

submarine ridge shifted the entrance to the bay considerably 

southward of its early Sangamonian position. 

A second ancestral drainage system of the Delaware 

River was eroded beneath the southern half of Delaware 

Bay when sea level fell (to about -279 ft) during the late 

Wisconsinan glacial maximum (fig. 14.1B). As sea level 

was lowered, the Cape May peninsula and adjoining submarine ridge became a highland, which forced the ancestral 

Delaware River to follow a course around the southern end 

of the ridge and to flow through the present bay-mouth area. 

The drainage system included ( 1) a trunk valley of the 

Delaware River beneath the central part of the bay; (2) a 

tributary valley formed by the convergence of secondary 

rivers along the Delaware coast; and (3) a channel of the 

Maurice River that followed along the western flank of the 

Cape May peninsular ridge (fig. 14.1B). Like its northern 

(late Illinoian) counterpart, the trunk valley of this system 

has a southeast trend, relief of 59 to 105 ft, widths of 2 to 

4 nmi (>3 nmi average), and a thalweg that deepens from 

- 128 to -154 ft down the bay. The system was cut into a 

variety of coastal-plain deposits of Miocene and younger 

age. 

Delaware Bay developed from the southern drainage 

system during the Holocene transgression. The paleogeography of the bay at different positions of lowered sea level 

(figs. 14.1C,D) was controlled primarily by the topography 

of the late Wisconsinan erosional surface. This surface was 

not appreciably altered during the transgression, either by 

14. Late Pleistocene and Holocene Development of Delaware Bay 61 
DELAWARE 

BAY 

DELAWARE 

75"20' 

S(OIII[Iti'AII'f(lfVIIOM:IIT'S 

0 9.&1£111AI. 

w::ITI»lWfTUN)S ~­ .ESTUUIH: lOPOII 

75'"20' 

NEW A 

39'10' 

74"50' 

75'"00'W 

Figure 14.1. Maps of Delaware Bay showing (A) tracklines along which seismic-reflection profiles were collected; (8) thalweg locations of ancestral drainage 

systems of the Delaware River; (Q paleogeography and 

sedimentary environments of the ancestral estuary 

when local relative sea level was at -131 ft ( -40 m) 

differential crustal movement or by erosion due to waves 

and tidal currents. 

During the Holocene transgression, the configuration 

of the ancestral Delaware estuary largely determined the 

areal distribution of subaerial, fluvial, tidal-wetland, 

barrier-beach, headland-beach, and open-estuarine sediDELAWARE 

BAY 

75"20' 

D 

38"50" 

74"50' 

7~50' 

approximately 12,000-15,000 yr ago; and (0) paleogeography and sedimentary environments of the 

ancestral estuary when local relative sea level was at 

-66ft (-20m) approximately 7,000--8,000 yr ago. A and 

8 modified from Knebel and Circe (1988). C and D 

modified from Knebel and others (1988). 

mentary deposits. Subaerially deposited (pretransgressive) 

sediments now beneath the bay consist primarily of gravelly, fine to coarse sands or mixtures of sands and muds that 

range in color from orange to blue gray to white. Fluvial 

sediments are light-colored, gravelly, coarse sands that 

commonly are 10 ft thick. Tidal-wetland deposits typically 

62 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
are gray-brown muds containing plant fragments and peat 

layers, although some deposits have variable amounts of 

sand, gravel. and shells. Barrier-headland beach sediments 

are dominantly fine to coarse sands with gravel and shell 

fragments. Open-estuarine deposits range from clayey silts 

containing thin beds of fine sand (turbidity-maximum 

deposits) to interlaminated muds and sands (reworked bay 

deposits) to clean, coarse sands (flood-tidal deposits). 

Fluvial conditions existed within the bay from the 

time of the late Wisconsinan lowstand (about 16,000-

18,000 yr ago) until the shoreline reached the present 

bay-mouth area. During this interval, coarse fluvial sediments accumulated along the axes of the main channels of 

the drainage system in response to the elevation of base 

level. Tidal activity did not affect sedimentation within the 

bay until relative sea level had reached about -164 ft. 

When relative sea level was at -131 ft ( -40 m), 

about 12,000-15,000 yr ago, a small estuary existed within 

the bay area (fig. 14.1C). The estuary included a narrow 

tidal river (less than 1 nmi wide), which extended more than 

16 nmi up the bay along the former trunk valley of the 

Delaware River, as well as a small contiguous embayment 

at the bay mouth. Primarily coarse-grained fluvial and 

tidal-river sediments accumulated within the bay area at this 

time. 

When relative sea level was at-98ft (-30m), about 

10,000-11,000 yr ago, the developing estuary encompassed 

two passages (0. 5-2 nmi wide), which were formed by the 

drowned major valleys of the ancestral drainage system. 

Near the present bay mouth, these passages merged into a 

relatively wide inlet channel {2-3 nmi wide). At this time, 

fine-grained sediments accumulated rapidly in the lower 

bay area, where the turbidity-maximum depocenter was 

located, and organic muds were deposited in tidal wetlands 

that occupied the mouths of most tributaries. Fluvial sediments, meanwhile, accumulated within those stretches of 

the tributaries that were not affected by the tides, and short 

barrier and headland beaches were present along the margins of the inlet channel. 

When local relative sea level was at-66ft (-20m), 

about 7,000-8,000 yr ago, the two major passages of the 

estuary were joined, except for a series of small intervening 

islands, and the estuary comprised about 30 percent of the 

present lower bay area (fig. 14.1D). By this time, the 

turbidity-maximum depocenter had moved landwarrl of the 

bay area, with the result that fine-grained sedimentation 

decreased in the open estuary. In addition, the fe+ch and 

tidal prism of the open estuary now caused large waves and 

strong tidal currents to ( 1) scour and rework previously 

deposited transgressive sediments, (2) transport sediments 

into the lower bay area from the continental shelf, and (3) 

form nearly continuous barrier and headland beaches along 

the lower bay shoreline (fig. 14.1D). 

When relative sea level was at-33ft (-10m), about 

5,000-6,000 yr ago, the estuary was nearly continu'1us and 

covered about 60 percent of the present bay area. This 

increase in continuity and size of the open estuary further 

enhanced the processes of sediment reworking an 1 transport. Moreover, the wave regime continued to incr~~ase the 

extent of barrier and headland beaches, especially along the 

southern margin of the bay, and it probably was responsible 

for the formation of shallow subtidal flats (less th11n 13 ft 

deep) near the shore. Tidal wetlands, meanwhile, covered 

relatively broad expanses along the lower reache2 of the 

tributary channels. 

Modern Delaware Bay is characterized by tw0 openestuarine sedimentary environments. One enviror'llent is 

distinguished by tidal-current transport of the surficial sands 

and by erosion of previously deposited estuarin~ strata; 

these conditions are prevalent under the relativr ly deep 

central part of the bay. The second environment i5' characterized by either sediment reworking or accumulation, 

processes which dominate across the shallow bay margins. 

REFERENCES CITED 

Gill, H.E., 1962, Ground-water resources of Cape May County, 

N.J.-Salt-water invasion of principal aquifers: New Jersey 

Department of Conservation and Economic Deve:lopment, 

Division of Water Policy and Supply, Special Report 18, 

171 p. 

Knebel, H.J., and Circe , R.C., 1988, Late Pleistocene drainage 

systems beneath Delaware Bay: Marine Geology, v. 78, 

p. 285-302. 

Knebel, H.J., Fletcher, C.H., Ill, and Kraft, J.C., 1988, Late 

Wisconsinan-Holocene paleogeography of Delaware Bay, 

a large coastal plain estuary: Marine Geology, v. 83, 

p. 115-133. 

14. Late Pleistocene and Holocene Development of Delaware Bay 63 

15. Nature and Timing of Deformation of Upper Mesozoic and Cenozoic Deposits in the 

Inner Atlantic Coastal Plain, Virginia and Maryland 

By R.B. Mixon, 1 D.S. Powars,1 and D.L. Daniels1 

INTRODUCTION 

U.S. Geological Survey (USGS) studies of Coastal 

Plain tectonism in Virginia and Maryland began in the 

middle 1970's. The two objectives were to recognize and 

map geologic structures in upper Mesozoic and Cenozoic 

deposits and to determine the nature and timing of deformation in Inner Coastal Plain areas. The ultimate goal was 

to help assess earthquake risk with regard to the safe siting 

and construction of nuclear generating stations. As the 

program wound down in the early 1980's, the emphasis 

shifted to integrated studies of the structural and stratigraphic framework of both the Inner and Outer Coastal 

Plain. 

PREVIOUS INVESTIGATIONS 

The initial field investigations were of the upper 

Mesozoic and Cenozoic deposits of the Inner Coastal Plain 

of Virginia (table 15.1) between Washington, D.C., and 

Richmond, Va. This area was selected for study because 

previous work (Mixon and others, 1972) had indicated 

faulting of Coastal Plain beds and because the intense 

dissection of the thin Coastal Plain formations near the Fall 

Line provides good outcrops and an abundance of structural 

control. Our early studies (Mixon and Newell, 1976, 1977, 

1978, 1982; Newell and others, 1978) recognized and 

described the Stafford fault system (fig. 15.1), a series of en 

echelon, northeast-striking, northwest-dipping, high-angle 

reverse faults that displace both the Paleozoic crystalline 

rocks of the Piedmont and the overlying Coastal Plain 

formations. The Stafford system is known to extend for 

more than 33 mi along the Virginia Fall Line and the 

northeast-trending reach of the Potomac River; its position 

supports the hypothesis that the Fall Line and major river 

deflections along it have been tectonically influenced 

(McGee, 1888; Mixon and Newell, 1977). 

The history of fault movement along the Stafford 

system, as determined from outcrop and borehole data and 

1

U.S. Geological Survey, Reston, VA 22092. 

trench studies (Mixon and Newell, 1977, 1978, 1982), 

indicates that compressional deformation began at least as 

early as the Early Cretaceous. Of special significar~e is a 

detailed trench study of the Dumfries fault zone west of 

Stafford, Va., where Ordovician slate, phyllite, and schist 

are thrust at a high angle over the Lower Cre .. aceous 

Potomac Formation (Newell and others, 1978). Crosscutting relations of subsidiary faults exposed in the trench 

clearly show reverse faulting confined to Potomac Formation beds of Early Cretacous age. Major deformathn also 

took place in the middle(?) Tertiary (post-Nanjemoy and 

pre-Calvert time) and in the late Tertiary (post-Calvert and 

pre-Choptank time (Mixon and Powars, unpub. data)). At 

least some Pliocene deformation along the Stafford system 

is indicated by as much as 1.5 ft of reverse-fault offset of 

the base of the upland gravel in an artificial cut r~ar the 

U.S. 1 highway bypass in south Fredericksburg, Va. 

(Potomac Electric Power Company, 1973; Mixon and 

Newell, 1982). About 1.0 ft of fault offset of the base of 

high-level Rappahannock River terrace deposits by the Fall 

Hill fault, a major strand of the Stafford system, indicates 

middle to late Pliocene or, possibly, younger faulting 

(Mixon and Newell, 1978, 1982). 

. During studies of the Stafford fault system, Mixon 

and Newell ( 1977) noted the striking alignment of 70nes of 

compressional faulting in the Virginia and Maryland 

Coastal Plain with linear zones of early Mesozoic extensional faulting in the Piedmont and in the crystalline 

basement beneath the Coastal Plain (fig. 15.1). The Coastal 

Plain compressional fault zones and the early 1\.tf~sozoic 

extensional faults are aligned, in tum, with Paleozoic 

thrusts and shear zones in the underlying baseme""t rock. 

For example, in Virginia, the Stafford fault system is 

aligned with the border faults of the earl~ Mesozo~c 

Farmville basin trend and with the Spotsylvama magnetic 

lineament (Neuschel, 1970; Pavlides, 1980), a P~~dmont 

feature representing a broad zone of en echelon faults or 

shear zones in the crystalline basement. The Lakeside 

mylonite (Farrar, 1984), which is adjacent to and roughly 

aligned with the Farmville basin (fig. 15.1), ap'1ears to 

represent a major shear zone in the Piedmont rocks along 

15. Deformation of Upper Mesozoic and Cenozoic Deposits, Inner Atlantic Coastal Plain, Virginia and Maryland 65 
Table 15.1. Age, thickness, and generalized lithology of rock units in the Inner Coastal Plain of Virginia 

[Color terms from Goddard and others (1948)] 

Rock unit Age Thickness (ft) lithology 

Terrace deposits 

Upland gravel 

Yorktown Formation 

Eastover Formation 

Choptank and Calvert 

Formations. 

Nanjemoy Formation: 

Woodstock Member 

Potapaco Member 

Marlboro Clay 

Aquia Formation 

Brightseat Formation 

Pleistocene and Pliocene 

Pliocene 

Pliocene 

Late Miocene 

Early and middle Miocene 

Early Eocene 

Early Eocene 

Paleocene 

Paleocene 

Paleocene 

0-50 

0-50 

0-90 

0-40 

0-135 

0-50 

50-90 

0-30 

0-125 

0-15 

Sand, gravel, clay-silt; gray, yellowish gray, and brown. 

Sand, gravel. silt; gray, yellowish orange, and reddish 

brown. 

Fine to coarse sand, gravelly in part; gray, yellow; contains 

Ophiomorpha. 

Fine shelly sand and silt; dark gray to bluish gray. 

Fine sand, clay-silt; olive gray, diatomaceous. 

Shelly, glauconitic quartz sand; muddy, micaceous, greenish gray. 

Shelly, glauconitic quartz sand; muddy, micaceous, greenish gray. 

Kaolinitic clay-silt, red to gray. 

Shelly, glauconitic quartz sand; light to da-k olive gray. 

Fine quartzose sand and silt; micaceous, olive gray to olive 

black. 

Potomac Formation Early and Late Cretaceous 0-1,400 Feldspathic sand, gravel, and illite-montmorillonitekaolinite clay. 

the Stafford-Spotsylvania-Farmville trend. Similarly, the 

Brandywine fault system in southern Maryland (Glaser, 

1971; Jacobeen, 1972; McCartan, 1989) includes northeasttrending Cretaceous and Tertiary reverse faults and structural highs that closely parallel the northwestern edge of an 

early Mesozoic rift basin present beneath the Coastal Plain 

cover. The Brandywine fault system and the underlying rift 

basin are aligned with the Richmond and Taylorsville early 

Mesozoic basins in Virginia. Deep test holes, water wells, 

and an aligned, east-dipping gravity gradient between the 

Brandywine and Richmond areas suggest continuity of 

faulting, rift-basin deposits, and basement terranes in Virginia and Maryland according to Mixon and Newell (1977), 

Wentworth and Mergner-Keefer (1983), and Mixon and 

Powars (1984). These workers concluded that CretaceousCenozoic faulting in the Virginia and Maryland Coastal 

Plain followed preexisting zones of weakness in the crust 

marked by early Mesozoic extensional faults and preMesozoic compressional shear zones. The style of faulting 

in this area is similar to that of the southeastern Atlantic 

Coastal Plain (Prowell and O'Connor, 1978; Prowell, 

1988). 

TAYLORSVILLE BASIN-SKINKERS NECK 

ANTICLINE STRUCTURAL TREND 

Our more recent investigations (Mixon and Powars, 

1984; Mixon and others, 1987; Powars, 1987) are concentrated east of Fredericksburg, Va., in King George and 

Caroline Counties, about 10-20 mi east and downdip of the 

Stafford fault system (figs. 15.1, 15.2). This area is of 

particular interest tectonically because it straddles the trace 

of the early Mesozoic Taylorsville basin bC'rder faults as 

projected from the Virginia Piedmont northeastward 

beneath a thin to thick cover of Coastal Plain deposits. 

Additionally, the Hylas cataclastic rocks, '"hich mark a 

major zone of late Paleozoic ductile shearing and thrusting 

that borders the west sides of the Richmond and Taylorsville basins in the Piedmont (Bobyarchick and Glover, 

1979), project northeastward along the buri~d part of the 

Taylorsville basin in the study area. Our m"pping in the 

Coastal Plain along the trend of these old structural discontinuities shows that the regional eastward dip of the overlying Cretaceous and Tertiary strata is interrupted at Skinkers Neck on the Rappahannock River by a long, linear, 

northeast-trending anticlinal fold (fig. 15.2). The fold 

repeats part of the upper Paleocene-lower Eocene stratigraphic section, including the uppermost Aqnia Formation 

and the lower Nanjemoy Formation (table 15.1). The dip 

reversal and repetition of section result in a wider than 

expected Paleogene outcrop belt in northeastern Virginia 

(Milici and others, 1963; Mixon and others, 1989). 

The principal fold structure, herein nam~d the Skinkers Neck anticline, 2 extends from the edge of the Coastal 

Plain near Bowling Green, Va., north-nortreastward for 

more than 25 mi to the vicinity of Fairview Beach on the 

Potomac River (fig. 15.2). Our structure-con .. cmr and isopach maps for Cretaceous and Tertiary mapr~ng horizons 

define a 3- to 5-mi-wide, low-amplitude, anticlinal fold that 

1

Mixon and Powars (1984) used the term "Skinkers Neck structure" 

in a more restricted sense for the narrow zone of faulting and folding along 

the northwest flank of the anticlinal structure. 

66 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
EXPLANATION 

• Drill hole penetrating Triassic rocks 

--- Zone of faults and folds 

+Anticline 

--- Geophysical lineament 

~:::.~ Coastal Plain-Piedmont boundary 

L~:i:Y;:::] Early Mesozoic 

20 MILES 

20 KILOMETERS 

VIRGINIA 

Figure 15.1. Alignment of the Stafford and Brandywine fault systems, early Mesozoic basins, and 

geophysical lineaments. Modified from Mixon and Newell (1982). 

15. Deformation of Upper Mesozoic and Cenozoic Deposits, Inner Atlantic Coastal Plain, Virginia and Marylar..f 67 
EXPIANATI">N 

-100- Structure contot•rs, interval20 ft; 

c:!::J) arrows indicate direction of dip 

--- Reverse fault, high angle U, upthrown s;de 

D, downthrown side 

~ Trace of anticliral axis, showing 

direction of plunge 

x Outcrop 

• USGS borehole 

• Waterwell 

• Test boring 

5 MILES 

5 KIL0~1ETERS 

Figure 15.2. Structure contours on the top of the Paleocene beds in the area of the Skinkers Neck anticline and Port 

Royal fault, northeastern Virginia and southwestern Maryland Coastal Plain. Cross section A-A' is sho\Nn in figure 

15.5. SL, sea level. 

is steeper to the northwest (figs. 15.2, 15.3). The axis of the 

gently northeast-plunging fold crosses the Rappahannock 

River at Skinkers Neck, a land area bounded on three sides 

by a large, northward-projecting meander bend of the river 

(see USGS topographic map of the Rappahannock Academy 7.5-minute quadrangle). The pronounced northward 

deflection of the Rappahannock River at this locality is 

thought to reflect the impingement of the river against the 

uplifted, relatively resistant, clayey and silty Miocene and 

Eocene strata of the northwest flank of the Skinkers Neck 

anticline. A detailed Bouguer gravity survey (fig. 15.4; see 

also regional gravity map of Daniels and Leo, 1985) helps 

to locate more precisely the western edge of the buried 

Taylorsville basin in this area. The basin edge and the axis 

of the Skinkers Neck anticline are approximately coincident. 

A northwest-southeast cross section (fig. 15.5) near 

Bowling Green, Va., provides some of the more detailed 

data presently available for interpreting the nature and 

timing of post-early Mesozoic deformation along the Skinkers Neck anticline. Control for the cross section consists of 

continuous cores and geophysical logs from four USGS 

coreholes and two water wells. All holes penetrated the 

Tertiary section and bottomed out in the upper part of the 

Lower and Upper(?) Cretaceous Potomac Formation. 

In the cross section, the northwest sid~ of the structural high is shown as a southeast-dippin.<J, high-angle 

reverse fault. Interpretation as a reverse fault, rather than a 

flexure, is based on (1) the abrupt, up-to·the-southeast 

displacement of the Paleogene beds as seen h outcrop and 

in our coreholes along the Rappahannock River (Mixon and 

others, 1989, sheet 2), (2) seismic-reflection lines in southem Maryland (Jacobeen, 1972; Potomac E'~-ctric Power 

Company, 1973) showing northeast-trending reverse faults 

involving the crystalline basement rock and overlying 

Coastal Plain strata, and (3) analogy with the nearby 

Stafford fault system, which clearly shows reverse-fault 

offset of Cretaceous and Paleogene formation 8 (Mixon and 

Newell, 1982; Mixon and others, 1989). Across the fault, 

vertical separation of the unconformity betw~en the Potomac Formation and the directly overlying upper Paleocene 

Aquia Formation (fig. 15.5) is about 50ft, wrereas vertical 

separation of the basal beds of the Nanjemoy Formation 

(lower Eocene) is only about half as much. T·ese relations 

and the absence of the Marlboro Clay (fig. 15. 5) on the 

upthrown side of the fault indicate an episod~ of faulting, 

uplift, and erosion in post-Aquia and pre-Natjemoy time. 

Post-Nanjemoy faulting and uplift are also indicated, but 

the amount of deformation is partly obscured by extensive 

erosion of the Nanjemoy prior to deposition of the lower 

68 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
EXPLANATION 

• Control point (borehole or water Vlell) 

-100- Isopachs, interval 20ft 

---Reverse fault, high angle 

U, upthrown side 

D, down thrown side 

--E-- Trace of anticlinal axis, showing 

direction of plunge 

5 MILES 

5 KILOMETERS 

Figure 15.3. lsopachs of lower Eocene beds (Nanjemoy Formation) in the area of the Skinkers Neck anticline and 

Port Royal fault, northeastern Virginia. Cross section A-A' is shown in figure 15.5. Modified from Mixon and 

Powars (1984). 

and middle Miocene Calvert Formation. Slight uplift and 

possible minor fault offset (5-10 ft) of the Calvert and 

Choptank Formations along the anticline are inferred on the 

basis of dip reversals (west dip) mapped in these units in 

King George County, Va. (Powars, 1987). The available 

drill data and surface mapping are not sufficient to clearly 

show the presence or absence of small-scale faulting and 

folding that may affect both the upper Miocene Eastover 

Formation and the Pliocene Yorktown Formation. 

As shown in the cross section, the Nanjemoy Formation thins markedly from southeast to northwest over the 

crest of the Skinkers Neck anticline. Our mapping of 

individual members of the Nanjemoy along the line of 

section indicates that the thinning occurs mainly by truncation of upper and middle Nanjemoy beds by the pre-Calvert 

erosion surface (Mixon, Powars, and L.E. Edwards, unpub. 

data). The abruptly thicker Nanjemoy section in the Lonesome Gulch borehole (fig. 15.5) is the result of preservation 

of younger beds in the relatively downfaulted block west of 

the Skinkers Neck anticline. The uppermost Aquia Formation and the Marlboro Clay are also truncated across the 

structure. However, some of the variation in thickness of 

the Aquia in this area occurs in the lower part of the unit 

thicker deposits fill paleotopographic lows, and deposits are 

thinner over pa1eotopographic highs. Marked thinning also 

occurs west of Bowling Green near the margin of the 

depositional basin where successively younger Aqnia beds 

lap across the Cretaceous strata onto the crystallir~ basement rock (Mixon, unpub. data). The thinning of the 

Nanjemoy and Aquia caused by truncation of th~ upper 

parts of the units-rather than by depositional thinning of 

the units as a whole-suggests episodic uplift and erosion of 

the anticline. 

PORT ROYAL FAULT 

A few miles east and downdip of the axis of the 

Skinkers Neck anticline, the structure-contour and isopach 

maps of the Paleocene and Eocene beds (figs. 15.2, 15.3) 

delineate the Port Royal fault, a zone of low-displacement, 

northwest-dipping, high-angle reverse faulting and monoclinal folding that strikes southwestward from Mathias 

Point Neck on the Potomac River to Port Royal and central 

Caroline County, Va. The sense of displacement is down to 

the coast (down to the southeast). In King George County, 

where the structure is well developed, displaceme"'t of the 

top of the Cretaceous beds is about 50 ft and is thought 

to result mainly from faulting. Displacement of tt'~ top of 

the Paleocene section (Aquia Formation and ~ tlarlboro 

15. Deformation of Upper Mesozoic and Cenozoic Deposits, Inner Atlantic Coastal Plain, Virginia and Maryla"d 69 
I i' II 

5 KILOMETERS 

Figure 15.4. Detailed gravity map of the 

Virginia-Maryland Coastal Plain along the 

trend of buried western border faults of the 

early Mesozoic Taylorsville basin. Contour 

interval is 1 mGal; contours dashed where data 

incomplete or unavailable. Grid shows 7.5-

minute quadrangles. The steep, east-dipping 

gravity gradient northeast of Bowling Green, 

Clay) appears to be about 30 ft. The overlying Eocene 

and Miocene section is also deformed, but much of the 

deformation may have occurred by folding rather than 

5 MILES 

I 

Va., is inferred to separate relatively dense 

crystalline rock on west, represented by gravity high, from less dense crystalline rock and 

lower Mesozoic basin fill on east. The steeper, 

upper part of gradient, shown by heavy dashed 

line, is thought to delineate the western edge 

of the Taylorsville basin. 

faulting. Displacement decreases southwestward along the 

Port Royal fault and, where the structure projects into the 

Bowling Green cross section (fig. 15.5), ap'Jears to be 

70 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
A 

NW 

FEET 

200 

150 

100 

50 

Sea level 

-50 

Ty 

Kp 

VERTICAL EXAGGERATION 99:1 

Skinkers Neck anticline 

I Fort 

A.P. Hill 

picnic 

area 

Te 

Tch 

Burke Range 

Avenue Corner 

0 

0 

Figure 15.5. Geologic cross section of the Skinkers Neck 

anticline and Port Royal fault, Bowling Green area, northeastern Virginia Coastal Plain. Location of section is 

shown in figures 15.2 and 15.3. Ty, Yorktown Formation; 

expressed as gentle folding and very low displacement 

faulting. The marked thickening of the Nanjemoy Formation between the Carters Comer and Smoots Pond coreholes 

(fig. 15.5) is accentuated by preservation of beds on the 

relatively down warped side of the structure. The absence of 

the Choptank Formation at the Carters Comer core site and 

southeastward along the line of section is a function of 

slight relative uplift of beds on the northwest side of the Port 

Royal fault and the angle of truncation of the unconformably overlying Eastover Formation. The Choptank Formation thickens to the northwest and is thickest in the 

structural low just west of the Skinkers Neck anticline. 

SUMMARY AND CONCLUSIONS 

1. En echelon, high-angle reverse faults of moderate displacement and low-amplitude folds are the two main 

types of structures identified in upper Mesozoic and 

Cenozoic deposits of the Virginia and Maryland Coastal 

Ty 

Te 

Tc 

Carters 

Corner 

2 KILOMETERS 

Port Royal fault 

I 

2 MILES 

Ty 

Tc 

Tn 

Smoots P~nd 

A' 

SE 

Te, Eastover Formation; Tch, Choptank Formaticn; Tc, 

Calvert Formation; Tn, Nanjemoy Formation; Tm, Marlboro Clay; Ta, Aquia Formation; Kp, Potomac 

Formation. 

Plain. The dominantly reverse nature of the faul'ing, the 

northeast trend of major structures, and the history of 

fault movement suggest that much of the Atlantic 

Coastal Plain has undergone northwest-mutheast 

compression for at least 110 m.y. (since tl'':' Early 

Cretaceous). 

2. Two extensive systems of late Mesozoic and Cenozoic 

faults have been mapped in the Coastal Plain of Virginia 

and Maryland. The Stafford fault system, paral1~ling the 

Fall Line in northeastern Virginia, is defined by 

northwest-dipping reverse faults that thrust Piedmont 

crystalline rocks southeastward at high angles over 

Coastal Plain strata. The mirror image Skinkers NeckBrandywine zone, parallel to and about 10-15 ni east of 

the Stafford fault system, includes southeas~ -dipping 

reverse faults and asymmetric anticlinal folds that are 

steeper to the northwest. 

3. Maximum reverse-fault offsets of the unccnformity 

between the crystalline basement rock and th~ directly 

15. Deformation of Upper Mesozoic and Cenozoic Deposits, Inner Atlantic Coastal Plain, Virginia and Maryland 71 
overlying Coastal Plain strata (generally the Lower 

Cretaceous Potomac Formation) range from 100 to 250 

ft. The amount of displacement of rock units by major 

reverse faults decreases upward through the Coastal 

Plain section, indicating recurrent movement through 

time. For example, offset of the base of the Paleocene 

Aquia Formation by any one of the Stafford faults is 

commonly about half as much as offset of the base 

of the directly underlying Lower Cretaceous Potomac 

Formation. 

4. Analysis of outcrops and trench exposures of the Stafford faults and of our cross sections of the Skinker's 

Neck anticline near Bowling Green (fig. 15.5) and King 

George, Va. (Mixon and Powars, unpub. data), indicate 

episodes of faulting, folding, uplift, and erosion in the 

Early Cretaceous, in latest Paleocene or earliest Eocene 

time, in the late early(?) Eocene (post-Nanjemoy and 

pre-Calvert), and in the middle Miocene (post-Calvert 

and pre-Choptank). Some gentle arching and (or) minor 

faulting of the upper middle Miocene Choptank Formation, the Pliocene "upland gravel," and high-level terrace deposits of latest Pliocene age have also occurred 

(Mixon and Newell, 1978, 1982). 

5. The aligned Stafford fault system, Spotsylvania magnetic lineament, Lakeside mylonite zone, and border 

faults of the early Mesozoic Farmville basin trend (fig. 

15.1) are believed to mark a long, narrow zone of ductile 

and brittle deformation that extends from the outer 

Piedmont northeastward into the Inner Coastal Plain of 

Virginia. In northeastern Virginia, relative down-tothe-southeast displacement of the crystalline basement 

rocks and the Coastal Plain deposits along the Stafford 

fault system controls the position of the Fall Line and the 

northeast-trending reach of the Potomac River estuary. 

We believe that the zone of deformation and associated 

downwarping of the inner edge of the Coastal Plain 

continues northeastward through Maryland and northern 

Delaware along the margin of the Chesapeake-Delaware 

embayment. 

6. Several workers have discussed the close association of 

the early Mesozoic border faults of the Richmond and 

Taylorsville basins with the late Paleozoic Hylas mylonite zone and have cited these structures as an example 

of preexisting fault control for Mesozoic basins (Bobyarchick and Glover, 1979; Swanson, 1986). Our mapping in the Coastal Plain along the strike of the Hylas 

zone and adjacent rift basins has identified Cretaceous 

and Tertiary structures, including the Skinkers Neck 

anticline and related faults, that are superposed on 

buried border faults of the Taylorsville basin, present in 

the subsurface in this area. These relationships indicate 

continued release of compressional stress along the 

Hylas zone and (or) reactivation and reversal of movement on the extensional faults of the early Mesozoic 

basins. The deformational history of the Coastal Plain 

strata in the Skinkers Neck area indicatef the continuation of a compressional stress field through much of late 

Mesozoic and Cenozoic time. The Port Royal fault and 

fold, a few miles east and downdip from the Skinkers 

Neck anticline, probably also represent reactivation of 

early Mesozoic faults present beneath the Coastal Plain 

cover. 

REFERENCES CITED 

Bobyarchick, A.R., and Glover, Lynn. III, 1979. Deformation 

and metamorphism in the Hylas zone and adjacent parts of the 

eastern Piedmont in Virginia: Geological Soc~ety of America 

Bulletin, v. 90, pt. 1, p. 739-752. 

Daniels, D.L., and Leo, G.W., 1985, Geologic interpretation of 

basement rocks of the Atlantic Coastal Plain: U.S. Geological 

Survey Open-File Report 85-655, 43 p., 4 sheets, scale 

1:1,000,000. 

Farrar, S.S .. 1984, The Goochland granulite terrane-Remobilized Grenville basement in the eastern Virginia Piedmont. in 

Bartholomew. M.J., ed., The Grenville evert in the Appalachians and related topics: Geological Society of America 

Special Paper 194, p. 215-227. 

Glaser, J.D., 1971, Geology and mineral resources of southern 

Maryland: Maryland Geological Survey Repo't of Investigations 15, 84 p. 

Goddard, E.N., and others, 1948, Rock-color chart: Washington, 

D.C., National Research Council, 6 p. (Republished by 

Geological Society of America, 1951; reprinted 1975.) 

Jacobeen, F.H., Jr., 1972, Seismic evidence for high angle 

reverse faulting in the Coastal Plain of Prine~ Georges and 

Charles Counties, Maryland: Maryland Geo1

ogical Survey 

Information Circular 13, 21 p. 

McCartan, Lucy, 1989, Atlantic Coastal Plain sedimentation and 

basement tectonics southeast of Washington, D.C.; 28th 

International Geological Congress Field Trip Guidebook 

T214: Washington, D.C.. American Geophysical Union, 

25 p. 

McGee, WJ, 1888. The geology of the head of Ch~sapeake Bay: 

U.S. Geological Survey Annual Report 7. p. 537-646. 

Milici. R.C., Spiker, C.T., Jr.. and Wilson, J.M., comps., 1963, 

Geologic map of Virginia: Charlottesville, Va., Virginia 

Division of Mineral Resources, scale 1:500,000. 

Mixon, R.B., Berquist. C.R., Newell, W.L., Johnson, G.H., 

Powars, D.S., Schindler, J.S., and Rader, E.K., 1989, 

Geologic map and generalized cross sections of the Coastal 

Plain and adjacent parts of the Piedmont. Virginia: U.S. 

Geological Survey Miscellaneous Investigations Series Map 

I-2033, 2 sheets, scale 1:250,000. 

Mixon. R.B., and Newell, W.L., 1976, Preliminary investigation 

of faults and folds along the inner edge of the Coastal Plain in 

northeastern Virginia: U.S. Geological Survey Open-File 

Report 76-330, 18 p., 5 sheets, scale 1:24,000. 

---1977, Stafford fault system-Structures documenting Cretaceous and Tertiary deformation along the Fall Line in 

northeastern Virginia: Geology, v. 5, p. 437---Ll40. 

---1978, The faulted Coastal Plain ntdrgin at Fredericksburg, 

Virginia, Guidebook for Tenth Annual Virginia Geology 

72 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Field Conference, October 13-14, 1978: Reston, Va., Virginia Academy of Sciences, 50 p. 

---1982, Mesozoic and Cenozoic compressional faulting 

along the Atlantic Coastal Plain margin, Virginia, in Lyttle, 

P. T. , ed. , Central Appalachian geology [Northeast -Southeast 

Sections meeting, Geological Society of America, 1982], 

Field trip guidebooks: Falls Church, Va., American Geological Institute, p. 26-54. 

Mixon, R.B., and Powars, D.S., 1984, Folds and faults in the 

Inner Coastal Plain of Virginia and Maryland-Their effect 

on distribution and thickness of Tertiary rock units and local 

geomorphic history, in Frederiksen, N.O., and Krafft, Kathleen, eds., Cretaceous and Tertiary stratigraphy, paleontology. and structure, southwestern Maryland and northeastern 

Virginia; Field trip volume and guidebook [for field trip held 

Oct. 17, 1984]: Reston, Va., American Association of 

Stratigraphic Palynologists, p. 112-122. 

Mixon, R.B., Powars, D.S., and Ward, L.W., 1987, Cenozoic 

stratigraphic and structural framework, western and southern 

parts of the Salisbury embayment, Virginia [abs.]: Geological 

Society of America Abstracts with Programs, v. 19, no. 2, 

p. 119. 

Mixon, R.B., Southwick, D.L., and Reed, J.C .. Jr., 1972, 

Geologic map of the Quantico quadrangle, Prince William 

and Stafford Counties. Virginia, and Charles County, Maryland: U.S. Geological Survey Geologic Quadrangle Map 

GQ-1044, scale 1:24.000. 

Neuschel, S .K., 1970, Correlation of aeromagnetics and aeroradioactivity with lithology in the Spotsylvania area, Virginia: 

Geological Society of America Bulletin, v. 81, 

p. 3575-3582. 

Newell, W.L., Prowell, D.C., and Mixon, R.B., 1978. A 

Piedmont-Coastal Plain fault contact; Stafford fault system, 

northeastern Virginia, in Mixon, R.B., and Newell, W.L., 

eds. , The faulted Coastal Plain margin at Fredericksburg, 

Virginia, Guidebook for Tenth Annual Virginia Field Conference, October 13-14, 1978: Reston, Va., Virginill Academy of Sciences, p. 34-40. 

Pavlides, Louis, 1980, Revised nomenclature and straf1:raphic 

relationships of the Fredericksburg Complex and Quantico 

Formation of the Virginia Piedmont: U.S. Geological Survey 

Professional Paper 1146, 29 p. 

Potomac Electric Power Company, 1973, Preliminat;' safety 

analysis report, Douglas Point Nuclear Generating Station, 

Units 1 and 2: Washington, D.C., v. 2, chapter 2.5, Geology 

and seismology, 150 p. 

Powars, D.S., 1987, Geology of the King George qua'irangle, 

King George County, Virginia, and a brief discu~sion of 

the regional stratigraphy and structure: Wasl-tington, 

D.C., George Washington University, M.S. thesis, 194 p. 

Prowell, D.C., 1988, Cretaceous and Cenozoic tectonism on the 

Atlantic coastal margin, in Sheridan, R.E., and Grow, J .A., 

eds., The Atlantic continental margin-U.S., v. I-2 ofThe 

geology of North America: Boulder, Colo., Geologkal Society of America, p. 557-564. (The Decade of North P merican 

Geology (DNAG) Project.) 

Prowell, D.C., and O'Connor, B.J., 1978, Belairfaultzcne-Evidence of Tertiary fault displacement in eastern Georgia: 

Geology, v. 6, p. 681--684. 

Swanson, M.T., 1986, Preexisting fault control for Hesozoic 

basin formation in eastern North America: Geology, v. 14, 

p. 419-422. 

Wentworth, C.M., and Mergner-Keefer, M.M., 1983, Regenerate 

faults of small Cenozoic offset-Probable earthquake sources 

in the Southeastern United States, in Gohn, G. S. , ed. , 

Studies related to the Charleston, South Carolina, errthquake 

of 1886-Tectonics and seismicity: U.S. Geological Survey 

Professional Paper 1313, p. S1-S20. 

15. Deformation of Upper Mesozoic and Cenozoic Deposits, Inner Atlantic Coastal Plain, Virginia and Maryhnd 73 

16. National Water-Quality Assessment Program Activities on the Delmarva Peninsula in 

Parts of Delaware, Maryland, and Virginia 

By Patrick j. Phillips,1 Robert j. Shedlock, 1 and Pixie A. Hamilton2 

INTRODUCTION 

The Delmarva Peninsula is one of three ground-water 

project areas in the U.S. Geological Survey's pilot National 

Water-Quality Assessment (NAWQA) Program. The pilot 

program will test and refine concepts and approaches for 

conducting a full-scale national water-quality assessment 

(Hirsch and others, 1988). At present (1988), the NAWQA 

Program consists of seven pilot projects: three that focus on 

ground water and four that focus on surface water. The 

goals of a full-scale NA WQA Program would be to provide 

a consistent national description of current water-quality 

conditions, to define long-term trends in water quality, and 

to relate observed water-quality conditions and trends to 

natural and human factors. This report describes the main 

objectives and approaches of the pilot ground-water 

NA WQA project in the Delmarva Peninsula. Because the 

range of hydrogeologic and geomorphic settings on the 

Delmarva Peninsula is similar to that in other areas along 

the U.S. Atlantic Coastal Plain, results from this project are 

expected to have broad interest and applicability. 

The Delmarva Peninsula lies east of Chesapeake Bay 

and west of the Atlantic Ocean and Delaware Bay; it 

includes most of Delaware and parts of Maryland and 

Virginia (fig. 16.1). The total land area of the peninsula is 

about 6,050 mi2

. Agriculture is the largest single land use in 

the study area, and it accounted for about 48 percent of the 

total land area in 1972-76 (U.S. Geological Survey, 1979a, 

b; 1981a, b). The remaining land was woodland (31 

percent), wetland (13 percent), urban land (7 percent), and 

barren land (1 percent). The study area is in the Coastal 

Plain physiographic province and is relatively flat; most of 

the study area is less than 100 ft above sea level. The 

peninsula contains a central upland bordered by broad 

lowlands. These lowlands are fringed by tidal wetlands near 

the coastlines. Part of the central upland consists of broad 

flats separated by deeply incised streams, whereas another 

part is poorly drained and hummocky. 

1

U.S. Geological Survey, Towson, MD 21204. 2

U.S. Geological Survey, Richmond. VA 23230. 

The aquifer system consists of a sequence of nine 

confined sand aquifers that dip to the east or southeast 

(Cushing and others, 1973). This sequence is overlain by a 

regionally extensive surficial aquifer that is mostly unconfined. The surficial aquifer is the main source of recharge to 

the underlying confined aquifers, which, with one exception, are truncated by the surficial aquifer. 

The three NA WQA ground-water pilot projects have 

five major activities: (1) analysis of available information; 

(2) low-density sampling throughout the study are"s for a 

wide range of constituents (referred to as a regional survey); 

(3) targeted sampling at a higher density in several smaller 

areas for selected groups of constituents; (4) supplemental 

geohydrologic and geochemical measurements; and (5) 

establishment of a network of wells for long-term sampling. 

ANALYSIS OF AVAILABLE INFORMATIO~l 

Existing data on ground-water quality and ancillary 

information have been analyzed to provide an initial assessment of regional ground-water quality and to test methods 

for investigating water quality in relatively large regions, 

such as the Delmarva Peninsula. Hamilton and others 

( 1989) described the sources, availability, accessibility, and 

geographic distribution of existing water-quality data for the 

study area and provided a preliminary analysis of these 

data. 

REGIONAL SURVEY 

One of the objectives of the regional survey is to 

describe ground-water quality, both areally and with depth, 

for the principal aquifers in the study area. A further 

objective is to provide a basis for improving the un 1erstanding of water-quality variations and problems in the study 

area, especially with regard to differences in land use, soils, 

and hydrogeologic setting. The samples collecte1 for the 

regional survey will be analyzed for all major ca~ions and 

anions, numerous trace metals and other trace elements, 

16. National Water-Quality Assessment Program Activities on the Delmarva Penim,,Jia 75 
76'00' 75'30' 75'00' 

39'00' 

37'30' 

EXPLANATION 

e Randomly spaced sites, each having a 

shallow and a deep well 

.6. Sites along cross sections 

D Local networks (high density) 

A --A' Line of geohydrologic cross section 

Figure 16.1. Network of wells in the surficial aquifer 

planned for the Delmarva pilot project. 

radionuclides, and organic constituents. The organic constituents include dissolved organic carbon, a suite of volatile organic compounds. and selected pesticides. Sampling 

sites will be distributed throughout each aquifer and will be 

unbiased toward known or suspected problem areas. The 

well network (fig. 16.1) will consist of three sets of wells: 

(1) a spatially stratified network of wells ir the surficial 

aquifer; (2) a set of wells in the surficial aquifer along 

east-west cross sections; and (3) a set of wells in each of the 

nine confined aquifers (not shown in fig. 16.1). 

The spatially stratified network of the surficial aquifer 

is intended to provide a representation of wfter quality in 

the Delmarva Peninsula at the broadest scale. Thirty-five 

sites were selected randomly throughout the peninsula; each 

site has a shallow and a deep well. Wells in the second set 

in the regional survey are along several lines of section that 

trend roughly east-west and extend from Chesrryeake Bay to 

Delaware Bay or to the Atlantic Ocean (fig. 16.1). These 

cross sections will provide approximately 30 additional 

sampling sites in the surficial aquifer in areas representative 

of different hydrogeologic and geomorphic settings. These 

cross sections were chosen primarily to depict changes in 

the thickness and hydrogeologic characteristics of the surficial aquifer system and to show regional p:--ofiles of the 

water table. The third set of wells in the regional survey 

network is in the confined aquifer system. Three wells will 

be chosen for each aquifer; one well will be in the subcrop 

zone, and two other wells will be located progressively 

farther downdip and. presumably, farther downgradient. 

The results of the regional survey are expected to 

allow broad comparisons between deep and shallow ground 

water in the surficial aquifer and between waters in the 

confined aquifers and those in the surficial aquifer. The 

total number of wells to be sampled during the regional 

survey will range from 120 to 150. Supplemertal sampling 

also may be done to collect samples from vari')US land-use 

areas, hydrogeologic and geomorphic settings, and classes 

of wells that may have been underrepresented in the 

regional survey. 

TARGETED SAMPLING 

The regional survey wells will be supp1emented by 

wells in small watersheds in a variety of hydrogeologic and 

geomorphic settings (fig. 16.1). This set of wells, known as 

the high-density network. consists of wells r1aced along 

transects in watersheds of a few square mile" or less to 

investigate water-quality patterns along local ground-water 

flow paths. Samples collected from this network will be 

analyzed for major ions, nutrients, selected perticides, and 

selected radionuclides. Because the watersheds for these 

transects are located along the major east-west cross sections, they should provide a link between local and regional 

patterns of water quality. 

76 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Results of water-quality sampling from the highdensity network will be used for several purposes. First, 

they will provide a measure of variations in water quality in 

more detail than is possible with the regional survey 

network. Second, these results will be used to relate the 

distribution of water-quality constituents to ground-waterflow patterns and to local variations in topography, soils, 

and land use. 

Finally, water-quality data collected at wells in the 

high-density network and at the regional-survey sites in 

agricultural areas will be used to study the distribution of 

agricultural chemicals in ground water in various hydrogeologic settings. Information on current and past croprotation practices and on use of specific pesticides will help 

to determine which pesticides' distribution will be analyzed. Temporal variations in the concentrations of agricultural chemicals in ground water will be studied by sampling 

selected wells before, during; and after the growing season 

for 1 year or more. 

GEOHYDROLOGIC AND GEOCHEMICAL 

MEASUREMENTS 

Supplemental geohydrologic and geochemical measurements will be made on samples from both the regional 

and local networks to study the relations among patterns of 

ground-water flow and water quality. These measurements 

will be made to study recharge-discharge relations in the 

shallow ground-water system, to determine differences in 

environmental isotopes in different parts of the aquifer 

system, and to investigate mineral-water interactions that 

may affect water quality. These efforts will provide physical and chemical data on human and natural effects on 

ground water. 

Recharge-discharge relations in the shallow groundwater system will be studied by observing temporal variations in water-table profiles in the high-density network and 

by using these profiles as the basis for cross-sectional 

simulations of the shallow ground-water system. The simulations will be used to investigate the horizontal and 

vertical dimensions of shallow ground-water-flow systems. 

The investigations of recharge-discharge relations are 

expected to help in understanding the relations between 

water quality and physical features of the land in more detail 

than can be obtained by use of traditional maps of surficial 

geology, soils, and land use. 

Environmental isotopes have been used in the last 30 

years to study recharge-discharge relations in aquifer systems, particularly in shallow flow systems. (See Back and 

Freeze, 1983, p. 294-297, for a short review of the 

subject.) Samples will be collected from wells in the 

subcrop areas of the confined aquifers and from selected 

wells in the high-density network. These samples will be 

analyzed for tritium and the stable isotopes of oxygen and 

hydrogen. Results from this effort will complemen+ simulations of vertical flow patterns in the shallow ground-water 

system. The results will be used primarily to determine the 

vertical penetration of local flow patterns so that the 

potential for anthropogenic substances to migrate in+o deep 

ground-water supplies can be assessed. 

Chemical analyses of ground-water samples from 

both the regional survey and targeted sampling effcrts will 

be used to identify mineral-water interactions that influence 

the chemical composition of ground water. In addition, 

petrographic observations and chemical analyses of soils 

and aquifer material will help to explain geoc'-'emical 

processes that may influence the transport and fate of trace 

elements and manmade organic constituents. 

ESTABLISHMENT OF A LONG-TERM SAMPLING 

NETWORK 

A long-term sampling network will be establ:~hed to 

evaluate temporal trends in ground-water quality in the 

study area. Collection of water-quality data fro"'l these 

wells will continue after the completion of the DP.lmarva 

pilot project. This network will include wells representing 

waters of different ages (where "age" indicates the time 

since water entered the ground-water-flow system), hydrogeologic and geomorphic settings, and land uses. The first 

step in determining the long-term sampling network will 

involve assigning the wells sampled during the study to 

groups based on the estimated age of the water in the well. 

These ages will be determined from studies of rechargedischarge relations, environmental isotopes, and hydrochemical water type. Although sites will be chosen to 

reflect a range of ground-water ages, most of the wells in 

the long-term sampling network will tap aquifers containing 

relatively young waters. 

REFERENCES CITED 

Back, William, and Freeze, R.A., eds., 1983, Chemkal hydrogeology: Stroudsburg, Pa., Hutchinson Ross, 416 p. 

Cushing, E.M., Kantrowitz, I.H., and Taylor, K.R., 1973, Water 

resources of the Delmarva Peninsula: U.S. Geological Survey 

Professional Paper 822, 58 p. 

Hamilton, P.A., Shedlock, R.J., and Phillips, P.J., 1989, 

Ground-water-quality assessment of the Delmarva Peninsula, 

Delaware, Maryland, and Virginia-Analysis of available 

water-quality data through 1987: U.S. Geological Survey 

Open-File Report 89-34, 71 p. 

Hirsch, R.M., Alley, W.M .. and Wilber, W.G., 1988, Concepts 

for a National Water-Quality Assessment Prog,~am: U.S. 

Geological Survey Circular 1021, 42 p. 

U.S. Geological Survey, 1979a, Land use and land cover, 1972, 

Wilmington, Delaware; New Jersey; Pennsylvania; Maryland: U.S. Geological Survey Land Use and Land Cover Map 

L-38, 1 sheet, scale 1:250,000. 

16. National Water-Quality Assessment Program Activities on the Delmarva Penin~ula 77 
---1979b, Land use and land cover, 1973, Salisbury, Maryland; Delaware; New Jersey; Virginia: U.S. Geological 

Survey Land Use and Land Cover Map L-65, 1 sheet, scale 

1:250,000. 

---198la, Land use and land cover, 1974--76, Baltimore, 

Maryland; Pennsylvania; Virginia; West Virginia: U.S. Geological Survey Land Use and Land Cover Map L-113, 1 

sheet, scale 1:250,000. 

---1981b, Land use and land cover, 1972, Wa.,hington, D.C.; 

Maryland; Virginia: U.S. Geological Survey Land Use and 

Land Cover Map L-201. 1 sheet, scale 1:250,000. 

78 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
17. Campanian to Quaternary Depositional Sequences in the Baltimore Canyon Trough and 

Their Relations to Deposits underlying the Middle U.S. Atlantic Coastal Plain 

By C. Wylie Poag1 

INTRODUCTION 

The Baltimore Canyon trough is a large depositional 

basin seaward of the Middle Atlantic Coastal Plain in 

Virginia, Maryland, Delaware, and New Jersey (fig. 17 .1). 

Several compilations of geologic, paleontologic, and seismostratigraphic data from the trough have been published in 

the last few years (various papers in Poag, 1985b; Poag and 

others, 1987; Ross and Haman, 1987; Sheridan and Grow, 

1988). 

For this region, 55 boreholes and multichannel 

seismic-reflection profiles collected along 10,000 km of 

tracklines constitute the principal foundation for the stratigraphic and depositional framework (Poag, 1985a, 1987a; 

Poag and Valentine, 1988). Poag (1987 a) illustrated and 

described this framework along a chronostratigraphic section that stretches 700 km from the Virginia Coastal Plain to 

the lower part of the Atlantic Continental Rise in the 

Hatteras basin (Deep Sea Drilling Project Site 603). The 

chief feature of this section is a succession of widespread, 

unconformity-bounded (allostratigraphic) depositional units 

(Poag, 1897b). 

The stratigraphic position of each unit conforms 

remarkably well with the supercycles of the sequencestratigraphy model (Vail and others, 1977; Haq and others, 

1987; Greenlee and others, 1988). The bounding unconformities can be recognized on the basis of biostratigraphic 

and lithostratigraphic discontinuities in outcrops and boreholes (Ward, 1984; Olsson and others, 1987; Olsson and 

Wise, 1987; Poag and Low, 1987; Poag, 1989; Miller and 

others, 1990) and (or) by angular relations between reflections on seismic profiles (Vail and others, 1977; Poag and 

Schlee, 1984; Poag and Mountain, 1987). Stratigraphic 

successions documented at the offshore boreholes can be 

extrapolated for hundreds of kilometers along the extensive 

network of interconnecting seismic profiles (Schlee, 1981; 

Poag and Mountain, 1987; Poag and Sevon, 1989). Recent 

studies of planktonic microfossils in Coastal Plain deposits 

(Olsson and others, 1987; Poore and Bybell, 1988; Poag, 

1

U.S. Geological Survey, Woods Hole, MA 02543. 

1989; Poag, unpub. data) allow detailed COJTelation 

between units under the Coastal Plain and offshcre allostratigraphic units. 

Using this stratigraphic and depositional framework, 

I have mapped the structural configuration, thickness, and 

distribution patterns of each allostratigraphic unit (Poag, 

1987a; Poag and Mountain, 1987; Poag and Sevon, 1989). 

The isopach maps are particularly useful for locating 

depocenters, tracing the principal routes of sedirrent dispersal, and determining the dominant provenance cf terrigenous components in each allostratigraphic unit. The following discussion is based on a limited selection of isopach 

maps and seismostratigraphic sections for a few of these 

allostratigraphic units. 

CAMPANIAN ALLOSTRATIGRAPHIC UNIT 

I will set the stage for a discussion of the Cenozoic 

depositional units by first describing the salient features of 

the Upper Cretaceous deposits. Seaward of what now are 

the Middle Atlantic States of Virginia, Maryland, Delaware, and New Jersey, the Upper Cretaceous (Canpanian) 

margin featured a broad, gently sloping continental shelt it 

was about 200 km wide and was covered by a blanket of 

terrigenous to marine and hemipelagic deposits less than 

100 m thick (Poag, 1987a; Poag and Sevon, 1989). In 

contrast, seaward of what now is Long Island, the Campanian shelf was the site of several deltaic prisms thicker than 

200 m. The greatest sediment thickness by far. }'')Wever, 

accumulated on the continental rise as submarine fans 

> 1 ,000 m thick near the base of the Long Island platform 

(fig. 17 .2). The pattern of isopachs is evidence that the 

Campanian sediments came mainly from the nort'l via the 

ancient Connecticut River and an undetermined river (or 

rivers) in eastern Massachusetts (which drained the New 

England Highlands; Poag and Sevon, 1989). Sirrilar relations characterized Maastrichtian deposition. 

During the Paleocene and early Eocene, however, the 

dominance of northern sediment sources diminished, as the 

central Appalachian Highlands became a majcr source 

17. Campanian to Quaternary Depositional Sequences, Baltimore Canyon TrorJgh 79 
PENNSYLVANIA 

• 

<v '~, 

~ ' 

~ 

~ 

~ I 

I 

\! 

7 0 

....... 

I 

I 

I 

...... ....... ....... 

' ....... ....... ....... 

'* 

EXPLANATION 

3---- SEISMIC LINES 

....... ....... ....... ....... 

'6' 

....... 

'lo 

-·- BOUNDARIES, BALTIMORE CANYON TROUGH e DRILL HOLE 

.... ··200m-·· ISOBATH 

0 25 50 IOOKM 

7 0 7 0 

Arr.OR 

6012 c. 

,.{)"· 

.... ,'V 

'<'s 

~ 

cj 

Q;)~ 

Figure 17.1. Locations of principal physiographic and geologic features, selected boreholes, and tracklines along which multichannel 

seismic-reflection profiles were collected in the 

Baltimore Canyon trough. AMCOR, Atlanf,-: 

Margin Coring Project; ASP, Atlantic Slo~ e 

Project; COST, Continental Offshore Stratigraphic Test; DSDP, Deep Sea Drilling Projec•. 

80 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Figure 17.2. Selected principal depocenters of the 

Baltimore Canyon trough and northern Hatteras basin 

during the Campanian to Quaternary. Depocenters 

are numbered (1-6) in chronological order from oldest (Campanian) to youngest (Quaternary). Principal 

drainage systems are indicated by heavy arrows; solid 

circles mark key boreholes; fine dotted lines are 

terrain. In addition, carbonate deposits became more abundant in shelf and deeper lithotopes (Poag, 1985a, 1987a). 

MIDDLE EOCENE ALLOSTRATIGRAPHIC UNIT 

By the end of the middle Eocene, a significant rise in 

relative sea level had trapped most continent-derived sediments on the continental shelf; this system was very 

different from the earlier Cenozoic and Late Cretaceous 

bathymetric contours indicating meters behw 

present sea level. Note temporal and spatial shift~ in 

sediment source between western (central Appalachian Highlands) and northern (Adirondack and New 

England Highlands) terrains. Depocenters for other 

Cenozoic sedimentary sequences are not illustrated 

in order to avoid cluttering the figure. 

depositional systems (Poag and Sevon, 1989). In tl'~ study 

area, the most striking sedimentary feature of the middle 

Eocene was an elongate ( ~200-km-long), currentdominated delta (fig. 17.2) reminiscent of the modem 

Amazon Delta (by analogy, it was probably a submarine 

delta). Its >400-m-thick depocenter is directly offshore 

from what now is Delaware Bay. Thus, by middle Eocene 

time, the dominant provenance of terrigenous detritus had 

shifted to the west (to the central Appalachian Hig,lands), 

and sediment moved seaward via the ancient Susquehanna 

17. Campanian to Quaternary Depositional Sequences, Baltimore Canyon Trough 81 
and Delaware Rivers, which took more direct routes eastward to the Atlantic than they do today (Poag and Sevon, 

1989). 

The Adirondack Highlands appear to have been an 

important, though secondary, sediment source, as evidenced by a large bird-foot delta (>200 m thick), which 

built out seaward of the ancient Hudson River mouth (fig. 

17 .2). Scattered, thin wedges ( ~200 m thick) of chiefly 

carbonate sediments formed slope aprons and submarine 

fans on the upper continental rise (Poag, 1987a). 

UPPER EOCENE ALLOSTRATIGRAPHIC UNIT 

The present distribution of upper Eocene sediments is 

quite limited compared to that of most other Cenozoic units 

(fig. 17 .2). A small, relatively thin depocenter ( ~ 100 m 

thick) is centered around what now is Cape May, N.J.; it 

was penetrated by the Anchor Gas-Dickinson No. 1 well 

(Brown and others, 1972; Poag, 1985a). A second small 

depocenter appears to have overlapped part of the seaward 

slope of the underlying middle Eocene delta, and an 

elongate, thin wedge of upper Eocene sediment is present at 

the shelf edge off New Jersey. This patchy distribution is 

partly a product of widespread erosion that took place 

during the early and late Oligocene. 

UPPER OLIGOCENE ALLOSTRATIGRAPHIC 

UNIT 

Lower Oligocene strata in the study area are too 

poorly known to map, but upper Oligocene strata have been 

identified in several outcrops (Ward, 1984; Poag and Ward, 

1987) and boreholes (Poag, 1985a, 1989: Poore and Bybell, 

1988) on the Coastal Plain and offshore. The principal 

depocenter (fig. 17 .2) is marked by an elongate, narrow 

prism (~200 km long, >300m thick), which accumulated 

along the seaward slope of the underlying middle Eocene 

delta. The chief source of sediment remained the central 

Appalachian Highlands (Poag and Sevon, 1989), as the 

ancient Susquehanna drainage system was dominant. Also, 

as in the middle Eocene, a secondary depocenter developed 

off the mouths of the ancient Hudson and Delaware Rivers 

(fig. 17 .2). Upper Oligocene depocenters are not yet known 

from the Hatteras basin, but thin, scattered patches of upper 

Oligocene strata are present on the outer shelf and slope, 

where they consist of chiefly pelagic carbonate deposits 

(Poag, 1985a; Poag and others, 1987). The patchy distribution of the upper Oligocene allostratigraphic unit appears 

to be, like that of the upper Eocene unit, the result of 

erosion. 

MIDDLE MIOCENE ALLOSTRATIGRAPHIC 

UNIT 

Progradation of middle Cenozoic depositional units 

toward the shelf edge continued through the early and 

middle Miocene. By the end of the middle Miocene, a 

shelf-slope profile similar to the modem one had been 

constructed (Poag, 1987a). The middle Miocene rate of 

sediment accumulation was an order of magnitude greater 

than that during any preceding interval of the Cenozoic, and 

this accelerated deposition formed a huge shelf-edge depocenter (> 1,300 m thick) due east of the mouth of the 

ancient Susquehanna River (fig. 17.2; Poa'! and Sevon, 

1989). Thick ( > 1 ,400 m) middle Miocene deposits also 

accumulated on the continental rise in large s·.tbmarine fans 

and contourite drifts, which contain predomi"'antly terrigenous constituents (Mountain and Tucholke, 1985; Tucholke 

and Mountain, 1986). The ancient Delaware and Potomac 

river systems were secondary sediment-dispersal routes at 

this time, but northern source terrains (Adiron1ack and New 

England Highlands) appear to have been lesf important. 

UPPER MIOCENE TO QUATERNARY 

ALLOSTRATIGRAPHIC UNITS 

Continued seaward progradation during the late Miocene, Pliocene, and Quaternary built relatively thick 

(300-400 m), elongate depocenters that perc~ed along the 

shelf edge (Poag, 1987a; Poag and Sevon, 1989), but the 

bulk of deposition (>800 m) during this time interval took 

place on the continental rise. Two broad depocenters ( ~ 100 

km wide) on the continental rise contain >600 m of upper 

Miocene to Quaternary sediments (fig. 17 .2). These sediments appear to have been channeled mainly through 

submarine canyons that incised the shelf edge. Large 

submarine fans and contourite drifts continued to characterize much of the deep-water deposition in the Patteras basin 

during this time (Tucholke and Mountain, 1986). Both 

western (central Appalachian Highlands) and northern 

(Adirondack and New England Highlands) source terrains 

contributed large quantities of sediment during the 

Quaternary. 

SUMMARY AND CONCLUSIONS 

In summarizing, let me re-emphasize that the Upper 

Cretaceous and Cenozoic deposits of the Middle Atlantic 

Coastal Plain accumulated along the western near-shore 

margin of a basin whose principal depocenters (for almost 

every allostratigraphic unit) are well offshore from the 

present Coastal Plain. The positions of these depocenters 

appear to be related directly to (1) the relative position of 

sea level, (2) the rate of sediment accumulatio'l, and (3) the 

provenance of the dominant sedimentary constituents for 

each allostratigraphic unit. These three properties have been 

subject to large-scale shifts through the last 80 m.y. Upper 

Cretaceous (Campanian-Maastrichtian) deposits are thickest 

on the northern part of the continental rise, whereas the 

continental shelf off the Middle Atlantic Coastal Plain 

82 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
received only a relatively thin blanket of Upper Cretaceous 

sediment. 

By middle Eocene time, however, a major rise in 

relative sea level trapped most terrigenous detritus on the 

continental shelf and allowed central Appalachian drainage 

systems to build a large submarine delta off Delaware Bay. 

A subsequent major pulse of terrigenous deposition brought 

central Appalachian detritus to unusually thick middle 

Miocene depocenters at the shelf edge and on the continental rise. During the rest of the Cenozoic, the continental rise 

hosted the thickest depocenters, and sediment was supplied 

in large volumes by northern sources, as well. 

During the 80 m. y. of Campanian to Quaternary 

time, the shelf edge was near its present location (fig. 17 .2); 

its position was controlled by a buried Upper Jurassic reef 

escarpment whose original relief was 1.5-2.0 km (Poag, in 

press). In contrast, the shoreline (fig. 17 .2) shifted laterally 

200 km or more during this time interval, reaching nearly to 

(or beyond?) the shelf edge during the lowest stands of sea 

level (for example, during Quaternary glaciations). During 

lowstands and the early stages of subsequent marine transgressions, erosion was widespread and often severe, modifying significantly the original distribution patterns and 

thicknesses of the allostratigraphic units (especially where 

the deposits were already thin) and creating their unconformable boundaries. 

It is essential that the regional perspective provided 

by the depositional and erosional history of the Atlantic 

offshore basins be incorporated into any interpretation of 

the various geologic and paleontologic aspects of the 

Atlantic Coastal Plain. 

REFERENCES CITED 

Brown, P.M., Miller, J.A., and Swain, F.M., 1972, Structural 

and stratigraphic framework and spatial distribution of permeability of the Atlantic Coastal Plain, North Carolina to 

New York: U.S. Geological Survey Professional Paper 796, 

79 p. 

Greenlee, S.M., Schroeder, F.W .. and Vail, P.R .. 1988, Seismic 

stratigraphic and geohistory analysis of Tertiary strata from 

the continental shelf off New Jersey; Calculation of eustatic 

fluctuations from stratigraphic data, in Sheridan. R.E., and 

Grow, J.A., eds., The Atlantic continental margin-U.S .. v. 

I-2 of The geology of North America: Boulder. Colo., 

Geological Society of America, p. 437-444. 

Haq, B.U., Hardenbol, Jan. and Vail, P.R .. 1987. Chronology 

of fluctuating sea levels since the Triassic: Science, v. 235, 

no. 4793, p. 1156-1167. 

Miller, K.G., Kent, D.V., Brower, A.N., Bybell, L.M., Feigenson, M.D., Olsson, R.K., amd Poore, R.Z., 1990, EoceneOligocene sea-level changes on the New Jersey Coastal Plain 

linked to the deep-sea record: Geological Society of America 

Bulletin, v. 102. no. 3, p. 331-339. 

Mountain, G.S., and Tucholke, B.E., 1985, Mesozoic and Cenozoic geology of the U.S. Atlantic continental slope and rise, 

in Poag, C. W., ed., Geologic evolution of the United States 

Atlantic margin: New York, Van Nostrand Reinhold, 

p. 293-342. 

Olsson, R.K., Melillo, A.J., and Schreiber, B.L., 1987, Miocene 

sea level events in the Maryland Coastal Plain and the 

offshore Baltimore Canyon trough, in Ross, C.A .. and 

Haman, Drew, eds .. Timing and depositional history of 

eustatic sequences-Constraints on seismic strati.<:.:raphy: 

Cushman Foundation for Foraminiferal Research Special 

Publication No. 24, p. 85-97. 

Olsson, R.K., and Wise, S.W., Jr., 1987, Upper Paleocene to 

middle Eocene depositional sequences and hiatuses in the 

New Jersey Atlantic margin, in Ross, C.A., and Haman, 

Drew, eds., Timing and depositional history of eustatic 

sequences-Constraints on seismic stratigraphy: Cushman 

Foundation for Foraminiferal Research Special Publication 

No. 24, p. 99-112. 

Poag, C.W., 1985a, Depositional history and stratigraph~c reference section for central Baltimore Canyon trough, in Poag, 

C.W., ed., Geologic evolution of the United States Atlantic 

margin: New York, Van Nostrand Reinhold, p. 217-264. 

-ed., 1985b, Geologic evolution of the Unitec States 

Atlantic margin: New York, Van Nostrand Reinhold. 383 p. 

---1987a, The New Jersey Transect-Stratigraphic framework and depositional history of a sediment-rich passive 

margin. in Poag, C.W., Watts, A.B., and others, Initial 

reports of the Deep Sea Drilling Project, Volume 95: Washington, D.C., U.S. Government Printing Office, p. 763-817. 

---1987b, Allostratigraphy-Principles and practice on the 

U.S. Atlantic margin [abs.]: Geological Society of America 

Abstracts with Programs, v. 19, p. 807. 

---1989, Foraminiferal stratigraphy and paleoenvironments of 

Cenozoic strata cored near Haynesville, Virginia: U.S. Geological Survey Professional Paper 1489-D, 20 p. 

---in press, Rise and demise of the Bahama-Grand Banks 

gigaplatform, northern margin of the Jurassic North Atlantic 

Seaway: Marine Geology. 

Poag, C.W., and Low, Doris, 1987, Unconformable sequence 

boundaries at Deep Sea Drilling Project Site 612, Ne·JJ Jersey 

Transect-Their characteristics and stratigraphic significance, in Poag, C. W. , Watts, A.B. , and others , Initial 

reports of the Deep Sea Drilling Project, Volume 9:: Washington, D.C., U.S. Government Printing Office, p. 453-500. 

Poag, C.W., and Mountain, G.S., 1987, Late Cretaceous and 

Cenozoic evolution of the New Jersey continental slope and 

upper rise-An integration of borehole data with seismic 

reflection profiles, in Poag, C.W., Watts, A.B., and others, 

Initial reports of the Deep Sea Drilling Project, Volume 95: 

Washington, D.C., U.S. Government Printing Office, 

p. 673-724. 

Poag, C.W., and Schlee, J.S., 1984, Depositional seque1ces and 

stratigraphic gaps on submerged United States Atlantic margin. in Schlee, J .S., ed., Interregional unconform:ties and 

hydrocarbon accumulation: American Association of Petroleum Geologists Memoir 36, p. 165-182. 

Poag, C.W., and Sevon, W.D., 1989, A record of Apralachian 

denudation in postrift Mesozoic and Cenozoic sed:mentary 

deposits of the U.S. middle Atlantic continental margin: 

Geomorphology. v. 2, p. 119-157. 

17. Campanian to Quaternary Depositional Sequences, Baltimore Canyon Trough 83 
Poag, C.W., and Valentine, P.C.. 1988, Mesozoic and Cenozoic 

stratigraphy of the United States continental shelf and slope, 

in Sheridan, R.E .. and Grow, J.A .. eds., The Atlantic 

continenta] margin-U.S .. v. I-2 of The geology of North 

America: Boulder, Colo .. Geological Society of America, 

p. 67-86. 

Poag, C.W., and Ward, L.W., 1987, Cenozoic unconformities 

and depositional supersequences of North Atlantic continental margins-Testing the Vail model: Geology, v. 15, 

p. 159-162. 

Poag, C.W., Watts. A.B., and others, 1987, Initial reports of the 

Deep Sea Drilling Project, Volume 95, covering Leg 95 of 

the cruises of the Drilling Vessel Glomar Challenger, St. 

John's, Newfoundland, to Fort Lauderdale, Florida, AugustSeptember 1983: Washington, D.C.. U.S. Government Printing Office, 817 p. 

Poore, R.Z., and Bybe11, L.M., 1988, Eocene to Miocene 

biostratigraphy of New Jersey core ACGS # 4-Implications 

for regional stratigraphy: U.S. Geological Survey Bulletin 

1829, 22 p. 

Ross, C.A .. and Haman, Drew, eds., 1987, Timing and depositional history of eustatic sequences-Constraints on seismic 

stratigraphy: Cushman Foundation for Foraminiferal 

Research Special Publication No. 24, 228 p. 

Schlee, J. S., 1981, Seismic stratigraphy of Baltimore Canyon 

trough: American Association of Petroleum Geologists Bulletin, v. 65. p. 26--53. 

Sheridan, R.E., and Grow, J.A., 1988, The Atlantic continental 

margin-U.S., v. I-2 of The geology of North America: 

Boulder, Colo., Geological Society of America, 610 p. 

Tucholke, B.E., and Mountain, G.S., 1986, Tertiary paleoceanography of the western North Atlantic Ocean. in Vogt, P.R., 

and Tucholke, B.E., eds., The western North Atlantic 

region, v. M of The geology of North America: Boulder, 

Colo., Geological Society of America, p. 631-650. 

Vail, P.R., Mitchum, R.M., Jr., Todd, R.G., Widmier. J.M .. 

Thompson, S .. III, Sangree, J.B., Bubb, J.N .. and Hatlelid, 

W. G. . 1977, Seismic stratigraphy and global changes of sea 

level, in Payton, C.E., ed., Seismic stratigraphy-Applications to hydrocarbon exploration: American Association of 

Petroleum Geologists Memoir 26, p. 49-212. 

Ward, L.W., 1984. Stratigraphy of outcropping Tertiary beds 

along the Pamunkey River-Central Virginia Coastal Plain, 

in Ward, L.W., and Krafft, Kathleen, eds., ftratigraphy and 

paleontology of the outcropping Tertiary bed' in the Pamunkey River region, central Virginia Coastal Plrin-Guidebook 

for Atlantic Coastal Plain Geological Associrtion 1984 Field 

Trip: Atlantic Coastal Plain Geological Association, 

p. 11-77. 

84 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of 

Virginia 1 

By D.S. Powars,2 R.B. Mixon,2 and Scott Bruce3 

INTRODUCTION 

Since 1985, a cooperative research effort has existed 

between the U.S. Geological Survey (USGS) and the 

Virginia State Water Control Board (VA-SWCB) to drill 

and study five coreholes in the Outer Coastal Plain of 

Virginia. The locations of the five coreholes-Dismal 

Swamp, Fentress. Kiptopeke, Exmore, and Jenkins 

Bridge-and of boreholes to basement from previous 

investigations are shown in figure 18.1. All these locations 

except Exmore are V A-SWCB research stations where 

individual wells monitor each aquifer penetrated. 

The Dismal Swamp and Fentress coreholes were 

continuously cored from the surface downward into Lower 

Cretaceous strata. The Exmore corehole was continuously 

cored from the surface downward into middle Eocene strata 

dominated in the lowermost 50 ft by reworked Lower 

Cretaceous boulders. The Jenkins Bridge corehole was 

continuously cored from the surface down to 490 ft and 

from 1 ,200 to 1 ,333 ft; it bottomed in Lower Cretaceous 

strata. The Kiptopeke corehole was continously cored from 

the surface down to 1 ,330 ft, where it just reached middle 

Eocene strata similar to those penetrated in the Exmore 

corehole, and from 1,733 to 1,753 ft; it bottomed in Lower 

Cretaceous strata. 

This report is a preliminary summary of ongoing 

lithostratigraphic investigations and includes biostratigraphic data from USGS colleagues on dinoflagellates 

(Lucy E. Edwards), Foraminifera (C. Wylie Poag and 

Thomas G. Gibson), Tertiary mollusks (L.W. Ward). 

Cretaceous mollusks (Norman F. Sohl), diatoms (George 

W. Andrews), pollen (Ronald J. Litwin), and ostracodes 

(Gregory S. Gohn). This report also includes lithologic (D. 

Powars, site log) and geophysical data from corehole 

MW4-1 in the City of Chesapeake (fig. 18.1). That 

1 Prepared in cooperation with the Virginia State Water Control 

Board. 1

U.S. Geological Survey, Reston, VA 22092. 3

Virginia State Water Control Board, P.O. Box 1143, Richmond, 

VA 23230. 

corehole penetrated Cretaceous to Pleistocene strata and 

was continuously cored from 350 to 996ft depth. Th~ cored 

interval penetrated Lower Cretaceous to Miocene strata and 

is part of an aquifer storage and recovery project for the City 

of Chesapeake. 

Before these holes were drilled, knowledge of the 

subsurface of the Outer Virginia Coastal Plain was derived 

primarily from studies of water-well cuttings and geophysical logs (Cederstrom, 1945a, b; Hansen, 1967; Sinnott and 

Tibbitts, 1968; Brown and others, 1972; Cushing and 

others, 1973; Meng and Harsh, 1988). The only available 

cores were from selected intervals in the Taylor # 1 oil test 

hole and the Moores Bridge well (labeled NOR-':':'-12 in 

fig. 18. 1) and from selected intervals at a few wellf drilled 

by the VA-SWCB. 

The new core data enable us for the first time to 

establish well-defined standard sections for Virginia's Outer 

Coastal Plain, which is divided by the mouth of the 

Chesapeake Bay into two areas: the Eastern Shore and 

southeastern Virginia. Lithologic, paleontologic, and geophysical data from these coreholes are being correlated with 

data from other wells in order to define the stratigraphic and 

structural configuration of this area. 

Acknowledgments 

Special thanks are given to the drillers who rrade this 

study possible, including the USGS team of Dennis W. 

Duty and Donald G. Queen and the V A-SWCB team of 

John P. Greason and Jay A. Owens. We thank Sherman 

Stairs. manager of the Eastern Shore of Virginia National 

Wildlife Refuge; Jim Owens, manager of the Dismal 

Swamp National Wildlife Refuge; military personnel at the 

Naval Auxiliary Landing Field Fentress; Dr. Robert E. 

Baldwin, chief scientist of the Eastern Shore Agriculture 

Experiment Station; and M. Carter Davis, Jr., landowner at 

the Jenkins Bridge site, for their cooperation and access to 

their properties. Finally. Steve Schindler and Greg Gohn' s 

assistance in the scientific review was very helpful and is 

greatly appreciated. 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virginia 85 
38° 

EXPLANATI')N 

+ Corehole 

rh Borehole used in 

T compilation of 

cross secfons 

e Boreholes to 

basement from 

previous 

investigafons 

25 MILES 

I 

25 KILOMETERS 

Figure 18.1. Structure contours on the top of pre-Cretaceous basement in the Virginia Coastal Plain. Contour 

interval equals 500ft. Compiled from Brown and others (1972), Hansen and Edwards (1986), Bayer and Milici 

(1987), Wilkes and others (1989), and unpublished data of the Virginia State Water Control Board and the U.S. 

Geological Survey. 

86 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
GEOLOGIC SETTING 

As shown in figures 18. 1 and 18.2. the Outer Coastal 

Plain of Virginia includes parts of two major structural 

features: the tectonic downwarp known as the Salisbury 

embayment on the north and the Norfolk arch on the south. 

The arch and basin configuration is typical for the Atlantic 

Coastal Plain and is generally characterized by stratigraphic 

thinning or by truncation of Cretaceous and Tertiary formations across the arches. 

In cross section A-A' (fig. 18.3), the northeast flank 

of the Norfolk arch is defined by the northeast-sloping 

basement surface and the southward stratigraphic thinning 

of Cretaceous and Tertiary strata across the arch. The 

southern end of the cross section is farther west than the 

northern end and, therefore, is updip structurally. Also, the 

NOR-T-12 welL the VB-T-4 test boring and the Kiptopeke corehole (see figs. 18.1 and 18.3) are several miles 

east of the cross section line and, therefore, are downdip 

structurally. 

Cederstrom ( 1945b) postulated a fault zone that 

generally trends west from Hampton Roads along the James 

River to the Fall Line because of his interpretation that 

Eocene beds (including what we now subdivide into Paleocene and Eocene strata) abruptly thicken north of the 

James River. Our data suggest that the water-covered area 

at the mouths of Chesapeake Bay and the James River is the 

most likely place for an eastward extension of Cederstrom's 

James River-Hampton Roads fault zone; such an extension 

would help explain the wide stratigraphic variations that 

exist between the Eastern Shore of Virginia and southeastem Virginia. 

BASEMENT ROCKS 

The only test holes to reach basement along the Outer 

Coastal Plain of Virginia are the Dismal Swamp ( -1,850 

ft). the NOR-T-12 (-2,576 ft), and the Taylor #1 

( -6,028 ft). Data from these holes and from seismic, 

gravity. and magnetic surveys indicate that the basement 

consists of Precambrian, Paleozoic, and lower Mesozoic 

(Triassic) rocks. 

LOWER AND LOWER UPPER CRETACEOUS 

DEPOSITS 

The Lower Cretaceous and lower Upper Cretaceous 

beds (Potomac Formation) consist of gray to greenish-gray. 

in part mottled red, brown, and yellow. poorly sorted, fine 

to coarse, quartzose and feldspathic sand, gravel, silt. and 

clay. Clays are primarily illite-smectite, illite, montmorillonite, and kaolinite and are of fluvial-deltaic origin; 

locally, they intertongue with glauconitic sands of marine 

origin. In the Taylor #1 test hole near the northern end of 

our cross section, the Potomac Formation is 4,690 ft thick 

100 

I I 

200 MILES I 

100 200 KILOMETERS 

""'- Cape Fear Arch 

-.._Charleston Embavment 

.__ Yamacraw Arch 

- Southeast Georgia Emb.'lyment 

- South Florid<: 

Embayment 

Figure 18.2. Principal basins and arches of the U.S. Atlantic Coastal Plain. Modified from Ward and Powars (1989, 

fig. 1). 

and includes pollen zones K1, I. II, and III (Robl';ns and 

others, 1975). In contrast, the Lower Cretaceous ard lower 

Upper Cretaceous deposits to the southeast in the Dismal 

Swamp corehole are only 1,290 ft thick. In the Dismal 

Swamp hole, only pollen zone liB and a barren interval, 

which may represent zone III, were recognized in cored 

intervals (R.J. Litwin, written commun .. 1988). The presence of some or all of the older pollen zones (K1, I, and II) 

in the uncored interval in the lowermost 767 ft is likely. As 

shown in cross section A-A' (fig. 18.3), these older pollen 

zones are nearly 3,180 ft of strata in the Taylor# 1 test hole 

and. therefore, represent the largest lateral variation in 

stratal thickness among the studied lithic units. 

UPPER CRETACEOUS DEPOSITS YOUNGER 

THAN POLLEN ZONE Ill 

Upper Cretaceous deposits younger than pollen zone 

III were penetrated in the subsurface of Virginia·· 5' Eastern 

Shore and in southeastern Virginia, where they range in 

thickness from 121 ft in the Jenkins Bridge corerole (fig. 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virginia 87 
sw 

A 

Dismal 

Swamp MW4-1 NOR-T-12 VB-T-4 Kiptopeke 

IV 

barren 

liB 

liB 

K1, I, II, liB, Ill, IV =pollen zones 

0 I' r I I I I\ 1 

0 10 

10 

I 

I 

20 MILES 

I 

20 KILOMETERS 

VERTICAL EXAGGERATION x140.8 

.......... 

Exmore 

CENOZOIC 

.......... .......... .......... .......... .......... .......... .......... .......... .......... .......... 

Lower Cretaceous 

.......... .......... .......... 

NE 

A' 

Jenkins Alftude 

Bridge Taylor #1 (in feet) 

Sea level 

--300 

--600 

--900 

--1200 

IV 

Ill 

-1800 

Ill? 

-2100 

liB -2400 

.......... .......... .......... liB? -2700 

II 

-3000 

-3300 

-3600 

-3900 

-4200 

-4500 

--4800 

K1 -5100 

K1 

--5400 

-5700 

--6000 

"R? 

--6300 

Figure 18.3. Diagrammatic geologic cross section to basement, Outer Coastal Plain of Virginia. Pollen data 

for Taylor #1 from Robbins and others (1975). line of section is shown in figure 18.1. 

88 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
sw 

A 

Dismal 

Swamp MW4-1 NOR-T-12 VB-T-4 Exmore 

NE 

A' 

Jenkins Altitude 

Bridge (in feet) 

Sea level 

-300 

-600 

Calvert Formation 

Lower Cretaceous beds 

0 I I I I I I I I I 

0 10 

10 

I 

I 

20 MILES 

I 

20 KILOMETERS 

VERTICAL EXAGGERATION x149 

-900 

-1200 

-1500 

-1800 

-2100 

-2400 

-2700 

Figure 18.4. Uppermost Mesozoic and Cenozoic geologic cross section, Outer Coastal Plain of Virginia. 

GS, glauconitic sand unit; RB, red beds; Tb, Brightseat Formation; Ta, Aquia Formation; Tm, Marlboro Clay; 

Tn, Nanjemoy Formation. Line of section is shown in figure 18.1. This section shows more detail for the 

upper part of the section shown in figure 18.3. 

18.3) to 348 ft in the Fentress corehole. As can be seen in 

cross section A-A' (fig. 18.4), the Upper Cretaceous 

deposits in southeastern Virginia (upper Cenomanian beds, 

glauconitic sand unit, and red beds) are much thicker than 

those in the Eastern Shore area (upper Cenomanian and 

lower Campanian beds). 

Southeastern Virginia 

In southeastern Virginia, Upper Cretaceous deposits 

can be divided into three lithic units~ in ascending order, 

they are upper Cenomanian beds consisting of marine and 

deltaic deposits, a glauconitic sand unit, and red beds. 

These units are described below. 

Upper Cenomanian beds.-The upper Cenomanian 

beds (equivalent to the Raritan Formation of New Jersey) 

range from 150 to 200 ft in thickness and were found 

throughout the study area as the lowest lithic unit of the 

Upper Cretaceous deposits younger than pollen zone III. In 

the Fentress corehole (fig. 18.5), the bottom 50 ft of this 

lithic unit consists of two fining-upward sequences. Abundant wood fragments suggest a nearshore-shelf to deltaic 

depositional environment. At Fentress, the bas~ of the 

upper Cenomanian deposits is marked by a sharp lithic 

contact at -1,035 ft elevation, where an olive-gray to 

light-gray, micaceous, lignitic, loose, medium to very 

coarse glauconitic quartz sand sharply overlies the Potomac 

Formation, which there consists of greenish-gray, silty and 

sandy clay, which grades downward into medium t~1 coarse, 

crossbedded sand. 

In the Dismal Swamp (fig. 18.6) corehole, tb~ lowest 

upper Cenomanian deposits consist of glauconWc sands, 

which grade upward into shelly, glauconitic silt, clay, and 

sand of marine origin. The base of the upper Cenomanian is 

an erosional unconformity; dark-gray to black, clayey, 

glauconitic, phosphatic, pyritic, carbonaceous, pebbly 

quartz sand overlies and is burrowed down into the Potomac 

Formation, consisting of white to light-gray clay showing 

some yellow mottling. Within a couple of feet, the~e Lower 

Cretaceous beds grade downward into multicolored sands 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virg~nia 89 
II> 

= 

""C' 

a 

I') 

II) 

II) 

c. 

:r 

CICI 

~ 

.... 

II> 

= = c: 

VI 

~ 

VI 

~ ~ 

fiJ 

::T 

0 

"C 

0 

::I -::T 

II) 

~ II) 

0 

0 

~ 

AI 

::I 

c. 

~ 

~ ::T 

~ 

a 

0 

CICI 

'< 

0 

""" :T 

II) 

~ 

iii 

a 

r:;· 

~ 

0 

m. 

e!.. 

""C' 

iii 

:r 

>- a: 

<( 

z 

a: 

w 

1-

<( 

::J 

0 

>- a: 

<( 

i= 

a: 

w 

IFENTRESS COREHOLE 

SYSTEM LITHOSTRATIGRAPHIC UNIT FORAM LITHOLOGY ~~~T~~~~ I AND SERIES ZONES 

I Upper 

15 .. (]) 

c: t- Sea (]) 

"." .; 0 _g_ (.) 

0 Tabb Formation N23 level ';) 

'Qi 

a: . 

- ~~ 

~p_ee.!:_ Chowan River Formation(?) N21 ·-- .-,.....-·~ .. """"'='• ••••• 

,---:,;. .. . : 

Q) 

Q) 

c: I Upper I I~~~· . ~~-:. ~·:-.. f--100 (..) 

.. 2 and Yorktown Formation N18- ~ ............ · ·"""· 

a: lower N20 .. >::; ." :::; ,..·'--~ ~ 

. ""' 

~ - " '-"" '- , 

.. :.._~ ~_.:: ~ ;. -200 

-· -·- ·-· -·- .. --:-._.· ._-;::; .: ~~ 

. -·-. 

-.---

·-· -· -·- Eastover Formation N17- :__:::: ·. =- . f- -300 

NlB ·-·-

-· -· .-::-~v-~:_'-~ 

-- ·- ·- Q) 

, ___ c: 

Q) 05 ·-·-· (..) a.. -· 0 a.. ----= . --....:.. :::-: I- -400 ~ :::> :.....=--.--=--- .. __:_v _:'~_·_ 

-· -· -· - . . . ·-·-

-·-· 

---

:_---:-..:__--= 1- -500 

St .. Marys Formation I N161~ ~--= . --

. -

-· 

-

Middle ~ · · - ···- ....... · ,..,..-;.,~,...J- -soo 

Lower 

Lower 

: ~ +u~~e~ L ____ A~~~~;~·~~·~ ____ J~ 

GAMMA-RAY LOG EXPLANATION 

D 

~ 

E2J 

D . . 

D . 

. 

~ C> - ~ 

~ 

~ 

'-../ '-../ 

~ 

Clay 

Clay- silt 

Very fine to fine sand 

Medium sand 

Coarse to very coarse 

sand 

Pebbles- gravel 

Chaotic boulder bed 

Limestone 

Shells 

Turritella 

T Paleosol 

~ Shark tooth 

.::>.... Lignitic fragment 

(some wood) 
... 

:= 

c: 

"tJ 

~ 

3 

0 

~ 

s: 

~ N 

0 

r;· 

I» 

= 0.. 

~ 

~ 

= 0 

N 

0 

r;· 

~ 

~ 

0 

0 

CJCI 

r;· 

("') 

a 

~ 

V'l 

~ 

!l 

s· 

.? 

0 

c 

~ ("') 

0 

~ e!.. 

-a 

i» 

:r 

0 

-

< 

cia" 

3" 

Di" 

1.0 

... 

Glauconitic sand unit 

Upper 

Upper Cenomanian beds*** 

00 

~ 

0 

w 

u 

~ ~----------+----------------------------1 

w 

~ 

u 

Lower Potomac Formation 

"0 

Q) 

c 

0 

N 

0 

z 

-"7-~-.--· ·--:---=-

~ 

- :.-=..: ·. =--: 

~-~t~t~~;-

~...:.~-~·-~·, 

. ....,.._.~"""'~ 

-I-·-· ......... -.-. -.- 7 - .. • :-..,-.-

-800 

-900 

-1000 

-1100 

-1200 

-1300 

. __:_- >-1400 

* Woodstock Member. ** Paspotansa and Piscataway Members. *** Pollen zone IV. 

F~gure 18.5. Lithic and gamma-ray logs of the Fentress corehole. The explanation shows patterns used in figures 18.5-18.7. Total depth of the Fentress 

borehole was 2,000 ft. Coring was continuous til 1,124 ft; the lowest cored 

interval is at 1,873 ft. Lithology is shown only for cored intervals. Foraminifera 

zones P4-P20 are extrapolated from dinocyst data from L.E. Edwards (written 

commun., 1988--89) and mollusk data from L.W. Ward (oral commun., 1988); 

zones N13-N14 are from benthic Foraminifera data provided by T.G. Gibson 

(oral commun., 1990); and zones N16-N23 are extrapolated from Gibson (1983). 
I.C 

t'oJ 

~ 

a 

I") 

1'1> 

1'1> 

c.. 

:r 

~ ...... 

I.C 

= = 

c: 

til 

~ 

til 

~ 

~ 

~ 

=- 0 

"C 

0 

::l 

:;. 

1'1> 

~ 

~ 

0 

(JQ 

'< 

~ 

::l 

c.. 

~ 

~ 

=- 6. 

a 

0 

~ 

s. 

:;. 

1'1> 

:e 

~ 

;;-=-

n 

2 

fll 

[ 

~ 

~ 

:r 

DISMAL.SWAMP COREHOLE 

SYSTEM FORAM ALTITUDE~ AND SERIES LITHOSTRATIGRAPHIC UNIT ZONES LITHOLOGY (IN FEETII GAMMA-RAY LOG 

QUATERNARY L . n Pleistocene Shirley Formation N23 .. _ o 

> a: 

<( 

1· '"·-~-~ . ··~-·I - - .,...... 

~ Upper 

~ and Yorktown Formation N18-

:..: o I ower N20 I . -"' ~ _ ........ 

....... ~ ~~~~-~ 

Sea 

level 

- ..... - ..., r-loo 

I I I I ~~~--:.~;.1 

~ I ~ I Eastover Formation I ~ ->OO 

g Upper 

~ St. Marys Formation 

Eocene Lower 

''''"'"' Upp" ' ~--··' """"''"". I ~l-. . -. 1--300 1tseat Formatron Pl c - • • · ~ • ~ 

~~ .-T •. T": ~. 

Red beds -- · - • -

Upper I G Ia uconitic sand unit I l ~: :":_--~..;, ~ -~--400 

Upper Cenomanian beds*** ·- -·-soo 

-600 
.... 

?' 

c: 

"'C 

~ 

3 

0 

~ 

~ 

~ 0 

;::;· 

~ 

:I 

Q.. 

1"'1 

II) 

:I 

0 

N 

0 

;::;· 

~ II) 

0 

0 

ac 

;::;· 

1"'1 

a 

~ 

tl'l 

II) 

~ 

o· 

~:I 

0 

c 

~ 

1"'1 

0 

~ 2!.. 

., 

~ :I 

s. 

ac 

~ 

3" 

~-

1.0 

w 

(/) 

::::> 

0 

LU 

u 

~ LU 

a: 

u 

Lower 

* Potapaco Member. 

Potomac Formation 

** Paspotansa Member. 

"'0 

(I) 

c 

0 

N 

0 

z 

Figure 18.6. Lithic and gamma-ray logs of the Dismal Swamp 

corehole. See figure 18.5 for explanation. Total depth of the 

Dismal Swamp borehole was 2,000 ft. Coring was continuous 

til1 ,113ft. The lowest core was from 1,853 ft below sea level. 

Basement was hit at -1,850 ft. Foraminifera zones P1c-P5 

1 ~· /:~·-·-~;.:~r 

~ --'--800 

-900 

-1000 

-1100 

-1200 

-1300 

-1400 

*** Pollen zone IV. 

and N16 are from T.G. Gibson (oral commun., 1987); zones 

P6a and P6b are extrapolated from dinocyst data from L.E . 

Edwards (written commun., 1987); and zones N17-N23 are 

extrapolated from Gibson (1983). 
and clays, which are oxidized red, purple, brown, and 

yellow. 

In the Fentress corehole, the lowermost 50 ft of 

nearshore and deltaic deposits is overlain by 115 ft of 

laminated to thick-bedded, olive-gray to dark-gray silt, 

clay, and fine to coarse sand containing variable amounts of 

glauconite, mica, shells. microfossils, wood. burrows, and 

pyrite that overall indicate a marine origin. This section 

contains numerous fining-upward sequences, which form a 

cyclic pattern. The sandier, coarser grained beds at the 

bases of sequences are generally more glauconitic and 

shelly than the overlying sediments. Many of the sandier 

shell beds and shell hashes (representing storm deposits) are 

cemented by calcium carbonate. In the Dismal Swamp 

corehole, 128 ft of these cyclic marine beds was penetrated, 

and their former proximity to a shoreline is indicated by the 

abundance of finely disseminated lignitic material scattered 

throughout the section. The presence of the mollusks 

Inoceramus arvanus and Exogyra lvoolmani in the marine 

section indicates a late Cenomanian age (N .F. Sohl, oral 

commun., 1988) and suggests correlation with unit E of 

Brown and others (1972), sequence 2 of Gohn (1988), and 

pollen zone IV (R.J. Litwin, written commun., 1988). 

This marine unit is truncated and overlain by darkgray, very fine grained, thinly laminated, very micaceous 

clayey silt to muddy sand containing abundant wood fragments that is 21.5 ft thick in the Dismal Swamp corehole 

and 33.9 ft thick in the Fentress corehole. The very 

abundant mica imparts a greasy feel to the core and cuttings 

and enhances recognition of the unit in well cuttings. These 

characteristics suggest a deltaic-lagoonal depositional 

environment. 

Glauconitic sand unit.-The glauconitic sand unit is 

a loose sand that was found only in the Dismal Swamp and 

Fentress coreholes, where its thickness is 54.5 and 59 ft, 

respectively. The small amount of recovered core, the drill 

cuttings, and the geophysical logs indicate that most of the 

unit is fine to very coarse glauconitic quartz sand that was 

deposited in a marine environment. In the Dismal Swamp 

corehole, the basal 0. 7 ft of this unit was recovered along 

with the contact with the underlying deltaic-lagoonal beds 

that make up the top of the upper Cenomanian unit. This 

contact is an erosional unconformity where light-green to 

olive-gray, poorly sorted, pebbly, muddy sand sharply 

overlies dark-gray, finely laminated, very micaceous 

(greasy feel), lignitic clayey silt. The basal bed of the 

glauconitic sand unit contains rip-up clasts from the underlying micaceous silt. The age of this unit has not been 

determined, but it overlies strata of late Cenomanian age 

and underlies strata of Danian age~ therefore, it is latest 

Cenomanian to earliest Danian (probably pre-Danian) in 

age. 

Red beds.-The red beds, like the glauconitic sand 

unit, appear to have a limited distribution near the Norfolk 

arch axis. The thickness ranges from 53.4 ft in the Dismal 

Swamp corehole to 91.3 ft in the Fentress corehole. The 

unit consists of a wide variety of lithologies, including 

homogeneous gray and green to mottled brig~t red, purple, 

yellow, orange, and brown sections of interbedded oxidized 

clay, silty clay, silty fine sand, and pebbly coarse sand. 

Some beds contain scattered mica, carbonac~~ous material, 

wood chunks, mud cracks, and rootlets. Several horizons 

are paleosols and are generally associated with the top of a 

fining-upward sequence. The bases of the fining-upward 

sequences are generally marked by a muddy pebbly sand 

that truncates the silty or sandy clay of an underlying 

paleosol. In the Dismal Swamp corehole, the l'<~se of the red 

beds is 363ft below sea level, where a gray to multicolored, 

interbedded, micaceous clayey sand to sandy clay sharply 

overlies the glauconitic sand unit, which consists of darkgreen to gray-green, fairly well sorted, fine to coarse quartz 

sand containing small amounts of glauconite and phosphate. 

The age of the red beds has not been determir~d. but it too 

must be latest Cenomanian to earliest Danian. In this report, 

the glauconitic sand unit and red beds together are tentatively correlated with unit D of Brown and others (1972) 

and sequence 3 of Gohn ( 1988). 

Eastern Shore of Virginia 

The Upper Cretaceous section younger than pollen 

zone III is thinner in the Eastern Shore area th:m it is in the 

southeastern Virginia area. In the Eastern Sl-tore area, it 

consists of marine to deltaic deposits. In the Jenkins Bridge 

corehole, upper Cenomanian beds 73 ft thick are overlain 

by lower Campanian beds 48 ft thick (G.S. Gohn, written 

commun., 1988). Reworked marine microfauna and clasts 

of Maastrichtian age in the lower upper Eocene channel fill 

or subaqueous debris flows of the Exmore an-i Kiptopeke 

coreholes indicate that thin Maastrichtian shelf deposits are 

locally present in the Eastern Shore area. 

LOWER TERTIARY DEPOSITS 

Lower Tertiary deposits consist primaril:' of glauconitic, clayey sands and silts. Microfauna indicate Paleocene, Eocene, and Oligocene units of marin~ origin. In 

southeastern Virginia, previously unrecognized equivalents 

of the lower Paleocene Brightseat Formation, upper Paleocene Aquia Formation, upper Paleocene and lower Eocene 

Marlboro Clay, and lower Eocene Nanjemoy Formation 

were found (L.E. Edwards, T.G. Gibson, and L.W. Ward, 

written and oral commun., 1988). In this area (see cross 

section A-A', fig. 18.4), the formations are relatively thin 

and are bounded by unconformities. 

The Brightseat Formation is a muddy glauconitic 

sand only a few feet thick. It is identified only in the Dismal 

Swamp corehole on the basis of Foraminifera (T.G. Gibson), calcareous nannofossils (L.M. Bybell), arri dinoflagellates (L.E. Edwards) (figs. 18.4 and 18.6). 

94 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
The Aquia Formation ranges in thickness from 15 to 

40 ft. It consists of shelly, glauconitic sand; phosphatic 

pebbles or very coarse glauconitic quartz sand marks the 

base of the unit. Dinocysts indicate that the entire unit in the 

Dismal Swamp corehole and the upper part of the Aquia in 

the Fentress corehole are equivalent to the outcropping 

Paspotansa Member of the Aquia (L.E. Edwards, written 

commun., 1987). The brachiopod Oleneothyris harlani 

indicates that the lower part of the Aquia in the Fentress 

corehole is equivalent to the outcropping Piscataway Member (L.W. Ward, oral commun., 1988). 

The Marlboro Clay consists of 10 to 16 ft of lightgray kaolinitic clay and is gradational with the underlying 

Aquia beds. 

The Nanjemoy Formation ranges from 3.5 to 23ft in 

thickness and consists of dark-olive-gray to olive-black, 

clayey, silty, fine to coarse, glauconitic quartz sand. It has 

a sharp, burrowed contact with the underlying Marlboro 

Clay. In the Dismal Swamp corehole, the Nanjemoy Formation includes Beds A and B (defined by Ward, 1984, 

1985, and Powars, 1987) of the Potapaco Member (L.E. 

Edwards, written commun., 1988). In the Fentress corehole, the Nanjemoy Formation consists of 8 ft of clayey 

silty very fine sand of the Woodstock Member, which is 

younger than the Potapaco Member. This unit is overlain by 

15 ft of coarser glauconitic sand containing dinocysts that 

suggest a middle or late Eocene or early Oligocene age 

(L.E. Edwards, written commun., 1989). The middle and 

late Eocene dinocysts are probably reworked into lower 

Oligocene deposits. 

The lower Tertiary deposits in the Eastern Shore area 

appear to consist mainly of strata younger than those in the 

southeastern Virginia and Inner Coastal Plain areas. The 

Eastern Shore section includes lower upper Eocene, upper 

Eocene, and lower and upper Oligocene glauconitic sands 

and silts. The lower Tertiary deposits were not cored in the 

Jenkins Bridge core hole; however, well cuttings and geophysical logs suggest that they consist of glauconitic, clayey 

and silty sands and probably include upper Eocene as well 

as lower and upper Oligocene and lower Miocene(?) deposits similar to those in the Exmore corehole (figs. 18 .4 and 

18. 7). Further evidence for the presence of these units in the 

Jenkins Bridge corehole is the presence of these units to the 

north in the Hammond oil test hole (see fig. 18.1, C.W. 

Poag, written commun., 1988). 

The lower upper Eocene beds (dated on the basis of 

foraminiferal assemblages studied by C.W. Poag, oral 

commun., 1991) are herein informally named the Exmore 

beds because they were discovered in the Exmore corehole; 

they were also found in the Kiptopeke corehole. They 

consist of as much as 221 ft of gray, clayey and silty, 

glauconitic sand containing abundant clasts and reworked 

fauna and flora from Lower Cretaceous (Albian), Upper 

Cretaceous (Cenomanian, Santonian, Campanian, and 

Maastrichtian), Paleocene, and lower and lower middle 

Eocene deposits (L.E. Edwards, C.W. Poag, ani R.J. 

Litwin, written commun., 1988). The clasts become larger 

and more abundant downward in the section, where 

boulder-sized material is common. Many clasts consist of 

friable, unconsolidated material that could not have traveled 

far. These observations support an inferred origin fer these 

unusual beds as either a subaqueous channel fill or z debris 

flow at the base of a paleoshelf or fault scarp. A charnel-fill 

origin is harder to explain because the coreholes are more 

than 30 mi apart; perhaps they hit the same channel (which 

may trend north), or perhaps they penetrated two s~parate 

channels. A multiple-channel origin is supported by data 

from north and south of the Virginia study area. Poag's 

(1985) seismic-reflection data for the New Jersey ccntinental shelf, slope, and rise reveal the presence of numerous 

early, middle, and late Eocene channels along the upper rise 

and slope. These channels are within a unit that has been 

traced to the shoreline. Popenoe's (1985) seismic-reflection 

data for the North Carolina continental shelf indkate the 

presence of a large Eocene channel. 

The lower Tertiary deposits thicken southwa~d from 

129ft in the Jenkins Bridge corehole to 371ft in the Exmore 

corehole to 480 ft in the Kiptopeke corehole. This thickening to the south is due to the presence of thicker derr:>sits of 

upper Eocene deposits. This thickening and the abrupt 

thinning and truncation of these deposits at and just south of 

the mouth of Chesapeake Bay indicate deposition in a 

subbasin bounded on the south by a paleoshelf or fault 

scarp. 

The upper Eocene deposits (Chickahominy Formation) are 99ft thick in the Exmore corehole and 259ft thick 

in the Kiptopeke corehole and consist primarily of olivegray, compact, glauconitic, micaceous, clayey silt and silty 

clay, which contain abundant microfauna (enough to give a 

white-speckled appearance), abundant finely cr~rstalline 

iron sulfide, and scattered shell fragments. The lower part 

of the section coarsens downward to a very fine to fine sand 

and contains pebbles and reworked microfauna from Upper 

Cretaceous through middle Eocene deposits (L.E. Edwards 

and C.W. Poag, written commun., 1988). The contact 

between the Exmore beds and the overlying Chickahominy 

Formation appears to be gradational. 

Lower Oligocene deposits were found in the Virginia 

Coastal Plain for the first time and are, herein, informally 

referred to as the Delmarva beds. These Delma~va beds 

consist of as much as 41 ft of olive-gray to grayi'lh-olive, 

micaceous, clayey, silty, very fine, glauconitic quartz sand 

containing scattered patches of pyrite and marcasite. This 

sand contains a fairly abundant microfauna, and many 

reworked specimens from Upper Cretaceous through middle Eocene deposits are concentrated in the basal p"rt of the 

section (L.E. Edwards and C.W. Poag, written C1

'Jmmun., 

1988). These beds coarsen upward to a very fin~ to fine 

sand. The base of the Delmarva beds is markr.d by an 

erosional unconformity representing a hiatus estimated to 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virgrnia 95 
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Foraminifera zones from planktonic Foraminifera data from C.W. Poag (written commun., 1987-91). 
have lasted 0.5-8 m.y. (C.W. Poag, written commun., 

1988). 

The upper Oligocene and lower Miocene(?) deposits 

found exclusively in the Exmore corehole appear to include 

strata that are equivalent to and younger than the Oligocene(?) deposits west of Chesapeake Bay (Old Church 

Formation of Ward, 1984, 1985, and Mixon and others, 

1989). These corehole deposits consist of about 45 ft of 

dark-olive-gray to greenish-black, glauconitic and phosphatic, fine to very coarse sand containing lesser amounts of 

quartz. The sand has an olive-brown clay-silt matrix. The 

section is noncalcareous except for about the top 10 ft, 

which contains a fairly abundant microfauna. In the core, 

the sharp burrowed contact between the upper Oligocene 

and lower Miocene(?) beds and lower Oligocene beds is 

probably an erosional unconformity. Foraminifera data 

(C.W. Poag, written and oral commun, 1990) suggest that 

the lower 1 7 ft of this glauconitic and phosphatic sand is late 

early Oligocene in age and that the upper 23 ft is early 

Miocene in age. In contrast, dinocyst data (L.E. Edwards, 

written commun., 1988) indicate that the same section is 

late Oligocene in age. Except for the increase in calcareous 

material in the top 10 ft. lithically this section appears very 

homogeneous and is, therefore, defined as one unit and is 

tentatively assigned to the Old Church Formation. 

UPPER TERTIARY DEPOSITS 

The upper Tertiary deposits consist of Miocene and 

Pliocene clays, silts, and very fine to very coarse sands, are 

variably diatomaceous, glauconitic, and shelly, and contain 

some indurated beds (cemented by calcium carbonate). 

Microfauna and macrofauna indicate a marine to restrictedmarine origin. The upper Tertiary deposits (fig. 18.4) 

generally form a northeastward-thickening wedge of sediments that range in thickness from 285 ft in the Dismal 

Swamp corehole to 1,022 ft in the Jenkins Bridge corehole. 

However, in the Kiptopeke corehole, all the stratigraphic 

formations are found at their lowest elevations; this low area 

suggests a correlation (possibly structural) with the late 

early Tertiary subbasin and the eastward extension of 

Cederstrom's (1945b) James River-Hampton Roads fault 

zone. The section includes the Calvert Formation (lower 

and lower middle Miocene), the St. Marys Formation 

(upper middle and upper Miocene), the Eastover Formation 

(upper Miocene), the Yorktown Formation (lower and 

upper Pliocene), and the Chowan River Formation (upper 

Pliocene); the Calvert Formation accounts for most of the 

thickening. The Choptank Formation (middle middle Miocene), which is found west of Chesapeake Bay, appears to 

be absent from Virginia's Eastern Shore and southeastern 

Virginia. Foraminifera data (C.W. Poag, written commun., 

1990) indicate that the only lower Miocene beds are 23ft of 

glauconitic, phosphatic sand in the Exmore corehole, which 

are interpreted as the upper part of the Old Church Formation. Dinocyst data for the same beds mggest a late 

Oligocene age. 

Diatom data (G.W. Andrews, written commun., 

1987-88) and Foraminifera data (C.W. P11ag and T.G. 

Gibson, written and oral commun., 1987-89) indicate that 

the Calvert Formation throughout the section is middle 

Miocene in age. The Calvert Formation is absent from the 

Dismal Swamp corehole, is 12 ft thick in the Fentress 

corehole, thickens to 458 ft in the Kiptopeke corehole, and 

gradually thickens to 550ft in the Jenkins Bridge corehole. 

The Calvert thins abruptly at and just south of the mouth of 

Chesapeake Bay. The thicker Calvert sections contain as 

many as 10 fining-upward sequences. At th~ base of each 

sequence is a light- to dark-olive-gray, clayey and silty, 

very fine to fine sand that commonly contains medium to 

coarse sand with scattered quartz and phosphate pebbles, 

phosphate and (or) glauconitic chips and grains, and very 

sparse to abundant shells. These basal sands grade upward 

into very fine sandy clay silt and diatomite. The basal 

contacts of the sequences are generally sharp and burrowed. 

Diatoms (G.W. Andrews, written commun., 1988) indicate 

that the Calvert Formation in the Exmore corehole includes 

9ft of the Fairhaven Member, 213ft of the Plum Point Marl 

Member, and 297 ft of the Calvert Beach Member. There 

the Calvert Beach Member has more sand than the rest of 

the Calvert Formation. 

Along the line of section, the St. Marys Formation is 

the oldest Tertiary unit that extends across th~ entire study 

area and overlies older units over the Norfolk arch. In the 

Dismal Swamp corehole, Foraminifera-rich s~ndy clays of 

the St. Marys Formation (upper Miocene part) unconformably overlie glauconitic sandy limestone of the Nanjemoy 

Formation (lower Eocene) (T.G. Gibson, oral commun., 

1990). The St. Marys consists of up to 189 ft of muddy, 

very fine sand and sandy clay and silt containing scattered 

shells, fairly abundant iron sulfide, and finely disseminated 

organic material. At the northern end of the study area, the 

St. Marys is found at the same elevation in both the Exmore 

and Jenkins Bridge coreholes and can be d:vided into a 

lower clayey silty section about 60 ft thick and an upper 

sandy shelly section 100 to 129 ft thick. To the south, the 

entire section is like the lower finer grained section. An 

erosional unconformity at the base of the St. ~1arys Formation is indicated by (except in the Dismal Swamp corehole) 

shelly, poorly sorted, woody, pyritic, very fine to coarse 

sand of the St. Marys abruptly overlying olive-gray clayey 

silt of the Calvert Formation (Calvert Beach Member). 

The Eastover Formation (upper Mioc~ne) extends 

across the entire study area and ranges in thickness from 69 

ft in the Dismal Swamp corehole to 256 ft in the Kiptopeke 

corehole. The Eastover consists of dark-gray to bluish-gray 

to greenish-gray, muddy fine sand interbedd~d with finer 

and coarser grained beds. The Eastover is sparsely to 

abundantly shelly, contains some shell hashes and indurated 

beds, and is, in part, glauconitic and micaceous. Macro98 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
fauna and microfauna indicate a shallow-water, marine to 

restricted-marine depositional environment. The mollusk 

Isognomon maxi/lata is a common species and is abundant 

in the upper half of the Eastover section in the Exmore 

corehole. In the Eastern Shore area, the upper half of the 

Eastover appears to be coarser grained than the lower half 

and may represent a regressive phase. 

The Yorktown Formation (lower and lower upper 

Pliocene) extends across the entire study area except where 

it has been cut out by Pleistocene channeling, as in the 

Eastville and Exmore paleochannels (Mixon, 1985; Colman 

and Mixon, 1988; D.S. Powars and R.B. Mixon, unpub. 

data). As seen in cross section A-A' (fig. 18.4), the 

Yorktown deposits differ from all other units by having a 

nearly horizontal base along the line of section. The 

Yorktown includes bluish-gray. greenish-gray, and darkgreenish-gray, very fine to coarse sand, in part glauconitic 

and phosphatic. The formation is commonly very shelly 

(locally becoming a bioclastic sand) and contains an abundant microfauna. The sands are commonly interbedded with 

gray and blue-gray sandy and silty clay. The basal part of 

the Yorktown coarsens downward into a pebbly, glauconitic, and phosphatic quartz sand sharply overlying and 

burrowed into the underlying Eastover Formation. The 

contact is an erosional unconformity. 

The Chow an River Formation (upper Pliocene) was 

reported (Gibson, 1983) in the Moores Bridge well (labeled 

NOR-T-12 in figs. 18.1 and 18.4) at depths from about 90 

to 115 ft and consists of blue-green fossiliferous clayey fine 

sand. It is also reported (Johnson and others, 1987) locally 

only in a few borrow pits (Gomez and Yadkin pits) and in 

the subsurface of southeastern Virginia, where it is as much 

as 51 ft thick in eastern Virginia Beach. It consists of 

interbedded silty fine sand, clayey silt, and bioclastic sand. 

Exposure of the Chowan River Formation in relatively 

shallow borrow pits less than 5 mi south of the NOR-T -12 

well suggests either a steep gradient between them (possibly 

caused by structural effects) or incorrect correlation. Several whole mollusks that washed out of the Kiptopeke pilot 

hole above 200 ft have been identified by L.W. Ward 

(written commun., 1990) as restricted to the Chowan River 

Formation. They probably came from a dark-greenish-gray, 

interbedded shelly to very shelly, silty fine sand and muddy 

fine sand containing a few scattered medium to coarse 

grains; the sands are present from -48 to -72ft elevation. 

A bioclastic silty fine to medium sand found in the Fentress 

corehole from -51 to - 65 ft elevation is correlated with the 

Chowan River Formation. 

QUATERNARY DEPOSITS 

The Quaternary beds include fluvial, estuarine, 

marginal-marine, and nearshore shelf sediments deposited 

during the Pleistocene glacial-interglacial regime. The Eastville and Exmore paleochannels are Pleistocene channels. 

representing ancient Susquehanna River courses, cut during 

sea-levellowstands (glacial intervals). Erosion of th~ Eastville paleochannel is thought by Colman and Mixon ( 1988) 

to have taken place about 150,000 yr ago. These workers 

report that the Exmore paleochannel was incised around 250 

Ma or, possibly, 450 Ma; these dates are based, respectively, on uranium-series and amino-acid-racemization data 

of Mixon and others (1982), Szabo (1985), and Wehniller 

and others (1988). The Eastville and Exmore paleoc'l.annel 

fills are transgressive sequences consisting, from bottom to 

top, of coarse fluvial gravel and sand, estuarine muds, and 

lower estuarine to open-bay sand and sandy mud t'lat are 

shelly in part. The channel fills are overlain by nearshoreshelf and barrier-spit deposits representing deposition during interglacial high stands. See Mixon ( 1985) and Mixon 

and Po wars ( 1985) for a more comprehensive study of the 

uppermost Cenozoic deposits in the Eastern Shore r'"ea. 

CONCLUSIONS 

1. Our new data indicate that both Virginia's Eastern Shore 

and the southeastern Virginia area appear to have undergone subsidence during the Early Cretaceous (Albian) 

and early Late Cretaceous (late Cenomanian) ard relative subsidence during at least part of Paleocene, 

Eocene, Oligocene, Miocene, and Pliocene tim~. 

2. The Upper Cretaceous and Tertiary strata in the Outer 

Coastal Plain of Virginia record a complex depositional, 

erosional, and tectonic history for the northward transition from the Norfolk arch to the Salisbury embryment. 

A zone of abrupt thinning and truncation of Upper 

Cretaceous and Tertiary formations at and just south of 

the mouth of Chesapeake Bay may be fault controlled. 

3. Thick Upper Cretaceous strata of marine and fluvialdeltaic origin are truncated northward across the mouth 

of Chesapeake Bay. The Upper Cretaceous marine and 

deltaic beds younger than pollen zone III (uppe~ Cenomanian beds, equivalent to Raritan Formation of New 

Jersey) are widespread and are as much as 200ft thick in 

southeastern Virginia. They overlie the Potomac Formation, which contains a barren pollen interval (possibly 

equivalent to pollen zone Ill) that overlies several 

hundred feet of strata that contain zone II pollen. In 

contrast, at the northern end of the Eastern Shore of 

Virginia in the Jenkins Bridge corehole, the upper 

Cenomanian beds are only 73ft thick and are ov~rlain by 

48 ft of lower Campanian marine deposits. 

4. In southeastern Virginia, red beds (paleosols) as much as 

100ft thick and glauconitic sands as much as 60ft thick 

are found between Upper Cretaceous beds of rrarine to 

deltaic origin and Danian beds (Brightseat Formation). 

Extensive development of these red paleosols O'l Cretaceous units indicates that the Norfolk arch area in 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virgirra 99 
southeastern Virginia underwent relative uplift and prolonged subaerial exposure during some of the time after 

the late Cenomanian and before the Danian. 

5. Thin remnants of Paleocene beds (the Brightseat and 

Aquia Formations and the lower part of the Marlboro 

Clay) and lower Eocene beds (the upper part of the 

Marlboro Clay and the Nanjemoy Formation) are present 

farther southward (as far south as the Dismal Swamp 

corehole) than was previously recognized. 

6. In the southern and central part of Virginia's Eastern 

Shore, the Tertiary section includes previously undescribed lower upper Eocene beds that contain abundant 

cobble- to boulder-sized clasts and reworked Foraminifera and dinocysts from older Paleogene and Cretaceous 

strata. These beds appear to represent multiple paleochannel fills or an extensive subaqueous debris flow as 

much as 221 ft thick. These strata truncate older Paleogene and Cretaceous units. The lower upper Eocene 

deposits are conformably overlain by very fossiliferous 

upper Eocene shelf deposits as much as 257 ft thick. 

Both units thicken toward the southern tip of the Eastern 

Shore and are truncated across the mouth of Chesapeake 

Bay; the truncation suggests a subbasin bounded on the 

south by a shallow paleoshelf and (or) a fault scarp. 

7. The upper Eocene deposits are overlain by previously 

undescribed lower and upper Oligocene and lower Miocene(?) glauconitic sands as much as 86 ft thick. The 

lower and upper Oligocene and lower Miocene(?) deposits are truncated southward near the southern end of the 

Eastern Shore. However, a couple of feet of the lower 

Oligocene unit is present in the Kiptopeke corehole, and 

15 ft is present in the Fentress corehole; thus, the unit is 

present only along the coast. 

8. The middle Miocene part of the Calvert Formation 

thickens abruptly northward across the mouth of Chesapeake Bay and maintains a thickness of about 500 ft 

across the northern part of the study area; this thickness 

suggests substantial subsidence of the Eastern Shore area 

during this time. 

9. The middle and upper Miocene St. Marys Formation is 

the oldest unit to extend across the entire study area and 

is overlain by the upper Miocene Eastover Formation. 

Lower and lower upper Pliocene marine deposits extend 

uniformly across the entire area, exhibiting little or no 

tilting between arch and basin areas, and are overlain, 

and locally deeply incised, by Quaternary deposits of 

fluvial to marine origin. 

REFERENCES CITED 

Bayer, K.C., and Milici, R.C., 1987, Geology and petroleum 

potential of Mesozoic and Cenozoic rocks, offshore Virginia: 

Virginia Division of Mineral Resources Publication 73, 

pt. D, 111 p. 

Brown, P.M., Miller, J.A., and Swain, F.M., 1972, Structural 

and stratigraphic framework, and spatial di~tribution of permeability of the Atlantic Coastal Plain, N')rth Carolina to 

New York: U.S. Geological Survey Profess:onal Paper 796, 

79 p. 

Cederstrom, D.J., 1945a, Geology and ground-water resources of 

the Coastal Plain in southeastern Virginia: Virginia Geological Survey Bulletin 63, 379 p. 

---1945b, Structural geology of southeastern Virginia: American Association of Petroleum Geologists Bulletin, v. 29, 

no. 1, p. 71-95. 

Colman, S.M .. and Mixon, R.B., 1988, The record of major 

Quaternary sea-level changes in a large coastal plain estuary, 

Chesapeake Bay, Eastern United States: Palaeogeography. 

Palaeoclimatology, Palaeoecology, v. 68, p. 99-116. 

Cushing, E.M., Kantrowitz, I.H., and Taylor, K.R., 1973, Water 

resources of the Delmarva Peninsula: U.S. Geological Survey 

Professional Paper 822. 58 p. 

Gibson, T.G., 1983, Stratigraphy of Miocene through lower 

Pleistocene strata of the United States central Atlantic Coastal 

Plain, in Ray, C.E .. ed., Geology and pale!ntology of the 

Lee Creek mine, North Carolina, I: Smithsonian Contributions to Paleobiology, no. 53, p. 35-80. 

Gohn, G.S., 1988, Late Mesozoic and early Cenowic geology of 

the Atlantic Coastal Plain-North Carolina to Florida, in 

Sheridan, R.E., and Grow, J .A .. eds., The Atlantic continental margin-U.S., v. I-2, of The geology of North 

America: Boulder, Colo., Geological Society of America, 

p. 107-130. 

Hansen, H.J., 1967, Hydrogeologic data from tl ~ Janes Island 

State Park test well (1,514 feet), Somerset County, Maryland: Maryland Geological Survey Basic Data Report 3, 24 p. 

Hansen, H.J .. and Edwards, Jonathan, Jr., 1986, The lithology 

and distribution of pre-Cretaceous basement rocks beneath 

the Maryland Coastal Plain: Maryland Geo10gical Survey 

Report of Investigations 44, 27 p. 

Johnson, G.H .. Ward, L.W., and Peebles, P.C.. 1987, Stratigraphy and paleontology of Pliocene and Pleistoc~ne deposits of 

southeastern Virginia, in Whittecar, G.R., e1., Geological 

excursions in Virginia and North Carolina: Norfolk, Va., Old 

Dominion University, Department of Geolog-ical Sciences, 

p. 189-218. 

Meng, A.A., III, and Harsh, J.F., 1988, Hydrog,~ologic framework of the Virginia Coastal Plain: U.S. Geo10gical Survey 

Professional Paper 1404-C, 82 p. 

Mixon, R.B .. 1985, Stratigraphic and geomorphic framework of 

uppermost Cenozoic deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological Survey 

Professional Paper 1067-G, 53 p. 

Mixon, R.B., and Powars, D.S., 1985, Middle Pleistocene 

depositional environments and facies sequenc~s, Accomack 

barrier complex, southern Delmarva Penins1.lla, Virginia: 

American Association of Petroleum Geologists, Eastern Section, Annual Meeting, Guidebook for Field Trip 2, 45 p. 

Mixon, R.B., Powars, D.S., Ward, L.W., and An-trews, G.W., 

1989, Lithostratigraphy and molluscan and diat')m biostratigraphy of the Haynesville cores-Outer Corstal Plain of 

Virginia, Chapter A of Mixon, R.B., ed., Geology and 

1 00 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
paleontology of the Haynesville cores-Northeastern Virginia Coastal Plain: U.S. Geological Survey Professional 

Paper 1489, 48 p. 

Mixon, R.B., Szabo, B.J., and Owens. J.P .. 1982, Uraniumseries dating of mollusks and corals, and age of Pleistocene 

deposits, Chesapeake Bay area, Virginia and Maryland: U.S. 

Geological Survey Professional Paper 1067-E, 18 p. 

Poag, C. W., 1985, Depositional history and stratigraphic reference section for central Baltimore Canyon trough. in Poag, 

C.W., ed., Geologic evolution of the United States Atlantic 

margin: New York, Van Nostrand Reinhold, p. 217-264. 

Popenoe. Peter, 1985, Cenozoic depositional and structural history of the North Carolina margin from seismic-stratigraphic 

analyses. in Poag, C.W .. ed .. Geologic evolution of the 

United States Atlantic margin: New York, Van Nostrand 

Reinhold, p. 125-187. 

Powars, D.S., 1987, Geology of the King George quadrangle, 

King George County, Virginia and a brief discussion of the 

regional stratigraphy and structure: Washington, D.C., 

George Washington University, M.S. thesis, 194 p. 

Robbins, E.l., Perry, W.J., Jr., and Doyle, J.A., 1975, Palynological and stratigraphic investigations of four deep wells in 

the Salisbury embayment of the Atlantic Coastal Plain: U.S. 

Geological Survey Open-File Report 75-307, 120 p. 

Sinnott, Allen, and Tibbitts, G.C., Jr.. 1968, Ground-water 

resources of Accomack and Northampton Counties, Virginia: 

Virginia Division of Mineral Resources, Mineral Resources 

Report 9, 113 p. 

Szabo, B.J., 1985, Uranium-series dating of fossil corals from 

marine sediments of southeastern United States Atlantic 

Coastal Plain: Geological Society of America Bulletir, v. 96, 

no. 3, p. 398-406. 

Ward, L.W., 1984, Stratigraphy and molluscan assembJages of 

the Pamunkey and Chesapeake Groups. upper Potomac 

River, in Frederiksen, N.O., and Krafft, Kathleen, eds., 

Cretaceous and Tertiary stratigraphy, paleontolo,r:y. and 

structure, southwestern Maryland and northeastern Virginia. 

Field trip volume and guidebook [for field trip held Oct. 17. 

1984]: Reston, Va., American Association of Strafgraphic 

Palynologists, p. 3-77. 

---1985, Stratigraphy and characteristic mollusks of the 

Pamunkey Group (lower Tertiary) and the Old Church 

Formation of the Chesapeake Group-Virginia Coastal Plain: 

U.S. Geological Survey Professional Paper 1346, 78 p. 

Ward, L.W., and Powars, D.S., 1989, Tertiary stratigraryhy and 

paleontology, Chesapeake Bay region, Virginia and Maryland, Field Trip Guidebook T216 for the 28th International 

Geological Congress: Washington. D.C., American Geophysical Union, 64 p. 

Wehmiller, J.F .. Belknap, D.F., Boutin, B.S., Mirecki. J.E., 

Rahim, S.D .. and York, L.L., 1988, A review of tre amino 

stratigraphy of Quaternary mollusks from United States 

Atlantic Coastal Plain sites: Geological Society of America 

Special Paper 227, p. 69-110. 

Wilkes, G.P., Johnson, S.S., and Milici, R.C .. 1989, Exposed 

and inferred early Mesozoic basins onshore and offshore, 

Virginia, gravity and aeromagnetic maps: Virginia Division 

of Mineral Resources Publication 94, scale 1:500,010. 

18. Uppermost Mesozoic and Cenozoic Geologic Cross Section, Outer Coastal Plain of Virgin:.'\ 101 

19. Stratigraphic and Structural Controls on Ground-Water Flow in the Coastal Plain 

Aquifers, North-Central Charles County, Maryland1 

By john M. Wilson,2 William B. Fleck/ Lucy McCartan,4 Laurel M. Bybell,4 George W. Andrewf ,

4 and 

Gilbert J. Brenner5 

INTRODUCTION 

Erosional truncation, facies changes, and sediment 

overlap control the hydrostratigraphic relations among the 

aquifers that supply ground water to the Waldorf area of 

Charles County, Md. Deformation of the Coastal Plain 

aquifers by faulting associated with the Brandywine fault 

system may also, in part, control the availability and flow of 

ground water in north-central Charles County. 

Waldorf lies in the north-central part of Charles 

County, Md., about 15 mi southeast of Washington, D.C. 

(fig. 19.1). The term "'Waldorf area" as used here defines an 

area within about a 5-mi radius of the center of Waldorf. 

The Maryland Geological Survey and the Water 

Resources and Geologic Divisions of the U.S. Geological 

Survey (USGS) have recently engaged in several cooperative research efforts in southern Maryland. This paper 

draws upon data gathered and results obtained from the 

following cooperative projects: a study of the hydrogeology 

and water-supply potential of the aquifers in the Waldorf 

area of Charles County, the drilling and analysis of a 

stratigraphic corehole in Waldorf, and the mapping of the 

surficial geology of Charles County. 

The hydrogeologic framework and a conceptual 

model of the aquifers at Waldorf were developed on the 

basis of local and regional stratigraphic and structural 

relations among the formations and aquifers. Lithologic 

data, geophysical logs. and micropaleontological analyses 

of cores were used to correlate the aquifer and formational 

boundaries in the subsurface. The hydrogeologic framework was the "architectural blueprint" used to construct the 

digital ground-water-flow model of the aquifers in the 

Waldorf area. The physical relations and hydraulic proper1

Prepared in cooperation with the Maryland Geological Survey. 2

Maryland Geological Survey, Baltimore, MD 21218. 3

U.S. Geological Survey, Towson, MD 21204. 4

U.S. Geological Survey. Reston, VA 22092. 5

Department of Geosciences, State University of New York, New 

Paltz, NY 12561. 

ties of the aquifers were represented numerically. These 

numerical values were input to the ground-wat~~r-flowmodel computer code written by McDonald and Harbaugh 

(1984). The flow model incorporates seven layers to simulate the seven water-bearing units that lie above the Lower 

Cretaceous Arundel Formation at Waldorf. The mcdel was 

calibrated for transient conditions from 1900 to 1985 by 

15 MILES 

I I I 

I I 0 1 5 KILOMETER'3 

EXPLANATION 

Trace of major reverse fault. 

dashed where inferred. 

U is upthrown block, 

D is downthrown block. 

• Observation well CH Be 43 

Figure 19.1. Trace of major reverse fau It within the 

Brandywine fault system in Prince Georges and Charles 

Counties, Md. 

19. Controls on Ground-Water Flow in Coastal Plain Aquifers, Charles County, Marylarri 103 
----- CALVERT 

---

- ----- NANJEMOY 

. . .....--_--_ ... . ~---

... . . : . . ---·. 

. · .!...- • ·--.. --.- .· .. 

. ---. . . 

NOT TO SCALE 

-==----

MAGOTHY 

EXPLANATION 

Unconformity 

Conformable contact 

~ -~_-Facies change 

-=- --= Clay 

·: :.:·.:.:: : Sand ... 

_ -~Confining unit 

:.;;__--====--

I Waldorf aquifer 

system 

.. : .. ::::Aquifer ....... 

Figure 19.2. Stratigraphic relations among the formations, aquifers, and confining units in the Waldorf area of Charles 

County, Md. Effects of faulting are not shown. 

comparison of simulated water levels with about 130 

hydrographs for observation wells throughout southern 

Maryland. 

STRATIGRAPHIC RELATIONS AND THEIR 

SIMULATION 

The two major hydrologic units that supply the 

Waldorf area's water needs are the Waldorf and the La Plata 

aquifer systems (fig. 19.2). The stratigraphically higher of 

the two aquifer systems is the Waldorf, which consists of 

three hydraulically connected aquifers. The uppermost 

aquifer of this system-the Monmouth-consists of a 

coarse quartz sand that probably is a nearshore facies of the 

marine, Upper Cretaceous Severn Formation. The middle 

aquifer-the Magothy-is a sand facies of tl'~ eastwardthickening, fluviomarine, Upper Cretaceous M.agothy Formation. The basal aquifer of the syste""l-the St. 

Charles-consists of sands within the fluviode1taic, Lower 

to Upper Cretaceous Patapsco Formadon. The name "Waldorf aquifer system" (Wilson, 1986), as used in this paper, 

104 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
refers to the Monmouth, Magothy, and St. Charles aquifers 

only within about a 5-mi radius of Waldorf. A relatively 

minor aquifer-the White Plains-underlies the St. Charles 

and overlies the La Plata aquifer system in the Waldorf area 

(fig. 19.2). 

Marine transgressions during the Late Cretaceous 

resulted in (1) erosional truncation of the Patapsco Formation and deposition of the overlying Magothy Formation 

and (2) erosional truncation of the Magothy Formation and 

deposition of the overlying Severn Formation. This beveling of underlying formations formed thin and leaky confining units and sand-on-sand contacts among the aquifers that 

compose the Waldorf aquifer system. Within 5 mi to the 

west and south of Waldorf, the Magothy and Severn 

Formations are completely eroded, and Paleocene sediments of the Brightseat and Aquia Formations overlap the 

Patapsco Formation. 

The three aquifers of the Waldorf aquifer system were 

modeled as three separate model layers. High leakance 

values were used to simulate breaches in the confining units 

of the Waldorf aquifer system. The hydraulic connections 

among these aquifers result in transmissivities greater than 

10,500 ft2/d (feet squared per day) in parts of the Waldorf 

area for the full thickness of the Waldorf aquifer system. 

The hydrologic boundaries formed by erosional truncation 

of the aquifers that make up the Waldorf aquifer system 

were simulated with no-flow conditions. 

The La Plata aquifer system is an interconnected 

series of fluviodeltaic sands within the lower part of the 

Patapsco Formation at Waldorf. These sands are separated 

by confining units that differ areally in thickness and 

effectiveness as confining units. In contrast to the Waldorf 

aquifer system, however, the La Plata aquifer system was 

modeled as a single layer. A northeastward trend of 

increasing sand thickness within the Patapsco Formation in 

southern Maryland is the result of facies changes within the 

Patapsco Formation (Hansen, 1969). As part of this trend, 

sand thicknesses of the La Plata aquifer system show a 

significant increase from the southern to the northern parts 

of the Waldorf area, and, as a consequence, transmissivities 

increase from less than 500 ft2

/d to greater than 3,000 ft2/d 

northeastward through the Waldorf area. In this paper, the 

name "La Plata aquifer system'' refers only to the lower 

Patapsco aquifers present in north-central Charles and 

southern Prince Georges Counties, Md. 

STRUCTURAL CONTROLS AND THEIR 

SIMULATION 

Stratigraphic correlations show that a northeaststriking series of en echelon faults, the Brandywine fault 

system (Jacobeen, 1972), extends through central Charles 

County. Mixon and Newell (1977) and Mixon and Powars 

( 1984) attributed the origin of the Brandywine fault system 

to reversal of movement, in response to regional co'llpressional stress, along a preexisting zone of crustal Wt'akness 

that was probably associated with a normal fault along the 

western edge of an extensive Triassic-Jurassic(?) basin. 

Faulting occurred during the Cretaceous, Paleocene. 

Eocene, and possibly later times. 

A major fault that strikes northeast through the 

western part of Waldorf (fig. 19.1) is most likely a 

continuation of J acobeen' s (1972) Danville fault. which is 

part of the Brandywine fault system. Like the Ganville 

fault, this fault is interpreted as an up-to-the-east, highangle reverse fault having as much as 250 ft of throw at the 

pre-Cretaceous basement. Seismic sections by Jacobeen 

(1972) show probable bed offsets extending up through the 

lower part of the Patapsco Formation. Folding is apparently 

the dominant structural effect of the basement faulting on 

the upper part of the Patapsco, the Magothy and Severn 

Formations, and the pre-Miocene (pre-Calvert) Tertiary 

formations. Additional subsurface faults associated with the 

Brandywine fault system-two northeast-trending and two 

east-trending faults-have been identified in northern 

Charles and southern Prince Georges Counties ty Lucy 

McCartan. 

Calibration of the digital ground-water-flow nodel of 

the Waldorf area was improved by lowering the transmissivity (aquifer thickness times horizontal hydraulic conductivity) of the aquifers in a narrow row of model cells that 

coincide with the trace of a major fault within the Brandywine fault system (fig. 19.3). The model transmissivities 

along the trace of this fault are 50 to 90 percent less than the 

values in the adjacent model cells. Either the aquifer 

thickness or horizontal hydraulic conductivity must be 

reduced to lower transmissivity. The following fault-related 

mechanisms could possibly lower aquifer transmi~sivity. 

Partial or total offset of sand beds along fault planes 

may impede the regional flow of ground water. Stratigraphic correlations and seismic sections (Jacobeen, 1972; 

Potomac Electric Power Company, 1973) indicate that bed 

offsets within the La Plata aquifer system are likely. Bed 

offsets may juxtapose aquifers and confining units; this 

juxtaposition would form at least a partial hydraulic barrier 

within the aquifer system that is equivalent to a major and 

rapid facies change in the aquifer. Hansen ( 1971) r0ted that 

a facies change that occurs over a short distance can 

constitute a hydrogeologic barrier that impedes th~ flow of 

recharge from the updip regions of an aquifer. 

Bed offsets in the aquifers that compose the Waldorf 

aquifer system are possible, but they are not as likely as bed 

offsets in the stratigraphically lower La Plata aquifer system. Outcrops of both the Nanjemoy Formation and Marlboro Clay in Charles County show faults (J.D. Glaser, 

Maryland Geological Survey, oral commun., 1988). Also, 

Dryden ( 1932) described possible faults in outcrC'':>S of the 

Pliocene upland deposits near the town of Upper 1 /farlboro. 

19. Controls on Ground-Water Flow in Coastal Plain Aquifers, Charles County, Maryla"~d 105 
_J 

w 

> 30 

w 

_J 

<( 20 

w 

()) 

.5 

0 10 

_J 

w 

co 0 0 

z 

<( 

-10 w 

> 

0 

co -20 <( 

fw 

w -30 t..... 

~ 

w -40 

0 

::::> 

t:: -50 f-

_J 1974 <( 

0 

76 78 80 82 84 

YEAR 

1986 

EXPLANATION 

+ Water levels calculated by flow mod€1 prior to 

lowering transmissivities along fault trace. 

o Water levels calculated by flow mode' after 

lowering transmissivities along fault trace. 

Water-level record from observation well CH Be 43 

(Magothy aquifer) 

Figure 19.3. Comparison of model-calculated water levels and hydrograph from well CH Be 43, which is screened in the 

Magothy aquifer. The well location is shown in figure 19.1. 

Two possible effects of faulting that could reduce 

aquifer thickness and cause reduced aquifer transmissivity 

are postdepositional erosion of upthrown areas or control of 

sedimentation patterns by faulting during deposition. The 

drill-hole data currently available are not sufficient to 

document any fault-related aquifer thinning. Near the 

boundary between Charles County and Prince Georges 

County, however, the Nanjemoy Formation thins by as 

much as 70 ft on the upthrown side of the fault shown in 

figure 19.1 relative to the downthrown side. 

Compaction of sediments caused by faulting may 

reduce an aquifer's hydraulic conductivity by decreasing 

aquifer porosity. Some soft-sediment deformation and consequent alteration of aquifer fabric are probable within these 

faulted Coastal Plain sediments. Permeability tests of cores 

would be needed to quantify any effect of faulting on 

hydraulic conductivity. 

CONCLUSIONS 

Erosional truncation, sediment overlap, and facies 

changes among and within formations are key factors 

governing the flow and availability of ground water in the 

mid-Atlantic Coastal Plain aquifers. In the Waldorf area, 

these processes have resulted in a stratigraphically complex 

aquifer system-the Waldorf aquifer system-that consists 

of hydraulically connected sands in three different formations. Additionally, regional facies changes have significantly increased sand thickness and, consequently, transmissivity in the La Plata aquifer system at Waldorf. 

Faulting of Coastal Plain sediments has the potential 

to affect aquifer transmissivity and influence ground-water 

flow by several processes. A hydraulic barrier may be 

formed by complete or partial juxtapositior of aquifers 

against confining units. Such a barrier is like1

y to exist in 

the La Plata aquifer system at Waldorf and is a possibility in 

the stratigraphically higher Waldorf aquifer system. Other 

possible causes of lowered transmissivity inc1ude thinning 

of aquifers as a result of fault-controlled s~dimentation 

patterns or postdepositional erosion of uplifted blocks. 

Additionally, soft-sediment deformation and compaction of 

an aquifer during faulting may reduce trans11issivity by 

lowering hydraulic conductivity through reduc+ion of aquifer porosity. 

REFERENCES CITED 

Dryden, A.L., Jr., 1932, Faults and joints in the Ccastal Plain of 

Maryland: Washington Academy of Sciences Journal. v. 22, 

nos. 16. 17, p. 469-472. 

Hansen, H.J., 1969, Depositional environments of subsurface 

Potomac Group in southern Maryland: Ameri~an Association of Petroleum Geologists Bulletin, v. 53, no. 9, 

p. 1923-1937. 

---1971, Common stratigraphic boundaries associated with 

Coastal Plain aquifers: Ground Water, v. 9. no. 1, p. 5-12. 

Jacobeen, F.H., Jr.. 1972, Seismic evidence for high angle 

reverse faulting in the Coastal Plain of Prince Georges and 

Charles Counties. Maryland: Maryland Geolo~ical Survey 

Information Circular 13, 21 p. 

McDonald, M.G .. and Harbaugh, A.W .. 1984, A m':ldular threedimensional finite-difference ground-water flow model: U.S. 

Geological Survey Open-File Report 83-875, 528 p. 

Mixon, R.B., and Newell. W.L., 1977, Stafford fa'Jlt systemStructures documenting Cretaceous and Tertiary deformation 

106 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
along the Fall Line in northeastern Virginia: Geology, 

v. 5, no. 7, p. 437-440. 

Mixon, R.B., and Powars, D.S., 1984, Folds and faults in the 

Inner Coastal Plain of Virginia and Maryland-Their effect 

on distribution and thickness of Tertiary rock units and local 

geomorphic history, in Frederiksen, N.O., and Krafft, Kathleen, eds., Cretaceous and Tertiary stratigraphy, paleontology, and structure, southwestern Maryland and northeastern 

Virginia, Field Trip Volume and Guidebook [for field trip 

held Oct. 17, 1984]: Reston, Va., American Assoc~ation of 

Stratigraphic Palynologists, p. 112-113. 

Potomac Electric Power Company, 1973, Prelimina_r:r safety 

analysis report, Douglas Point Nuclear Generating Station, 

Units 1 and 2: Washington, D.C., v. 2, chapter 2.5, Geology 

and seismology, 150 p. 

Wilson, J.M., 1986, Stratigraphy, hydrogeology, and water 

chemistry of the Cretaceous aquifers of the Waldorf1La Plata 

area, Charles County, Maryland: Maryland Geolog~r.al Survey Open-File Report 86--02-2, 66 p. 

19. Controls on Ground-Water Flow in Coastal Plain Aquifers, Charles County, Maryla..,.d 107 

Southeastern Coastal Plains 

20. Lithologic Changes in Fluvial to Marine Depositional Systems in Paleogene Strata of 

Georgia and Alabama 

By Thomas G. Gibson 1 

INTRODUCTION 

Most studies of Paleogene strata of the eastern Gulf of 

Mexico Coastal Plain have concentrated on west -central and 

western Alabama (Copeland, 1966; Jones, 1967; Toulmin, 

1977) where the pioneering work by Smith, Johnson, and 

Langdon (1894) established many of the stratigraphic units. 

As part of the 1894 study, Langdon recognized some of 

their units along river sections in eastern Alabama. Little 

subsequent work was done in the Paleogene strata of eastern 

Alabama and westernmost Georgia until the study by 

Toulmin and LaMoreaux ( 1963). They considered the strata 

in eastern Alabama and western Georgia as a connecting 

link between the Gulf of Mexico and Atlantic Coastal Plains 

and recognized in the Chattahoochee River valley most of 

the stratigraphic units found farther west in Alabama. 

Shortly thereafter, Newton ( 1965, 1968) published maps of 

two of the counties in eastern Alabama along the Chattahoochee River. I began mapping Paleocene to middle 

Eocene strata from western Georgia (west of the Flint 

River) to eastern Alabama (east of the Pea River) in 1977 

and continued through 1982. 

Relatively high elevations of 500 to 650 ft are found 

in the Paleogene outcrop belt of eastern Alabama and 

western Georgia. Dissection by the Chattahoochee River 

and its tributaries, here flowing at elevations slightly above 

100ft, has resulted in high relief along the drainage system. 

The Paleogene strata have a southward dip of around 20-30 

ft/mi; this gentle dip combined with the high relief results in 

an outstanding series of north-south exposures of each 

formation along about 30 mi. As the wide outcrop belt was 

in the transition area from marginal-marine to open-marine 

environments during the Paleogene, the change from nonmarine or marginal-marine sediments to open-marine facies 

is present in many of the formations. Furthermore, the 

larger outcrops may expose more than 90 ft of section in an 

area where the formations are generally less than 100 ft 

1 U.S. Geological Survey. Reston. VA 22092. 

thick. Thus, several formational contacts may b~ seen 

within a single outcrop, and these exposures are a considerable aid in tracing lithologic changes. I used a U.S. 

Geological Survey (USGS) drilling rig equipped to take 

continuous cores in some critical locations in my mapping 

area in western Georgia and eastern Alabama during 1979 

to 1982. The drill cores, commonly obtained in locations 

just downbasin from the outcrop exposures of a particular 

formation, were used to augment the outcrop sections. The 

coreholes usually penetrated through several formations and 

yielded a more complete thickness of some lithofacies and 

also better preserved paleontologic materials. 

This paper summarizes the facies changes in nine 

formations; some of these changes were previously documented (Gibson, 1980, 1982a, b, c; Bybell and Gibson, 

1985). As the facies changes typically involve the transition 

from marginal-marine environments in the north to openmarine environments in the south, I can locate the approximate present position and elevation of the shorelines for 

each Paleogene unit and note differences in their kr:ations. 

Acknowledgments 

Laurel M. Bybell (USGS) helped greatly by providing calcareous nannofossil biostratigraphic data. I b~nefited 

from stimulating discussions with Juergen Reinhardt 

(USGS) on sedimentary structures and their use in paleoenvironmental interpretation. 

FACIES CHANGES AND SHORELINE 

LOCATIONS 

The study area extends from Clayton, Ala., on the 

northwest and Elba on the west to Blakely, Ga., on the 

southeast (fig. 20.1). Seven stratigraphic intervals containing nine formations were studied in this area (fig. 20.2). 

The Clayton Formation consists of marine facies over much 

of this area and contains marginal-marine stratr only at 

high elevations near its northernmost outcrops. Limited 

20. Lithologic Changes in Fluvial to Marine Depositional Systems in Paleogene Strata of Georgia and Alabama 1 09 
A L 

N 

r 0 

I 

0 

A 

6 

I 

I 

10 

12 

I 

I 

20 

M 

• Clayton 

Baker • 

A 

• Ozark 

MILES 

KILOMETERS 

· Fort 

Gaines 

Blakely 

<( • 

(!) 

0: 

0 

w 

(!) 

Figure 20.1. Chattahoochee River valley and surrounding study area in Alabama and Georgia. 

exposures of the Porters Creek Formation are found only in 

upbasin localities and contain only marine facies; limited 

exposures of the Naheola Formation are found only in 

downbasin localities and contain only marginal-marine 

facies. The Nanafalia Formation contains marine facies. 

and its updip equivalent, the Baker Hill Formation, contains 

mostly marginal-marine facies. The Tuscahoma Formation 

is composed largely of marginal-marine facies except for 

one extensive marine sequence at the base. The Bashi 

Formation contains marine facies, and its updip equivalent, 

the Hatchetigbee Formation, contains mostly marginalmarine facies. The Tallahatta Formation contains both 

marine and marginal-marine facies. 

The lithologies of the Paleogene units vary because of 

differences in the depositional environments in which they 

formed and also because of differences in the rate of supply 

of clastic sediments into the basin. Carbonate sediments are 

dominant in shallow-marine facies of the Clayton Formation: they were deposited during the early Paleocene when 

little clastic material was supplied to eastern Alabama. 

Carbonate sediments are essentially absent, however, from 

outcrop sections of the middle and upper Paleocene and 

lower Eocene units; these units were deposited when larger 

amounts of clastic material were supplied through deltaic 

input. Glauconitic sediments are common in the marine 

parts of the Tuscahoma Formation and throughout the 

Nanafalia and Bashi. Clay is the dominant clastic sediment 

in the Baker Hill Formation; it was deposited in marginalmarine environments. The fine sands of tre Bashi and 

Hatchetigbee Formations rapidly thin downba"in; this thinning indicates that much of the sediment supply was trapped 

in shallow-marine environments, possibly l'~cause of a 

rapid rise in sea level during the time of deposition (Gibson, 

1980). The Tuscahoma represents the major time of significant clastic input into this area; it thickens to nearly 200 ft 

of interlaminated clay and silt in downba<;'in outcrops 

(Toulmin and LaMoreaux, 1963). 

In the following section of the paper, brief discussions of the lithologic facies in each formation are followed 

by the paleoenvironmental interpretations ani inferences 

about the location and elevation of the shoreline. The ages 

of the formations and shoreline placements c.re shown in 

figure 20.2. 

Clayton Formation 

Down basin outcrops of the Clayton along the Chattahoochee River near Fort Gaines consist almo~t entirely of 

locally sandy limestone of neritic origin (Toulmin and 

LaMoreaux, 1963). Upbasin, at elevations around 530ft in 

the type area at Clayton, Ala., the lower part of the 

formation is dominated by medium-grained, well-sorted 

sand containing a low-diversity molluscan fauna. This basal 

11 0 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
UJ 

z 

0 

co oN 

:E zCi! 

~ Oa: 

SERIES 1-UJ llli:u.. 

CJ 

w j~ c( D.~ a: 

~ w 

..J 

c 

c 

w :i 

z 

50 w 

0 

0 

w 

Ill 

:I 

0 

UJ 

a: 

C( 

~ C( 

0 

EUSTATIC SEA LEVEL 

(ABOVE PRESENT SEA LEVEL) 

APPROXIMATE SHORELINE 

ELEVATIONS 

150 90 30 0 M 

FORMATIONS IN 

EASTERN 

ALABAMA 

ANDWESTEPN 

GEORGIA 

BASHI & HATCHETIGBEE 

FORMATIOtlS 

TUSCAHOMA 

FORMATIO"l 

NANAFALIA & BAKER HILL 

~ FORMATIONS 

CLAYTO~~ 

FORMATION 

990 660 330 0 FEET 600 500 400 300 200 100 0 FEET 

Figure 20.2. Correlation of Paleocene to middle Eocene formations and proposed shoreline elevations in the Chattahoochee River valley. Time scale, biostratigraphic zonation, and eustatic curves from Haq and others (1987). 

sand is overlain by well-sorted sand containing shell banks 

largely composed of oysters and a clay bed with abundant 

leaf remains (Gibson, 1980). These deposits are suggestive 

of very shallow marine deposition with some restricted 

marine interfingering. To the northwest of Clayton at 

elevations between 600 and 650 ft, sand becomes the sole 

lithology; this sand may be crossbedded and contain Ophiomorpha. These outcrops suggest that the transition from 

marine to shoreface and marginal-marine environments 

during Clayton deposition occurred someplace around a 

present elevation of 600 to 650 ft. 

Porters Creek Formation 

The only exposures of the Porters Creek Formation in 

the study area are near Clayton, Ala. Apparently, most of 

this unit was eroded during the significant period of low sea 

level that followed its deposition. The only facies exposed 

is a waxy, dark, silty clay (Gibson, 1980). The lower part 

of this unit, exposed at 545 ft elevation, contains a 

foraminiferal assemblage indicative of neritic environmental depths of 120 to 180ft or possibly slightly deeper. This 

interpretation would indicate a shoreline at elevations of 

650 ft or slightly higher, similar to or slightly higher than 

that existing during deposition of the Clayton Fonnation. 

Naheola Formation 

The N aheola is also very restricted in its present 

distribution, being found only in sinkholes develop~d in the 

top of limestone of the Clayton near Fort Gaines. The 

micaceous fine sand and carbonaceous clay were ceposited 

in brackish waters (Gibson and others, 1980) and indicate 

that the shoreline was at a lower elevation than the 110 ft at 

which these deposits are found. These beds were criginally 

placed in the Gravel Creek Sand Member of the rTanafalia 

Formation (Gibson, 1980), but subsequent pollen studies 

suggest that they belong to the underlying Naheola Formation (N.O. Frederiksen, oral commun., 1988). 

Nanafalia and Baker Hill Formations 

The fossiliferous, glauconitic sands of the I :r anafalia 

Formation are found in the Chattahoochee River valley at 

Fort Gaines at elevations of about 120 ft. The coarse clastic 

20. Lithologic Changes in Fluvial to Marine Depositional Systems in Paleogene Strata of Georgia and Alabama 111 
sediment, along with large lignitic logs and a dominantly 

oyster molluscan fauna, suggests that these deposits formed 

in very shallow marine environments. In outcrops and 

coreholes within 1-2 mi to the north of Fort Gaines, strata 

correlative with the glauconitic sands of the Nanafalia are 

gravelly sand containing large-scale crossbeds. Within 

another mile northward, the strata are largely kaolinitic and 

bauxitic clay interbedded with crossbedded medium sand. 

These cross bedded sand and kaolinitic clay beds were called 

the Baker Hill Formation (Gibson, 1982a). The Baker Hill 

Formation continues for about 20-30 mi to the northwest of 

Fort Gaines. In its more upbasin localities, it consists of 

gravelly sand in unidirectional large-scale crossbeds. The 

northward change from shallow-marine glauconitic sand of 

the Nanafalia through the cross bedded gravelly sand of the 

Baker Hill, considered to be shoreface deposits, to the 

kaolinitic clays, determined to be of marginal-marine origin 

(Gibson and others, 1980), occurs at elevations of about 

120-130 ft which are, therefore, the approximate shoreline 

elevations. 

Tuscahoma Formation 

The basal, transgressive, gravelly, clay-clast-bearing 

glauconitic sand of the Tuscahoma is found at elevations 

around 435 ft south of Baker Hill. The lithology and the 

occurrence of abundant Venericardia and oysters suggest 

that these deposits are part of a shoreface complex and that 

the shoreline was nearby. A rapid upward change to 

interbedded silt and clay deposited in marginal-marine and 

then in nonmarine environments (Gibson and others, 1980) 

and a large increase in thickness downbasin suggest rapid 

progradation during latest Paleocene time. 

Bashi and Hatchetigbee Formations 

The basal fossiliferous, glauconitic sand of the Bashi 

Formation changes upbasin to crossbedded sand of the 

Hatchetigbee Formation. The Hatchetigbee outcrops of fine 

to medium sand containing multidirectional, small-scale 

crossbeds and clay drapes change northward to gravelly 

medium sand containing larger, unidirectional crossbeds. 

The latter deposits are interpreted as very nearshore bar 

sands and suggest a nearby shoreline location at elevations 

around 465 ft. As many as six depositional cycles can be 

observed in the Bashi along the Pea River near Elba and 

suggest significant fluctuations in sea level during deposition of this formation. The basal cycle discussed here 

represents the most extensive marine transgression of the 

Bashi. 

Tallahatta Formation 

The upbasin deposits of the Tallahatta consist of 

clay-clast-bearing, highly crossbedded, gravelly sand. Beds 

in the lower part of the formation do not show indications of 

marine deposition until elevations of 160 ft are reached 

northwest of Blakely. There, strata of sligh+ly glauconitic 

medium sand contain fragmented shell mater:al and suggest 

that the shoreline was nearby. 

PALEOGENE SHORELINES 

As biostratigraphic placement of these strata was 

given by Gibson and others (1982), the shore1

ine elevations 

listed here can be compared (fig. 20.2) with the worldwide 

eustatic curves in the Cenozoic cycle chart of Haq and 

others (1987). Times of concurrence between the relative 

highstands of sea level observed in this region and the 

eustatic sea-level curves are seen in the Clayton, Porters 

Creek, lower Tuscahoma, and Bashi Formaf·'Jns. Relative 

sea-level stands indicated here by the Nanafdia and Tallahatta Formations are lower than the eustatic sea-level curves 

of Haq and others ( 1987). These differen -:-es could be 

explained by local to regional upwarping or downwarping 

in the Chattahoochee area or by the need for better calibration in the eustatic curves. If uplifting or down warping 

between or within the times of deposition of the formations 

in this area influenced the relative shoreline elevations, then 

comparison of these shoreline differentials with those indicated by other well-dated sequences of this age can give 

some history of vertical movements in this area. If only 

slight uplifting or downwarping occurred in th:s area during 

the Paleocene-middle Eocene, then this area can be 

extremely useful in determining the magnitud~ of sea-level 

changes that are difficult to determine frorr the seismic 

record alone. 

REFERENCES CITED 

Bybell, L.M., and Gibson, T.G., 1985. The Eoc~ne Tallahatta 

Formation of Alabama and Georgia; its litl:'ostratigraphy, 

biostratigraphy, and bearing on the age of fre Claibornian 

Stage: U.S. Geological Survey Bulletin 1615. 20 p. 

Copeland, C.W., ed., 1966, Facies changes in the Alabama 

Tertiary-Guidebook for the fourth annual field trip: University, Ala., Alabama Geological Society. 103 p. 

Gibson, T.G .. 1980, Facies changes of lower Paleo:?ene strata, in 

Reinhardt, Juergen, and Gibson, T.G., Upper Cretaceous and 

lower Tertiary geology of the Chattahoochee River valley, 

western Georgia and eastern Alabama, in Fre~'. R.W .. ed., 

Excursions in southeastern geology. v. II [Guidebook]-

Geological Society of America Annual Meeting, Atlanta, 

Ga.: Falls Church, Va., American Geological Institute, 

p. 402-411. 

---1982a, New stratigraphic unit in the Wilcox Group (upper 

Paleocene-lower Eocene) in Alabama and Georgia: U.S. 

Geological Survey Bulletin 1529-H, p. H23-P32. 

---1982b, Paleocene to middle Eocene depositional cycles in 

eastern Alabama and western Georgia, in Arden. D.D .. 

112 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Beck, B.F., and Morrow, Eleanore, eds., Proceedings; 

Second Symposium on the Geology of the Southeastern 

Coastal Plain, March 5-6, 1979, Americus, Ga.: Georgia 

Geologic Survey Information Circular 53, p. 53-63. 

---1982c, Revision of the Hatchetigbee and Bashi Formations 

(lower Eocene) in the eastern Gulf Coastal Plain: U.S. 

Geological Survey Bulletin 1529-H, p. H33-H41. 

Gibson, T.G., Edwards, L.E., and Frederiksen, N.O., 1980, 

Biological interpretation of depositional environments in 

lower Paleogene strata, in Reinhardt, Juergen, and Gibson, 

T.G., Upper Cretaceous and lower Tertiary geology of the 

Chattahoochee River valley, western Georgia and eastern 

Alabama, in Frey, R. W., ed., Excursions in southeastern 

geology, v. II [Guidebook] -Geological Society of America 

Annual Meeting, Atlanta, Ga.: Falls Church, Va., American 

Geological Institute, p. 428-431. 

Gibson. T.G., Mancini, E.A .. and Bybell, L.M., 1982, Paleocene 

to middle Eocene stratigraphy of Alabama: Gulf Coast 

Association of Geological Societies Transactions, v. 3 2, 

p. 449-458. 

Haq, B.U., Hardenbol, Jan, and Vail, P.R., 1987, Chrcnology 

of fluctuating sea levels since the Triassic: Science, v. 235, 

no. 4793, p. 1156-1167. 

Jones, D.E., 1967, ed., Geology of the Coastal Plain of Alabama-Guidebook for Geological Society of r'merica 

Annual Meeting, New Orleans, La., 1967, Field Trir No. 1: 

University, Ala., Alabama Geological Society, 113 p. 

Newton, J.G., 1965, Geologic map of Barbour County, Alabama: 

Alabama Geological Survey Map 33. 

---1968, Geologic map of Henry County, Alabama: Alabama 

Geological Survey Map 70. 

Smith, E.A., Johnson, L.C., and Langdon, D.W., Jr .. 1894. 

Report on the geology of the Coastal Plain of Alabama: 

Montgomery, Ala., Alabama Geological Survey, 759 p. 

Toulmin, L.D., 1977, Stratigraphic distribution of Paleoc·~ne and 

Eocene fossils in the eastern Gulf Coast region, Vo1ume 1: 

Alabama Geological Survey Monograph 13, 602 p. 

Toulmin, L.D., and LaMoreaux, P.E., 1963, Stratigraphy along 

Chattahoochee River, connecting link between Atlantic and 

the Gulf Coastal Plains: American Association of Petroleum 

Geologists Bulletin, v. 47, no. 3, p. 385-404. 

20. lithologic Changes in Fluvial to Marine Depositional Systems in Paleogene Strata of Georgia and Alabaml 113 

21. Correlation, Age, and Depositional Framework of Subsurface Upper Santonian and 

Campanian Sediments in East-Central South Carolina 

By Gregory S. Gohn 1 

INTRODUCTION 

The subsurface Cretaceous section of the South Carolina Coastal Plain consists of clay-, silt-, and sanddominated units that were deposited in a variety of paleoenvironments during the Cenomanian through the 

Maastrichtian (Valentine, 1982; Colquhoun and others, 

1983; Owens and Gohn, 1985; Sohl and Owens, 1991 ). 

Herein, the stratigraphy and depositional history of the 

upper Santonian and Campanian parts of this section in 

east-central South Carolina are described briefly. 

In the present study area (fig. 21.1), the upper 

Santonian and Campanian sections display obvious lateral 

and vertical facies changes within cyclic, unconformitybounded stratigraphic units. Unit contacts typically juxtapose nearshore sands and silts at the top of one unit beneath 

deeper water clay-silts or glauconitic sands at the bottom of 

the overlying unit. These contacts can be traced throughout 

the study area despite lateral facies changes, and they 

provide a basis for defining five informal stratigraphic units 

that are both lithostratigraphic (mappable on the basis of 

lithology) and allostratigraphic (unconformity bounded). 

These units were deposited during transgressive-regressive 

cycles; each has deeper water marine beds at the base and 

relatively nearshore marine deposits at the top. The lithofacies patterns within these units are typical of the deltaic 

and delta-related sections that characterize the Cretaceous 

of the Atlantic Coastal Plain (Owens and Gohn, 1985). 

Regionally, the lithologies, stratigraphic positions, and ages 

of the five units suggest at least partial correlation with the 

deposits historically assigned to the outcropping Black 

Creek Formation of the Carolinas (Swift and Heron, 1969; 

Sohl and Owens, 1991 ) . 

The drill-hole data base for the present study area is 

very limited, particularly when compared to the data available for hydrocarbon-producing basins (for example, see 

the papers selected by Roy, 1980). Most water wells in 

east-central South Carolina bottom in Paleocene or Eocene 

aquifers, and only a few municipal and industrial wells 

1

U.S. Geological Survey, Reston, VA 22092. 

penetrate the deeper Cretaceous beds. Electric and gamma 

logs typically are the only material available for study from 

many water wells, although additional geophysical logs, 

drillers' logs, and cuttings are available for some wells. The 

water-well data are supplemented, however, with data from 

a few stratigraphic and (or) hydrologic test hole~. Two 

continuously cored stratigraphic test holes in the vrestem 

part of the area (fig. 21.1), USGS-Clubhouse Crossroads 1 

(CCl) and USGS-St. George 1 (StG1), are the come~stones 

of the present study. 

Despite its shortcomings, the existing data base is 

adequate for regional assessments of thickness and lithology 

trends although details are generally lacking except locally. 

In addition, depositional facies can be inferred from the 

geophysical logs for individual wells and then extraoolated 

to infer regional facies trends. 

SECTIONS IN CLUBHOUSE CROSSROADS 1 

AND ST. GEORGE 1 

The continuously cored sections in CC 1 and StG 1 

provide most of the direct lithologic information for the 

studied sections and nearly all the biostratigraphic information. Both holes were drilled into dominantly fine grained, 

calcareous marine beds of the upper Santonian and Campanian units; therefore, they provide a considerable amount of 

biostratigraphic data, much of which has been publi~hed for 

CCl (Hazel and others, 1977; Rattner and Wise, 1980). 

The section in CC 1 has been included in most regional 

stratigraphic and geohydrologic studies of the area (for 

example, studies by Brown and others, 1979; Cobuhoun 

and others, 1983; Gohn, 1988). 

Five stratigraphic units have been identified as summarized in table 21. 1. In CC 1, units 1, 4, and 5 are 

individually about 100 to 150ft thick and consist entirely of 

marine clay-silts (fig. 21.2). Each unit grades upward from 

silty clays at the bottom (distal prodelta) to slightly coarser 

clayey silts and muddy fine sands (proximal prodelta) at the 

top. Eastward from CCL the upper parts of these units 

become distinctly coarser grained, and well-sorted delta21. Subsurface Upper Santonian and Campanian Sediments in East-Central South Carolina 115 
SOUTH CAROUNA 

BERKELEY 

CI iARLESTON 

25 MILES 

25 KILOMETERS 

Figure 21.1. Drill holes in east-central South Carolina mentioned in this 

report. Cross section A-A' is shown in figure 21.4. Abbreviations for 

drill-hole names: StG1 = USGS-St. George 1, CC1 = USGS-Clubhouse 

Crossroads 1, IP = Isle of Palms water well, and MP =Morgan Point water 

well. 

front sand bodies dominate the upper part of each unit. 

Sands do occur at the top of unit 3 at CCI; there unit 3 

consists of clay-silts in its lower half (prodelta) and wellsorted quartz sand containing Ophiomorpha at the top 

(delta-marginal barrier?). Unit 2 consists of clayey 

glauconite-quartz sand in which calcareous nodules are 

common. Unit 2 is interpreted herein as erosionally truncated; nearshore beds at the top of the unit have been 

removed, and only the deeper water marine lower part of 

the unit remains. 

In StG I (fig. 21.3), units 3 and 4 consist of prodelta 

clay-silts. However, unit 5 is represented by a relatively 

thin nearshore section of poorly sorted clay~y sands and 

sandy clays, much of which contains a restricted ostracode 

fauna. Units I and 2 cannot be traced lithologically (or 

faunally) from CCI to StG I and are considered to be absent 

from StGI. 

Planktic faunas and floras in the two corehole sections define the Santonian and Campanian ages of these 

sediments (table 2I.l ). At CC 1, the presence of Eprolithus 

jloralis and a member of the Aspidolithus -parcus group 

within unit I (table 2I.l), as well as the fos~ils in unit 2, 

suggests that the Santonian-Campanian bourr:lary can be 

placed near I. 700ft within unit I. The last app~arance of E. 

116 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 21.1. Upper Santonian, Campanian, and lower Maastrichtian datums in the USGS-Clubhouse Crossroads 1 and 

USGS-St. George 1 wells, South Carolina 

[Fossil abbreviations following species names: en, calcareous nannofossils; m, mollusks; os, ostracodes; and pf, planktic Foraminifera. Depths in 

feet below the surface. For USGS-St. George 1, C.W. Poag and W.A. 

Bryant (both of the U.S. Geological Survey) identified the planktic 

Foraminifera, and P.C. Valentine (USGS) identified the calcare')us nannofossils. The fossil data from USGS-Clubhouse Crossroads 1 are principally from Hazel and others (1977) and Rattner and Wise (1980). Units 1 

and 2 are missing from St. George 1] 

CC1 StG1 

Lower Maastrichtian datums: 

Lowest occurrence of Globotruncana aegyptiaca (pf) ......................................... . 804 1,000 

Highest occurence of Flemingostrea subspatulata (small form) (m) ............................ . 1,030 not studied 

Lowest occurrence of Exogyra costata (m) ................................................... . 1,066 not studied 

Campanian datums: 

Top of unit 5 .........................................................................•.... 1,072 1,031 

Lowest occurrence of F. subspatulata (small form) (m) ....................................... . 1,090 not studied 

Highest occurrence of Exogyra ponderosa (m) ............................................... . 1,162 not studied 

Top of unit 4 .................••...............................•......................•.... 1,214 1,082 

Highest occurrence of Fissocarinocythere gapensis (os) ....................................... . 1,263 1,095 

Highest occurrence of Haplocytheridea insolita ( os) .......................................... . 1,263 1,095 

Lowest occurrence of H. insolita (os) ........................................................ . 1,338 1,168 

Top of unit 3 .......................................................................•...... 1,344 1,177 

Highest occurrence of Fissocarinocythere pittensis (os) ....................................... . 1,410 1,260 

Highest occurrence of Ventilabrella glabrata (pf) ............................................. . 1,457 not found 

Lowest occurrence of F. gapensis (os) ....................................................... . 1,480 1,280 

Lowest occurrence of Quadrum sissinghii (en) ............................................... . not found 1,320 

Lowest occurrence of Ceratolithoides aculeus (en) ............................................ . 1,500 1,320 

Lowest occurrence of Rugoglobigerina rugosa (pf) ........................................... . 1,504 1,320 

Top of unit 2 ............................................................................. . 1,544 missing 

Highest occurrence of Marthasterites furcatus (en) ............................................ . 1,560 not found 

Lowest occurrence of Ventilabrella glabrata (pf) ............................................. . 1,600 not found 

Top of unit 1 ............................•...................................•............. 1,644 f'1'issing 

Lowest occurrence of Aspidolithus pare us group (en) ......................................... . 1.690 1,320 

Upper Santonian datums: 

Highest occurrence of Eprolithus flora/is (en) ................................................ . 1.713 not found 

Sole occurrence of Heterohelix reussi (p[) ................................................... . 1,713 not found 

Top of Middendorf Formation ............................................................ . 1,754 1,325 

jloralis is generally placed at the Santonian-Campanian 

boundary or within the late Santonian (Perch-Nielsen, 

1985, top of Zone CC 16). The presence of Marthasterites 

furcatus with a member of the Aspidolithus parcus group 

indicates an early Campanian age (Zone CC18 of PerchNielsen, 1985) for unit 2 at Clubhouse Crossroads. 

The presence of Quadrum sissinghii, Ceratolithoides 

aculeus, and Rugoglobigerina rugosa, as well as the 

absence of M. furcatus, in unit 3 in both cores indicates an 

early to middle Campanian age for unit 3. This distribution 

also suggests that units 1 and 2 found in CC 1 are missing at 

St. George. In addition to the nannofossil data, ostracode 

data are useful; the interval containing the overlap of the 

ranges of the ostracodes Fissocarinocythere pittensis and F. 

gapensis occurs at the same stratigraphic position within 

unit 3 in both drill holes. 

The planktic fossils in units 4 and 5 provide less 

resolution than those in units 2 and 3, although they are 

compatible with a Campanian age. The highest occurrences 

of the ostracodes Fissocarinocythere gapensis and Haplocytheridea insolita in unit 4 (with Antibythocypris elongata 

in CC1) indicate a late Campanian age for that unit (Hazel 

and Brouwers, 1982). Haplocytheridea insolita is restricted 

to unit 4 in both wells. The Campanian-Maas~richtian 

boundary is placed at the top of unit 5 in CC 1 on the basis 

of the lowest occurrence of Exogyra costata just above the 

top of unit 5 and the distribution of the small form of 

Flemingostrea subspatulata (see Sohl and Christopher, 

1983). The Maastrichtian species Globotruncana aegyptiaca first occurs about 30 ft above the top of unit 5 in StG 1. 

On the basis of its stratigraphic position, unit 5 is recessarily of late Campanian age. 

21. Subsurface Upper Santonian and Campanian Sediments in East-Central South Carolin;o 117 
Units 

Maastrichtian 

sediments 

5 

4 

3 

2 

Middendorf 

·Formation 

Gamma 

Depth 

below 

surface, 

in feet 

1000 

1200 

1400 

1600 

1800 

Figure 21.2. Gamma log for the studied 

section in USGS-Clubhouse Crossroads 1, 

Dorchester County, S.C. The boundaries 

of Santonian-Campanian unit 1 and Campanian units 2 through 5 are shown. 

EXAMPLE OF REGIONAL FACIES 

DISTRIBUTION 

The distribution of depositional lithofacies in unit 4 is 

described in this section as a representative example of the 

facies patterns found in the studied sequences. As seen in 

figures 21.3 and 21.4, unit 4 is thickest in the eastern part 

of the study area, as represented by the Isle of Palms (IP) 

and Morgan Point (MP) wells, and thins to the west and 

northwest. Similarly, the collective thickness of well-sorted 

sand bodies within unit 4, as interpreted primarily from 

geophysical logs, also is greatest in the east and decreases to 

the west. Well-sorted sands are absent from unit 4 in the 

CCI and StGl sections. 

Units 

Maastrichtian 

5 

4 

3 

Middendorf 

Formation 

Depth 

below 

surface, 

in feet 

~::--: 

1100 

+-' 1200 ::1 

0 

1300 

Gamma --7 ReS'istivity --7 

Figure 21.3. Gamma and electrical resistivity logs for the 

studied section in USGS-St. George 1, Dorchester County, 

S.C. The boundaries of Campanian units 3 t"lrough 5 are 

shown. 

The geophysical logs for the IP and MP wells show a 

strong differentiation of sediments into clay- and sanddominated intervals (fig. 21.4). In these Pells, unit 4 

coarsens upward from a basal clay-silt into two or more 

sand bodies separated by thinner clay-silt laye~s. The sands 

tend to be well sorted and to have sharp upp~r and lower 

contacts. 

The sand-dominated sections are interpreted to represent delta-front and proximal prodelta derosition. The 

lower, finer grained parts of the sections repres ~nt the initial 

progradation of the prodelta above a basal transgressive 

unconformity. The well-sorted sands having sharp contacts 

are delta-front deposits, possibly barriers fomed by wave 

redistribution of river-supplied sediments (see examples in 

Roy, 1980). To the west, the fine-grained sec':ions lacking 

major sand bodies represent prodelta deposits on the margin 

of the delta lobe( s). 

118 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
A 

Clubhouse 

Crossroads 1 

SP R 

UNIT5 

prodelta 

UNIT3 

SP 

Isle of 

Palms 

1300 R 

Morgan 

Point 

Figure 21.4. Distribution of facies in unit 4. Location of the section is shown in figure 21.1. Electric logs are shown for each 

well: SP = spontaneous potential log, R = resistivity log. Depths are in feet. 

SUMMARY 

Although generalized herein, a relatively complete 

picture of the depositional history of the studied section 

has evolved through the integration of sedimentary facies 

analysis with modern biostratigraphic zonations. Five 

unconformity-bounded, lithologically distinct units containing diagnostic late Santonian and Campanian fossils can be 

traced in the subsurface of east -central South Carolina. 

Each unit contains a mosaic of sedimentary facies that 

represents initial marine transgression and subsequent delta 

progradation. The recognition of five stratigraphic units 

within an interval that is traditionally assigned to only 

one formation (Black Creek) suggests a greater stratigraphic complexity than is indicated by the traditional 

nomenclature. 

REFERENCES CITED 

Brown, P.M., Brown, D.L., Reid, M.S., and Lloyd, O.B., Jr., 

1979, Evaluation of the geologic and hydrologic factors 

related to the waste-storage potential of Mesozoic aquifers in 

the southern part of the Atlantic Coastal Plain, South Carolina 

and Georgia: U.S. Geological Survey Professional Paper 

1088, 37 p. 

Colquhoun, D.J., Woollen, I.D., Van Nieuwenhuise, D.S., 

Padgett, G.G., Oldham, R.W., Boylan, D.C., Bishop, J.W., 

and Howell, P.D., 1983, Surface and subsurface stratigraphy, structure, and aquifers of the South Carolina Coastal 

Plain: Columbia, S.C., University of South Carolina, Department of Geology, 78 p. 

Gohn, G.S., 1988, Late Mesozoic and early Cenozoic geology of 

the Atlantic Coastal Plain-North Carolina to Florida, in 

Sheridan, R.E., and Grow, J .A., eds., The Atlantic continental margin-U.S., v. 1-2, of The geology of North 

America: Boulder, Colo., Geological Society of America, 

p. 107-130. 

Rattner, J.G., and Wise, S.W., Jr., 1980, Upper Cretaceous 

calcareous nannofossil biostratigraphy of South Carolina: 

South Carolina Geology, v. 24, no. 2, p. 41-117. 

Hazel, J.E., and Brouwers, E.M., 1982, Biostratigraryhic and 

chronostratigraphic distribution of ostracodes in the 

Coniacian-Maestrichtian (Austinian-Navarroan) in the Atlantic and Gulf coastal province, in Maddocks, R.F., ed., Texas 

Ostracoda; Guidebook of excursions and related p1pers for 

the Eighth International Symposium on Ostracoda: Houston, 

Tex., University of Houston, Department of Geo~ciences, 

p. 166--198. 

Hazel, J.E., Bybell, L.M., Christopher. R.A .. Frederikst'n, N.O., 

May, F.E., McLean, D.M., Poore, R.Z., Smith, C.C., Sohl, 

N.F., Valentine, P.C., and Witmer, R.J., 1977, Biostratigraphy of the deep corehole (Clubhouse Crossroads corehole 

1) near Charleston, South Carolina: U.S. Geological Survey 

Professional Paper 1028-F, p. 71-89. 

Owens, J.P., and Gohn, G.S .. 1985, Depositional histcry of the 

Cretaceous Series in the U.S. Atlantic Coastal Plain-Stratigraphy, paleoenvironments, and tectonic controls of sedimentation, in Poag, C.W., ed., Geologic evolution of the United 

States Atlantic margin: New York, Van Nostrand Reinhold, 

p. 25-86. 

Perch-Nielsen, Katharina, 1985, Mesozoic calcareous nannofossils, in Bolli, H.M., Saunders, J.B., and Perch-Nielsen, 

Katharina, eds., Plankton stratigraphy: New Yo-k, Cambridge University Press, p. 329-426. 

Roy, E.C., Jr., ed., 1980, Depositional systems in the G•1lfCoast, 

v. 1 of Readings in Gulf Coast geology: Gulf Coast Association of Geological Societies, l 7 4 p. 

21. Subsurface Upper Santonian and Campanian Sediments in East-Central South Carolira 119 
Sohl. N.F., and Christopher, R.A., 1983, The Black CreekPeedee formational contact (Upper Cretaceous) in the Cape 

Fear River region of North Carolina: U.S. Geological Survey 

Professional Paper 1285, 37 p. 

Sohl, N.F., and Owens, J.P., 1991, Cretaceous stratigraphy of 

the Carolina Coastal Plain, in Horton, J.W., Jr., and Zullo, 

V .A., eds., The geology of the Carolinas-Carolina Geological Society 50th anniversary volume: Knoxville. Tenn., 

University of Tennessee Press, p. 191-220. 

Swift, D.J.P., and Heron, S.D., Jr., 1969, Stratigraphy of the 

Carolina Cretaceous: Southeastern Geology. v. 10, no. 4, 

p. 201-245. 

Valentine, P.C., 1982. Upper Cretaceous subsurface stratigraphy 

and structure of coastal Georgia and South Carolina: U.S. 

Geological Survey Professional Paper 1222, 33 p. 

120 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern Florid.~ 1 

By Lucy McCartan,2 A.D. Duerr/ and R.M. Hawkins2 

INTRODUCTION 

This report describes our research on the clay mineralogy of rocks in De Soto County, Fla., sampled in two 

holes (fig. 22.1). We examined and sampled the uppermost 

440 ft of the 829-ft-long core from the Regional Observation and Monitor-Well Program (ROMP) 17 corehole, and 

we obtained cuttings from the 835-ft-deep Dees well about 

10 mi southeast of the ROMP 17 corehole. 

The ROMP 17 and Dees wells are stratigraphic 

control sites and ground-water monitoring wells drilled 

by the Southwest Florida Water Management District 

(SWFWMD) and the U.S. Geological Survey (USGS), 

respectively. Prior to the present study, the clay minerals in 

these wells had not been examined in detail. This report 

gives some of the preliminary results of a cooperative study 

to determine the ground-water resources, ground-water 

quality, and mineralogy of the surficial units and subsurface 

units in the area. 

Clay minerals in the ROMP 17 core are restricted 

almost exclusively to dolomitic rocks. They occur in 

discrete beds and are disseminated in semi-indurated to 

well-indurated dolomitic rocks. Two of the clay minerals, 

palygorskite and sepiolite, are magnesium rich; also, a 

poorly crystalline phase referred to informally as "RE" in 

this report, has both refractory and expandable layers and 

may contain magnesium. Limestones in the same core have 

no clay minerals. 

The clay-mineral distribution is interesting for three 

reasons. First, sepiolite and palygorskite are highly adsorbent; both are used commercially to adsorb organic pollutants. We infer that naturally occurring sepiolite and palygorskite function as ground-water filters. Where they occur 

in discrete beds or where they compose more than 15 

percent of the total rock, they also function as leaky 

confining beds. Second, the clear pattern of clay minerals in 

dolomite and not in limestone in the ROMP 17 core is 

1

Prepared in cooperation with the Florida Geological Survey and the 

Southwest Florida Water Management District. 2

U. S. Geological Survey, Reston, VA 22092. 3

U.S. Geological Survey, Tampa, FL 33614. 

dissimilar to the mixed mineralogy in a suite of cuttings 

from the Dees well. The mixing of minerals in tb~ Dees 

well appears to be an artifact of the drilling process. Finally, 

Mg-rich. clay is a significant clue to the depositional and 

postdepositional history. 

Acknowledgments 

A.D. Duerr was partly supported by the SWFWMD. 

The SWFWMD is also responsible for the Regional Observation and Monitor-Well Program. We thank the Florida 

Geological Survey for access to the ROMP 17 core. and for 

samples. Jonathan Arthur arranged for the core srmpling, 

and Thomas Scott provided a detailed, unpublish~d lithologic log of the 829-ft-long core. We appreciate cC'mments 

by Ruth Deike, John Hosterman, and Milan Pavici. (all of 

the USGS) on earlier drafts of this report. 

as· 

DESOTO COUNfY 

ROMP 17 

• • 

DEES 

0 100 MILES I I I I 

0 100 KILOMETERS 

Figure 22.1. Locations of the ROMP 17 corehole and 

the Dees well, De Soto County, Fla. 

22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern FlorHa 121 
SERIES 

Miocene 

Oligocene 

Eocene 

Scott (1986, 1988) 

UNIT 

Peace 

River 

Formation 

upper 

unnamed 

member 

Tampa 

Member 

Nocatee 

Member 

Bone 

Valley 

Member 

Arcadia 

Formation 

Suwannee Formation 

Ocala Group 

Miller (1986) 

UNIT SERIES 

Hawthorn 

Formation 

Miocene 

Tampa 

Limestone 

Suwannee Oligocene Limestone 

Ocala Eocene 

Limestone 

Figure 22.2. Stratigraphic nomenclature for the upper Eocene-Miocene series in 

southwestern Florida. 

STRATIGRAPHY 

The part of the ROMP 17 core that was studied 

sampled four units-the Hawthorn Formation (Miocene), 

the Tampa Limestone (Miocene), the Suwannee Limestone 

(Oligocene), and the Ocala Limestone (Eocene)-according 

to an unpublished log by Thomas M. Scott (Florida Geological Survey, 1983), which followed the nomenclature of 

Miller (1986). Scott's published stratigraphic nomenclature 

for the ROMP 17 core (in Johnson, 1986; see also Scott, 

1986, 1988) is as follows: 

Hawthorn Group, 26-439 ft 

Peace River Formation, including the Bone 

Valley Member, 26-99 ft 

Arcadia Formation, 99-439 ft 

upper unnamed member, 99-208 ft 

Tampa Member, 208-292 ft 

Nocatee Member, 292-439 ft 

Suwannee Formation, 439-829 ft 

The simpler scheme of Miller (1986) is used in this report. 

The two schemes are compared in figure 22.2. 

Geophysical logs indicate that the same formations 

(according to Miller's (1986) nomenclature) are in both the 

ROMP 17 and Dees wells. The contacts are deeper in the 

Dees well because the regional structure dip::- toward the 

south. 

METHODS AND MINERALOGY 

The upper 440ft of the ROMP 17 core (fig. 22.3) was 

examined, and small samples were taken for X-ray diffraction (XRD) analysis and optical microscopy. X-ray diffractograms of the core samples (fig. 22.4) were co'11pared with 

those of cuttings from the Dees well (fig. 22.5). Core 

samples were lightly crushed and attached to glass slides 

with amyl acetate. This method was necessary because of 

the limited amount of material available from the core. 

Cuttings from the Dees well were disaggregat~d or lightly 

crushed in deionized water to make a slurry. The clay-sized 

fraction (containing particles smaller than 2 f.Lm) was 

separated by centrifuging the slurry. The clay-sized particles were then sedimented onto a glass slide, air dried, and 

X-rayed with CuKcq radiation. Because clay and nonclay 

minerals are in both suites of samples, the ef~ects of the 

different procedures appear to be minimal. 

Untreated samples that had diffraction peaks lower 

than 8.8 A (10° 28) were treated and then X-rayed again. 

122 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
DEPTH 

(FEET) 

SURFICIAL UNIT 

(POST-MIOCENE) 

HAWTHORN 

FORMATION 

(MIOCENE) 

TAMPA 

LIMESTONE 

(MIOCENE) 

SUWANNEE 

LIMESTONE 

(OLIGOCENE) 

LITHOLOGY 

SAND, CLAY, 

SHELL 

.. · ... 

~~ 

. \"· .. ;: ... \"·· .. 

\ \ \ c=. 

=-- c=. 

'\ \ 

\ \ \ 

\ \ \ \ 

.. \" ... , .. · .. \. ·. 1\· .. \" ·: "\• ... •\: 

1:,:.~. ·. ·~·~ ... ::~ ~---.-.~ . •• "l\•: •• :·.· •.•. 

GAMMA RAY 

. . :.::: .. ·.: :·.~:·.-.;~ 

\ 

\ \ \ 

\ \ \ 1\ \ \ \ .. · ........ ·. ·. 

1\ \ 

I 1\ ' ' ' ' ' ' -= \ \ 1\ \ \ · ... ·.· . . ·:·.·. ·· . 

. . : ... 

• \ \ \ 

EXPLANATION 

h·:·.-::>1 Sand ~ Dolomite 

§@ Silt and clay • Sample 

~Limestone 

RESISTIVITY 

(SINGLE POINT) 

Figure 22.3. Lithologic, gamma-ray, and resistivity logs and stratigraphy of the ROMP 17 

corehole. Gamma-ray and resistivity logs are from the files of the Southwest Florida 

Water Management District (SWFWMD). Lithology is from the SWFWMD and from core 

samples. Sand, silt, and clay in this core typically contain carbonate minerals. Formational contacts are from an unpublished log (dated 1983) provided by Thomas M. Scott, 

Florida Geological Survey; nomenclature is from Miller (1986). 

22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern FlorirJa 123 
ROMP 17 

p 

~ U5 

z 

w 

1-

~ 

10 

20 10 

EXPLANATION 

RE Refractory-expandable 

mixed-layer clay 

S Sepiolite 

P Palygorskite 

Q Quartz 

C Calcite 

D Dolomite 

6 

20 

DEGREES 26 

5 

ANGSTROMS 

4 

Q D 

72 

D 

74 

c 

1-

w HAWTHORN w 

u. 

~ FORMATION 

:i 

1-

a.. 

w 

Cl (MIOCENE) 

147 

273 

TAMPA 

352 LIMESTONE 

(MIOCENE) 

358 

30 

3 

Figure 22.4. X-ray diffractograms of minerals in lightly crushed samples from the ROMP 17 con~. 

Samples with diffraction peaks lower than 8.8 A (10° 28) were glycolated. See figure 22.1 for location 

of well. 

124 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
DEES 

s 

~ U5 

z 

w 

I-

~ 

M + I/S 

10 

20 10 

EXPLANATION 

1/S Illite/smectite 

M Montmorillonite 

S Sepiolite 

P Palygorskite 

K Kaolinite (standard) 

0 Quartz 

C Calcite 

D Dolomite 

20 

DEGREES 29 

6 5 4 

ANGSTROMS 

D 

c 

30 

3 

147 

223 

231 

HAWTHORN 

FORMATION 

268 (MIOCENE) 

Iw 

w 

u... 

~ 

:i 

Ia.. 

w 

0 

330 

408 TAMPA 

562 

675 

LIMESTONE 

(MIOCENE) 

SUWANNEE 

LIMESTONE 

(OLIGOCENE) 

OCALA 

LIMESTONE 

835 (EOCENE) 

Figure 22.5. X-ray diffractograms of minerals in the clay-sized fraction (less than 2 

t:J..m) of cuttings from the Dees well. Samples with diffraction peaks lower than 8.8 

A (10° 28) were glycolated. See figure 22.1 for location of well. 

22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern Florida 125 
One slide was heated to 350 oc for 1 hour; another slide was 

vapor glycolated overnight and X-rayed again. 

After slides were heated, diffractograms showed that 

all the peaks in the range from 10 to 35 A (8.8°-2.5° 28) for 

untreated samples became somewhat broader except those 

of illite/smectite mixed-layer clay and montmorillonite. 

These peaks collapsed to about 10 A (8.8° 28). Because of 

the large proportion and good crystallinity of montmorillonite (drilling mud) in the samples from-562ft and -675 

ft in the Dees well, the 10-A peak is distinct. Heating of the 

small proportion of poorly crystalline illite/smectite in 

samples from -231 ft and -330 ft in the Dees well 

produced a low 10-A peak that is masked under the large 

shoulder of the combined sepiolite and palygorskite peaks. 

The shifting of the peaks is due to the escape of water 

loosely held in the structure and the subsequent collapse of 

basal planes to the illite d-spacing (10 A). Retention of 

some, but not all, of the intensity of sepiolite, palygorskite, 

and RE peaks reflects the presence of both refractory layers 

and water layers. 

Increase of basal-plane spacing due to absorption of 

ethylene glycol, from about 14.7 A (6° 28) to about 17.7 A 

(5° 28) occurred only in illite/smectite mixed-layer clay and 

montmorillonite (fig. 22.5). Minerals were identified by 

comparing peaks on the diffraction traces from untreated 

samples with those listed in the Joint Committee on Powder 

Diffraction Standards (1974, 1981) data book. Illite/ 

smectite was distinguished from montmorillonite on the 

basis of peak shape and the height of the low-angle saddle 

(Reynolds and Hower, 1970). Illite/smectite in these samples has a broad, low, irregular peak and a high saddle on 

the lower angle side of the peak. Montmorillonite has a 

sharp, narrow peak and a low saddle. All the minerals 

except quartz permit significant ionic substitution, and so 

minor discrepancies between the published X-ray patterns 

and those in figures 22.4 and 22.5 are assumed to be a result 

of differences in ionic substitution. 

Minerals from three units in the ROMP 17 core 

between-17ft and-440ft are identified on the XRD trace 

(fig. 22.4). Cuttings from the Dees well between -147 and 

-835ft were X-rayed (fig. 22.5); the Ocala Limestone was 

sampled in both wells. but data are available at present only 

from the Dees well. Mineralogy of the cuttings is far more 

mixed than that in the core; there appears to be little 

partitioning of Mg-bearing minerals in Dees well samples. 

Nevertheless, the cuttings gave at least a general picture of 

the most important minerals-low-Mg calcite, dolomite, 

palygorskite, and sepiolite. 

ADSORPTION BY PALYGORSKITE AND 

SEPIOLITE 

Palygorskite (Mg5Si80 20(0H)iH20)4 ·4H20) and 

sepiolite (Mg8Si 120 30(0H2) 4 (H20)4 ·8H20) are similar 

fibrous clays. Their large capacity to adsorb various compounds is related to their very fine grained fibrous habit. 

Because their structures have channels, it was once assumed 

that they would absorb molecules in the ch~nnels. However, Barrer (1978) has shown that, although water and 

ammonia may enter the channels after heat treatment, other 

materials such as nitrogen and alcohols are confined to the 

outer part of the structures. Moreover, fibrous clays selectively adsorb certain hydrocarbons. Palygorskite has long 

been used as an adsorbing medium for crganic fluids 

(Patterson, 1974), and surface-modified ser1olite is also 

now available commercially. Research is cc ntinuing into 

modifications that enhance the selectivity ard volumetric 

aspects of sepiolite sorption (Alvarez and others, 1987; 

Perez-Castells and others, 1987). 

The degree to which untreated fibrous chys in natural 

environments filter ground water and modify ground-water 

chemistry is not well known. In areas such as southwestern 

Florida, where potable ground-water suppli~s are being 

depleted, an understanding of the behavior of such minerals 

is essential. 

COMPARISON OF CORE SAMPLES Ar 'D 

CUTTINGS 

The ROMP 17 corehole and the Dees well are about 

10 mi apart, and they intersect the same units. Yet the 

mineralogic pattern appears to be significantly different in 

the two wells. In the ROMP 17 core, nearly pure limestone 

consisting of low-Mg calcite alternates with dolomite that 

contains palygorskite, sepiolite, quartz, and RE, a phase 

that has both expandable and refractory layers. The cuttings 

from the Dees well are a mixture of drilling mud (termed 

"bentonite," but mineralogically almost pure m':lntmorillonite, at -562 and -675 ft), dolomite, calcite, kaolinite. 

palygorskite, sepiolite. and illite/smectite. The only "pure" 

limestone in the Dees well occurs in the Ocalr Limestone; 

perhaps by that depth, the recirculation of clays from higher 

units and drilling mud had ceased (water was used below 

-675 ft instead of drilling mud). However, th~ sample at 

-147ft in the Dees well is a clay-free dolomit~ that has no 

counterpart in the ROMP 17 core. 

Some variation between wells 10 mi arart is to be 

expected. Depositional lithofacies in carbonate banks 

change over short distances (see section below on paragenesis). However, it is equally likely that the mbred mineralogy of the cuttings is an artifact of the drilling process. 

More work on cores from southwestern Florida will enable 

us to clarify this point. Until then, relating the mineralogy 

of cuttings to ground-water quality is probably inadvisable. 

PARAGENESIS 

Partitioning of Mg-rich carbonate minerals and Mgrich clay minerals in Florida is unlikely to be accidental. 

Such partitioning also occurs in Cretaceous deposits in 

126 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Texas (Deike, 1991). The distribution of dolomite and 

calcite may be related genetically to the distribution of clay 

minerals. Similarly. the diagenetic processes that led to 

dolomitization of the primary biogenic calcium carbonates 

(Friedman, 1964; Shinn, 1972: Plummer. 1977; Land, 

1982; Plummer and others, 1983; Thayer and Miller, 1984) 

may have been partly responsible for the presence of 

magnesium in the clays (Weaver and Beck, 1977; Fisher, 

1988). 

The sequence as a whole is typical of modem deposits 

in carbonate banks and sabkhas (Miller, 1986), which 

accumulate in warm. shallow marine water and adjacent 

supratidal flats. However. modem formation of Mg-rich 

clay has been reported only in association with submarine 

volcanic vents (Bowles and others. 1971). The Mg-rich clay 

minerals in southwestern Florida may have resulted from 

localized concentration of magnesium through processes 

such as evaporation of seawater (Weaver and Beck. 1977: 

Fisher, 1988), dissolution of volcanic ash derived from the 

Caribbean (Case and Holcombe. 1980) or the west (Gilluly. 

1965), or recrystallization ofhigh-Mg calcite (Chave, 1954) 

or dolomite (Plummer, 1977; Plummer and others, 1983). 

CONCLUSIONS 

Palygorskite and sepiolite are Mg-rich clays that tend 

to adsorb organic molecules in ground water that flows 

through units containing them. Their distribution may be an 

important consideration in the assessment of ground-water 

quality and pollution potential in southwestern Florida. 

Lithology, mineralogy, and, therefore, stratigraphy 

are more accurately represented by core samples than by 

cuttings. Projects need to be designed with this difference in 

mind. 

REFERENCES CITED 

Alvarez, A., Santaren, J., Perez-Castells, R., Casal, B .. RuizHitzky. E., Levitz, P., and Fripiat, J.J., 1987, Surfactant 

adsorption and rheological behavior of surface-modified sepiolite, in Schultz, L.G., vanOlphen, H., andMumpton, F.A., 

eds., Proceedings of the International Clay Conference, 

1985: Bloomington, Ind., Clay Minerals Society, 

p. 370-374. 

Barrer, R.M., 1978, Sorption and molecule sieving by layer 

silicates. Chapter 8 of Zeolites and clay minerals as sorbents 

and molecular sieves: New York, Academic Press. 

p. 407-497. 

Bowles, F.A., Angino, E.A., Hosterman, J.W., and Galle. O.K., 

1971. Precipitation of deep-sea palygorskite and sepiolite: 

Earth and Planetary Science Letters. v. 11, no. 4, 

p. 324-332. 

Case, J.E .. and Holcombe, T.L., 1980, Geologic-tectonic map of 

the Caribbean region: U.S. Geological Survey Miscellaneous 

Investigations Series Map 1-1100, 3 sheets, scale 

1:2,500,000. 

Chave. K.E .. 1954, Aspects of the biogeochemistry of magnesium-[Pt.] 1, Calcareous marine organisms; [Pt.] 2, Calcareous sediments and rocks: Journal of Geology. v. 62, no. 3, 

p. 266-283; no. 6, p. 587-599. 

Deike, R.G., 1991. Comparative petrology of cores from two test 

wells in the eastern part of the Edwards aquifer, south -central 

Texas: U.S. Geological Survey Water-Resources ln'restigations Report 87--4266. 142 p., 1 pl. 

Fisher, R. S., 1988. Clay minerals in evaporite host rocl-s. Palo 

Duro Basin, Texas Panhandle: Journal of Sedimentary Petrology, v. 58, no. 5, p. 836-844. 

Friedman, G .M.. 1964. Early diagenesis and lithification in 

carbonate sediments: Journal of Sedimentary Pe+rology, 

v. 34, no. 4. p. 777-813. 

Gilluly. James, 1965, Volcanism, tectonism, and plutonis'll in the 

Western United States: Geological Society of Amer~ca Special Paper 80, 69 p. 

Johnson. R. A. , comp. , 1986, Shallow stratigraphic core tests on 

file at the Florida Geological Survey: Florida Geological 

Survey Information Circular 103. 431 p. 

Joint Committee on Powder Diffraction Standards, 1974, Selected 

powder diffraction data for minerals-Data book (1st ed.): 

Swarthmore, Pa .. Joint Committee on Powder Diffraction 

Standards, 833 p., and first supplement, 1981. 463 p. 

Land, L.S., 1982, Dolomitization: American Association of 

Petroleum Geologists Education Course Note Series no. 24, 

20 p. 

Miller, J.A .. 1986, Hydrogeologic framework of the Floridan 

aquifer system in Florida and in parts of Georgia, P labama, 

and South Carolina: U.S. Geological Survey Pro+~ssional 

Paper 1403-B, 91 p. 

Patterson, S.H., 1974, Fuller's earth and other industrial mineral 

resources of the Meigs-Attapulgus-Quincy district, Georgia 

and Florida: U.S. Geological Survey Professional Pcner 828, 

45 p. 

Perez-Castells, R., Alvarez, A .. Gavilanes, J., Lizarbr, M.A., 

Martinez del Pozo, A., Olmo, N., and Santaren, J .. 1987, 

Adsorption of collagen by sepiolite. in Schultz, L.G., van 

Olphen, H., and Mumpton, F.A., eds., Proceedin:!,S of the 

International Clay Conference, 1985: Bloomington, Ind., 

Clay Minerals Society, p. 359-362. 

Plummer, L. N. , 1977, Defining reactions and mass transfer in part 

of the Floridan aquifer: Water Resources Research, v. 13, 

no. 5, p. 801-812. 

Plummer, L.N., Parkhurst, D.L., and Thorstenson, D.C., 1983, 

Development of reaction models for ground-water systems: 

Geochimica et Cosmochimica Acta, v. 47, no. 4, 

p. 665-686. 

Reynolds, R.C .. Jr., and Hower. John, 1970, The nature of 

interlayering in mixed-layer illite-montmorillonites: Clays 

and Clay Minerals, v. 18, p. 25-36. 

Scott, T.M .. 1986, A revision of the Miocene lithostratigraphic 

nomenclature, southwestern Florida: Gulf Coast Association 

of Geological Societies Transactions, v. 36, p. 553-560. 

---1988. The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin 59, 

148 p. 

22. Magnesium-Rich Clay Minerals in Tertiary Carbonate Rocks of Southwestern Florida 127 
Shinn, E.A., 1972, Recent dolomite, Sugarloaf Key, in Ginsburg. 

R.N., ed., South Florida carbonate sediments: Sedimenta II 

(Miami, Fla., University of Miami), p. 62--67. (Reprint of a 

1964 field trip guidebook. ) 

Thayer, P.A., and Miller, J.A., 1984, Petrology of lower and 

middle Eocene carbonate rocks, Floridan aquifer, central 

Florida: Gulf Coast Association of Geological Societies 

Transactions, v. 34, p. 421-434. 

Weaver, C.E., and Beck, K.C., 1977, Miocene of the southeastem United States; a model for chemical sedimentation in a 

perimarine environment: New York, Elsevier, 234 p. 

(Reprinted from Sedimentary Geology. v. 17. nos. 1-2, 

1977.) 

128 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
23. Celestine (SrS04 ) in Hardee and De Soto Counties, Florida 1 

By Lucy McCartan,2 L.N. Plummer,2 j.W. Hosterman,2

'

3 E. Busenberg/ E.J. Dwornik/ A.D. Duerr,4 

R.L. Miller, 4 and j.L. Kiesler4 

INTRODUCTION 

Celestine (SrSO 4 ) has been identified in cuttings from 

two drill holes (Newbern Grove and Dees) in Hardee and 

De Soto Counties, south-central Florida (fig. 23.1), where 

it is found in small quantities in the Hawthorn Formation 

(Miocene), the Suwannee Limestone (Oligocene), and the 

Avon Park Formation (Eocene). Celestine, 5 a member of 

the barite group, is the principal ore of strontium. It is a 

relatively rare mineral that is found in some limestones, 

sandstones, and evaporite deposits and also is associated 

with volcanic rocks and metallic veins (Ford, 1932). Celestine also has been reported by Cook and others ( 1985) from 

the A von Park Formation in the TR 18-2 drill hole in 

Hernando County, Fla. (fig. 23 .1). Thermodynamic speciation calculations indicate that water in the Upper Floridan 

aquifer is in equilibrium with the celestine it contains in the 

Newbern Grove and Dees drill holes. This equilibrium 

suggests that celestine is widely distributed; so far, we have 

found it in only a few samples. The presence of celestine in 

substantial quantities would indicate unusual chemical conditions after and possibly during deposition of the host 

sediment. 

This preliminary report describes the occurrence of 

celestine and ground-water characteristics in the study area. 

The paragenesis of celestine is discussed in two parts. The 

first part is a speculative account of the possible early 

diagenetic formation of celestine. The second part relates 

the modern distribution of celestine to hydrochemical 

facies. An understanding of the origin of celestine will aid 

in prediction of the evolution of water quality in southcentral Florida. 

1 Prepared in cooperation with the Southwest Florida Water Management District and the Florida Geological Survey. 2

U.S. Geological Survey, Reston, VA 2.2092. 3

Deceased. 

4

U.S. Geological Survey, Tampa, FL 33614. 5

The name celestine (Fleischer, 1987) is currently used by the U.S. 

Geological Survey. 

Acknowledgments 

A.D. Duerr was partly supported by the So'Ithwest 

Florida Water Management District (SWFWMD). The 

SWFWMD is also responsible for the Regional Observation 

and Monitor-Well Program (ROMP). Thomas Scott, Florida Geological Survey, supplied copies of his unpublished 

lithologic logs for the ROMP 16 and ROMP 26 drill holes. 

We thank Craig Hutchinson, U.S. Geological Survey 

(USGS), Tampa, Fla., for the St. Petersburg gypsum 

HARDEE 

COUNTY 

Newbern• 

Grove 

DESOTO 

COUNTY 

•Dee 

0 100 MILES 

1 00 KILOMETERS 

Figure 23.1. Locations of three Florida drill holes in 

which celestine has been found. Dees well and 

Newbern Grove well were drilled by the U.S. Geological Survey and are discussed in this re'1ort; 

TR 18-2 was described by Cook and others (1985). 

23. Celestine (SrS04 ) in Hardee and De Soto Counties, Florid" 129 
DEPTH BELOW 

SURFACE 

IN FEET DEES ROMP ROMP NEWBERN 

16 26 GROVE 

0 .-- _? HAWTHORN 

FORMATION 

(MIOCENE) 

---?-

200 

TAMPA 

LIMESTONE 

(MIOCENE) 

400 

---?- --

SUWANNEE 

600 LIMESTONE 

(OLIGOCENE) 

---?- +- OCALA 

LIMESTONE 800 

(EOCENE) 

---?- -

1,000 TO 942FT 

AVON PARK 

FORMATION 

c (EOCENE) I 

I 

1,200 I 

I 

TO 1,280 FT 

TO 1,320 FT 

1,400 

Figure 23.2. Stratigraphic columns showing depths at 

which celestine (C) was found in the Dees and Newbern 

Grove wells. Unpublished logs for ROMP wells 16 and 26 

are from Thomas Scott and the files of the Florida Geological Survey, Tallahassee, Fla., and the U.S. Geological 

Survey, Tampa, Fla. Correlations are tentative. TD, total 

depth of well. 

sample that was chemically analyzed. We appreciate 

reviews by Ruth Deike and Sam Altschuler, both of the 

USGS. 

STRATIGRAPHY AND MINERALOGY 

Celestine occurs as fine sand-sized grains in limestones, dolomites, and phosphatic sands in south-central 

Florida. Because samples that contain celestine were collected from several depths in the Dees and Newbern Grove 

drill holes (fig. 23.2), we know the general lithologic 

association, but the exact context of the sulfate cannot be 

determined without thin sections. The specific gravity ( SG) 

of celestine is 3.9 and exceeds the specific gravities of 

calcite (2. 7) and dolomite ( 2. 9). Thus, celestine may lag 

behind both calcite (CaC03) and dolomite (CaMg(C03h) as 

cuttings move up the borehole during drilling, and samples 

are likely to contain cuttings of different densities from 

strata many feet apart. 

Anhydrite (CaS04 ) and gypsum (CaS04 ·2H20) were 

looked for but not found in the cuttings. 6 The major 

occurrence of sulfate minerals in south-central Florida is in 

the lower confining unit of the Floridan a1uifer system, 

so-named because of its impermeability to ground water and 

its low porosity. The top of the lower confining unit in this 

area is more than 2,000 ft below the lowest celestine sample 

(Miller, 1986). 

Celestine was discovered by optical microscopy in a 

bromoform (SG=2.85) concentrate of the fin~ sand fraction 

of disaggregated cuttings from a depth of 1 ,083 ft in the 

Newbern Grove well. It makes up about 99 volume percent 

of the heavy concentrate, about 50 volume percent of the 

fine sand fraction, and about 0.25 volume percent of the 

whole sample. Celestine was identified by comparison of 

peaks on a CuKaq X-ray diffraction trace (fg. 23.3) with 

those on a published standard celestine X-ray diffraction 

pattern (Joint Committee on Powder Diffracfon Standards, 

1986). The chemical composition was confirmed by X-ray 

dispersion on a scanning electron micros-cope (SEM). 

Celestine grains on the SEM appear as irregular, narrow, 

honeycombed plates, which typically have one or more 

smooth surfaces (fig. 23.4). Under the opticrl microscope, 

celestine grains are short, colorless, irregular prisms that 

have many voids or inclusions. The indices of refraction 

are about 1.62, the optic angle (2V) is fairly high, extinction is parallel, and birefringence is first-order white and 

gray. In at least one sample, collected from r depth of 675 

ft in the Dees well, celestine is partly replaced by calcite. 

CELESTINE AND GROUND-WATER CHEMISTRY 

Water in the Upper Floridan aquifer in Hardee and De 

Soto Counties has anomalously high concentrations of Sr2+ 

(fig. 23.5, table 23 .1) and SO~-. The median concentration 

of Sr2+ in U.S. drinking water is 0.11 mg/L (Hem, 1985). 

The highest values reported in U.S. wells ar~ 52 mg/L, in 

Wisconsin (Skougstad and Horr, 1963), and 57 mg/L, in 

Port Charlotte, Fla. (Steinkampf, 1982; see also Black and 

Brown, 1951). The maximum value reported in this study is 

43 mg/L (table 23.1). The Sr2+ concentration increases 

rapidly from the regional potentiometric high at Polk City 

along a southwestward ground-water flow path (Back and 

Hanshaw, 1970) that includes wells at Zolfo Springs, 

ROMP 26, and ROMP 10 (figs. 23.6 and 23. 7). Along the 

flow path, Sr2

+ concentration peaks at the Zolfo Springs 

well at 31.0 mg/L and then decreases along the flow path 

toward the southwest, whereas so~- concent-ation continues to increase (fig. 23. 7). High concentration'S of Sr2

+ also 

are present southeast of the flow path in De Soto County. 

The Sr2

+ concentration shown for ROMP 10 in figure 23.5 

is 34.0 mg!L; in figure 23.7, it is 19.0 mg/L. The two 

6

Barite (BaS04 ), the major component of some drilling tluids, was 

also looked for but not found. The primary drilling tluid used in the two 

drill holes was water. 

130 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
20 30 40 50 

DEGREES 29 (<;uK..,) 

D-spacings (in degrees 2 theta and angstroms) and relative 

peak intensities (1/1 0 ) for celestine from a depth of 1,083 ft 

in the Newbern Grove well, Florida, and for standard 

celestine 

[Data for standard celestine are from the Joint Committee on Powder 

Diffraction Standards (I 986, card 5-593). Other reflections (angstroms/intensity) in the range from 2° to 50° 28 listed in the standard file that did not 

appear on the trace of the Florida sample: 4.23/11, 3.29/98 (masked by the 

quartz peak in the Florida sample), 2.73/63, 2.39/7 , 2.38/17 , 2.16/7, 

2.14/25 , 2.00/48, 1.95/15. In addition, the card states that there are "10 

other reflections" that are not listed. Dot leaders mean no reflection 

reported] 

Newbern Grove celestine Standard celestine 

D-spacing 1/1 0 0

28 A 

D-spacing 1/10 0

28 A 

16.3 5.4 2 

20.9* 4.3* 6* 

23.4 3.8 22 23 .6 3.77 35 

24.6 3.6 II 24.9 3.57 2 

25.7 3.5 II 

26.4 3.4 3 26.0 3.43 30 

26.7* 3.3* 19* 

27.7 3.2 99 28.1 3.18 59 

29.8 3.0 32 30.1 2.97 100 

32.5 2.8 22 

33.3 2.7 67 33.5 2.67 49 

34.4 2.6 5 34.7 2.58 6 

35.4 2.54 9 

36.1 2.51 7 

37.4 2.49 20 

39.3 2.29 27 

40.6 2.22 9 40.0 2.25 18 

41.2 2.19 9 

42.0 2.20 8 40.9 2.21 5 

44.0 2.06 100 44.3 2.04 55 

44.9 2.02 30 44.4 2.04 57 

46.4 2.00 17 45.2 2.01 40 

48.3 1.88 7 

48.9 1.86 7 49.1 1.86 7 

*Peak for internal quartz standard. 

Figure 23.3. X-ray diffractogram of celestine in cuttings 

from a depth of 1,083 ft, Newbern Grove well, Hardee 

County, Fla. Celestine was crushed and attached to glass 

slide with amyl acetate. Quartz (26.7° and 20.9° 28) is an 

internal standard. Table lists peaks from Newbern Grove 

celestine and standard celestine. 

Figure 23.4. Scanning electron micrograph of celestine 

grains in cuttings from a depth of 1,083 ft in the Newbern 

Grove well, Hardee County, Fla. Grains are approximately 

0.1 mmacross. 

values were obtained at different times. The lower measurement was made after permitting the well to flow for 

several hours and is considered the more accurate of the 

two. 

Thermodynamic speciation calculations made by 

using the computer program WATEQF (Plummer and 

others, 1976) indicate that ground water in the Upper 

Floridan aquifer is initially undersaturated with celestine 

and gypsum at the Polk City potentiometric high (fig. 23. 7). 

As the water moves southwestward along the flow path, the 

saturation indices of both minerals increase; apparently, the 

water reaches equilibrium with celestine near Zolfo Springs 

and beyond but never reaches equilibrium with gypsum 

along the flow path (fig. 23.7). These calculations indicate 

that celestine initially dissolves along the flow path. Dissolution of Sr-bearing gypsum further increases the dissolved 

Sr content. As the ground water reaches saturation with 

celestine near Zolfo Springs, further dissolution of gypsum 

causes precipitation of celestine and causes the observed 

decrease in Sr2+ concentration (fig. 23 .7). The data suggest 

that the present ground-water diagenetic environment is 

dissolving celestine in some places and redepositing it at 

points further down the hydrologic gradient in the Upper 

Floridan aquifer system. Aragonite is not present in the 

section and is not providing Sr2

+ in the modem groundwater system in the study area. Recrystallized shells that 

were originally aragonite indicate that aragonite may have 

been an early diagenetic source of Sr2

+. 

23. Celestine (SrS04 ) in Hardee and De Soto Counties, Florida 131 
334, 335 (ZOLFO SPRINGS) 

332 '\. 333 

• 32631.0 J2 0 15.0 19.0 . 320 

1~8 I 

298 

• 12.0 

304 

• 14.0 

277 

• 23.0 

265 

307 

9~2 

NEWBERN GROVE WELL 

• 

I 

I 

I 

I 

I 

I 

I 

I 1~ I 

--~}~ ~~6-~ _ _r----------------- 2~1----------i 

68 I 

143 

• 1.8 

46 

• 27.0 

172 

• 2.0 

139 

• 1.4 

92 

83 ·3.6 

• 11.0 

32(ROMP10) 

244 (ROMP 26) 

214 '\- 212 . ". . 16.0 24.0 10.0 

197 

.11.0 

171 

• 3.1 

120 

•4.9 

116. 110 

19.0 •3.4 

58 

21.0 • 

DEES • WELL 

37 

• 

8~ 

1.3 

199 

• 8.9 

132 

• 24.0 

85 (ROMP 16) 

•23.0 77 

e79 • 22.0 6.9 

26 

• 

. I 

230 23.8 .237 22.0• 226 

219 13.0• 19.0 22.0 

1 !o 2~6 2~4 2~0 I 

19.0 22.0 28.0 182 

173 174 •19.0 

21 .o• 9.8• 17.0 e162 

149• •169 22 0 18.0 21 .0 22.0 . 146.22.0 

22w.134 

102~ 22.0 

6.8 101 

• 1.8 

• 34.0 43.0 11.0 13 

19.0• 

6 

• 28.0 

•12 

37.0 

---------------------------------------J 

10MILES 

10 KILOMETERS 

Figure 23.5. Concentration of Sr2+ in ground water in Hardee and De Soto Counties, Fla. 

Decimal numbers indicate maximum concentration of Sr+, in milligrams per liter (mg/L), for 

water in each well ; other numbers refer to well localities (table 23.1). 

DISCUSSION 

The present distribution of celestine in south-central 

Florida, as inferred from the mineral samples and the 

presence of high Sr2

+ concentrations in ground water of the 

Upper Floridan aquifer, is a result of early and late 

diagenetic processes. In the early processes, the major ions 

that presently control the ground-water chemistry were 

trapped in solid phases (minerals). Subsequently, as freshwater was added in the recharge area and sea level changed, 

the distribution of celestine changed from an early diagenetic pattern to the present, late diagenetic pattern. 

Early Diagenesis 

The ions most likely involved in the generation of 

celestine during or soon after deposition of the host sediment are Ca2 +, Mg2 +, Sr2 +, SO~ , and HCO;-. Clues to 

132 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 23.1. Concentration of strontium in ground water in Hardee and DeSoto Counties, Fla. 

[Data are from the files of the U.S. Geological Survey, Tampa, Fla. Only values measured after 1972 were used; many older measurements are inaccurate. 

NGVD, National Geodetic Vertical Datum] 

Locality 

number 

(fig. 23.5) 

De Soto County: 

6 

12 

13 

26 

32 (ROMP 10) 

37 

46 

58 

77 

79 

80 

83 

85 (ROMP 16) 

91 

92 

101 

102 

110 

116 

120 

132 

134 

135 

139 

143 

146 

149 

162 

169 

170 

171 

Altitude of 

land surface 

(feet above 

NGVD of 

1929) 

36 

42 

42 

47 

35 

47 

34 

40 

61 

64 

62 

54 

54 

81 

73 

? 

? 

65 

? 

? 

68 

82 

80 

55 

49 

87 

86 

89 

80 

90 

62 

Total 

depth 

of well 

(feet) 

900 

2,160 

1,210 

460 

411 

1.189 

1,411 

418 

396 

1,500 

Concentration 

of dissolved 

strontium, Sr2 + 

(milligrams 

per liter) 

28.0 

37.0 

19.0 

11.0 

19.0, 34.0 

43.0, 34.0 

27.0 

21.0 

6.9 

22.0 

335 1.3 

384 11.0 

942 23.0 

1,478 21.0 

335 3.6 

291 1.8 

? 6.8 

353 3.4 

? 1.2, 19.0 

350 4.9 

1.412 

1,508 

1.461 

250 

430 

1,525 

1,492 

1,018 

1,350 

300 

327 

24.0 

22.0 

22.0 

1.4 

1.8 

22.0 

18.0 

22.0 

19.0, 20.0, 21.0 

22.0 

3.1 

the early diagenetic processes may be found by examining 

the difference between the concentration of these ions in 

seawater of normal salinity (35 parts per thousand) and their 

proportions in minerals in accumulating sediments, where 

the amount of calcite (CaC03) is equal to the amount of 

dolomite (CaMg(C03h), and both are more abundant than 

gypsum (CaS04 ·2H20). All three minerals are much more 

abundant than celestine (SrS04 ). The differences are due in 

part to intrabasinal biologic and climatic controls and to the 

contribution of magnesium by extrabasinal sources such as 

volcanic ash. 

Biogenic CaC03 in the form of calcite and aragonite 

shells accounts for most or all of the carbonate as deposited 

originally. A small amount of Sr2

+, typically less than 1 

mole percent (Plummer and Busenberg, 1987), commonly 

Locality 

number 

(fig. 23.5) 

De Soto County: 

172 

173 

174 

182 

197 

199 

200 

204 

206 

212 

214 

219 

226 

230 

237 

238 

244 (ROMP 26) 

261 

Hardee County: 

265 

277 

298 

304 

307 

320 

326 

332 

333 

334 (Zolfo Springs) 

335 (Zolfo Springs) 

Altitude of 

land surface 

(feet above 

NGVD of 

1929) 

59 

86 

89 

91 

20 

80 

90 

91 

89 

34 

62 

90 

89 

90 

93 

91 

75 

94 

75 

54 

86 

78 

75 

83 

55 

90 

65 

65 

65 

Total 

depth 

of well 

(feet) 

320 

294 

300 

1,426 

208 

1,300 

1,443 

1,271 

1,421 

Concentration 

of disso,ved 

strontium, s~+ 

(milligrams 

per liter) 

2.0 

11.0,8.8, 7.7, 

10.0. 21.0 

5.6, 9.8 

19.0 

11.0 

8.9 

28.0 

19.0, 19.0, 22.0 

19.0 

257 10.0 

893 16.0 

895 12.0 

1,343 13.0 

765 22.0 

1,361 22.0 

1,505 19.0 

1,320 24.0 

284 3.9, 6.8 

1,345 

1,196 

1,280 

350 

343 

140 

326 

321 

1,002 

1,002 

933 

1.7 

23.0 

12.0 

14.0 

9.2 

1.8 

19.0 

15.0 

3.5, 32.0 

31.0, 30.0 

28.0 

enters the aragonite structure during the precipitation of 

shell material. Thus, the likely starting materials are 

Ca1 _xSrxC03 (where x=O to 0.03) and seawater. The 

presence of algal laminae and macroscopic Foraminifera at 

several levels in the area indicates episodes of hypersalinity 

(Applin and Applin, 1944). As brine from sabkhas adjacent 

to the submerged carbonate platform moves downward 

through the accumulating calcium carbonates, mrgnesium 

reacts with CaC03 to form dolomite (Land, 1982). During 

intervening periods of lower salinity, Sr2

+ can be released 

as aragonite recrystallizes to low-Mg calcite (Weiss and 

Wilkinson, 1988). The paucity of aragonite in pre-late 

Pleistocene shell deposits suggests that most Sr2

+ is 

released from aragonite soon after deposition (Harris and 

Matthews, 1968; Halley and Harris, 1979). In the hot, arid 

23. Celestine (SrS04 ) in Hardee and De Soto Counties, FlorkJa 133 
ALTITUDE, 

IN FEET 

400 

-2000 

3 

ZOLFO 

SPRINGS 

4 

ROMP 26 

LOWER FLORIDAN AQUIFER 

-2800 

-3600 

0 20 40 60 80 

DISTANCE FROM RECHARGE AREA. IN MILES 

Figure 23.6. Geologic cross section southward from Polk City, Fla., along groundwater flow path. North is at the left. Ionic concentration data from Miller (1986); 

concentration increases are shown by thickening of lines representing wells. Upper 

and middle confining units are discontinuous and leaky in places, including Polk City. 

Polk City is near the center of the potentiometric high that marks the recharge area. 

500 

400 

100 

NORTH SOUTH 

DISTANCE FROM RECHARGE AREA, 

IN MILES 

0 

-1~ 

f= X (/) w ~ 0 

-2~ ~ 

z 

I 0 

~ -3 ~ 

!;( 

(/) 

-4 

Figure 23.7. Concentrations of SO~- and Sr2+ and saturation indices of gypsum and celestine for wells shown in 

figure 23.6 (Plummer, unpub. data). Wells 3 (Zolfo 

Springs), 4 (ROMP 26), and 5 (ROMP 10) also appear in 

figure 23.5. Celestine is precipitating where the saturation 

index is near zero. 

part of the climatic cycle, the Sr2+ in the meteoric solution 

could react with the concentrated so~- in the brine to form 

celestine if Ca2

+ were not also available. 

Under most circumstances, Ca2 + is, ir fact, abundantly available. Seawater and brine originally have five 

times as much Mg2+ as Ca2+ (Hood and Pytkowicz, 1974), 

but as Mg2+ is used up in early dolomitization, the brine 

becomes enriched in Ca2

+. This enrichment promotes the 

precipitation of gypsum rather than celestine. However, if 

Mg2 + is introduced to balance the excess Ca2 +, then Ca2 + 

and Mg2+ can combine with HCO; to fom interstitial 

dolomite. Actually, dolomite can be precipitated if the 

Mg2

+ /Ca2+ ratio is greater than about 3 (Pierre. and others, 

1984), but in the Florida Keys, dolomite is precipitated 

where interstitial brine has a Mg2

+ /Ca2+ ratio of 40/1 

(Shinn, 1972). Dolomitization would remov~ Ca2+ and 

enhance the possibility of SrS04 precipitation. 

The richest sources of Mg2

+ are volcanic rocks. 

Rivers draining basic volcanic rocks in Australia supply 

abundant Mg2

+ to the Coorong Lagoon (table 23.2), where 

dolomite is precipitated (von der Borch, 1976). Although 

we cannot find evidence linking south-central Florida rivers 

with volcanic source rocks in the Cenozoic, sorre mafic ash 

from Eocene through Miocene volcanic ev~nts in the 

Caribbean (Case and Holcombe, 1980) and we<;'tem North 

America (Gilluly, 1965) probably was spread by wind and 

water over the carbonate banks and sabkhas of the Florida 

peninsula during the Eocene through Miocene .. Mg2 

+ would 

134 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 23.2. Some chemical and mineralogical characteristics of south-central Florida and three other gypsum-bearing 

localities 

[Y. abundant; y. present but not abundant; N. not present] 

South-central Florida 

Coorong Lagoon, 

Lake Alexandrina, 

Australia 

Ojo de Liebre Lagoon, 

Baja California, 

Mexico 

Southern U.S. 

Atlantic 

Coastal Pla;n 

Setting ...................... . Subsurface carbonates; Alkaline lake; carbon- Shoreline bay; noncarbonate substrate; 

Holocene. 

Subsurface mixr.d carbonates and 

phosphatesiliciclastic rC'cks; 

Eocene-~iocene. 

Eocene-~iocene. ate substrate; Holocene. 

References ................... . This report; ~iller, von der Borch, 1976 .. Pierre and others, 

1984. 

Gohn. 1988; Weaver 

1986; Thayer and and Beck. 1977. 

~iller, 1984. 

Celestine .................... . y N 

Gypsum ..................... . yl y 

Calcite ...................... . 

Aragonite .................... . 

y y 

i y 

Dolomite .................... . y y 

Halite ....................... . N N 

y N 

N 

y 

y 

N 

y 

y 

Y, 3 N 

N 

y 

y 

y2 

y 

N 

sr+ highly concentrated N 

interstitially. 

~ain Sr2+ source ............ . Brine, aragonite4 . • . . • Holocene aragonite 

substrate. 

Pleistocene aragonite 

in highlands. 

Brine. aragonit~. 

~g-clays .................... . y N N 

~ain ~gH source ........... . Seawater. . . . . . . . . . . . . Volcanic source 

rocks. 

Seawater. ........... . 

y 

Seawater. 

Inferred secondary source 

of ~g +. 

Volcanic ash......... None ............... . None ............... . Volcanic ash. 

1

Gypsum is mainly 2,000 ft or more below lowest celestine sample. 2

In pre-late Pleistocene deposits, most aragonite has recrystallized to calcite. 3

Wide variations laterally. 4

Aragonite is inferred to have been the original mineralogy of many mollusk shells that are now calcite or are represented by empty mo1ds. 

be released easily from the highly unstable glass in the ash 

as it reacted with the brine. Both dolomite and celestine 

could then precipitate from Mg-rich brine. Other evidence 

that may be explained by the interaction of Mg-rich ash 

and brine is the presence of the Mg-rich clays palygorskite ((MgA1)5(SiA1)80 22(0Hh·8H20) and sepiolite 

(Mg4Si60 15(0Hh·6H20) in cuttings from the Dees well, in 

cores from nearby wells (McCartan, Trommer, Owens, and 

Hawkins, article 24, this volume), and at many other 

localities in Florida, Georgia, and South Carolina (Weaver 

and Beck, 1977) (table 23.2). 

Late Diagenesis 

Petrologic studies that reveal multiple episodes of 

dolomitization in Eocene and Paleocene rocks in central 

Florida (Thayer and Miller, 1984; see also Randazzo and 

Hickey, 1978) are applicable to De Soto and Hardee County 

rocks. These complexities are due to processes such as 

climatic changes (brine produced in arid times followed by 

freshwater flushing during humid times), rises in sea level 

(flushing of brine or freshwater by normal seawater). and 

changes accompanying rising temperature and presEure due 

to burial. 

Another indicator of diagenesis is the difference 

between the present chemical composition of suh:urface 

minerals and the chemical composition of experimentally 

grown minerals. Our preliminary analysis of a gypsum 

sample from the middle confining unit in a well in St. 

Petersburg, about 60 mi west of Lake Garfield (fig. 23.6), 

reveals 0.08 mole percent strontium. Kushnir's (1980) 

gypsum grown at 30 oc from seawater concentrated to three 

times normal salinity contains 0.18 mole percent strontium. 

The strontium deficit in the St. Petersburg gypsum may be 

a result of recrystallization of gypsum in equilibrium with 

less saline water (lchikuni and Musha, 1978) or primary 

precipitation in a brine relatively depleted in Sr2

+. 

The distribution of hydrochemical facies reflects 

modem diagenetic processes acting on previously deposited 

minerals. Using the hydrochemical data of Back znd Hanshaw (1970), Plummer (1977) and Plummer ani others 

(1983) showed that the predominant diagenetic reaction in 

the study area is dedolomitization, that is, the net dissolution of dolomite and the precipitation of calcite criven by 

23. Celestine (SrS04 ) in Hardee and DeSoto Counties, Floricl'l 135 
gypsum dissolution. Accompanying the dedolomitization 

reaction are many other diagenetic reactions that occur to a 

lesser extent, including sulfate reduction (Plummer and 

others, 1983) and dissolution and reprecipitation of celestine (this study). Currently, celestine is being dissolved 

upgradient and reprecipitated at points further down the 

hydrologic gradient to the southwest as CaS04 continues to 

dissolve. If sea level does not rise, all celestine eventually 

will be flushed seaward. 

Kushnir ( 1986) considered several models for the 

origin of celestine and the evolution of the dissolved Sr 

content of ground water in contact with CaS04 -bearing 

rocks. In one model (mechanism A). water rich in NaCl and 

Sr2

+ (several hundred milligrams per liter) precipitates 

SrS04 upon contact with CaS04 -bearing rocks. This reaction probably occurs deep in sedimentary basins but is 

currently not occurring in the Upper Floridan aquifer. In 

Kushnir's (1986) second model (mechanism B), water 

having low NaCl content and low Sr2

+ content (approximately 1 mg/L) flows into a zone of Sr-bearing CaS04 • 

Release of Sr2+ by dissolution of CaS04 causes a rapid rise 

in dissolved Sr content, and if celestine saturation is reached 

prior to CaS04 saturation, further dissolution or recrystallization of CaS04 causes precipitation of celestine and a 

subsequent lowering of dissolved Sr content. Our observations in Hardee and De Soto Counties. Fla., confirm that 

Kushnir· s mechanism B is operating downgradient: however, the presence of celestine in the rocks up gradient of the 

CaS04-bearing zone must be explained by another mechanism. Relatively dilute ground water attains high dissolved 

Sr content (fig. 23.5) and approaches celestine saturation 

before reaching the CaS04 zone. Therefore, dissolution or 

recrystallization of CaS04 is not the mechanism whereby 

Sr2

+ concentration is increased in the upgradient part of the 

flow path. Other possible mechanisms for this part of the 

flow path include dissolution or recrystallization of aragonite (Kinsman, 1969) and dissolution of preexisting celestine. Along the flow path of figure 23.6, the water chemistry suggests that the CaS04 zone begins between Lake 

Garfield and Zolfo Springs (fig. 23. 7). The precipitation of 

celestine. which begins when ground water enters the 

CaSO 4 zone, causes a decrease in dissolved Sr content 

downgradient of Zolfo Springs (fig. 23. 7). 

FACTORS AFFECTING CELESTINE DEPOSITION 

AND NONDEPOSITION IN OTHER AREAS 

Celestine is reported in notable amounts from one 

other Coastal Plain locality, in central Texas (Pearson and 

Rettman, 1976; Deike, 1991). It is in the Edwards Limestone (Cretaceous), where it coexists with calcite, dolomite. 

gypsum, and fluorite. Thin sections of the Edwards Limestone reveal that celestine fills bioclast molds in units 

composed of secondary dolomite and that it also occurs as 

late diagenetic precipitates along fractures. The celestine 

appears to have been introduced, or at least reprecipitated. 

well after lithification of the host sediment. In this respect, 

it is similar to the A von Park Formation occurrence in 

Hernando County, Fla. (Cook and others, 19°5). Similarly, 

Sr2

+ -rich ground water in Ohio is associated with celestinebearing evaporitic rocks, and adjacent shales do not have 

high Sr2

+ levels (Feulner and Hubble, 1960). However, 

ground water approaching celestine saturation (maximum 

Sr2+ concentration= 15 mg/L and SO~- con:-entration typically greater than 1,300 mg/L) is present in the Madison 

Limestone (Mississippian) in Montana, South Dakota, and 

Wyoming, but celestine has not been found in cores from 

the area (Busby and others. 1991). Because of the apparent 

lack of celestine in a variety of other settings where its 

components are abundant (table 23.2), the presence of 

celestine in south-central Florida cannot be explained 

readily by reference simply to burial, climafr. or sea-level 

changes, and the release of Sr2

+ during recrystallization of 

aragonite and gypsum. Further petrologic anrl geochemical 

studies may yield new evidence of the special conditions 

necessary for the formation of celestine. 

CONCLUSIONS 

The distribution of celestine in south-central Florida 

is a result of early concentration and trapr~ng of Sr2+, 

SO~-, Mg2 +, HCO;, and Ca2 + in solid phases (minerals) 

in carbonate and evaporite deposits and th~ subsequent 

dissolution and reprecipitation of celestine by ground-water 

processes. 

REFERENCES CITED 

Applin. P.L., and Applin, E.E.R., 1944, Regional subsurface 

stratigraphy and structure of Florida and southern Georgia: 

American Association of Petroleum Geologists Bulletin, 

v. 28, no. 12, p. 1673-1753. 

Back, William, and Hanshaw, B.B., 1970, Comparison of chemical hydrogeology of the carbonate peninsulas of Florida and 

Yucatan: Journal of Hydrology, v. 10. no. 4, p. 330-368. 

Black, A.P .. and Brown, Eugene. 1951, Chemical character of 

Florida's waters. 1951: Florida Board of Conservation, Division of Water Survey and Research, Water Survey and 

Research Paper 6, 119 p. 

Busby. J.F., Plummer, L.N., Lee. R.W., and Ha"'shaw. B.B .. 

1991, Geochemical evolution of water in the Madison aquifer 

in parts of Montana. South Dakota, and W~'<:~ming: U.S. 

Geological Survey Professional Paper 1273-F, 89 p. 

Case, J.E., and Holcombe, T.L., 1980, Geologic-te~tonic map of 

the Caribbean region: U.S. Geological Survey Hiscellaneous 

Investigations Series Map 1-1100, 3 sl"leets, scale 

1:2,500,000. 

Cook, D.J .. Randazzo, A.F .. and Sprinkle. C.L., 1985, Authigenic fluorite in dolomitic rocks of the Floridan aquifer: 

Geology, v. 13, no. 6, p. 390-391. 

136 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Deike, R. G., 1991, Comparative petrology of cores from two test 

wells in the eastern part of the Edwards aquifer, south-central 

Texas: U.S. Geological Survey Water-Resources Investigations Report 87-4266, 142 p., 1 pl. 

Feulner, A.J., and Hubble, J.H., 1960, Occurrence of strontium 

in the surface and ground waters of Champaign County, 

Ohio: Economic Geology, v. 55, no. L p. 176-186. 

Fleischer, Michael, 1987, Glossary of mineral species (5th ed.): 

Tucson, Ariz., Mineralogical Record, 227 p. 

Ford, W.E., 1932, A textbook of mineralogy, with an extended 

treatise on crystallography and physical mineralogy, by 

Edward Salisbury Dana (4th ed., revised and enlarged by 

W.E. Ford): New York, John Wiley and Sons, 851 p. (11th 

printing, 1948. ) 

Gilluly, James, 1965, Volcanism, tectonism, and plutonism in the 

Western United States: Geological Society of America Special Paper 80, 69 p. 

Gohn, G. S., 1988, Late Mesozoic and early Cenozoic geology of 

the Atlantic Coastal Plain-North Carolina to Florida, in 

Sheridan, R.E., and Grow, J.A., eds., The Atlantic continental margin-U.S., v. I-2 of The geology of North 

America: Boulder. Colo., Geological Society of America, 

p. 107-130. 

Halley, R.B., and Harris, P.M., 1979, Fresh-water cementation of 

a 1 ,000-year-old oolite: Journal of Sedimentary Petrology, 

v. 49, no. 3, p. 969-988. 

Harris, W.H., and Matthews, R.K., 1968, Subaerial diagenesis 

of carbonate sediments-Efficiency of the solutionreprecipitation process: Science, v. 160, no. 3823, p. 77-79. 

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water (3d ed.): U.S. Geological 

Survey Water-Supply Paper 2254, 264 p. 

Hood, Donald, and Pytkowicz, R.M., 1974, Chemical oceanography, section 1 of Smith, F.G.W., ed., Handbook of marine 

science. v. I: Cleveland, Ohio, CRC Press, p. 3-70. 

lchikuni, M., and Musha, S., 1978, Partition of strontium 

between gypsum and solution: Chemical Geology, v. 21, 

p. 359-363. 

Joint Committee on Powder Diffraction Standards, 1986, Mineral 

powder diffraction file-Data book: Swarthmore, Pa., Joint 

Committee on Powder Diffraction Standards, 1390 p. 

Kinsman, D.J.J .. 1969, Interpretation of Sr2+ concentrations in 

carbonate minerals and rocks: Journal of Sedimentary Petrology. v. 39, no. 2, p. 486-508. 

Kushnir, Jacob, 1980, The coprecipitation of strontium, magnesium, sodium. potassium and chloride ions with gypsum. An 

experimental study: Geochimica et Cosmochimica Acta, 

v. 44. no. 10, p. 1471-1482. 

Kushnir, S. V., 1986. The epigenetic celestite formation mechanism for rocks containing CaS04 : Geochemistry International. v. 23, no. 4, p. 1-9. (Translation from Geokhimiya. 

1985, no. 10. p. 1455-1463.) 

Land, L.S., 1982, Dolomitization: American Association of 

Petroleum Geologists Education Course Note Series no. 24, 

20 p. 

Miller, J.A., 1986, Hydrogeologic framework of the Floridan 

aquifer system in Florida and in parts of Georgia, Alabama, 

and South Carolina: U.S. Geological Survey Professional 

Paper 1403-B. 91 p. 

Pearson, F.J., Jr., and Rettman, P.L., 1976, Geochemical and 

isotopic analyses of waters associated with the Etiwards 

Limestone aquifer, central Texas: Reston, Va., U.S. Geological Survey. 35 p. 

Pierre, Catherine, Ortlieb, Luc, and Person, Alain, 1984, Supratidal evaporitic dolomite at Ojo de Liebre Lagoon: nineralogical and isotopic arguments for primary crystallization: 

Journal of Sedimentary Petrology, v. 54, no. 4, 

p. 1049-1061. 

Plummer, L.N .. 1977, Defining reactions and mass transfe~ in part 

of the Floridan aquifer: Water Resources Research, v. 13, 

no. 5, p. 801-812. 

Plummer, L.N., and Busenberg, Eurybiades, 1987, Thermodynamics of aragonite-strontianite solid solutions; results from 

stoichiometric solubility at 25 and 76 °C: Geochimica et 

Cosmochimica Acta, v. 51, no. 6, p. 1393-1411. 

Plummer, L.N., Jones, B.F .. and Truesdell, A.H., 1976, 

WATEQF-A Fortran IV version of WATEQ, a computer 

program for calculating chemical equilibrium of natural 

waters: U.S. Geological Survey Water-Resources Investigations Report 76-13, 61 p. (Revised and reprinted Jan. 1984, 

70 p.) 

Plummer, L.N., Parkhurst, D.L., and Thorstenson, D.C., 1983, 

Development of reaction models for ground-water systems: 

Geochimica et Cosmochimica Acta, v. 47, no. 4, 

p. 665-686. 

Randazzo, A.F .. and Hickey, E.W., 1978, Dolomitization in the 

Floridan aquifer: American Journal of Science, v. 277, no. 8, 

p. 1177-1184. 

Shinn, E.A., 1972, Recent dolomite, Sugarloaf Key, in Ginsburg. 

R.N., ed., South Florida carbonate sediments: Sedimenta II 

(Miami, Fla., University of Miami), p. 62--67. (Reprint of a 

1964 field trip guidebook.) 

Skougstad, M. W. , and Horr, C. A. , 1963, Occurrence and distribution of strontium in natural water: U.S. Geologicrl Survey 

Water-Supply Paper 1496-D, p. D55-D97. 

Steinkampf, W.C., 1982, Origins and distribution of saline 

ground waters in the Floridan aquifer in coastal southwest 

Florida: U.S. Geological Survey Water-Resources hvestigations Report 82-4052, 34 p. 

Thayer, P.A .. and Miller, J.A .. 1984. Petrology of lower and 

middle Eocene carbonate rocks. Floridan aquifer. central 

Florida: Gulf Coast Association of Geological Societies 

Transactions, v. 34, p. 421-434. 

von der Borch, C. C.. 1976, Stratigraphy and fom1ation of 

Holocene dolomitic carbonate deposits of the Coorong area, 

South Australia: Journal of Sedimentary Petrolog:r, v. 46, 

no. 4, p. 952-966. 

Weaver, C .E., and Beck, K. C.. 1977. Miocene of the southeastem United States; a model for chemical sedimentation in a 

perimarine environment: New York, Elsevier. 234 p. 

(Reprinted from Sedimentary Geology. v. 17, nos. 1-2. 

1977.) 

Weiss, C.P., and Wilkinson, B.H., 1988, Holocene ce""'lentation 

along the central Texas coast: Journal of Sedimentary Petrology, v. 58, no. 3, p. 468--478. 

23. Celestine (SrS04 ) in Hardee and De Soto Counties, Florida 137 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Florida 1 

By Lucy McCartan,2 j.T. Trommer/ J.P. Owens,2 and R.M. Hawkins2 

INTRODUCTION 

A sinkhole complex in Pinellas County, Fla. , has 

formed in the Tampa Limestone of Miocene age (figs. 24.1 

and 24.2). It is filled mainly with quartz sand from the 

overlying unit, which is presumably of Pleistocene age. As 

much as 15 ft of leached limestone separates the surficial 

sand from the less weathered limestone below. Thirty-four 

holes 12-74 ft deep were drilled in 1987-88 to establish the 

stratigraphy in the area and to install ground-water monitoring wells. Six of these have been studied in detail. In this 

report, we describe split-spoon and auger samples from 

these drill holes and provide a preliminary interpretation of 

their mineralogical significance. 

Acknowledgments 

This study was conducted by the U.S. Geological 

Survey (USGS) in cooperation with the Pinellas County 

Sewer System, which provided some support for Trommer. 

Reviews by Craig Hutchinson and David Soller (both of the 

USGS) led to improvements in the report. 

METHODS 

Split-spoon samples are taken by pushing a hollow 

steel or brass pipe with a plastic liner ahead of a drill bit 

attached to auger stems. Therefore, split-spoon samples 

generally are more representative of the geologic unit from 

which they are taken than the material on the auger flights. 

For this reason, the two types of samples are distinguished 

in this report. Drill holes WP, FL3, T3, and T2 were 

sampled by the split-spoon method; only auger samples are 

available from 2ndFL and Surf2. 

Subsamples were selected from the plastic split-spoon 

liners and bags of auger samples for separation and mineralogical analyses. Ten to 20 cm3 of coarse-grained material 

(sand) and about 1 cm3 of fine-grained material (silt and 

1

Prepared in cooperation with the Pinellas County Sewer System. 2

U.S. Geological Survey, Reston, VA 22092. 3

U.S. Geological Survey, Tampa, FL 33634. 

clay) were used for mineralogical analyses. Clay-sized 

minerals were extracted from all samples by mixing them 

with deionized water. The muddy water was decanted and 

centrifuged to permit recovery of the fraction containing 

particles finer than 2 J.Lm. Clay was then sedimented on 

glass slides, air dried, and X-rayed with CuKa 1 radiation. 

Minerals in the clay fraction were identified by comparison 

of peaks between 2.5° and 12.5° 28 with those in the 

standard data book (Joint Committee on Powder Diffraction 

Standards, 1974, 1981). Untreated samples yielding peaks 

between 2.5° and 8.8° 28 were vapor glycolated overnight 

and X-rayed again. Glycolation causes the main peak for 

illite/smectite mixed-layer clay to shift from 6° to about 5o 

28; this shift enables us to discriminate between this 

mineral and dioctahedral vermiculite, whose main peak 

remains at about 6o. 

Sand-sized material was wet sieved to remove clay 

and to separate the fine sand fraction (80-200 mesh; 

0.18-0.07 mm); the sand was then dried at 110 oc. Light 

and heavy fine sand fractions were then separated in 

bromoform (specific gravity of 2. 85). The mineral grains 

were identified in index oil mounts examined under a 

petrographic microscope. Nonopaque heavy minerals (figs. 

24.3 and 24.4, table 24.1) were characterized as nonresistant (hornblende, garnet, monazite, and sphene), intermediate (staurolite, sillimanite, kyanite, and andalusite), and 

resistant (zircon, tourmaline, rutile, and spinel) on the basis 

of their observed resistance to chemical dissolution and 

physical abrasion (Owens and others, 1983). Heavy minerals were estimated to compose less than 5 percent of all the 

samples. Phosphate is abundant in some samples from 

2ndFL and WP but was not quantified. 

The proportion of carbonate minerals was determined 

by repeated treatment of selected whole subsamples with 10 

percent hydrochloric acid. The weight of the dried sample 

after acid treatment was subtracted from the dry weight of 

the original sample. 

STRATIGRAPHIC NOMENCLATURE 

The Florida Geological Survey has suggested changes 

in the stratigraphic nomenclature for Miocene rocks in 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Florida 139 
Figure 24.1. Map of part of a sinkhole complex in the 

study area, Pinellas County, Fla., showing topography 

(contour intervai=S ft), locations of drill holes from which 

split-spoon samples (WP, FL3, T3, and T2) and auger 

southwestern Florida. These changes reflect Scott's (1986, 

1988) correlation of cores and cuttings. The simpler scheme 

of Miller ( 1986) is used in this report. The two schemes are 

compared in figure 24.5. 

. ..;:r •. . 

1 MILE 

1 KILOMETER 

samples (2ndFL and Surf2) were taken, and line of stratigraphic section A-A' (fig. 24.6). Figure 24.2 depicts the 

same part of the Dunedin 7.5-minute quadrangle shown 

here. 

MINERALOGY 

The noncarbonate fraction of the Tampa Limestone is 

mainly quartz , but it contains as much as 20 percent 

140 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
82 45' 

.------------------------------------. 28'07'30" 

• 

~ surf ~n .,.--T2 

2nd FL-@ '®" I':'\ -

2 

+20 ~/ +2---c:o' 

T3 ~ ,@ -11 

'-./: -~1 • •• ~-. • • 

wp..-!!-

-6 

• 

• c-F~~ 

1 MILE 

0 1 KILOMETER 

Figure 24.2. Structure contours of base of surficial sands in part of the northeast corner of the 

Dunedin, Fla., 7.5-minute quadrangle. Numbers are feet above or below sea level; contour 

interval is 10 ft. Tick marks on inner contour line indicate a depression. Other sinkholes (a 

few feet in diameter) were suggested by ground-penetrating radar surveys conducted in 

Pinellas County from 1986 to 1988 (J.T. Trommer, unpub. data). Unlabeled black dots are 

control drill holes (not discussed in this report) for which the depth to the base of surficial 

sand is known. At points not enclosed in contour lines, the surficial sand may be as much as 

9ft thick. 

feldspar. A very small proportion of the total volume is clay 

minerals, and the predominant phase is illite/smectite. The 

most abundant heavy minerals are ilmenite, zircon, tourmaline, rutile, and garnet. 

The mineralogy of the overlying sand is more mature 

than that of the Tampa Limestone. There is very little 

feldspar, and the resistant heavy minerals are more abundant in the sand than in the limestone. Quartz is the most 

abundant mineral in the clay-sized fraction of the surficial 

sand, and kaolinite is the next most abundant mineral. Illite, 

illite/smectite, and vermiculite are present in small 

amounts. 

The intervening limestone residuum has some characteristics of both the fresher limestone below and the sand 

above. It has slightly less feldspar than the limestone but 

more than the sand. Similarly, the residuum has a slightly 

lower proportion of garnet and other fairly nonresistant 

heavy minerals than the limestone but has a larger proportion than the sand. The main clay-sized minerals in the 

residuum are illite/smectite in WP and T2, kaolinite in T3, 

and calcite in 2ndFL. 

Fine Sand Fraction 

The high proportion of staurolite, sillimanite, kyanite, and garnet in the heavy-mineral suite of the fine sand 

fraction (table 24.1) indicates that the terrigenous component of the Tampa Limestone and the overlying sand was 

derived originally from a metamorphic source, snch as the 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Flor:da 141 
ALTITUDE 

(FEET) 

~ 

WP 

GROUND 

SURFACE 

GRAY ... ·· 

SAND •· .. WITH .. · 

PLANT· .... ::::1 

::::1 FRAGMENTS · • : ." 

e BROWN ILTY -:-. · 

~SAND TO GRAY-·-.-:-· 

a: GREEN CLAY ~ 

TAMPA 

LIMESTONE 

WHITE 

LST 

LITHOLOGIC LOG 

SAND 

SG>2.85 SG<2.85 

CD 

!i 

Color (see explanation below right) 

Sand 

-

LST 

Clay and silt 

Limestone 

Plant fragment or residue 

Limestone, >50 percent CaC03 

CLAY 

1/S 

MINERALOGY OF THE FINE SAND FRACTION 

SG Specific gravity 

NR Nonresistant (G, garnet) 

I Intermediate (St. staurolite; Sil, sillimanite; 

K, kyanite) 

R Resistant (Z, zircon; T, tourmaline; R, rutile;) 

Q Quartz 

Feldspar 

MINERALOGY OF THE CLAY-SIZED FRACTION 

Q Quartz 

K Kaolinite 

V Vermiculite 

I Illite 

1/S Illite/smectite, mixed-layer clay 

C Carbonate mineral 

STRATIGRAPHY 

Ql 

Q2 

Q3 

Residuum 

Tampa Limestone 

Holocene unit 

Younger Pleistocene unit 

Older Pleistocene unit 

Weathered Tampa Limestone 

Miocene 

Figure 24.3. Lithology and mineralogy of drill holes WP and FL3, 

Pinellas County, Fla. Locations are shown in figure 24.1. Columns 

labeled sand and clay convey the dominant minerals present in 

fine sand (approximately 0.25-0.06 mm) and clay (clay is <2 ~J-m) 

size categories. The nonopaque heavy sand minerals are further 

divided into nonresistant (to chemical weathering), intermediate, 

and resistant groups. The three figures in a line represent the 

total percentage of each heavy-mineral group within the nonopaque minerals. Minerals indicated near each number have 

Ql 

+ 

02 

G3a 

This 

report 

<D 

0 

G) 

Q) 

® 

® 

@ 

(j) 

® 

® 

@) 

® 

© 

Fl3 SAND 

GROUND 

SURFACE 

SG>2.85 SG<2.B~ 

100% 70 110% 

SAND ·.·· 

' .. ·®<D LIGHT- . ·. · 

BROWN · • .' .. · @) l 

QUARTZ : ·.:. 

SAND .' . : 

TAN •. ·@ QUS~R~~ •• .' .' •• 

GRAY 

AND .. 

11!11. (j) BROWN •• •. · 

QUARTZ .•• 

SAND . 

COLOR 

I 1 I I 

NR • I • R 

St z • 47 51 

St z • 32~ 68 

4 St z • 36jl 60 

St z •27 71 

I 

Sil ;l.T.R • 55 44 

I 

I 

I 

I '----1--

I 

I 

I 

G St I T 

30. 33• 37 

Goddard and others (1948) 

10 YR 8!6 Pale yellow orange 

8!2 Very pale orange 

7/6 Dark yellow orange 

1/4 Gray orange 

4/2 Dark yellow brown 

2/2 Dusky yellow brown 

6/2 Pale yellow brown 

5YR 3/4 Medium brown 

5Y 9!1 Yellow gray 

8/1 Yellow gray 

7!2 Yellow gray 

4!2 Olive gray 

5GY 8/1 Light greenish gray 

97 

CLAY 

the highest frequency percentages. Quartz makes up more than 

90 percent of the fine sand fraction of the surficial unit, but 

feldspar is as much as 23 percent of the noncarbonate sand in 

residuum and fresh limestone samples. The relative amount of 

each mineral in the clay-sized fraction is shown in the right 

column by letter symbols. Colors to the left of the graphic 

lithology column were described in the field; colors designated 

by circled numbers to the right were noted at the time of the 

laboratory analysis. 

142 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
ALTITUDE 

(FEET) 

40 

35 

30 

25 

20 

15 

10 Q2 

T3 SAND 

GROUND SG >2.85 SG < 2.85 

SURFACE 0 100%70 100% 

BLACK .: : N R • I • R Q • F QUS~R~~ ·: .... @ St Z 

: ·.: :_: G) -29 70 

LIGHT-BROWN :::< f4\ TO TAN · • •·. \.:!:/ 

QUARTZ SAND .' :··.: • .. :··· .. .· .. 

·::·· .. : ® 

TAN ·.:_.:.:·: @ 

QUARTZ ::·.':'· 

SAND .:·..-:.-.~~ 

~:: ::::: 

z 

45 

z 

33 

99. 

100 

-5 BROWN QUARTZ SAND • · : : 

-10 

-15 

-20 

TAMPA LST 

-25 LIMESTONE 

-30 

-35 

-40 

-45 

CLAY 

Q-K>I/S>I 

G»K 

G»K-1/S-1 

Q2 

c 

T2 SAND 

SG >2.85 SG < 2.85 

0 100%70 100% 

NR•I•R QeF 

EXPLANATION 

PHOSPHATE GRAINS 

'VV'- IRON OXIDE CRUST 

CLAY 

1/S 

E9 CALCAREOUS CONCRETION 

OTHER SYMBOLS ARE EXPLAINED IN FIGURE 24.3. 

Figure 24.4. Lithology and mineralogy of drill holes T3 and T2, Pinellas County, Fla. Locations are shown in 

figure 24.1. Symbols are the same as those in figure 24.3. 

Piedmont rocks of Georgia. Potassium feldspar, abundant 

only in the limestone and limestone residuum, indicates a 

granitic (potassium-rich) source. Together, the feldspar and 

heavy-mineral suite reflect a granitic-metamorphic terrane. 

Ilmenite, the most abundant opaque mineral, typically is between a quarter and half of the total heavymineral fraction of the Pinellas County sediments. Ilmenite 

is found in most metamorphic, igneous, and sedimentary 

rocks, and so it is not useful as a provenance indicator. 

Similarly, quartz is common in most rocks of intermediate 

to felsic composition and contributes little to the discussion 

of provenance. 

Phosphate minerals except monazite are included in 

the opaque heavy minerals column in table 24.1 although 

some grains are not opaque. Phosphate other than monazite 

in the surficial sand is reworked from either the Tampa 

Limestone or younger Miocene phosphatic units that are 

present east of the study area (Johnson, 1986: Scott, 1986). 

Monazite is a detrital mineral derived from the Piedmont of 

Georgia. 

Resistant minerals are more abundant in the sands 

than in the limestone and residuum. This relative abundance 

suggests that the sand was derived mainly from the Tampa 

Limestone rather than directly from the Piedmont. During 

reworking, less resistant minerals were abraded and dissolved more rapidly than more resistant minerals. Another 

explanation, which seems much less likely, is that a 

sedimentary rock unit other than the Tampa Lime~tone was 

the source of the mineral suite that characte'i.zes the 

surficial sands in Pinellas County. 

Clay Fraction 

Very little clay is present in the fresh limestone. 

Kaolinite is the most abundant clay mineral in th~ surficial 

sands and the residuum. Quartz, however, is the most 

abundant mineral (clay sized but not a clay mineral) in the 

clay-sized fraction of the surficial sands, and its origin is 

discussed below. 

The presence of a minor amount of sepiolite in the 

2ndFL well may reflect a high concentration of rragnesium 

in the environment of deposition or in early postdepositional 

ground water (Weaver and Beck, 1977; Fishe:r, 1988). 

Judging from the vertical distribution of clay mine:rals in the 

drill holes, we infer that illite/smectite mixed-layer clay was 

the major detrital clay phase incorporated in the Tampa 

Limestone. 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Florida 143 
..... 

.a:. 

.a:. 

-= a 

l"'l 

f'l) Table 24.1. Mineralogy of selected lithologic samples from the Pinellas County, Fla., sinkhole complex f'l) 

c.. 

:r [All values in frequency percent except those for calcite, which are in weight percent. Dot leaders ( ... ), mineral not found; na, not analyzed. Heavy minerals have specific gravities greater than 2. 85. Fine (1Q 

~ sand fraction: H, hornblende; G, garnet; M, monazite; Sph, sphene; St. staurolite; Sil, sillimanite; K, kyanite; A, andalusite; Z, zircon; T, tourmaline; R, rutile; Sp, spinel. Feldspar is all potassium feldspar . ..... 

1..0 Clay-sized fraction: Q, quartz; V, dioctahedral vermiculite; K. kaolinite; 1/S, illite/smectite mixed-layer clay; I, illite; C. calcite; H. halloysite; Sep, sepiolite] 

= = c Depth Fine sand fraction Cll Clay-sized ~ below Nonopaque heavy minerals Opaque Cll Well Unit fraction 

~ surface Nonresistant Intermediate Resistant heavy Light minerals (<2 J.Lm) ~ (feet) H G M Sph St Sil K A z T R Sp minerals Quartz Feldspar Calcite1 

"" :r "' Split-spoon samples 0 

"C WP Residuum .......... 17 4 21 2 24 4 31 12 1 41 90 10 43 liS 0 ... ... ... . .. :I FL3 Q1? ................ 5-7 2 34 9 3 37 8 9 22 99 1 Q>K>V>I :r ... ... ... ... . .. .. . f'l) Q2 ................. 10-12 ... . .. ... . .. 23 8 1 1 46 10 12 ... 26 97 3 ... na ~ f'l) Q2 ................. 22 3 1 ... . .. 26 7 2 1 37 7 16 ... 22 100 . .. .. . Q>K>V>I 0 Q2 ................. 27 1 18 5 3 1 39 12 20 26 100 Q>K>V>I 0 ... ... . .. ... . .. .. . (1Q Q2 ................. 35 99 1 Q>K>I '< ... ... ... . .. . .. ... . .. ... ... ... ... ... ... .. . I» Q3a ................ 48 1 20 31 2 2 15 18 12 27 100 na :I ... . .. ... ... . .. .. . c.. Q3b ............... 72 28 2 24 5 4 11 18 8 35 77 23 na ~ ... . .. ... ... ... f'l) Residuum .......... 74 ... . .. ... . .. ... ... .. . ... .. . ... ... . .. .. . 87 13 64 K>I 0 

:r T3 Q2 ................. 6 1 20 3 5 1 53 3 14 31 100 na 6.. ... ... ... . .. ... ... 

a Q2 ................. 10 ... ... ... .. . ... ... . .. ... . .. ... ... ... ... 99 1 .. . Q=K>IIS>I 

0 Q2 ................. 20 ... . .. ... . .. 43 8 4 . .. 23 15 8 ... 24 100 . .. ... Q>>K (1Q 

'< Q2 ................. 25 45 15 6 1 16 12 5 24 100 Q>>K=IIS=I 0 ... . .. . .. ... . .. ... . .. 

- Q2 ................. 27 6 1 41 6 6 22 9 10 28 100 <1 na - ... ... ... . .. .. . :r 

f'l) Residuum .......... 47 5 1 ... ... 30 . .. 12 2 10 10 31 ... 45 92 8 ... K>I>>Q 

:e Tampa Limestone ... 57 7 8 3 ... 21 4 13 1 19 9 14 ... 50 84 16 85 c 

AT T2 Q2 ................. 17 3 1 1 19 11 5 37 5 17 1 40 100 :a ... ... ... .. . na r;· Residuum .......... 27 5 9 ... . .. 30 2 14 ... 16 11 13 . .. 84 84 16 71 liS ~ 

0 Auger samples I» 

"' [ 2ndFL Residuum .......... 3-6 4 3 ... . .. 30 7 4 2 32 13 4 ... 23 93 7 ... K=IIS>I 

-= Residuum .......... 6-9 ... ... ... ... 29 11 5 3 40 6 7 . .. 41 90 10 ... C>H=IIS=K>Sep AT Unknown .......... 12.5-14 5 2 38 3 7 1 34 6 4 38 94 6 36 1/S=K>I :r ... ... . .. Unknown .......... 14-15.5 3 28 24 ... 13 2 5 . .. 5 13 7 ... 52 82 18 44 I+Sep 

Surf2 Q2 ................. 11-12 ... 1 ... ... 22 7 5 ... 41 6 17 .. . 25 92 8 ... K>I 

Q2 ................. 12-12.4 ... . .. ... .. . ... . .. ... ... . .. ... ... .. . . .. 86 14 .. . K=I>IIS --

'Calcite weight percent was determined by digestion of a measured subsample by HCI. Calcite was not counted with quartz and feldspar. Some dolomite may be present. 
Scott ( 1986, 1988) 

Series Unit 

Pleistocene 

and Surficial sand 

Pliocene 

Bone 

Peace Valley 

Member 

River 

Formation 

Miocene 

Upper Arcadia 

unnamed Formation 

member 

Tampa 

Member 

Nocatee 

Member 

Oligocene Suwannee Formation 

a. 

:::::l 

2 

(.9 

E 

0 

..c: 

+-' 

s 

ro 

I 

Miller (1986) (details in 

Pleistocene units added) 

Unit Series 

02,03 Pleistocene Surficial sand 

Hawthorn 

Formation 

Miocene 

Tampa 

Limestone 

Suwannee Oligocene Limestone 

Figure 24.5. Stratigraphic nomenclature for Oligocene to Pleistocene units in Pinellas County, Fla. 

Mineral Evidence of Weathering 

This part of the discussion of the mineralogy of 

Pinellas County deposits is based on empirical studies of 

in-place weathering of Coastal Plain sediments along the 

Atlantic seaboard (Owens and others, 1983; McCartan and 

others, 1984). The mineralogy of surficial deposits in 

Pinellas County is similar to that in Atlantic Coastal Plain 

Quaternary deposits. The conclusions derived from the 

previous mineralogical studies follow: (1) if texture, composition, and depth are consistent in the section, then earlier 

deposits will have a lower proportion of nonresistant minerals than later deposits; (2) if sediment is of a single age. 

composition, and texture, then material nearer the surface 

will have a lower proportion of nonresistant minerals; and 

(3) abundant silt, clay, and authigenic cement tend to 

preserve the original mineralogy by impeding ground-water 

flow. An abundance of carbonate minerals would tend to 

buffer the ground water at pH= 8.4 (Garrels and Christ, 

1965), and this may retard leaching of minerals. This 

buffering may be the reason that garnet, feldspar, 

and illite/smectite are so abundant in the limestone and 

residuum. 

The sand at the Pinellas site has very little finegrained material, and so ground water flows freely through 

it and minerals undergo continuous alteration. Qurutz is the 

most abundant mineral in the clay-sized fraction of the 

surficial sands. Clay-sized quartz is produced by physical 

disintegration of sand-size quartz grains due to chemical 

weathering (Pavich and others, 1989) and is typically found 

in sand dunes (Soller, 1988). Although some of the finegrained quartz may be due to weathering processes at the 

site, most was probably deposited by wind and may have 

come from distant sources. 

Most of the feldspar has altered to kaolinite and illite. 

Most of the small amount of illite/smectite has broken down 

into illite and smectite layers; all the smectite and some of 

the illite have altered to vermiculite. Gamet and other 

nonresistant heavy minerals have dissolved or have altered 

to complex oxides and hydroxides. 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Floricla 145 
ALTITUDE 

(FEET) 

50 -

25 

-25 

-50 

A 

Q2 

RES 

LST 

A 

A' 

\PRESENT 

\ EROSIONAL 

\ SURFACE 

\ 

\ 

Q2 

RES 

LST 

FL3 

Figure 24.6. Stratigraphic section A-A' based on wells 

in which split-spoon samples were taken. See figure 

24.1 for line of section. A, Stratigraphy inferred for the 

site: Q1, Holocene; Q2, Q3a, Q3b, Pleistocene; RES, 

residuum on Tampa limestone; LST, Tampa LimeThe presence of dioctahedral vermiculite in FL3, a 

hole that penetrates the deepest part of a sinkhole (fig. 

24.6A), is of particular importance. Although vermiculite is 

found down to at least 27 ft in FL3, it is not present in T3. 

Conversely, small amounts of illite/smectite were found at 

10 and 25ft below the surface in T3, but none is present in 

FL3, where the base of the sand is about 73 ft below the 

surface. Vermiculite is usually present in undisturbed 

weathering profiles more than 60,000 yr old (Owens and 

others, 1983; McCartan and others, 1984). The differences 

in FL3 and T3 clay mineralogy suggest that the sand at T3 

is significantly less weathered than the sand in the bottom of 

the FL3 section and that the T3 section has been stripped of 

several feet of weathered sand (fig. 24.6B). Figure 24.6B 

extrapolates the area of eroded sands to T2 and WP 

although the clays from the surficial sand in those holes 

have not yet been studied. However, the least resistant of 

the heavy minerals, hornblende, is 3 percent of the heavymineral fraction at 17 ft in T2, which is comparable to the 

percentages at 22 ft in FL3 and 27 ft in T3. It may, 

therefore, be inferred that illite/smectite is also present. By 

analogy with T3, T2 also appears to have been stripped. 

8 

A 

WP 

FL3 T3 

EXPLANATION 

T2 

INFERRED ORISINAL 

DEPOSITIONAL SURFACE 

A' 

DEPOSITS THAT HAVE BEEN 

STRIPPED (HYPOTHETICAL) 

stone (Miocene). V, dioctahedral vermiculite. B, The 

distribution of vermiculite, which is present only in 

the upper part of FL3, may be due to erosion of 

adjacent vermiculite-bearing deposits and infilling of 

the sinkhole axis at FL3, indicated by arrows. 

DISCRIMINATION OF PLEISTOCENE UNITS 

Contacts at the top and base of the weathered limestone were determined in the field and are further supported 

by mineralogical studies. However, field observations alone 

were insufficient to delineate units within the surficial sand. 

Using all the available data (figs. 24.3, 24.~. and 24.6, 

tables 24.1 and 24.2), we conclude that th~ sand was 

deposited in beach and dune environments during one or 

more high stands of sea level in the Pleistocene and that 

some of the sand has been redistributed since the last 

sea-level high stand. The most significant rrineralogical 

evidence supporting a pre-Holocene age is the presence of 

vermiculite. 

The bulk of the sand can be assigned to one unit on 

the basis of mineralogy (figs. 24.3, 24.4, and 24.6A; tables 

24.1 and 24.2). We designate that unit ''Q2" to reflect our 

belief that it was deposited during the most recent preHolocene sea-level high stand and to distinguish it from 

Holocene deposits, which we designate "Ql." The only 

sediment that may be assignable to Q 1 is the upper 5-8 ft of 

FL3; however, Q2 from the upper part of th~ weathered 

146 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Table 24.2. Selected mineralogical characteristics of stratigraphic units in the Pinellas County, Fla., sinkhole 

complex 

[Abbreviations are defined in table 24.1. Semicolons separate the three 

classes of nonopaque minerals shown in table 24.1] 

Fine sand fraction 

Potassium 

Age and unit 

Predominant feldspar Predominant 

nonopaque (percentage clay 

heavy of non- minerals 

minerals carbonate 

Late Pleistocene: 

Q2 ................... St; Z 

Q3a .................. St,Sil; Z,T,R 

Q3b .................. G; St; T 

Holocene to Miocene: 

Residuum on 

Tampa Limestone ... St; Z,T,R 

Miocene: 

Tampa Limestone. . . St; Z,R 

fraction) 

<3 

<3 

23 

K 

K 

unknown 

6-18 K, 1/S 

16 unknown 

section surrounding the deepest part of the sinkhole (at FL3) 

may have been eroded and washed into the depression in Q 1 

time. The absence of illite/smectite from what otherwise 

looks like the top of the Q2 sequence at FL3 may be due to 

reworking, which would permit more thorough oxidation of 

the minerals. 

Between the depths of 40 and 7 4 ft in FL3 are two 

sand units that have heavy-mineral suites substantially 

different from that of Q2. In particular, the presence of 

abundant sillimanite at 48 ft, which is assumed to represent 

the 40- to 60-ft interval, is unique at the Pinellas County 

site. It is also unusual throughout the surficial sands 

of Florida (Martens, 1928, 1935). We designate this 

sillimanite-bearing sand "'Q3a." The greater age signified 

by Q3 is justified only by its stratigraphic position. There is 

no firm evidence indicating whether Q3 was deposited 

during the same sea-level high stand as Q2 or during the 

previous one. The lowest and, therefore, oldest of the sand 

beds is between 60 and 7 4 ft in FL3: we have designated it 

"Q3b." Its sand mineralogy is similar to that of residuum 

and limestone at the site (tables 24.1 and 24.2). The 

absence of sillimanite indicates a change in sources between 

Q3b and Q3a; this change may have occurred over a long or 

a short time. 

The mineralogy of samples from one auger hole, 

Surf2 (fig. 24.1), indicates that the unit sampled is Q2 

(table 24.1). The other auger hole, 2ndFL, is unusual in that 

the clay-sized fraction of the sample from 6 to 9ft below the 

surface contains abundant calcite and halloysite. Halloysite 

is one of the early weathering products of feldspar (Owens 

and others, 1983) and is related to kaolinite. Sepiolite, a 

Mg-rich fibrous clay, may also be present in small amounts. 

The most abundant opaque heavy mineral in this zone is 

pyrite, which was not found in other samples from the site. 

The material in the 2ndFl drill hole is probably in weathered 

Tampa Limestone (residuum); the zone from 6 to 9ft was 

originally a clay-rich bed within the Tampa. 

CONCLUSIONS 

The preliminary results of this pilot study on the 

mineralogy of surficial sands in western Pinellas County 

have provided a basis for the interpretation of the provenance, depositional history, and weathering of the sands. 

The bulk of the surficial sand can be attributed to rew"1rking 

of weathered limestone, but all the noncarbonate minerals 

in both the sand and the limestone were originally d~rived 

from metamorphic rocks in the Piedmont of Georgia. 

Weathering after deposition of the sand during the Pleistocene is mainly a result of oxidation caused by reaction of 

ground water with the minerals. The mineralogy of the 

Pinellas County site can now be compared with that of 

surficial sands at other Coastal Plain sites in Florida and 

elsewhere. 

REFERENCES CITED 

Fisher, R. S., 1988, Clay minerals in evaporite host roc1<:, Palo 

Duro Basin, Texas Panhandle: Journal of Sedimentary Petrology, v. 58, no. 5, p. 836-844. 

Garrels, R.M., and Christ, C.L., 1965, Solutions, minerals, and 

equilibria: New York, Harper and Row, 450 p. 

Goddard, E.N., and others, 1948, Rock-color chart: Wastington, 

D.C., National Research Council, 6 p. (Republished by 

Geological Society of America, 1951; reprinted 197 5.) 

Johnson, R.A., comp., 1986, Shallow stratigraphic core tests on 

file at the Florida Geological Survey: Florida Geological 

Survey Information Circular 103, 431 p. 

Joint Committee on Powder Diffraction Standards, 1974, ~~lected 

powder diffraction data for minerals-Data book (1st ed.): 

Swarthmore, Pa., Joint Committee on Powder Diffraction 

Standards, 833 p., and first supplement, 1981, 463 p. 

Martens. J.H.C., 1928, Beach deposits of ilmenite, zircon and 

rutile in Florida: Florida State Geological Survey 19th Annual 

Report, p. 124-154. 

---1935, Beach sands between Charleston, South Carolina, 

and Miami, Florida: Geological Society of America P•llletin. 

v. 46, no. 10, p. 1563-1596. 

McCartan, Lucy. Lemon, E.M., Jr., and Weems, R.E., 1984, 

Geologic map of the area between Charleston and Orangeburg, South Carolina: U.S. Geological Survey Misce1

laneous 

Investigations Series Map 1-1472, scale 1:250,000. 

Miller, J.A., 1986, Hydrogeologic framework of the Floridan 

aquifer system in Florida and parts of Georgia, Alabama, and 

South Carolina: U.S. Geological Survey Profession1l Paper 

1403-B, 91 p. 

Owens, J.P., Hess, M.M., Denny, C.S., and Dwomik, E.J., 

1983, Postdepositional alteration of surface and near-surface 

24. Mineralogy of a Sand-Filled Sinkhole Complex in Pinellas County, Floridc- 147 
minerals in selected Coastal Plain formations of the middle 

Atlantic States: U.S. Geological Survey Professional Paper 

1067-F, 45 p. 

Pavich, M.J., Leo, G.W., Obermeier, S.F., and Estabrook, J.R., 

1989, Investigations of the characteristics, origin, and residence time of the upland residual mantle of the Piedmont of 

Fairfax County, Virginia: U.S. Geological Survey Professional Paper 1352, 58 p. 

Scott, T .M., 1986, A revision of the Miocene lithostratigraphic 

nomenclature, southwestern Florida: Gulf Coast Association 

of Geological Societies Transactions, v. 36, p. 553-560. 

---1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Surv~y Bulletin 59, 

148 p. 

Soller, D.R., 1988, Geology and tectonic histo-y of the lower 

Cape Fear River valley, southeastern North Carolina: U.S. 

Geological Survey Professional Paper 1466-A, 60 p. 

Weaver, C.E., and Beck, K.C., 1977, Miocene of the southeastern United States-A model for chemical sedimentation in a 

perimarine environment: New York, Elsevie¥, 234 p. 

148 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
25. lon-Exchange Control of Radium-226 Activities in Ground Water of Sarasota County, 

Florida 1 

By Ronald L. Miller2 

Water from wells in Sarasota County, Fla. 

(Kaufmann and Bliss, 1977; Miller and Sutcliffe, 1985), 

commonly exceeds the 5-pCi/L maximum contaminant 

level (MCL) set for Ra-226 (radium-226) plus Ra-228 in the 

National Drinking Water Regulations (U.S. Environmental 

Protection Agency, 1987). Concern that mining and processing of phosphate ore may increase radioactivity in the 

ground water of west-central Florida prompted several 

studies during the seventies (U.S. Environmental Protection 

Agency, 1973; Guimond and Windom, 1975; Irwin and 

Hutchinson, 1976; Kaufmann and Bliss, 1977). Kaufmann 

and Bliss ( 1977) studied Ra-226 in ground water of Sarasota 

County and surrounding counties and concluded ( 1) that 

elevated Ra-226levels in ground water of Sarasota County 

result from natural enrichment processes, such as dissolution of minerals in the Hawthorn Formation or the migration 

from deep aquifers of mineralized ground water enriched in 

Ra-226, and (2) that occasional incidents of Ra-226 contamination of ground water in surrounding counties resulting from leakage from phosphate mines and chemical plants 

were likely to recur, but that the extent of contamination 

was not well defined because of monitoring deficiencies. A 

later study, however, revealed that radioactivity in ground 

water having low specific conductance did not migrate more 

than about a hundred meters from two phosphate chemical 

plants that were 14 and 34 yr old and from a 2-yr-old pond 

containing phosphate clay waste (Miller and Sutcliffe, 

1984). 

This report will compare the radioactivity found in 

ground water from phosphate mining areas and from Sarasota County and discuss the relation between the activity of 

dissolved Ra-226 and specific conductance. For this discussion, water having a specific conductance of 700 J.LS/cm at 

25 °C or less will be called fresh. Water having a specific 

conductance of more than 700 J.LS/cm at 25 °C will be called 

high-conductance water. 

1

Prepared in cooperation with the Florida Department of Environmental Regulation. 

2

U.S. Geological Survey, Tampa, FL 33634. 

Miller and Sutcliffe ( 1985) found that the highest 

Ra-226 activities in ground water of Sarasota Count:r occur 

in the parts of the upper Hawthorn Formation rnd the 

overlying Tamiami Formation (both of late Tertia')' age) 

that contain high-conductance water. High Ra-226 activities 

in ground water are associated with both of the two 

high-conductance water types found in Sarasota County: 

seawater and water containing a calcium magnesium strontium sulfate. They hypothesized that alpha-particle recoil 

ejects Ra-226 from the insoluble phosphate ore into ground 

water where the Ra-226 is subsequently scavenged by the 

abundant clays associated with phosphate deposits. Over 

time, these clays (montmorillonite, attapulgite, kr0linite, 

and illite, according to Boody and Barwood, 1982, p. 6) 

accumulate significant amounts of Ra-226 if groun1 water 

remains fresh. Where high-conductance water contacts 

clay, high concentrations of cations in the water compete 

with Ra-226 for ion-exchange sites on the clays ani, thus, 

release more Ra-226 into the ground water. The high 

Ra-226 activities in ground water of the upper Hawthorn 

and the Tamiami Formations in Sarasota County rrobably 

occur because ( 1) high-conductance water moved into these 

formations recently with respect to the 1 ,600-yr half-life of 

Ra-226, or (2) the residence time of ground water is long 

enough for the alpha-recoil process to build Ra-226 activities in high-conductance ground water to their current 

levels. It seems likely that both processes are o~curring 

and that their relative importance varies spatirlly and 

temporally. 

Regression lines for Ra-226 activity and specificconductance data ( 1) from the upper Hawthorn Fom1ation in 

Sarasota County (Sutcliffe and Miller, 1981) and (2) from 

the Hawthorn Formation and mined land at an inland 

phosphate mine (Miller and Sutcliffe, 1982) were both 

significant at the 95-percent confidence level and were not 

significantly different from each other (fig. 25.1). These 

relations support the ion-exchange mechanism proposed 

above and can be used to explain why the phosphate-mining 

areas contain an abundance of uranium-238 decay series 

radionuclides but have lower levels of dissolved Ra-226 in 

ground water than parts of Sarasota County. In the 

25. lon-Exchange Control of Radium-226 Activities in Ground Water of Sarasota County, Florit'~ 149 
15~----------~------------~ 

a: 

~ :J 

a: 

w 

a.. 

en 

w 

a: 10 :::> 

u 

0 

u 

a: 

~ 

<0 

N 

N 

~ :::> 

~ 5 a: 

c 

w 

> ...J 

0 

en 

en 

C5 

• Upper Hawthorn Formation 

in Sarasota County 

• Upper Hawthorn Formation 

and mined land at 

inland phosphate mine 

• 

• • 

500 1000 

SPECIFIC CONDUCTANCE, 

IN MICROSIEMENS PER CENTIMETER 

AT 25 DEGREES CELSIUS 

Figure 25.1. Comparisons of radium-226 

activity and specific-conductance data in 

Sarasota County, Fla. (Sutcliffe and Miller, 

1981), and an inland phosphate mine 

(Miller and Sutcliffe, 1982). 

phosphate-mining areas, the freshwaters of the Hawthorn 

Formation allow the clays to hold most of the Ra-226 

released by alpha-particle recoil, whereas, in parts of 

Sarasota County, the high-conductance waters of the Hawthorn Formation allow more Ra-226 to remain in solution 

rather than adsorb to clays. 

The ion-exchange release of Ra-226 from clays 

exposed to high-conductance water has been documented 

(Miller and others, 1990). Dilutions of seawater were mixed 

with parts of a well-mixed section of a sample core from a 

phosphate mine and two samples of phosphatic clayey 

wastes (slimes) from two phosphate mines. As shown in 

figure 25.2, the activity of dissolved Ra-226 increased with 

salinity to about 2 pCi of exchangeable Ra-226 per gram of 

air-dried solids at a salinity of about 35 ppt (parts per 

thousand). If one assumes a porosity of0.4, a density of the 

solid phase of 2. 7 g/cm3 , and a salinity of 35 ppt, then a 

Ra-226 radioactivity of about 8,000 pCi/L is calculated as 

an upper limit for pore water in an aquifer composed of 

these materials. The actual pore water activity, however, 

would be significantly less than 8,000 pCi/L because of the 

large water-to-solids ratio used in these experiments 

(5.1-11.5 g of air-dried solids in 900 mL of solution). 

These experiments demonstrate that, for the phosphatemmmg area, (1) clays not previously exposed to highconductance water contain a substantial amount of 

~ 

<( 

a: 

(!) 

a: 

w 

a.. 

en 

w 

a: 

:::> 

u 

0 

u 

a: 

~ 

cD 

N 

N 

:E 

:::> 

C5 

<( 

a: 

• o Clay wastes 

• Phosphate mine core 

10 20 30 40 

SALINITY, IN PARTS PER THOUSAI\ID 

Figure 25.2. Release of radium-226 from 

three solid-phase samples. 

exchangeable Ra-226; (2) where clays are present, they 

control dissolved Ra-226 radioactivities; and (3) the release 

of Ra-226 is related to specific conductance a'ld, therefore, 

to dissolved solids in the water. 

Because a direct relation exists between dissolved 

solids and dissolved Ra-226, ground water from Sarasota 

County that contains more than 5 pCi/L of Ra-226 usually 

also exceeds the MCL's for hardness or disfolved solids. 

Consequently, ground water that is high in Fa-226 would 

probably not be used as a public water supply without 

receiving softening or reverse osmosis treatnent, both of 

which also reduce Ra-226 below the MCL. 

REFERENCES CITED 

Boody, P.W., and Earwood, H.L., 1982, Phosphatic clay bibliography 1973-1981: Bartow, Fla., Florida Institute of Phosphate Research, 83 p. 

Guimond, R.J., and Windom, S.T., 1975, Radioactive distribution in phosphate products, by-products, effluents, and 

wastes: Washington, D.C. , U.S. Environmertal Protection 

Agency, Office of Radiation Programs, Criteria and Standards Division Technical Note ORP/CSD-75-3, 30 p. 

Irwin, G.A., and Hutchinson, C.B., 1976, Reconnaissance water 

sampling for radium-226 in central and northern Florida, 

December 1974-March 1976: U.S. Geological Survey 

Water-Resources Investigations Report 76-10?, 16 p. 

Kaufmann, R.F., and Bliss, J.D., 1977, Effects of phosphate 

mineralization and the phosphate industry on radium-226 in 

ground water of central Florida: Washington. D.C. , U.S. 

Environmental Protection Agency Report U"). EPN520-

6-77-010, 115 p. 

150 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Miller. R.L., Kraemer, T.F., and McPherson, B.F., 1990, 

Radium and radon in Charlotte Harbor Est.Iary, Florida: 

Estuarine, Coastal and Shelf Science [London], v. 31, no. 4, 

p. 439--457. 

Miller, R.L., and Sutcliffe, Horace, Jr., 1982, Water-quality and 

hydrogeologic data for three phosphate industry wastedisposal sites in central Florida, 1979-1980: U.S. Geological 

Survey Water-Resources Investigations Report 81-84, 77 p. 

---1984, Effects of three phosphate industrial sites on groundwater quality in central Florida, 1979 to 1980: U.S. Geological Survey Water-Resources Investigations Report 83--4256, 

184 p. 

---1985, Occurrence of natural radium-226 radioactivity in 

ground water of Sarasota County, Florida: U.S. Geological 

Survey Water-Resources Investigations Report 8..1.-4237, 

34 p. 

Sutcliffe. Horace, Jr., and Miller, R.L., 1981, Data on groundwater quality with emphasis on radionuclides, f1rasota 

County, Florida: U.S. Geological Survey Open-File Report 

80-1223, 13 p. 

U.S. Environmental Protection Agency, 1973, Reconnaissance 

study of radiochemical pollution from phosphate rock mining 

and milling: Denver, Colo. , U.S. Environmental Protection 

Agency, Office of Enforcement, National Field Investigations Center. 82 p. 

---1987, National drinking water regulations as amended 

through October 28, 1987: Washington, D.C., U.S. Environmental Protection Agency, parts 141-143, p. 526-595. 

25. !on-Exchange Control of Radium-226 Activities in Ground Water of Sarasota County, Florida 151 

26. Sedimentary Cycles and Sequence Stratigraphy in the Eastern Gulf of Mexico Coastal 

Plain 

By juergen Reinhardt1'

2 

INTRODUCTION 

The sedimentary record of coastal transgressions and 

regressions along the passive southeastern margin of North 

America provides data for testing models of eustatic sealevel fluctuations. This paper presents a brief summary of 

the Upper Cretaceous stratigraphy mapped in the Chattahoochee River valley area in western Georgia and eastern 

Alabama (fig. 26. 1) and discusses its relation to Cretaceous 

cycles depicted by Haq and others (1987). Each Upper 

Cretaceous formation in the study area contains facies 

deposited in middle shelf to alluvial-flood-plain environments that migrated across this area largely in response to 

shoreline changes associated with eustatic fluctuations in 

sea level. The architecture of the cycles resulting from these 

fluctuations is described below. 

I mapped this area from 1976 to 1983 (1) because the 

formations are better exposed in the dissected topography 

than they are in most other parts of the eastern Gulf of 

Mexico Coastal Plain and (2) because the sedimentary 

record from at least the late Santonian through the middle 

Maastrichtian is fairly complete. U.S. Geological Survey 

biostratigraphers who collaborated with me in defining the 

ages of formations were Norman F. Sohl, who studied 

mollusks, Charles C. Smith (presently with Unocal), who 

studied the calcareous nannofossils, and Raymond A. 

Christopher (presently with Atlantic Richfield Company), 

who studied the pollen and spores. 

STRATIGRAPHY, LITHOFACIES, AND 

SEDIMENTARY CYCLES 

The Upper Cretaceous formations in the study area 

are, from oldest to youngest, the Tuscaloosa Formation, 

Eutaw Formation, Blufftown Formation, Cusseta Sand, 

Ripley Formation, and Providence Formation (fig. 26.1). 

The Tuscaloosa Formation unconformably overlies crystal1

U.S. Geological Survey, Reston, VA 22092. 2

Deceased. 

line rocks of probable lower Paleozoic age and, in tum, is 

unconformably overlain by the Eutaw Formation. These 

contacts both represent substantial periods of S'Ibaerial 

exposure, weathering, and erosion; locally .. paleo<cols, or 

fossil soils, are immediately below the contac+s. The 

boundaries between the younger Cretaceous units are less 

obvious unconformities, but they are marked by sharp 

lithofacies changes and associated erosional surfac~s. 

During much of the Late Cretaceous Epoch, the 

shoreline trended east-west across the Chattahoochee River 

valley and then turned generally northwest-southe"'st west 

of the river (fig. 26.1). The shoreline position at any time 

was the controlling factor in the spatial distrib·1tion of 

continental and marine lithofacies. In downdip exposures 

along the Chattahoochee River valley, continental lithofacies are limited to the Tuscaloosa Formation, but in updip 

areas, continental lithofacies equivalent to the younger 

Cretaceous units, except the Ripley Formation, are found to 

the northeast in the drainage divide between the Flint and 

the Chattahoochee Rivers (fig. 26.1). The repetition of a 

limited number of lithofacies in the Chattahooch~e River 

valley region was first noted by Eargle (1950). These 

sedimentary cycles have been described in considerable 

detail for both the Upper Cretaceous (Reinhardt, 1980, 

1982) and lower Tertiary (Gibson, 1980; Gibson an-i others, 

1982). 

The Chattahoochee cycles are similar in their internal 

organization to cycles in the lower Tertiary of Texas 

(Fisher, 1964) and the Upper Cretaceous of New Jersey 

(Owens and Sohl, 1969). They consist of a basal t~ansgressive phase, an inundative or highstand phase, and a regressive phase at the cycle top. In general, the cycles are highly 

asymmetrical, as the basal transgressive phase nakes up 

less than 10 percent of the cycle, and the other pha<ces make 

up the rest of the cycle's thickness. Overall, the sedim~ntary cycles record a rapid transgression followed tv manne 

sedimentation and a gradual shoreline regression. 

The composition of each phase of a sedimentary cycle 

depends on the extent of the marine trangression and the 

paleogeographic position of any given geologic section. 

The transgressive phase generally consists of a brsal sand, 

26. Sedimentary Cycles and Sequence Stratigraphy in the Eastern Gulf of Mexico Coastal Plc'o 153 
0 20 MILES 

0 20 KILOMETERS 

EXPLANATION 

CSJ CIIill] 

TERTIARY ROCKS BLUFFTOWN FORMATION 

D 

PROVIDENCE FORMATION EUTAW FORMATION 

[JIJ 

RIPLEY FORMATION TUSCALOOSA 

-

FORMATION 

CUSSETA SAND CRYSTALLINE ROCKS 

Figure 26.1. Generalized geologic map of the Cretaceous units in the Chattahoochee River valley region on the 

northeastern margin of the Gulf of Mexico Coastal Plain. Heavy line trending generally east-west is the approximate 

maximum inland shoreline position during the Eutaw transgression. Figure modified from Reinhardt (1980). 

154 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
CHRONO· SEQUENCE as EUSTATIC RELATIVE SHORELINE MOVEMENT IN 

::e STRATIGRAPHY STRATIGRAPHY SEA LEVEL CHATTAHOOCHEE 2: 

w U) 0 RELATIVE CHANGE OF RIVER VALLEY CYCLES 0 !:!::! z STAGE UJ cC a: _. COASTAL ONLAP (ABOVE PRESENT SEA LEVEL) w ~ LAND BASIN U) 0 LAND BASIN 250 200 150 100 50 0 M 

65 PALEOCENE DANIAN \ ~ 65 

1.2 

1.1 \ 67 (_ 

\ 68 c - 70- U) MAASTRICH- 4.5 Kp -1o 

::::) TIAN ( 71 c Kr 

0 4.4 

w Kc 

75- (..) \ 75 l -75 

<( 1-

4.3 uppe· 77.5 

1-- CAMPANIAN 4.2 ~ Kb 

w '------;u- '--.. 79 

ao- \ 80 ( -so 

a: 3.5 lowe· 

(..) 83 Kb 3.4 \ t as- a: -

\ 85 Ke -as 

SANTONIAN 3.3 

w 3. 2 \ 87.5 

D.. CONIACIAN 88.5 

9()- ~ D.. 

3.1 90 ==- -90 TURONIAN -2.7 90.5 

~ :::) 2.5 :---2.6 \ 91 Kt 

CENOMANIAN 2. 4 ......_ 93 c ~ ""' 94 

gs- 95.5 -95 2.2 '\.. 

++4+J--.l+l- lYPE 1 UNCONFORMITY • SHELF SUBAERIAU Y EXPOSED 800 600 400 200 0 FT 

Figure 26.2. The relation of Upper Cretaceous depositional cycles in the Chattahoochee River valley to the model of 

coastal onlap and eustatic sea-level curves of Haq and others (1987). Kt, Tuscaloosa Formation; Ke, Eutaw Formation; Kb, 

Blufftown Formation; Kc, Cusseta Sand; Kr, Ripley Formation; and Kp, Providence Formation. 

commonly crossbedded, and an overlying massive transgressive lag deposit or a ravinement. In downdip areas, a 

transgressive lag bed (containing phosphate and quartz 

pebbles, reworked shell, and bone) immediately overlies 

the top of the preceding cycle, as little sediment accumulated during the marine transgression. 

The inundative phase contains the deepest water 

deposits; most of these are massive to fissile marine clays 

containing a diverse but diminutive fauna, which typically 

occurs near the base of the phase. Fine glauconitic sands 

and shelly marls make up most of the downdip sediments 

deposited during the inundative phase, whereas cross bedded sands representing tidal inlet and strandplain deposits 

are preserved in updip areas. Shoaling in the sedimentary 

basin, as sedimentation exceeded subsidence, delimited the 

top of the sedimentary cycle. 

At this stage, the barrier shoreline typically "jumped" 

seaward as offshore sandbars emerged, and back-barrier 

sediments accumulated in the lagoon behind them. The 

regressive phase varies in thickness and generally consists 

of laminated carbonaceous silt and clay or massive, mottled 

silty clay. In updip areas. alluvial-flood-plain clays and 

lensoid, crossbedded, alluvial-channel sands accumulated 

during this aggradational phase. 

SHORELINE MIGRATION AND SEQUENCE 

STRATIGRAPHY 

A sea-level-fluctuation curve inferred from shoreline 

movements was first published for the Cretaceom deposits 

of the Chattahoochee River valley by Reinhard~ (1980). 

Numerous stratigraphic refinements have been suggested 

since that time (for example, by Donovan, 1985; Skotnicki 

and King, 1986, 1989; Frazier, 1987), and several models 

have been proposed to explain the relative timing and 

distribution of major transgressive and regressive events 

recorded in the eastern Gulf of Mexico Coastal F'ain. The 

chronology of deposition is based largely on the biostratigraphy of the deposits as summarized by Sohl and Smith 

(1980). Publication of sea-level-fluctuation curv·~s for the 

Cretaceous by Haq and others (1987) permits their comparison with cycles in the Chattahoochee River valley area (fig. 

:26.2), and the remaining text will be such a comparison. 

26. Sedimentary Cycles and Sequence Stratigraphy in the Eastern Gulf of Mexico Coastal Pl.,.in 155 
Deposition of the Tuscaloosa Formation appears to 

have been temporally coincident with the highest inferred 

worldwide sea levels for the Mesozoic and Cenozoic Eras. 

Prior to the deposition of the Tuscaloosa, the eastern Gulf of 

Mexico Coastal Plain was emergent and tectonically stable, 

as indicated by the preservation of mature paleosols on the 

bedrock surface underlying the Tuscaloosa (Sigleo and 

Reinhardt, 1988). The pollen record indicates that the 

Tuscaloosa was deposited in the Chattahoochee River 

valley during the late Cenomanian and possibly the early 

Turonian (Christopher, 1982). The unlikely association of a 

major clastic wedge with an inferred maximum sea-level 

highstand is most readily explained by assuming that 

substantial uplift was taking place in the Appalachians at 

this time. 

About 4-5 m.y. elapsed between deposition of the 

top of the Tuscaloosa and the marine transgression marking 

the base of the Eutaw Formation. Very high worldwide sea 

levels are inferred from the depositional record in places 

like the western interior of the United States during this 

period for which the Chattahoochee River region has no 

record. Therefore, subsidence of the region must not have 

taken place prior to the Santonian, when the area was first 

inundated by the sea. Beginning with the base of the Eutaw, 

deposition for the next 19-20 m. y. was relatively continuous, and interruptions (nondeposition or erosion) were less 

than a single biostratigraphic zone (probably less than 0.5 

m.y.) at cycle boundaries. This relatively continuous deposition suggests that the rate of subsidence or down warping 

along the inner edge of the Coastal Plain was relatively 

constant and probably approximated the rate of accumulation, roughly 20 m/m. y. 

The relation of Eutaw lithofacies to shoreline position 

and migration has been carefully considered by Frazier 

(1987). Frazier suggested that the lower part of the Eutaw 

was deposited during the transgressive phase in cycle 3.3 of 

Haq and others ( 1987) and concluded that this deposition 

took place during about 1.5 m.y. Because much of the 

Eutaw cycle consists of back-barrier facies (regressive 

phase of the cycle), rather than of highstand deposits, and 

the transgressive lag is at or near the base of the unit, I 

would argue that little record of the initial Eutaw coastal 

onlap has been preserved. Rather, the basal transgressive 

lag was probably deposited close in time and space to the 

updip limit of the maximum marine transgression. 

Mollusks and poorly preserved calcareous nannofossils in the basal Eutaw suggest that the unit may be as old as 

early Santonian or that the base may be as young as late 

middle Santonian (Sohl and Smith, 1980). If a minimum 

age for the basal Eutaw is assumed, then the topmost Eutaw 

sediments were deposited at about 85 Ma, the age of the 

downlap surface of Haq and others (1987). The regressive 

phase of the Eutaw began to be deposited as soon as the 

basin shoaled enough for a new barrier system to form 

seaward of the outcrop belt. The landward migration of that 

barrier system across the restricted facies of the Eutaw 

marks the base of the Blufftown Formation. 

The 150-m-thick Blufftown presents a"' outstanding, 

yet relatively untested, opportunity for comparing Chattahoochee cycles with the sequence stratigraphic model of 

Haq and others (1987). Reinhardt (1982) described two 

cycles, separated by a transgressive lag, for the Blufftown 

on the basis of exposures along the Chattahoochee River. 

The base of the lower cycle is close to the SantonianCampanian stage boundary, and most of the cycle is of early 

Campanian age~ see Sohl and Smith (1980) fer a discussion 

of the basal age assignment of latest Santonia1 versus early 

Campanian based on nannofossils and molJusks, respectively. The upper Blufftown is thought to be middle and late 

Campanian. 

The boundary between the two cyclt>s within the 

Blufftown has not been accurately placed biostratigraphically, but it may correspond to the major cycle boundary 

between cycles 3.5 and 4.1 ofHaq and others (1987). Using 

different criteria for shallowing and deepening of the basin, 

Skotnicki and King ( 1986) postulated three sedimentary 

cycles for the Blufftown. In either interpretation, most 

Blufftown deposits represent inner to middle shelf deposits 

(highstand deposits) consisting of massive, glauconitic fine 

sands and marls. 

Within the time interval of lower Bluff•own deposition, two cycles are shown by Haq and others (1987). 

Although the sequence boundary shown wittin the lower 

Blufftown interval is not considered a major "boundary, we 

should look for some indication of the postulated shallowing, especially in updip areas. The eustatic curves and the 

coastal onlap pattern suggested for the uppe:" part of the 

Blufftown are even more complex, as three episodes of 

highstand deposition were separated by times of downlap. 

The cycles of Haq and others ( 1987) imply that considerable 

detail in terms of sea-level fluctuation could be more 

completely resolved or tested for in parts of tl'~ Blufftown 

Formation in the Chattahoochee River valley. 

Mollusks have been used to assign the Cusseta Sand 

to the late Campanian and earliest Maastrichtian (Sohl and 

Smith, 1980). The contact that separates the upper Blufftown cycle from the basal Cusseta appears to b ~ coincident 

with a major sequence boundary in the sequence stratigraphy of Haq and others (1987). In outcrop, scatt~red pods of 

carbonaceous clay at the top of the Blufftown are evidence 

for abrupt shallowing. The coarse sands at the base of the 

Cusseta are widespread, thicken updip, and appear to 

correspond well to the transgressive phase of cycle 4.4 of 

Haq and others ( 1987). 

The transition to highstand deposits represented by 

the Ripley Formation was associated with a widespread 

marine transgression in western and into central Georgia. 

Such a widespread transgression is unexpected from the 

model of Haq and others (1987) because the relrtive coastal 

onlap is shown as less than onlap during other parts of the 

156 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
Cretaceous. We might, therefore, speculate that subsidence 

of the basin during the early Maastrichtian might have been 

greater than subsidence at other times during the Late 

Cretaceous. 

Skotnicki and King (1989) have postulated two progradational cycles in the Ripley on the basis of well logs in 

central and eastern Alabama. They have equated those 

depositional cycles with eustatic cycles 4.4 and 4.5 on the 

chart by Haq and others ( 1987). This interpretation creates 

substantial problems in reconciling the placement of the 

overlying Upper Cretaceous units. 

Following deposition of the Ripley, the area was 

subaerially exposed. Donovan ( 1985) documented the 

incised topography that separates the Ripley and Providence 

Formations and the valley fill deposited during a marine 

lowstand in the middle to late middle Maastrichtian. Donovan (1985) informally defined the Alexander's Landing 

beds for this stratigraphic interval. Although the unit has not 

been mapped in detail, its surface and subsurface distribution resolves anomalous biostratigraphic relations between 

units previously mapped as Providence Sand and Ripley 

Formation in the Chattahoochee River valley (Sohl and 

Koch, 1986). The Alexander's Landing beds are a lowstand 

wedge that may have been deposited at the beginning of 

cycle 4.5 of Haq and others (1987). 

Donovan (1985, 1986) divided the Providence Formation into an upper and lower member. These units were 

defined as shallowing-upward sequences separated by a 

transgressive disconformity. Donovan's level of stratigraphic resolution, as well as his detailed analysis of the 

shoreline configuration and changes in the Providence, 

greatly exceeds that in the analysis of the underlying 

Cretaceous units. The two depositional cycles identified by 

Donovan in the Providence have no counterpart in the 

cycles of Haq and others (1987). 

The downdip equivalent of the Providence is the 

Prairie Bluff Chalk. The substantial hiatus between these 

units and the overlying Clayton Formation (Danian) has 

been the focus of considerable study in central Alabama 

because of its implication for Cretaceous-Tertiary boundary 

questions (Reinhardt and others, 1986). In downdip areas, 

the hiatus may have been as short as l m. y. , and deposition 

may have begun again prior to the beginning of the Tertiary, 

but in the Chattahoochee River valley section, the hiatus 

appears to have been 2-3 m. y., and it included the 

boundary interval. For a review of the boundary relations, 

see Jones and others (1987), Donovan and others (1988), 

and Mancini and others (1989). 

CONCLUSIONS 

The correlation between Upper Cretaceous sedimentary cycles related to shoreline migration across the eastern 

Gulf of Mexico Coastal Plain and the cycles of Haq and 

others ( 1987) is generally good from the middle Santonian 

to the middle Maastrichtian. Preservation of specific. transgressive events was controlled in large part by the subsidence history of the northeastern margin of the Gulf of 

Mexico basin. Although several worldwide sea-level highstands have been reported in the late Early and early Late 

Cretaceous, there is no record of marine deposits associated 

with these transgressions in the surface geology of the 

eastern Gulf of Mexicio Coastal Plain. 

Although each of the unconformity-bounded units in 

the Chattahoochee River valley section has unique sedimentary and faunal characteristics, similar lithofacies patterns 

are preserved in each sedimentary cycle. Most contacts 

between sedimentary units represent relatively short depositional hiatuses and can be related with greater or lesser 

confidence to the major and some minor sequence boundaries in the sequence stratigraphy of Haq and others ( 1987). 

The Eutaw Formation cycle correlates well with tre upper 

part of cycle 3. 3. The lower Blufftown cycle corresponds to 

cycles 3.4 or 3.5 or both. Similarly, the upper Blufftown 

cycle is within cycles 4.1, 4.2, and (or) 4.3. The two 

Blufftown cycles appear to be separated by a major 

sequence boundary. 

The Cusseta corresponds to the transgressive phase of 

cycle 4.4, and the Ripley Formation consists of h;ghstand 

deposits in that same cycle. Finally, the Providence Formation consists of two depositional sequences, which probably 

accumulated during cycle 4.5. The major lowst:md that 

followed the deposition of the Providence in the early to 

middle late Maastrichtian led to emergence of tl ~ entire 

Gulf of Mexico Coastal Plain until shortly before tl ~ end of 

the Cretaceous. The marine transgression associated with 

the oldest Tertiary deposits in the eastern Gulf of Mexico 

Coastal Plain did not deposit sediments in the Chattahoochee River valley prior to the middle Danian. 

REFERENCES CITED 

Christopher, R.A., 1982, Palynostratigraphy of the basal Cretaceous units of the eastern Gulf and southern Atlantic Coastal 

Plains, in Arden. D.D., Beck, B.F., and Morrow, Eleanore. 

eds., Proceedings [of the] Second Symposium on the Geology of the Southeastern Coastal Plain [held] March 5-6, 

1979, Americus, Ga., U.S.A.: Georgia Geologic Survey 

Information Circular 53, p. 10-23. 

Donovan, A.D., 1985, Stratigraphy and sedimentolcgy of the 

Upper Cretaceous Providence Formation (western Georgia 

and eastern Alabama): Golden, Colo., Colorado School of 

Mines, Ph.D. dissertation, 236 p. 

---1986, Sedimentology of the Providence Formation, in 

Reinhardt, Juergen, ed., Stratigraphy and sedimentology of 

continental, nearshore, and marine Cretaceous seiiments of 

the eastern Gulf Coastal Plain, Field Trip 3 at the annual 

meeting of the Society of Economic Paleontologists and 

Mineralogists and the American Association of Petroleum 

26. Sedimentary Cycles and Sequence Stratigraphy in the Eastern Gulf of Mexico Coastal Pl"in 157 
Geologists, June 18-20, 1986: Georgia Geological Society 

Guidebooks, v. 6, no. 3, p. 29--44. 

Donovan, A.D., Baum, G.R., Blechschmidt, G.L., Loutit, T.S., 

Pflum. C.E .. and Vail, P.R., 1988, Sequence stratigraphic 

setting of the Cretaceous-Tertiary boundary in central Alabama. in Wilgus. C.K., and others, eds., Sea level 

changes-An integrated approach: Society of Economic Paleontologists and Mineralogists Special Publication 42, 

p. 299-307. 

Eargle, D.H., 1950, Geologic map of the Selma Group in eastern 

Alabama: U.S. Geological Survey Oil and Gas Investigations 

Preliminary Map 105, scale 1:250,000. 

Fisher, W.L., 1964, Sedimentary patterns in Eocene cyclic 

deposits, northern Gulf Coast region, in Symposium on 

cyclic sedimentation: Kansas Geological Survey Bulletin 

169' v. 1, p. 151-1 70. 

Frazier, W .J., 1987, A guide to facies stratigraphy of the Eutaw 

Formation in western Georgia and eastern Alabama, in 

Geology of the Fall Line; A field guide to structure and 

petrology of the Uchee Belt and facies stratigraphy of the 

Eutaw Formation in southwestern Georgia and adjacent 

Alabama-Georgia Geological Society, 22nd annual field 

trip, Oct. 9-11, 1987: Georgia Geological Society Guidebooks, v. 7, no. 1, p. Bl-B25. 

Gibson, T.G., 1980, Facies changes of lower Paleogene strata, in 

Reinhardt, Juergen, and Gibson, T .G., Upper Cretaceous and 

lower Tertiary geology of the Chattahoochee River valley, 

western Georgia and eastern Alabama, in Frey, R. W., ed., 

Excursions in southeastern geology, v. II [Guidebook]-

Geological Society of America, 1980 Annual Meeting, 

Atlanta, Ga.: Falls Church, Va., American Geological Institute, p. 402--411. 

Gibson, T.G., Mancini, E.A., andBybell, L.M., 1982, Paleocene 

to middle Eocene stratigraphy of Alabama: Gulf Coast 

Association of Geological Societies Transactions, v. 32, 

p. 449--458. 

Haq, B.U., Hardenbol, Jan, and Vail, P.R., 1987, Chronology of 

fluctuating sea levels since the Triassic: Science, v. 235, 

no. 4793, p. 1156-1167. 

Jones, D.S., Mueller, P.A., Bryan, J.R., Dobson, J.P., Channell, 

J.E.T., Zachos, J.C., and Arthur, M.A., 1987, Biotic, 

geochemical, and paleomagnetic changes across the Cretaceous/Tertiary boundary at Braggs, Alabama: Geology, 

V. 15, p. 311-315. 

Mancini, E.A., Tew, B.H., and Smith, C.C., 1989, CretaceousTertiary contact, Mississippi and Alabama: Journal of Foraminiferal Research, v. 19, p. 93-104. 

Owens, J.P., and Sohl, N.F., 1969, Shelf and deltaic paleoenvironments in the Cretaceous-Tertiary formations of the New 

Jersey Coastal Plain, in Subitzky, Seymour, ed., Geology of 

selected areas in New Jersey and eastern Pennsylvania and 

guidebook of excursions: New Brunswick, N.J .. Rutgers 

University Press, p. 235-278. 

Reinhardt, Juergen, 1980, Upper Cretaceous stratigraphy and 

depositional environments, in Reinhardt, Ju~rgen, and Gibson, T.G .. Upper Cretaceous and lower Tertiary geology of 

the Chattahoochee River valley. western Gecrgia and eastern 

Alabama. in Frey, R. W., ed., Excursions in southeastern 

geology, v. II [Guidebook]-Geological Soc:ety of America, 

1980 Annual Meeting, Atlanta, Ga.: Falls Church, Va .. 

American Geological Institute, p. 386-392. 

---1982, Lithofacies and depositional cycles in Upper Cretaceous rocks, central Georgia to eastern Alabama, in Arden, 

D.D., Beck, B.F., and Morrow, Eleanore, ecs., Proceedings 

[of the] Second Symposium on the Geology of the Southeastern Coastal Plain [held] March 5-6, 1979, Americus, Ga., 

U.S.A.: Georgia Geologic Survey Informathn Circular 53, 

p. 89-96. 

Reinhardt, Juergen, Schindler, J.S., and Donova,, A.D., 1986, 

Latest Cretaceous and earliest Tertiary sedimentation in the 

eastern Gulf Coastal Plain [abs.]: Geological Society of 

America Abstracts with Programs, v. 18, p. 728. 

Sigleo, W.R., and Reinhardt, Juergen, 1988, Palecsols from some 

Cretaceous environments in the southeastern United States, in 

Reinhardt, Juergen, and Sigleo, W.R .. eds., Paleosols and 

weathering through geologic time-Principle<:. and applications: Geological Society of America Spec:(.l.l Paper 216, 

p. 123-142. 

Skotnicki, M.C., and King, D.T., Jr., 1986, Dep1sitional facies 

and sea-level dynamics of the Blufftown Fo:tllation, lower 

Campanian of east Alabama: Southeastern G~.ology, v. 27, 

no. 2, p. 53--67. 

---1989, Depositional facies and eustatic effec•<; in the Upper 

Cretaceous (Maastrichtian) Ripley Formation, central and 

eastern Alabama: Gulf Coast Association of Geological 

Societies Transactions, v. 39, p. 275-284. 

Sohl, N.F., and Koch, Carl, 1986, Molluscan biostratigraphy and 

biofacies of the Haustator bilira assemblage ZO"e (Maastrichtian) of the East Gulf Coastal Plain, in Reintardt, Juergen, 

ed., Stratigraphy and sedimentology of con:<:inental, nearshore, and marine Cretaceous sediments of th ~ eastern Gulf 

Coastal Plain, Field Trip 3 at the annual n·~eting of the 

Society of Economic Paleontologists and Mineralogists and 

the American Association of Petroleum Geologists, June 

18-20, 1986: Georgia Geological Society Guidebooks, v. 6, 

no. 3, p. 45-56. 

Sohl, N.F., and Smith, C.C., 1980, Notes on Creta-:-eous biostratigraphy, in Reinhardt, Juergen, and Gibson, T.G., Upper 

Cretaceous and lower Tertiary geology of the Chattahoochee 

River valley, western Georgia and eastern Alabama, in Frey, 

R.W., ed., Excursions in southeastern geology, v. II [Guidebook]-Geological Society of America, 1980 Annual Meeting, Atlanta, Ga.: Falls Church, Va., American Geological 

Institute, p. 392--402. 

158 Proceedings, 1988 USGS Workshop on the Geology and Geohydrology of the Atlantic Coastal Plain 
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