General Geology of the 

Mississippi Embayment

By E. M. GUSHING, E. H. BOSWELL, and R. L. HOSMAN

WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

GEOLOGICAL SURVEY PROFESSIONAL PAPER 448-B

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

First printing 1964 

Second printing 1968

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402
CONTENTS

Page

Abstract Bl

Introduction.. __ 1

Method of study 3

Acknowledgments-__ ____. 4

Geology- 4

Stratigraphy, _______ 5

Paleozoic rocks _ 5

Cretaceous System 5

Lower Cretaceous Series 5

Trinity Group _._ ____ 9

Upper Cretaceous Series __ 9

Tuscaloosa Group _ 10

Massive sand 10

Coker Formation.___._ _____ 10

Gordo Formation.... _.__ 10

Woodbine Formation 11

Eagle Ford Shale. ______________ 11

McShan Formation._______ __._ 11

Eutaw Formation______________ 11

Tokio Formation._.____________ 11

Blossom Sand and Bonham Marl..__.__ 11

Selma Group _____ _______ 11

Mooreville Chalk_____________ 11

Coffee Sand_______________ 12

Demopolis Chalk___________.___._ 12

Ripley Formation _ ...... 12

Prairie Bluff Chalk and Owl Creek

Formation ____________ 12

Demopolis Formation...___..._____ 13

Brownstown Marl... . _... 13

Ozan Formation___.___________ 13

Annona Chalk ______...____ 13

Marlbrook or Taylor Marl _____ 13

Navarro Group ____ 13

Saratoga Chalk___ _______ _____ 13

Nacatoch Sand._________________ 13

Arkadelphia Marl_______________ 13

Tertiary System ___ _ 14

Paleocene Series. _ 14

Midway Group__________________ 14

Clayton Formation....-______ 14

Kincaid Formation____________ 14

Stratigraphy Continued

Tertiary System Continued 

Paleocene Series Continued 

Midway Group Continued 

Porters Creek Clay____ 

Wills Point Formation.. 

Naheola Formation

Eocene Series._. .. 

Wilcox Group. 

NanafaUa Formation __ 

Tuscahoma Sand.. 

Hatchetigbee Formation__ ___ 

Berger and Saline Formations and

Detonti Sand_.__. ... 

Naborton Formation ___ 

Dolet Hills Formation 

Claiborne Group 

Tallahatta Formation_________ 

Carrizo Sand. 

Mount Selman Formation ___________

Cane River Formation._____________

Winona Sand_____ _ 

Zilpha Clay..._._ ___ _ 

Sparta Sand 

Cook Mountain Formation___ _ 

Cockfield Formation._______ 

Jackson Group.__ _ .___

Moodys -Branch Formation... 

Yazoo Clay____.___________

Oligocene Series._______________________

Miocene Series._________ 

Quaternary System. ...

Structure .

Mesozoic Era____ _.

Triassic Period. _ _.

Jurassic Period....

Cretaceous PeriodCenozoic Era. 

Tertiary Period 

Quaternary Period.

Physiography.. .

Selected bibliography .

Page

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in
IV CONTENTS

ILLUSTRATIONS

[Plates are in pocket]

PLATE 1. Fence diagram showing geology of Mississippi embay ment.

2. Geologic sections of Mississippi embayment. 

FIGURE 1. Map showing area of study.___________________________________________________________ B2

2. Mean annual temperature in the Mississippi embayment________________________________________ _ 3

3. Mean annual precipitation in the Mississippi embayment----_____________ _ ___ ________ 4

4-8. Contour maps showing configuration of:

4. Top of the Paleozoic rocks______________________________ _________ __ 8

5. Top of the Cretaceous System..______________________ _ _________ 9

6. Base of the sandy zone above the Porters Creek Clay._______________________ _ ____ _________ 15

7. Base of the Cane River Formation or its equivalents.______ _ _ ________ 19

8. Top of the Sparta Sand_________________________ __ _______________ 20

9. Structure map of the Mississippi embayment_____ 22

10. Physiographic map of the Mississippi embayment. ___ _ 24

TABLES

Page

TABLE 1. Stratigraphic columns____________________________________________________ B6 

2. Oil tests and wells shown on fence diagram and geologic sections..-. _ _ 7
WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT

By E. M. GUSHING, E. H. BOSWELL, and R. L. HOSMAN

ABSTRACT

As the first phase in the study of the water resources of the 

Mississippi embayment, the regional geologic structure and 

stratigraphy are defined. The Mississippi embayment comprises 

about 100,000 square miles in the Gulf Coastal Plain. It is a 

wedge-shaped region extending from its apex in southern Illinois 

southward to about the 32d parallel and includes parts of 

Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, 

Missouri, Tennessee, and Texas.

Most of the major geologic units include water-bearing strata 

that form vast aquifers, many of which cross State boundaries 

and are of regional importance. The deep-lying Jurassic rocks 

are not known to contain potable water, but the Cretaceous, 

Tertiary, and Quaternary deposits include numerous aquifers, 

most of which contain fresh water at shallow to moderate depths.

Geologically, the Mississippi embayment is a syncline which 

plunges to the south and whose axis generally parallels the 

Mississippi River. The syncline is filled with sedimentary rocks 

ranging in age from Jurassic to Quaternary and reaching a 

maximum thickness of about 18,000 feet in the southern part 

of the region. The lithology and continuity of the geologic units 

are variable because of modifying structural features and because 

of the differing depositional environments during the geologic 

evolution of the region. On the basis of interpretations of 

electric logs and some drillers' logs, contour maps were prepared 

showing configuration of the top of the Paleozoic rocks, the top 

of the Cretaceous System, the base of the sandy zone above the 

Porters Creek Clay, the base of the Cane River Formation or its 

equivalents, and the top of the Sparta Sand. A fence diagram 

and four sections show the stratigraphic relation of the major 

geologic units, and for areas near the outcrops of these units the 

sections are more detailed.

Important structural features in the embayment are the Sabine 

and Monroe uplifts, the Jackson dome, the East Texas and Desha 

basins, and the Arkansas and Pickens-Gilbertown fault zones. 

These structures, all of post-Paleozoic age, were formed, in part, 

contemporaneously with the sedimentation of the embayment 

and have had considerable influence on the depositional environment of the region.

INTRODUCTION

For several years the need for an appraisal of the 

water resources of the Mississippi embayment has been 

recognized by people associated with the development 

of the region. Most of the water-resources investigations in the embayment have been made in cooperation 

with State, county, and municipal agencies and have 

been restricted to local areas where the need for information was most urgent. Reports on these studies give 

valuable information on parts of the embayment, but 

they do not treat the subject of water resources on a 

regional basis.

The present study, begun in August 1957, is a part of 

the Federal program of the U.S. Geological Survey. 

The study is being made to provide an overall picture of 

the water resources so that these resources can be 

developed thoroughly and managed efficiently. This 

report is one of a series that will describe the results of 

the successive phases of the study.

Proper development, use, and conservation of the 

water resources can be achieved only through an understanding of the regional geologic environment and its 

influence on the response of the hydrologic system to 

climate and to water-supply development. Within the 

limits of time, personnel, and data available, the objectives of the study are aimed toward: (a) defining the 

regional geologic structure and stratigraphy and determining their influence on the movement, availability, 

and quality of the ground water; (b) determining areas 

of ground-water recharge and discharge, the directions 

and rates of flow between these areas, the influence of 

these areas on the low-flow characteristics of the streams, 

and the influence of artificial withdrawals on the groundwater reservoirs; (c) determining the relation between* 

the geology and the low-flow characteristics of streams, 

the expected low flows of streams on a frequency basis, 

and the storage requirements for maintaining certain 

minimum flows; (d) studying the relation between 

streams and ground-water reservoirs; (e) relating, by 

study of chemical analyses, the chemical quality of the 

water to its geographic and geologic environment; and 

(f) determining the downdip extent of fresh water in the 

formations and the presence of chloride, fluoride, nitrate, 

and other chemical constituents which in excess concentrations could possibly restrict the usefulness of the 

water.

The Mississippi embayment, as defined in this report, 

comprises about 100,000 square miles in the Gulf 

Coastal Plain. From its apex in southern Illinois, the

Bl
B2 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

embayment fans out southward to about the 32d parallel 

and includes parts of Alabama, Arkansas, Illinois, 

Kentucky, Louisiana, Mississippi, Missouri, Tennessee, 

and Texas. (See fig. 1.) Some of the larger cities 

within the region are: Tuscaloosa, Ala.; Jackson, Miss.; 

Monroe and Shreveport, La.; Texarkana, Ark.-Tex.; 

Little Eock, Ark.; and Memphis, Tenn.

For some millions of years this region was an embayment periodically occupied by an arm of the sea in 

which as much as several thousand feet of sediments 

were deposited. Deposits of sand now form vast 

regional aquifers (water-bearing units), some of which

are known to produce large quantities of water. These 

aquifers extend across State and topographic boundaries 

and underlie various watersheds.

The embayment is drained by several large streams, 

most of which belong to the Mississippi River system. 

An area in the southeastern part of the region is drained 

by tributaries of streams which flow separately into the 

Gulf of Mexico.

The region has a moderate climate. The mean 

annual temperature ranges from about 58° F in the 

northern part of the region to 66° F in the southern part 

(fig. 2), and the mean annual precipitation ranges

KANSAS

KENTUCKY

L~- L -

ARKANSAS

»*"\ X \

Little Rock

FIGURE 1. Map showing area of study.
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B3

33

32° L_

FiOTnut22. Mean'annual temperature, in degrees Fahrenheit, in the Mississippi embayment. (Data from records of U.S. Weather Bureau.)

generally from 48 inches in the northern part to 56 

inches in the southern part (fig. 3). Although the 

annual precipitation is high, most of it occurs during the 

winter and spring; droughts are common during the 

summer and fall.

The economy of the region is basically agricultural, 

but industry has become increasingly important since 

World War II. The diversification and mechanization 

of agriculture have resulted in a surplus of manpower, 

most of which is being absorbed by the expansion of 

industry. The population, although still predominantly 

rural, is becoming urban. Further industrial expansion 

probably will occur because of available manpower, 

natural resources, and economical transportation. 

Increasing demands on available water supplies will 

be made, and the future economy of the embayment is 

largely dependent upon intelligent utilization and 

management of the region's water resources.

One of the first phases of an areal water-resources 

study is to define the generalized structure and stratigraphy so that more detailed subsurface studies and

the correlation of the water-bearing units can be made. 

This report summarizes the general geology of the 

region.

METHOD OP STUDY

Description of the generalized regional structure and 

stratigraphy is based primarily on the interpretation 

of the available electric logs of wells and oil test holes. 

In areas where electric logs are not available, attempts 

were made to use available drillers' logs; generally, 

however, these logs were not detailed enough for 

accurate correlation with the electric logs. Most of 

the geologic interpretation is based on previously established and generally recognized unit boundaries. Some 

microscopic and micropaleontologic examinations of 

well cuttings were made to verify the interpretation of 

the electric and drillers' logs.

On the basis of the interpretations, a fence diagram 

showing the geology of the region, a structure map, 

four regional geologic sections, and five contour maps 

were prepared.
B4

95"

WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

94" 93" 92" 91° 90° 89"

35 "( ^l"--^

34

33

32°

FIGURE 3. Mean annual precipitation, in inches, in the Mississippi embayment. (Compiled from maps of U.S. Weather Bureau and records of

Tennessee Valley Authority.)

Work on the ground-water phases of the study is 

under the direction of E. M. Gushing. Fieldwork and 

data synthesis and analysis to date (1960) were done 

by J. G. Newton for Alabama, R. L. Hosman for 

Arkansas, L. M. MacCary and T. W. Lambert for 

Kentucky, W. H. Walker and C. E. Harris, Jr., for 

Louisiana, E. H. Boswell for Mississippi, G. K. Moore 

and J. H. Criner, Jr., for Tennessee, and E. T. Baker, 

Jr., and William Ogilbee for Texas. Lithologic and 

micropaleontologic studies are being made by S. M. 

Herrick. Work on the surface-water phases is under the 

direction of P. R. Speer, and that on the quality-ofwater phases is under the direction of M. E. Schroeder.

ACKNOWLEDGMENTS

The suggestions, assistance, and cooperation of the 

following State officials and members of their staffs 

are gratefully appreciated: Walter B. Jones, State 

Geologist, Geological Survey of Alabama; Norman F. 

Williams, Geologist-Director, Arkansas Geological and

Conservation Commission; John C. Frye, Chief, Illinois 

Geological Survey; Wallace W. Hagan, Director and 

State Geologist, Kentucky Geological Survey; Arthur 

C. McFarlan, Head of Geology Department, University 

of Kentucky; Leo W. Hough, State Geologist, Louisiana 

Geological Survey; Tracy W. Lusk, Director and State 

Geologist, Mississippi Geological Survey; Thomas R. 

Beveridge, Director and State Geologist, Missouri Geological Survey; William D. Hardeman, State Geologist, 

Tennessee Division of Geology; and the late John T. 

Lonsdale, former Director, Texas Bureau of Economic 

Geology. These officials also furnished or made available geologic information and many electric logs and 

sets of well cuttings for this study. Shell Oil Co., 

Jackson, Miss., allowed the authors access to the well 

cuttings in its repository.

GEOLOGY

Within the Mississippi embayment, sediments ranging in age from Jurassic to Quaternary have been
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B5

deposited and have a maximum thickness of about 

18,000 feet in the southern part of the region. Units 

ranging in age from Cretaceous to Quaternary crop 

out within the area of study (pi. 1). These units of 

gravel, sand, silt, clay, lignite, marl, chalk, and limestone range in thickness from zero at the outcrop of 

Paleozoic rocks to several thousand feet at the axis of 

the embayment structural trough.

This report is concerned primarily with the stratigraphic relationship and areal extent of the units of 

Late Cretaceous age and younger, and with the general 

correlation of the units within the embayment. Table 

1 shows the stratigraphic columns used by the U.S. 

Geological Survey (May 10, 1961) for the Upper Cretaceous, Paleocene, Eocene, and Oligocene units in the 

area of study.

STRATIGRAPHY

Available electric logs of wells and oil tests in the 

embayment were used to define the generalized regional 

stratigraphy. The geologic interpretations of the logs 

are based primarily on established and generally recognized unit boundaries. Some microscopic and micropaleontologic examinations of well cuttings were made 

to verify these boundaries.

The geologic contacts shown on a regional fence 

diagram (pi. 1) include the top of the Paleozoic rocks, 

the top of the Lower Cretaceous Series, the top of the 

Upper Cretaceous Series, the base of the sandy zone 

immediately above the Porters Creek Clay, the top of 

the Wilcox, the top of the Claiborne Group, and the 

top of the Jackson Group. The Oligocene and Miocene 

Series are shown as a unit, as is the Quaternary System.

Plate 2 is a group of regional geologic sections. 

These sections show the correlation of the groups or 

larger units in the embayment and the stratigraphic 

position of most of the formational units near their 

areas of outcrop. In the extreme northern part of the 

embayment, Eocene deposits have not been subdivided. 

Facies changes in the units in this interval and the lack 

of subsurface information have prevented the tracing 

of the recognized unit boundaries from the southern 

part of the region into the northern part. Fossils, 

which would be useful in the attempt to subdivide 

these Eocene units, apparently do not exist in the 

northern part of the embayment.

Wells shown on the fence diagram and on the sections 

are listed in table 2. The well numbers are those used 

in each State by the district office of the Branch of 

Ground Water of the U.S. Geological Survey.

PALEOZOIC BOCKS

Although igneous intrusive rocks occur in some 

places, the basement rocks that form the synclinal 

structure of the Mississippi embayment are mostly of

Paleozoic age, ranging from Cambrian to Pennsylvanian. 

Although irregular, the slope of the Paleozoic surface 

is generally toward the axis of the embayment in the 

northern part of the region and changes gradually 

toward the Gulf of Mexico on the southern flanks. 

Figure 4 is a contour map showing configuration of the 

top of the Paleozoic rocks.

Within the embayment, near its periphery, water in 

rocks of Paleozoic age is utilized.

CRETACEOUS SYSTEM

Deposits of Cretaceous age rest unconformably on 

rocks of Paleozoic age throughout the embayment 

except in the extreme southern part, where Lower 

Cretaceous deposits overlie truncated Jurassic strata. 

The Cretaceous sediments are mostly of marine origin 

and are largely calcareous, ranging from sands to clays, 

chalks, and marls. Some reef-type limestones are 

present locally.

The dip of Cretaceous strata is generally toward 

the axis of the embayment except in the southern 

part of the region, where the dip gradually swings 

southward toward the Gulf of Mexico. Structural 

features within the embayment affect the dip of Cretaceous strata locally.

Figure 5 is a contour map showing the configuration 

of the top of the Cretaceous System.

LOWER CRETACEOUS SERIES

The 34th parallel marks the approximate northernmost limit of Early Cretaceous deposition in the 

Mississippi embayment. Post-Early Cretaceous erosion during the rise of the Monroe uplift completely 

removed the Lower Cretaceous rocks in southeastern 

Arkansas and part of northeastern Louisiana; Lower 

Cretaceous beds are truncated around the southern 

flank of the uplift.

Lower Cretaceous rocks do not crop out on the 

eastern side of the embayment. However, in Mississippi and Alabama they occur in the subsurface as 

thick sands, clays, and shales. Lower Cretaceous beds 

crop out in a westward-trending band in southwestern 

Arkansas and southeastern Oklahoma, and extend downdip into Louisiana and Texas. These beds have been 

designated the Trinity Group, which comprises 

several formations.

Southwestern Arkansas is the only area in the Mississippi embayment where fresh ground water is obtained 

from wells drilled into these rocks. Analysis of electric 

logs indicates that the Lower Cretaceous deposits may 

contain fresh water in a small area in east-central 

Mississippi and western Alabama but that elsewhere in 

Mississippi and in Alabama the water is probably too 

mineralized for most uses.

298-803 O - i
wOi

TABLE 1. Stratigraphic columns

Northeastern Texas

[Bowie, Cass, Marion, 

and Harrlson Counties]

Eocene Series 

Clalborne Group 

Sparta Sand 

Mount Selinan Formation

Weches Greensand Member 

Queen City Sand

Member 

Reklaw Member 

Carrizo Sand 

Wilcox Formation 

Palepcene Series 

Midway Group 

Wills Point Formation

Kincaid Formation

Upper Cretaceous Series

Nayarro Group, undiflerentiated 

Taylor Marl 

Annona Chalk 

Brownstown Marl 

Blossom Sand 

Bonham Marl 

Eagle Ford Shale 

Woodbine Formation

Northern Louisiana

[North of 32d parallel]

Oligocene Series

Vicksburg Formation 

Eocene Series 

Jackson Group 

Yazoo Clay 

Moodys Branch

Formation 

Claiborne Group 

Cockfleld Formation 

Cook Mountain

Formation 

Sparta Sand 

Cane River Formation 

Carrizo Sand

Northern LouisianaCon t nued

Eocene and Paleocene

Series

Wilcox Group 

Dolet Hills Formation

Naborton Formation

Paleocene Series 

Midway Group 

Porters Creek Clay 

Clayton Formation 

Upper Cretaceous Series 

Arkadelphia Marl 

Nacatoch Sand 

Saratoga Clay 

Marlbrook Marl 

Annona Chalk 

Brownstown Marl 

Tokio Formation 

Eagle Ford Shale 

Woodbine Formation

Arkansas

Eocene Series 

Jackson Group, undifferentiated 

Claiborne Group 

Cockfleld Formation 

Cook Mountain

Formation 

Sparta Sand 

Cane River Formation

Carrizo Sand 

Wilcox Group, undifferentiated' 

Paleocene Series 

Midway Group, undiflerentiated * 

Upper Cretaceous Series 

Arkadelphia Marl 

Nacatoch Sand 

Saratoga Chalk 

Marlbrook Marl 

Annona Chalk 

Ozan Formation 

Brownstown Marl 

Tokio Formation 

Woodbine Formation

Missouri

Eocene Series

Wilcox Formation 

Paleocene Series 

Midway Group 

Porters Creek Clay 

Clayton Formation 

Upper Cretaceous Series 

Owl Creek Formation 

McNairy Sand

Illinois

Eocene Series 

Wilcox Group, undifferentiated 

Paleocene Series 

Midway Group 

Porters Creek Clay 

Clayton Formation 

Upper Cretaceous Series 

McNairy Sand

Kentucky

Eocene Series 

Claiborne Group, undifferentiated 

Wilcox Group, undifferentiated 

Paleocene Series 

Midway Group 

Porters Creek Clay 

Clayton (?) Formation

Upper Cretaceous Series 

McNairy Sand 

Tuscaloosa Formation

Tennessee

Eocene Series 

Jackson (?) Formation 

Claiborne Group, undifferentiated 

Wilcox Group, undifferentiated 

Paleocene Series 

Midway Group 

Porters Creek Clay 

Clayton Formation

Tennessee Continued

Upper Cretaceous Series

Owl Creek Formation

Ripley Formation 

McNairy Sand

Member

Coon Creek Tongue

Demopolis Formation

Coffee Sand

Eutaw Formation

Tuscaloosa Formation

Northern Mississippi

[Northern part]

Eocene Series

Jackson Group, undifferentiated 

Claiborne Group

Cockfleld Formation

Cook Mountain

Formation

Sparta Sand

Zilpha Clay

Winona Sand

Tallahatta Formation

Holly Springs

Sand Member

Wilcox Formation

Paleocene Series

Midway Group

Porters Creek Clay

Tippah Sand Lentil

Clayton Formation

Upper Cretaceous Series

Selma Group

Owl Creek Formation

Ripley Formation

Chiwapa Member

McNairy Sand

Member

Cook Creek

Tongue

Transitional clay

Demopolis Chalk

Coffee Sand

Eutaw Formation

Tombigbee Sand

Member

McShan Formation

Tuscaloosa Group,

undifferentiated

Northern Mississippi

[Southern part]

Eocene Series 

Jackson Group, undifferentiated

Claiborne Group

Cockfleld Formation

Cook Mountain

Formation

Sparta Sand

Zilpha Clay

Winona Sand

Tallahatta Formation

Wilcox Formation

Paleocene Series

Midway Group 

Naheola Formation

Porters Creek Clay

Clayton Formation

Upper Cretaceous Series

Selma Group

Prairie Bluff Chalk

Ripley Formation

Demopolis Chalk

Bluffport Marl

Member

Mooreville Chalk

Arcola Limestone

Member

Eutaw Formation

Tombigbee Sand

Member

McShan Formation

Tuscaloosa Group,

undifferentiated

Central Mississippi

Oligocene Series

Forest Hill Sand and

Red Bluff Clay 

Eocene Series

Jackson Group

Yazoo Clay

Shubuta Member

Pachuta Marl

Member

Cocoa Sand Member

North Creek

Member

Moodys Branch

Formation

Claiborne Group

Cockfleld Formation 

Cook Mountain

Formation

Gordon Creek

Shale Member

Potterchitto Sand

Member

Archusa Marl

Member

Sparta Sand

Zilpha Clay

Winona Sand

Tallahatta Formation

Neshoba Sand

Member

Basic City Shale

Member

Meridian Sand

Member

Wilcox Formation

Bashl Marl Member

Fearn Springs

Member

Central MississippiContinued

Paleocene Series

Midway Group 

Naheola Formation

Porters Creek Clay

Matthews Landing Marl Member

Clayton Formation

Upper Cretaceous Series

Selma Group

Prairie Bluff Chalk

Ripley Formation

Demopolis Chalk

Bluffport Marl

Member

Mooreville Chalk

Arcola Limestone 

Member

Eutaw Formation

McShan Formation

Tuscaloosa Group

Gordo Formation

Coker Formation

Massive sand

Western Alabama

Eocene Series

Claiborne Group

Tallahatta Formation

Meridian Sand

Member

Wilcox Group

Hatchetigbee Formation

Bashi Marl Member

Tuscahoma Sand

Bells Landing

Marl Member

Oreggs Landing

Marl Member

Nanafalia Formation

Oramplan Hills

Member

Middle member

Gravel Creek

Sand Member

Western AlabamaContinued

Paleocene Series

Midway Group 

Naheola Formation

Coal Bluff Marl

Member

Oak Hill Member

Porters Creek Formation

Matthews LandIng Marl Member

Clayton Formation

McBryde Limestone Member

Pine Barren

Member

Upper Cretaceous Series 

Selma Group

Prairie Bluff Chalk

Ripley Formation

Demopolis Chalk

Bluffport Marl

Member

Mooreville Chalk

Arcola Limestone

Member

Eutaw Formation

Tombigbee Sand

Member

McShan Formation

Tuscaloosa Group

Gordo Formation

Coker Formation

Upper unnamed

member

Eoline Member

Massive sand

s

f>1-3

H

to

W

co

O

d

So

00

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1-3

M

B

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co

co

cotj

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IX)

KJ

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2

i Wilcox Group (Eocene Series), undifferentiated. Wilcox Group (Paleocene Series), upper part undiflerentiated; Dolet Hills and Naborton Formations lower two units. 

»in ascending order, \\ ilcox Group Arkansas in bauxite area comprises Berger Formation, Saline Formation, and Detonti Sand 

'In ascending order, Midway Group in Arkansas bauxite area comprises Kincaid Formation and Wills Point Formation.
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B7

TABLE 2. Oil teats and wells shown on fence diagram and geologic sections

County or 

parish

Do.... 

Ashley -

Arkansas. ..

Do .......

Clark... ...... 

Clay. .....

Do ......

Do.. .....

Do .....

Little River 

Do . ....

Do.......

Do.. 

Miller.. ......

DoDo.. .....

Do--.....

Do _ . ...

Do.. 

Do- .

Do ...

St. Francis 

Do... .....

Do........

White 

Galloway.. ...

Carlisle.... ...

Fulton.. ......

Bienvllle......

Do .....

Do... .....

Do .....

Do .....

Do........

Do -

Do .....

Do- ...

Do... .....

Do .....

Do........

Do .....

Madison _ .

Do........

Do .....

Do........

Well

1-51 .......... 8-23

FF-35 ........

88-24. ........

58. ____ ....

75 .............

76 ...... ....

84.. _____ .. 

17 __ . ........

16..... ........

69 .............

6........ ......

3. _______ .

63.. _ . .......

2 ..............

10 .............

36.. __ . .....

37.............

6. __ . .......

54. ____ . _ .

20........ .....

38.......... ...

98 .

10 .............

98 .............

1 ..............

39 .............

40. ............

41 .............

43.............

3 ..............

11 _______

7Q

74 _______

101. ...

11 ............

67 ............

102 ............

61 ............

97 ............

105............

79

2 ..............

S1229.1-120.4..

dnoo A ortft Q

S946.1-92.3 

18 

9. __ ... .....

10 .........

1 __ . ........

2 ___ . ........

3 ..............

4 . . _ .

5... ...........

6..............

7. .............

8..............

13. ____ ....

14 .............

15. ............

16.............

17 .............

31.............

29... ..........

30...... ....... 

22 .............

23... .....

24.... __ ....

Company or driller

Alabama

Blair Oil & Gas Co.... ...

....do...... ___ .........

Perry trust).

J. F. Stone- ...........

Gallatin Drilling Co __

TATI n or lr TTI t*

H. M. Mills _____ .....

Carter Oil Co. ___ . ....

Estabrook, HiU & Crider..

R. E. Smith ..............

B. E. Smith. _____ ...

Peters Drilling Co. ....

States Oil Co.... ..........

Kentucky

South Central Petroleum

Co. 

Sterett Drilling Co. ....

Mt. Carmel Drilling CoLouisiana

Monsanto Chemical Co ..

Arkla Oil Co. ............

J. W. Fair.. ...... ........

Co.

ing Co.

V. S. Parham .............

Curtis Kinard _______

Barnsdall Oil Co. & C. N.

Valerious. 

The Texas Co.. ..........

Well name

U.S. Geol. Survey test

well

Do.

E. P. Fox 1.

Kunnicutt 1.

Ruby Martin 1

Dierks 1.

to to 1

Nichols 1.

McClouth 1.

M W^ Jones 1

"WooHS F&rrns 1

G. R. Shankle 1.

Loftinl.

Sol Nathan 1.

Pearl Tones Cherry 1.

T. J. Wilson 1.

Florence Smith 1.

Ozley 1.

Mattie Pitts 3.

Bell 2.

Fly 2.

Bell A-l.

W. C. Agurs 2.

R. F. Odom 1.

Ilemphill 1.

Katlian-Johnson 1.

Soudhelmer 1.

W. W. Doles 1.

County or 

parish

Do... .....

Ouachlta _

Union ........

Do.... ....

Do . ....

West Carroll..

Attala ........

Do.... ....

Do ..

Calhoun. . .

Do........

Clay. ........

Do........

DoDo 

Do.. ..

Do .....

DoDo 

Do.. .

Do ....

Do.. ....

Lee...........

Do __ ...

Leflore.. ...

Do.. 

Do.... 

Do.. . -

Newton.. .....

Noxubee. 

Prentiss ....... 

Do... 

Do... 

Do 

Do.... 

DoDo. 

Do... 

DoDo 

Yazoo. . ....

DoPo 

Do... .-

Well

L

25.. ____ ...

26 .............

21 .............

27. __ . __ .

19 ______ ..

«u« »*.«..._.. 11 .............

12 __ .

28... __ .

6. .............

13 ............

3 ..............

6 ______ ...

3 ..............

5. ___ . _ ...

2 ..............

2. ..........

6 ..............

1 ..............

1 ..............

12 ............

4. ___ . ___ .

38 ............

48 ..... .......

67 ............

1206 ...... ....

1231 _____ .

7 ..............

14 ______ .

20 ............

22 ______ .

43

6 _

14....... ......

15 ..........

1 ... ........

5 ___ . ___ .

6 ....

4... ...... ..

9 .

78..... .

1 _ .....

2 _ ..... _ ...

6 ..... 

8. ..

Fll.. ..... .

J22 ..

11 _ ..........

31....... ......

10 ..

4 ..

2 ,.... 

4. ..

9 .........

6 ... .... ..

10 

11 . .......

12.............

13. 

2- _ .. _ ....

27. __ ........

43 

5 ... .

8...... . .

1 __ .. __ . ...

27 ...

49. _ .........

71.. ....

Company or driller

Duisiana Continued

Justiss-Mears Oil Co ......

Atlantic Refining Co... ...

H. J. Heartwell.. .. ...

Hunt Oil Co ..............

Pure Oil Co _____ . ...

Mississippi

Shell Oil Co... ___ ......

Dudley S. Weaver et al..

Honolulu Oil Co. ........

Seaboard Oil Co ..........

Sinclair Oil Co............

Henson & Rife Co.... ....

Atlantic Refining Co.. ....

Union Producing Co ......

B. H. Williams & H. H.

Womble.

Fred Mellen _ ..........

Kingwood Oil Co. &

Kemp Drilling Co.

Plains Production Co .....

Premier Oil Refining Co..

Leonard Jones ............

J. E. Treadway & D. C.

Latimer.

A. H. Rowan. ___ .. ....

Sohio-Fleishman .. ...

Marshall R. Young et al..

Ray Northern & A. W.

Williams Drilling Co.

Rogers Lacy.. __ ...

Wanete Oil Co ............

Harold K. Boysen ........

J. F. Michael..... 

R. A. Ellison .

Exchange Oil Co .

Ray, Shortridge & Wilson 

Drilling Co. 

Shell Oil Co.... ___ .....

H. H. Hamilton. __ ......

Sun Oil Co................

sion Co.

Carloss Well Supply Co ... 

Layne-Central Co _ . ....

Monsanto Chemical Co ...

Union Producing Co.. _ .

send.

Latex-Gulf Oil Co _ . 

Ohio Oil Co. . .

Louisiana-Mississippi Oil

Co.

Marshall R. Young .... 

Lewis & La Rue.. ___ ..

Gulf Refining Co _ .......

Marshall R. Young. __ ..

Texas Co.... _ . __ ......

Magnolia Petroleum Co...

Frontier Oil Refining

Corp.

Steward Oil Co. et al... ...

Northern Ordnance Co ....

J. W. Sorrels.... _ .......

Well name

Evans 2.

E. M. Clark 1.

Walter Maxey 1.

linl.

GriflBn 1.

Kilpatrick 1.

Jacinta Sales 1.

CosteUo 1.

H. H. Wheeless 1.

M. C. Rutherford 1.

D. R. Davis2.

J. L. Williams 1.

Epperson 1.

W.J.&T.W. Green 1.

R. G. Dunning 1.

Withers Estate 1.

Connecticut General

Life Insurance Co. 1.

Mrs. A. G. Williams 1.

Jackson Ready-MixBell-Anding 1.

E. L. Gray 1.

J. S. Taylor 1.

Landstreet-Lipbam 1.

La Rue 1.

Blind Institute 1.

Unger-Darnell 1.

J. W. Eakin 1.

J. Garland 1.

Board of Supervisors 1.

Fleming 1.

Kentucky Lumber Co.

1.

J. J. Shelburne 1.

Beadles & Fredricks 1.

Denkman Lumber Co.

1.

Temple-Harmon unit

1.

W. H. Neely 1.

Wildwood Plantation

1.

J. J. Ross 1.

Kirkland 1.

Hilma Wall 1.

City of Booneville 

water well. 

City of Baldwyn

water well. 

Leon 1.

A. Y. Keith 1.

Gaylord Container

J. R. Cooper 1.

J. R. Dockery 1.

C. E. Shores 1.

Ogilvle 1. 

L. Westbrook 1.

T. P. Cason et al. 1.

H. P. Tatiim 1.

A. B. Hintson 1.

Martin Estate 1

F. C. Martin 1.

Chancellor 1.

Ruth Creekmore 1.

Koppers Co. 1.

Bank 1.

C. S. Stoner 1.

Ledbctter 1.
B8 WATER RESOURCES OF THE MISSISSIPPI EMBATMENT

TABLE 2. Oil tests and wells shown on fence diagram and geologic sections Continued

County or 

parish

New Madrid,

Do........ 

Pemiscot ......

Stoddard. ...

Do........

Dyer.. ........

Fayette ..... 

Hardeman ....

Henderson ....

Lake

Lauderdale ...

Madison ......

Do .....

Well

6614 ...........

6809 ...........

8882. _____ . 

7222...........

8573 __ . ...

9205.. .........

Dy:G-l_ 

Fa:J-l_ 

Hr:G-32 ...

He:K-3 ......

Lk:E-17.. 

Ld:O-4.._ .

Mn:H-l.__. ...

Md:M-l.. ....

Md:N-l.__ 

Company or driller

Missouri

U.S. Bureau of Mines .....

M. H. Marr . . .......

Henderson Oil Co.. .......

Lazarov & Bobilio Oil Co 

W. Atkeison Well Supply

Co.

Benz.

.. do... ...... .......

Well name

E. Phillips 1.

R. B. Oliver, Jr. 1.

W. J. Crutcher 1.

Rehms 1.

Field 1.

Beasley 1.

T. A. Lee. 1.

Petrie 1.

T-2-M. 

U.S. Qeol. Survey T-l-M.

County or 

parish

Shelby... .....

Do 

Do. 

Do .....

Do........

Do.. .

Do 

Do........

Do... __ .

Well

Sh:L-5..._ .

Sh:O-169.--_.

Sh:U-12......

BD-1620701...

BD-1644102 

DB-1659302...

DB-1664404...

DB-3503302 

DB-3506303...

LK-3520503...

LK-3536204...

SX-3512102....

Company or driller

Tennessee Continued

Memphis Light, Gas &

Water Div. 

Lion Oil & Refining Co ...

Texas

J. K. Wadley.. ....

Permac Oil & Gas Co.,

Inc. 

Atlas Oil & Refining Co

Arkla Oil Co.... ..........

Humble Oil & Refining Co.

D. E. & R. T. Whelan... .

nedy.

Well name

Memphis Light, Gas &

Water Div. 25.

R. C. Vollmer 1.

Tidwell 1.

Laura Thomas 1.

E. Turner 1.

Co. 1. 

Mrs. Sloan Taylor 1.

C. A. Bell 1.

S. L. Orr 1.

95" 94

37'

\ ILLINOIS

EXPLANATION

Contour interval 200 feet 

Datum is mean sea level

Compiled from data submitted by 

J. G. Newton for Alabama; R. L. 

Hosman for Arkansas; T. W. 

Lambert for Kentucky; E. H. 

Boswell for Mississippi and G. K. , i 

Moore for Tennessee r _J._._

-T ARKANSAS

33 j, i jVr"!

32° 

FIGURE 4. Contour map showing configuration of the top of tho Paleozoic rocks.
GENERAL GEOLOGY OP THE MISSISSIPPI EMBAYMENT B9

95° 94" 93° 92° 91° 90° 89° 88° 87"

37°

36°

35°

34°

33°

32°

EXPLANATION

0 50 100 MILES

Contour interval 200 feet 

Datum is mean sea level

Compiled from data submitted by 

J. G. Newton for Alabama; R. L. 

Hosman for Arkansas; T. W. 

Lambert 'for Kentucky; C. E. 

Harris, Jr., and W. H. Walker for 

Louisiana; E. H. Boswell for Mississippi; G. K. Moore for Tennessee 

and E. T. Baker, Jr., for Texas

\ ILLINOIS JL<-' ^

,^-^-U^-/^/ \ A

FIGURE 5. Contour map showing configuration of the top of the Cretaceous System.

Two other formations of Early Cretaceous age, the 

Goodland Limestone (Hill, 1891, p. 504, 514) and the 

Kiamichi Formation (Hill, 1891, p. 504, 515) overlie 

the Trinity Group and have a combined maximum 

thickness of about 70 feet. As these two units crop 

out in only a very small area in Arkansas near the 

Oklahoma State line, occur in the subsurface only in 

northeastern Texas and a small area in southwestern 

Arkansas, and are not a source of ground water, they 

are not treated further in this report.

Trinity Uroup

The Trinity Group (Hill, 1888, p. 188) in Arkansas 

consists in ascending order, of the Pike Gravel (Miser 

and Purdue, 1918a, p. 20), the Delight Sand (Imlay, 

1944), the Dierks Limestone (Miser and Purdue, 1918a, 

p. 21), the Holly Creek Formation (Vanderpool, 1928, 

p. 1079-1080) including the Ultima Thule Gravel 

Member (Miser and Purdue, 1918a, p. 21), the De 

Queen Limestone (Miser and Purdue, 1918a, p. 22), 

and the Paluxy Sand (Hill, 1891, p. 504). This differentiation applies only in the immediate vicinity of the

outcrop. The thickness of the group in outcrop is 

about 1,500 feet, and it may exceed 2,500 feet in the 

subsurface.

The Paluxy Sand is the most important water-bearing 

unit in the Trinity Group. The Pike Gravel and the 

Ultima Thule Gravel Member of the Holly Creek 

Formation yield moderate quantities of fresh water to 

wells in and near their outcrops.

UPPER CRETACEOUS SERIES

The entire Mississippi embayment was inundated by 

the Late Cretaceous sea to a point at least 20 miles 

north of Cairo, 111. Before the sea retreated at the end 

of the Cretaceous Period, hundreds of feet of sediment 

were deposited in the embayment. The Upper Cretaceous strata are thickest along the axis and in the 

southern part of the embayment. They thin eastward 

and westward toward the flanks and northward toward 

the apex of the trough. These rocks consist predominantly of sand, clay, marl, and chalk that are mostly 

of marine origin. Generally, aquifers of the Upper 

Cretaceous contain fresh water in and near their
BIO WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

outcrops, and the degree of mineralization in the water 

increases downdip.

The Upper Cretaceous beds crop out in a wide band 

along the entire eastern flank of the embayment, in the 

northeast corner of Texas, and in the southwest corner 

of Arkansas. A small outcrop occurs along the Fall 

Line in northeastern Arkansas, but elsewhere along the 

western flank the Upper Cretaceous rocks are overlapped 

by younger sediments.

Tuscaloosa Group

The basal Upper Cretaceous beds on the eastern side 

of the embayment originally were assigned to the Tuscaloosa 

Formation (Smith and Johnson, 1887, p. 18). These 

beds in Alabama and Mississippi now constitute the 

Tuscaloosa Group (originally defined by Monroe and 

others, 1946, p. 191; redefined by Drennen, 1953a, p. 

528), which includes the Coker and Gordo Formations. 

In the subsurface of central Mississippi and western 

Alabama, a basal unit known as the massive sand is 

also included in the group.

In Tennessee and Kentucky the basal Cretaceous 

beds, lithologically similar to those of the Tuscaloosa 

Group, remain assigned to the Tuscaloosa Formation. 

These beds may be as much as 180 feet thick (MacCary, 

1960, written communication) and consist of wellrounded pebbles ranging in size from 1 inch to 6 inches. 

They also contain varying amounts of sand and clay. 

A hard conglomerate is present in places where the 

pebbles, mostly chert, are cemented with iron oxide. 

The Tuscaloosa Formation, largely removed by erosion, 

is of deltaic origin. Although the formation is not 

extensive, it does yield moderate amounts of water to 

wells in and near its outcrop.

Massive sand. The term "massive sand*," was first 

used by McGlothlin (1944). The sand was correlated 

with the Cottondale Formation (of former usage) by 

Monroe, Conant, and Eargle (1946, p. 210-211) and by 

Eargle in later work (1946, 1948). When Drennen 

(1953a) reclassified the Tuscaloosa Group, he abandoned 

the term "Cottondale Formation," formerly applied to 

the basal unit of the group, because the deposits 

assigned to this unit were included in the redefined 

Coker Formation. Drennen (1953, p. 530) describes 

the Coker Formation as being "correlative with that 

part of the lower Tuscaloosa above the massive sand." 

Although the term "Cottondale Formation" was 

abandoned, the informal term "massive sand" is still 

used for the basal sand unit of the Tuscaloosa Group in 

western Alabama and central Mississippi.

Drennen (1953a, table 2) tentatively correlates the 

massive sand with the Vick Formation (Conant, 1946), 

which crops out only in Bibb County, Ala. The Vick 

Formation, however is Early (?) Cretaceous (Monroe,

1955, p. 13), whereas the massive sand is probably 

Late Cretaceous. Until the massive sand is shown to 

be the subsurface equivalent of the Vick Formation or 

a suitable geographic name is designated, the informal 

name "massive sand" is applied to the unit. Whether 

this unit is of formational rank, is a basal member of 

the Coker Formation, or is a part of the Eoline Member 

of the Coker Formation remains to be determined.

The massive sand is "a series of medium- to coarsegrained sands * * * " (according to McGlothlin, 1944, 

p. 40). Interbedded shale and clay occur in the thick 

beds of coarse sand, chert, and quartz gravel which 

compose the main body of the unit. The thickness of 

the massive sand ranges from zero at its northern 

limit, slightly south of the 34th parallel, to a possible 

maximum of 500 feet in the southern part of the region. 

The massive sand overlies beds of Early Cretaceous age 

in central Mississippi and western Alabama, and northward it overlies Paleozoic rocks. Although the massive 

sand is not generally used as a source of ground water, 

it is potentially one of the most important aquifers in 

the embayment.

Coker Formation. The Coker Formation (originally 

defined by Monroe and others, 1946, p. 197-200; 

redefined by Drennen, 1953a, p. 532-536) ranges in 

thickness from a few feet to about 400 feet (excluding 

the massive sand) in the subsurface in Alabama and 

central Mississippi. In Alabama, the Coker has been 

subdivided into the Eoline Member and an upper 

unnamed member.

The Eoline Member (Monroe and others, 1946, 

p. 194-197) consists of thin-bedded clay, sandy 

clay, shale, and sand, mostly of marine origin; subordinate beds of sand occur throughout the unit. The 

overlying unnamed member is composed of multicolored 

clay and shale containing subordinate sand beds. The 

Coker Formation lies upon the massive sand and upon 

Paleozoic rocks where the massive sand is absent.

Although the Coker Formation is not extensively 

used for ground-water supplies, it seems to be a potential 

source in many areas in Alabama and Mississippi.

Gordo Formation. The Gordo Formation (Monroe 

and others, 1946, p. 200-204) generally ranges in thickness from 100 to 400 feet in the subsurface. It is 

composed of thick beds of sand containing gravel in the 

lower part and multicolored clay and shale interbcdded 

with sand in the upper part. It is absent in the subsurface in northwestern Mississippi. The basal gravel 

of the Gordo Formation rests unconformably on the 

clays of the upper unnamed unit of the Coker 

Formation.

The Gordo Formation is an important aquifer in 

Alabama and Mississippi.
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT Bll

Woodbine Formation

The Woodbine Formation (Hill, 1901, p. 293) is the 

basal unit of the Upper Cretaceous Series hi northeastern Texas, northern Louisiana, and southern 

Arkansas and lies unconformably upon Lower Cretaceous rocks. It has been correlated with the Tuscaloosa Group on the eastern side of the region. The 

formation reaches a maximum thickness of about 350 

feet hi the subsurface and consists of sand, clay, gravel, 

and some reworked volcanic material. The only outcrop in the area of study is hi southwestern Arkansas. 

The Woodbine yields small quantities of water to 

domestic wells in and near its outcrop.

Eagle Ford Shale

The Eagle Ford Shale (Hill, 1887, p. 298) overlies 

the Woodbine Formation hi Louisiana and Texas but 

does not crop out in the embayment. It consists of 

several hundred feet of dark-colored shale, sandy shale, 

and subordinate beds of sand. The formation is not 

present on the Sabine uplift, where it has been removed 

by erosion. The Eagle Ford Shale does not yield water 

to wells in the embayment.

M cSnan Formation

The McShan Formation (Monroe and others, 1946, 

p. 204-207), probably equivalent to the Eagle Ford 

Shale, crops out in Alabama and Mississippi, where it 

reaches a thickness of 200 feet or more hi the subsurface. It consists of laminated micaceous glauconitic 

gray clay, fine sand, and lenticular beds of fine to 

medium glauconitic sand. The formation is overlapped 

by the Eutaw Formation hi northern Mississippi and 

is absent farther north.

In subsurface mapping the McShan is generally included in the lower part of the Eutaw Formation. 

The McShan is an important aquifer in eastern 

Mississippi and western Alabama.

Eutaw Formation

In the subsurface in Tennessee, Mississippi, and 

Alabama the Eutaw Formation (Hilgard, 1860, p. 61) 

ranges in thickness from zero to more than 400 feet. 

The main body of the formation is composed of gray 

clay interbedded with fine glauconitic sand. Thin 

beds of fine to medium glauconitic sand are common 

and are fairly persistent near the base of the formation, 

which is normally marked by a thin bed of fine gravel. 

The sands are commonly crossbedded or show distinct 

stratification. A persistent sand at the top of the 

formation, known as the Tombigbee Sand Member 

(Hilgard, 1860, p. 61), is massive, highly glauconitic, 

calcareous, and fossiliferous in the upper part. The 

Eutaw Formation overlies the McShan Formation in 

Alabama and Mississippi, where the contact generally 

can be recognized on the outcrop. In the subsurface, 

however, the two units are generally mapped together

as the Eutaw Formation. The Eutaw Formation is 

an important aquifer hi eastern Mississippi and western 

Alabama.

Toklo Formation

The Tokio Formation (originally defined by Miser 

and Purdue, 1918a, p. 19, 24; restricted by Dane, 1926) 

in Arkansas and northern Louisiana ranges hi thickness 

from 50 to more than 300 feet in the subsurface and is 

probably equivalent to the Eutaw Formation. The 

Tokio is composed mainly of poorly sorted crossbedded 

yellow and white sands, gray sandy clay, and a basal 

bed of novaculite gravel. Gravel lenses are scattered 

throughout the formation, and the gray clay contains 

varying amounts of lignite. The Tokio Formation 

unconformably overlies the Woodbine Formation in 

the outcrop area in southwestern Arkansas. It supplies 

moderate quantities of water to numerous wells in and 

near its outcrop.

Blossom Sand and Bonnam Marl

The Blossom Sand (Gordon, 1909, p. 371, 373) and 

Bonham Marl (Stephenson, 1927, p. 8) in northeastern 

Texas are equivalent to the Tokio Formation in 

Arkansas (Dane, 1929, p. 42^3, 81) and Louisiana 

and to the Eutaw Formation in Alabama, Mississippi, 

and Tennessee. Only the Blossom Sand is hydrologically important. The Blossom has a maximum 

thickness of about 350 feet in the subsurface. It 

consists of interbedded sand and clay and is predonjinantly clayan areas where it is thickest. Its usefulness 

as an aquifer is restricted to the vicinity of the outcrop.

Selma Group

In Alabama and Mississippi the Selma Group 

(Smith, Johnson, and Langdon, 1894, p. 15) includes the 

Upper Cretaceous formations between the top of the 

Eutaw Formation and the base of the Midway Group. 

These formations in western Alabama and eastern 

Mississippi, in ascending order, are the Mooreville 

Chalk, the Demopolis Chalk, the Kipley Formation, 

and the Prairie Bluff Chalk. In the northern part of 

Mississippi the Selma Group, hi ascending order, 

includes the Coffee Sand, the Demopolis Chalk, the 

Kipley Formation, and the Owl Creek Formation.

The formations of the Selma Group are equivalent 

to those in Arkansas, northern Louisiana, and northeastern Texas which are between the top of the Tokio 

Formation or the Blossom Sand and the base of the 

Midway Group.

Mooreville Chalk, The Mooreville Chalk (Stephenson, 1917, p. 246), including the Arcola Limestone 

Member (Stephenson and Monroe, 1938, p. 1655-1657) 

at the top, has a maximum thickness of more than 250 

feet hi central and southern Mississippi and western 

Alabama. It is an impure chalk or chalky marl containing scattered thin beds of very fine sand. Some
B12 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

sandy zones are extremely glauconitic, especially those 

in the upper part of the formation. The Arcola Limestone Member is a moderately hard limestone, commonly penetrated by marine borings.

The Mooreville Chalk is equivalent to the Brownstown Marl of Arkansas, northern Louisiana, and northeastern Texas. In northern Mississippi the Mooreville grades into sand and becomes the lower part of 

the Coffee Sand. The Mooreville Chalk is not an 

aquifer.

Coffee Sand. The Coffee Sand (Safford, 1864, p. 

361) in Tennessee and northern Mississippi is a facies 

equivalent of the Mooreville Chalk and the lower part 

of the Demopolis Chalk. Near its outcrop the Coffee 

Sand may be as much as 200 feet thick. It is made up 

largely of a series of stratified and crossbedded sands 

and clays. The sands are generally fine and varicolored; in many places they contain an abundance of 

mica and in some places glauconite and pyrite. The 

clays are highly carbonaceous and contain an abundance 

of plant remains. The Coffee Sand is an important 

aquifer.

Demopolis Chalk. The Demopolis Chalk (Smith, 

1888), including the Bluffport Marl Member (Monroe, 

1956, p. 2740-2742) at the top, is about 500 feet thick 

in central Mississippi and western Alabama. The 

Bluffport Marl Member has a maximum thickness of 

about 50 feet.

The Demopolis Chalk in Mississippi and Alabama is 

a relatively pure chalk; the Bluffport Marl Member at 

the top is an impure chalk which grades into the 

overlying Kipley Formation. Northward, the upper 

250 feet of the chalk becomes clayey, and the remainder 

becomes a part of the Coffee Sand. In Tennessee this 

clayey unit is called the Demopolis Formation. The 

Demopolis does not contain any aquifers.

Ripley Formation. The Ripley Formation (Hilgard, 

I860, p. 62) in Alabama, Mississippi, and Tennessee 

has a maximum thickness of about 400 feet. In 

northern Mississippi the formation includes, in ascending order, the transitional clay, Coon Creek Tongue, 

McNairy Sand Member, and Chiwapa Member. In 

Tennessee it includes, in ascending order, the Coon 

Creek Tongue and the McNairy Sand Member. Only 

the McNairy Sand occurs in Kentucky, Illinois, and 

Missouri, and it has formational status in these States. 

The undifferentiated Kipley Formation typically consists of clay, sandy clay, sand, and thin beds of 

sandstone.

A zone of clay above the Demopolis Chalk was described as the transitional clay by Conant (1941, p. 

22), who assigned the unit to the Ripley Formation. 

The transitional clay is in the same stratigraphic position and may be the lateral facies of the Bluffport Marl

Member of the Demopolis Chalk. The units are 

lithologically similar. Sohl (1960, p. 11) states that 

the transitional clay " * * * consists primarily of clays 

which become increasingly arenaceous and argillaceous 

upward as they grade into sand of the Ripley and increasingly calcareous downward as they grade into the 

Demopolis Chalk." The transitional clay in outcrop 

averages less than 50 feet thick.

The Coon Creek Tongue (Wade, 1917, p. 74) is about 

180 feet thick near the outcrop area in northern Mississippi (Parks, 1960, p. 67). The lower part of the 

unit grades into the underlying transitional clay of the 

Ripley Formation; the main body of the typical Coon 

Creek Tongue is a dark-gray glauconitic micaceous 

fossiliferous fine sand interbedded with clay.

The McNairy Sand Member (Stephenson, 1914, p. 

22) is about 200 feet thick near the Mississippi-Tennessee State line. Southward, it underlies the Chiwapa 

Member and gradually grades into the upper marine 

sand and clay of the Ripley Formation in northern 

Mississippi. The McNairy Sand Member is a medium 

to coarse sand, which is white to brown in subsurface 

samples; in the outcrop it is varicolored and crossbedded, and characteristically includes indurated layers 

of tubular ferruginous sandstone.

The Chiwapa Member (Mellen, 1958, p. 49) occurs 

in northern Mississippi. The member "* *^ * is 

characteristically a 'bored' or 'horsebone' limestone or 

calcareous sandstone, an irregularly indurated stratum 

of shallow marine sediment approximately 80 feet in 

thickness at the top of the Ripley, and it can be traced 

for a north-south distance of 85 miles, more or less." 

The Chiwapa Member crops out from Tippah County, 

Miss., southward to Clay County.

Sands of the Ripley Formation, particularly the 

McNairy Sand Member and the Chiwapa Member, are 

excellent aquifers.

Prairie Bluff Chalk and Owl Creek Formation. The 

Prairie Bluff Chalk (Winchell, 1857, p. 84) is the uppermost unit of the Upper Cretaceous Series in western 

Alabama and Mississippi. In extreme northern Mississippi it is represented by the Owl Creek Formation 

(Hilgard, 1860, p. 85), a facies which extends into 

Tennessee and Missouri and possibly into Kentucky 

and Illinois. The Prairie Bluff Chalk is from 30 to 

70 feet thick and the Owl Creek Formation is about 45 

feet thick in the subsurface. The Prairie Bluff Chalk 

is a gray to white slightly sandy massive chalk which 

grades northward into the highly fossiliferous dark-gray 

fine micaceous silty sand and clay of the Owl Creek 

Formation. The formations rest unconformably on 

the Ripley Formation (the McNairy Sand in Missouri), 

and underlie unconformably the Midway Group. 

Neither formation is an aquifer.
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B13

Demopolis Formation

The unit which has been called the "Selma Clay" 

in Tennessee (Glenn, 1906, p. 26) is here called the 

Demopolis Formation. Recent mapping of the Cretaceous sediments by E. E. Russell for the Tennessee 

Division of Geology has shown that this unit, which 

overlies the Coffee Sand and underlies the Ripley 

Formation in Tennessee, is the upper part of the 

Demopolis Chalk of the Selma Group in Mississippi. 

Russell* (written communication) states that "the 

unit is composed of massive calcareous clays, marls, 

and some chalky materials." He calls the unit the 

Demopolis Formation, and the name is appropriate.

Brownstown Marl

The Brownstown Marl (originally defined by Hill, 

1888, p. 86-87; restricted by Dane, 1926) lies unconformably on the Tokio Formation in Arkansas and 

northern Louisiana and on the Blossom Sand in northeastern Texas. It is equivalent to the Mooreville 

Chalk of Alabama and Mississippi. The Brownstown 

Marl has a maximum thickness of about 280 feet in 

the subsurface in southwestern Arkansas and consists 

of dark-gray to tan fossiliferous calcareous clay, gray 

marl, sand, and sandy clay. It yields small amounts 

of highly mineralized water to a few wells in its outcrop.

Ozan Formation

The Ozan Formation (Dane, 1926) has a maximum 

thickness of about 200 feet in southwestern Arkansas. 

It varies from fossiliferous gray sandy marl, sand, 

sandy limestone, and clay to chalk and marl. A layer 

of glauconitic sand occurs at the base. The Ozan 

Formation unconformably overlies the Brownstown 

Marl. It yields small amounts of highly mineralized 

water to a few wells in southwestern Arkansas.

Annona CliaXk

The Annona Chalk (originally defined by Hill, 1894, 

p. 308; restricted by Dane, 1926) overlies the Ozan 

Formation in southwestern Arkansas and the Brownstown Marl in northern Louisiana and in parts of northeastern Texas. The Annona is as much as 100 feet 

thick in Arkansas and as much as 400 feet thick in 

Louisiana and Texas, where the lower part is probably 

equivalent to tne Ozan Formation. The Annona is a 

massive hard bluish-gray to white fossiliferous chalk, 

and in Texas some chalky marl beds occur in the lower 

part. The Annona is equivalent to part of the Demopolis Chalk of Alabama and Mississippi. It does not 

yield water to wells.

Marlbrook or Taylor Marl

The Marlbrook Marl (orignially denned by Hill, 

1888, p. 84-86; restricted by Stephenson, 1927, p. 15) 

occurs in Louisiana and Arkansas. In Texas its

i Russell, E. E., Professor, Dept. of Geology, Mississippi State University, 

Starkville, Miss.

equivalent is the upper part of the Taylor Marl. The 

Marlbrook has a maximum thickness of about 300 

feet in the subsurface. It is a fossiliferous chalky blue 

to gray marl containing some glauconitic sand and, 

locally, thin beds of chalk. It does not yield water to 

wells.

Navarro Group

The Navarro Group (Shumard, 1861, p. 189) in 

northeastern Texas has not been subdivided. It 

includes the units between the top of the Taylor Marl 

and the base of the Midway Group. The Navarro 

Group is equivalent to the Ripley Formation and the 

Prairie Bluff Chalk or the Owl Creek Formation of 

Alabama, Mississippi, and Tennessee.

In Texas, west of the area of study, the Navarro 

Group has been divided, in ascending order, into the 

Neylandville Marl, Nacatoch Sand, Corsicana Marl, 

and Kemp Clay. In Arkansas and Louisiana the units 

between the top of the Marlbrook Marl and the base 

of the Midway Group have not been assigned to a group. 

These units include, in ascending order, the Saratoga 

Chalk (Saratoga Clay in Louisiana), Nacatoch Sand, 

and Arkadelphia Marl.

Saratoga Chalk

The Saratoga Chalk (originally defined by Branner 

1898, p. 53; restricted by Dane, 1926), called the Saratoga Clay in Louisiana, is 20 to 60 feet thick in Arkansas 

and is probably equivalent to the Coon Creek Tongue 

of the Ripley Formation. It is a white fossiliferous 

sandy chalk and has a thin glauconitic and phosphatic 

zone at its contact with the Marlbrook Marl, which it 

overlies unconformably. It does not yield water to 

wells.

Nacatocli Sand

The Nacatoch Sand (originally defined by Veatch, 

1905, p. 180, 183; restricted by Dane, 1929, p. 117- 

119) in Arkansas and Louisiana is virtually equivalent 

to the Ripley Formation. It ranges in thickness from 

about 100 to 500 feet in the subsurface. It is generally 

a massive crossbedded yellowish to gray fine sand, 

which is in part glauconitic and which is interbedded 

with hard sandy limestone and light-gray clay and marl; 

clay and marl are more abundant in the lower part of 

the formation. The Nacatoch Sand supplies moderate 

quantities of water to wells in its outcrop area and for 

several miles downdip.

ArkadelpMa Marl

The Arkadelphia Marl (originally denned by Hill, 

1888, p. 53-56; restricted by Dane, 1929, p. 144-145), 

the equivalent of the Prairie Bluff Chalk and the Owl 

Creek Formation, is the uppermost unit of the Upper 

Cretaceous Series in Arkansas and Louisiana. It has 

a maximum thickness of about 200 feet in the subsurface. The Arkadelphia Marl consists generally of
B14 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

dark-blue fossiliferous marl interbedded with sandy 

limestone and may be glauconitic and chalky in part. 

It has an uncomformable but lithologically gradational contact with the underlying Nacatoch Sand. 

The Arkadelphia Marl does not yield water to wells.

TERTIARY SYSTEM

The Tertiary System in the Mississippi embayment 

comprises deposits of the Paleocene, Eocene, Oligocene, 

Miocene, and Pliocene (?) Series. Tertiary rocks occur 

either in the subsurface or crop out in about 75 percent 

of the region. Their maximum thickness is about 

7,000 feet at the axis of the embayment at the southern 

limit of the region. The sediments are mostly unconsolidated and consist mainly of sand, clay, and shale.

The Tertiary System overlies the Cretaceous System with marked unconformity, and it is overlain in 

most places by alluvial deposits, terrace deposits, or 

loess, all of Quaternary age.

Several major Tertiary artesian aquifers supply 

ground water to large areas of the Mississippi 

embayment.

PALEOCENE SERIES

The Paleocene Series underlies the Eocene Series 

and overlies the Upper Cretaceous Series. It is composed of nearly 1,000 feet of sediments, in which dark 

clay is predominant. The Midway Group constitutes 

the entire series except in northern Louisiana, where 

the lower part of the Wilcox Group is included.

Midway Group

In northern Mississippi, Tennessee, Kentucky, Illinois, Missouri, and northern Louisiana, the Midway 

Group (Smith, 1886, p. 14) comprises, in ascending order, 

the Clayton Formation and Porters Creek Clay. In Arkansas, except in the bauxite area, the Midway Group is 

undifferentiated. In the Arkansas bauxite area and in 

northeastern Texas the Kincaid and Wills Point Formations compose the group. In central Mississippi 

and western Alabama the Naheola Formation is included in the Midway, but beds presumed to be equivalent to the Naheola have been assigned to the overlying 

Eocene Series in other areas. The Naborton and Dolet 

Hills Formations of Paleocene age in Louisiana, probably partly equivalent to the Naheola Formation, are 

grouped with the Wilcox on the basis of lithology.

The maximum subsurface thickness of the Midway 

Group is about 1,000 feet at the axis of the embayment 

at the southern limit of the region. The thickness near 

the outcrop area ranges from a known minimum of 

180 feet in Kentucky to about 600 feet in parts of Texas, 

Louisiana, Arkansas, Mississippi, and Alabama.

The Midway Group is composed predominantly of 

marine clay and shale but includes subordinate sand 

and limestone beds. The basal limestone of the Clayton

Formation unconformably overlies the Cretaceous System. The contact with the overlying Wilcox Group is 

indeterminate in most places, but in Alabama and 

adjacent parts of Mississippi the contact between the 

basal beds of the Wilcox Group and the top of the 

Naheola Formation has been mapped. In other areas 

the contact may be defined by weathered zones, deposits 

of kaolinitic material, bauxite, residuum, or other 

lithologic evidence of unconformity.

Figure 6 is a contour map showing configuration of 

the sandy zone immediately above the Porters Creek 

Clay. The base of this zone, as shown on electric logs, 

is used as the top of the Midway Group.

Clayton Formation. The Clayton Formation (Langdon, 1891, p. 595) is commonly about 35 feet thick, 

but in many places in the outcrop area it is much 

thinner or missing because of overlap by the Porters 

Creek Clay.

The Clayton Formation is composed mostly of limestone, calcareous sand, and sandstone, all of marine 

origin. In some places it is lithologically very similar 

to underlying Cretaceous sediments but may be differentiated paleontologically. In other places a basal conglomerate marks the contact. Conant (1941, p. 27-32) 

recognizes two units in the Clayton Formation in 

northern Mississippi, a basal limestone and marl member and an upper member. Weathered exposures in 

northern Mississippi are composed mostly of dark-red 

sand, generally ferruginous and glauconitic. The contact with the overlying Porters Creek Clay is generally 

gradational. The Clayton Formation contains no 

important aquifers.

Kincaid Formation. The Kincaid Formation (Gardner, 1933b, p. 744) is the basal unit of Paleocene age in 

northeastern Texas and in the Arkansas bauxite area. 

The Kincaid rests unconformably on Upper Cretaceous 

and older rocks. In the Arkansas bauxite area, where 

the formation is apparently very irregular in thickness, 

it directly overlies the Paleozoic in some places (Gordon, 

Tracey, and Ellis, 1958, p. 13-25). The average 

thickness of the formation in the embayment is about 

30 feet. The formation consists predominantly of 

glauconitic sand, clay, and limestone, all of marine 

origin. In places there is a basal conglomerate composed of reworked material from underlying beds. The 

Kincaid Formation is correlative with the Clayton 

Formation.

Sandy beds in the Kincaid Formation yield small 

quantities of water to wells.

Porters Creek Clay. The Porters Creek Clay (Safford, 

1864, p. 361, 368), called the Porters Creek Formation 

in Alabama, is less than 180 feet thick in the subsurface 

in western Kentucky but thickens to almost 1,000 

feet near the axis of the embayment at the southern
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B15

Approximate limit of Midway Group 

o so 100 MILES

Contour interval 200 feet 

Datum is mean sea level

Compiled from data submitted by 

J. G. Newton for Alabama; R. L 

Hosman for Arkansas; T. W. 

Lambert for Kentucky; C. E. 

Harris, Jr., and W. H. Walker for 

Louisiana; E. H. Boswell for Missis- | 

sippi; G. K. Moore for Tennessee 

and E. T. Baker, Jr., for Texas

|| ALABAMA f

34'

33

32°

FIQUKE 6. Contour map showing configuration of the base of sandy zone above the Porters Creek Clay.

limit of the region. The formation thins markedly 

to less than 100 feet over some structural highs in the 

subsurface but elsewhere changes in thickness are 

gradual.

In most of the embayment the Porters Creek is very 

dark gray or black blocky clay. Subordinate beds of 

sand occur in several places, and the Tippah Sand 

Lentil (Lowe, 1915, p. 64) is a recognized member in 

extreme northern Mississippi. Ferruginous concretions and layers are common. In the northern part of 

the region the upper part of the formation is composed 

of interbedded or laminated fine sand and gray clay. 

The Porters Creek does not include any important 

aquifers.

In Alabama and southeastern Mississippi, the 

Matthews Landing Marl Member (Smith, 1886, p. 13), 

a very glauconitic sandy fossiliferous marl or sandstone 

that is generally less than 10 feet thick, is the uppermost unit of the Porters Creek. It is a well-defined 

stratigraphic marker in western Alabama and eastern 

Mississippi, where its fauna and marine lithology are

distinctive. Northward, it becomes a thin marl and 

loses its identity in Winston County, Miss.

Wills Point Formation. The Wills Point Formation 

(originally defined by Penrose, 1890, p. 19; redefined 

by Plummer, 1927) is the uppermost formation of 

Paleocene age in northeastern Texas and in the Arkansas 

bauxite area. It is underlain by the Kincaid Formation 

and overlain by the Wilcox Formation or Group. 

The Wills Point is predominantly gray to green calcareous clay of marine origin. The upper part of the 

formation is sandy in places and appears to grade into 

sands of the overlying Wilcox. The average thickness 

of the formation is about 500 feet. The Wills Point 

Formation is not known to yield fresh water to wells 

in the embayment.

Naheola Formation. In western Alabama nnd eastern 

Mississippi, the Naheola Formation (Smith, 1886, p. 

13) is a part of the Midway Group. The formation 

thins from about 200 feet in Alabama to less than 100 feet 

in Mississippi. In western Alabama the Naheola Formation is divided into the Oak Hill Member below and
B16 WATER RESOURCES OF THE MISSISSIPPI EMBATMENT

the Coal Bluff Marl Member above. In the remainder 

of the embayment, where the Matthews Landing Marl 

Member of the Porters Creek Clay has not been identified, beds equivalent to the Naheola Formation are 

sometimes included in the Porters Creek or, for lithologic reasons, in the overlying Wilcox.

The Oak Hill Member (Toulmin, LaMoreaux, and 

Lanphere, 1951, p. 42) consists characteristically of 

thinly laminated fine sand and silty clay. In places, 

a bed of lignite, defining the contact with the overlying 

Coal Bluff Marl Member (Smith, 1886, p. 12), forms 

the top of the member. The Coal Bluff Marl Member 

is predominantly marine sand and clay, which includes 

a fossiliferous bed (LaMoreaux and Toulmin, 1959, p. 

83).

Sandy beds in the Naheola Formation are water 

bearing in western Alabama and the adjacent parts of 

Mississippi but are not important hydrologically in the 

remainder of the embayment.

EOCENE SERIES

The Eocene Series crops out or underlies about 70 

percent of the embayment. It is thickest in the southeastern part of the region, where marine phases provide 

a basis for unit differentiation. The Eocene rocks are 

divided, in ascending order, into the "Wilcox Group or 

Formation, Claiborne Group, and Jackson Group or 

Formation.

Wilcox Group

The "Wilcox Group (Crider and Johnson, 1906, p. 5, 

9) includes, in ascending order, the Nanafalia Formation, Tuscahoma Sand, and Hatchetigbee Formation 

in western Alabama and the Berger and Saline Formations and Detonti Sand in the Arkansas bauxite area. 

In northern Louisiana the Naborton and Dolet Hills 

Formations of Paleocene age are considered a part of 

the Wilcox Group. The Wilcox Group is undifferentiated in Arkansas (except in the bauxite area), Illinois, 

Kentucky, and Tennessee. In Mississippi, Missouri, 

and northeastern Texas, the Wilcox is considered to be 

a formation.

Although undifferentiated, the Wilcox in the subsurface of northern Mississippi, northeastern Arkansas, 

Tennessee, Kentucky, and Missouri contains at least 

two distinct lithologic units a lower predominantly 

sand unit and an upper predominantly shale or clay 

unit. The sandy unit is called the "1,400-foot" sand 

(Klaer, 1940, p. 92) of the Memphis area (pi. 2), which 

has been traced for considerable distances in the northern part of the embayment (Schneider and Gushing, 

1948, p. 3). This sand is an important source of 

ground water in the region.

Nanajalia Formation. The Nanafalia Formation 

(Smith, 1886, p. 12), has a maximum thickness of

about 230 feet. It is the basal formation of the Wilcox 

Group in western Alabama, where it consists of sand, 

marl, and clay. Kaolinitic and bauxitic material is 

disseminated through the formation in some places. 

Locally, deposits of bauxite and kaolin occur in the 

lower part of the Nanafalia Formation or in the equivalent part of the Wilcox. In western Alabama the 

Nanafalia Formation comprises three members (LaMoreaux and Toulmin, 1959, p. 98), which, in ascending 

order, are the Gravel Creek Sand Member, the middle 

member, and the Grampian Hills Member.

According to LaMoreaux and Toulmin (1959, p. 98), 

the Gravel Creek Sand Member "consists of white to 

yellow medium- to coarse-grained crossbedded sand 

with stringers and thin lenses of fine gravel and clay 

pebbles." It is correlative with the Fearn Springs 

Member (Mellen 1939, p. 33) of the Wilcox Formation 

of Mississippi. The Fearn Springs Member includes a 

basal coarse sand and an upper laminated fine sand and 

gray clay (Hughes, 1958, p. 148). The middle member 

of the Nanafalia Formation includes the Ostrea thirsae 

beds. These beds also occur in the basal part of the 

Eocene Series in Louisiana (Durham and Smith, 1958, 

p. 5-6). The Grampian Hills Member of the Nanafalia 

Formation consists of gray clay and beds of glauconitic 

sand and sandstone (LaMoreaux and Toulmin, 1959, p. 

100).

The Nanafalia Formation and its equivalents in the 

lower part of the Wilcox form one of the most important 

aquifers in the Mississippi embayment. The "1,400- 

foot" sand of the Memphis area may be equivalent, in 

part, to the Nanafalia Formation.

Tuscahoma Sand. The Tuscahoma Sand (Smith, 

Johnson, and Langdon, 1894, p. 162-170) is composed 

of lenticular fine sand, gray clay, and laminated fine 

sand and clay, all containing some lignite. In western 

Alabama the formation includes the Greggs Landing 

Marl Member (Smith, 1886, p. 12) and the Bells Landing 

Marl Member (Smith, 1883, p. 256). These marine 

beds become indistinguishable from the rest of the 

Wilcox Formation northwestward in Mississippi.

The average thickness of the Tuscahoma Sand is 

about 350 feet. Because of its fine grain size and 

lenticularity, the Tusrahoma Sand is not used as extensively as a source of water as the Nanafalia Formation.

flatchetigbee formation. The Hatchetigbee Formation (Smith, 1886, p. 10) is the youngest formation of 

the Wilcox Group in western Alabama. The formation 

is predominantly gray lignitic clay and fine sand but 

contains scattered beds of lignite. The Bashi Mail 

Member (Heilprin, 1882, p. 158-159), a distinctive 

fossiliferous marine bed at the base of the formation, 

overlies the Tuscahoma Sand. The Bashi Marl Member
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT BIT

has been tentatively identified as far north as southern 

Winston County, Miss. (McNeil, 1946, p. 21-22). 

Lenticular beds of sand are locally important as aquifers.

Berger and Saline Formations and Detonti Sand. 

In the Arkansas bauxite area, the Wilcox Group comprises the Berger and Saline Formations and the Detonti 

Sand, which have been described in detail by Gordon, 

Tracey, and Ellis (1958, p. 38-58). Elsewhere in 

Arkansas, the group has not been divided. The equivalence of these formations to those described in 

Alabama or Louisiana has not been shown. The Berger 

Formation is about 25 feet thick in outcrop and is 

composed of lignitic sand and clay characteristic of the 

Wilcox; bauxitic and kaolinitic material occurs in beds 

throughout the formation.

Naborton Formation. Murray (1948, p. 94-95) describes the Naborton Formation as "calcareous, buff to 

gray, fine- to medium-grained sands, clays, and lignitic 

silts." The formation reaches a maximum thickness of 

about 200 feet. The thin-bedded or laminated structure of the beds and the stratigraphic position of the 

unit suggest that the Naborton may be partly equivalent to the Oak Hill Member of the Naheola Formation.

The Naborton Formation crops out in a small area 

in northwestern Louisiana and is extensive in the subsurface. It is not known to contain an aquifer in the 

embayment, but it is an important source of ground 

water in DeSoto and Red River Parishes, La.

Dolet Hills Formation. The Dolet Hills Formation 

(Murray, 1948, p. 105) consists of fine to medium massive sand and subordinate clay and lignite. It is 

extensive in the subsurface, has a maximum thickness 

of 125 feet, and crops out in the same general area as 

the Naborton Formation. It is probably partly 

equivalent to the Naheola Formation.

Above the Dolet Hills Formation are undifferentiated 

beds of sand and clay (Murray, 1948, p. 138) which are 

also considered to be of Paleocene age. These beds, 

together with the Naborton and Dolet Hills Formations, 

are included in the Wilcox Group in Louisiana on the 

basis of lithology.

Claibome Group

Rocks of the Claibome Group (Conrad, 1848, 

p. 280-283) are known to crop out in all States included 

in this investigation except Illinois and Missouri. In 

the northern part of the embayment, some beds previously designated as members of the Wilcox may be 

members of the Claibome Group because of the broad 

overlap by the Claibome Group in the region.

The maximum thickness of the Clairborne Group, 

about 2,600 feet, occurs in the subsurface in the 

southern part of the embayment. The group is composed of marine and nonmarine sand, sandy clay, clay, 

shale, and limestone. In the southern part of the

region, the Claibome Group can be subdivided into 

formations, on the basis of marine beds. In the 

northern part of the region the Claiborne Group is 

undifferentiated.

The group, in ascending order, is composed of the 

following units: The Tallahatta Formation, Winona 

Sand, and Zilpha Clay, and their equivalents the 

Carrizo Sand and Mount Selman Formation in Texas 

and the Carrizo Sand and Cane River Formation in 

Arkansas and Louisiana; the Sparta Sand; the Cook 

Mountain Formation; and the Cockfield Formation. 

In Kentucky and Tennessee the Claibome Group is 

undifferentiated.

Tallahatta Formation. The Tallahatta Formation 

(Dall, 1898, p. 344) in Alabama and Mississippi is 

equivalent to the Carrizo Sand and to the Reklaw 

Member and Queen City Sand Member of the Mount 

Selman Formation of Texas and to the Carrizo Sand 

and the lower part of the Cane River Formation of 

Arkansas and Louisiana.

The Tallahatta Formation in Alabama includes the 

Meridian Sand Member. In central Mississippi it 

includes the Meridian Sand Member, Basic City Shale 

Member, and Neshoba Sand Member. In northern 

Mississippi it includes the Holly Springs Sand Member.

The Tallahatta Formation in western Alabama and 

eastern Mississippi averages about 90 feet in thickness. 

In north-central Mississippi it thickens to about 200 

feet in outcrop, and it may reach a thickness of 400 

feet in the subsurface.

The Meridian Sand Member (Lowe, 1933, p. 1, 

105-106) of the Tallahatta Formation crops out in 

western Alabama and in Mississippi. It is the basal 

member of the Claiborne Group and is equivalent 

to the Carrizo Sand of Arkansas, Louisiana, and 

Texas. The thickness of the Meridian Sand Member 

is variable, averaging probably more than 100 feet. 

Brown (1947, pi. 9) shows the maximum thickness 

to be 490 feet in the subsurface in Holmes County, 

Miss.

The Meridian Sand Member is fine to very coarse 

quartz sand, which is characteristically crossbedded. 

The contact with the underlying Wilcox Group is 

determined by the presence of lignitic clay or shale 

or highly carbonaceous material characteristic of the 

Wilcox.

The Meridian Sand Member is a productive aquifer 

in the embayment. The basal part of the "500-foot" 

sand (Klaer, 1940, p. 92) of the Memphis area (pi. 2) 

probably is equivalent to the Meridian Sand Member.

The Basic City Shale Member (Brown and Adams, 

1943, p. 43) is composed of sparsely fossiliferous lightcolored claystone, siltstone, and shale. Ledges of 

orthoquartzite (buhrstone) are common. The Basic
B18 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

City Shale Member is not an important aquifer 

except in northwestern Mississippi, where sandy facies 

of the unit occur.

The Neshoba Sand Member (Thomas, 1942, p. 24) 

of the Tallahatta Formation occurs in central Mississippi and is about 50 feet thick. It gradually thickens 

northward and is in the subsurface in central and 

northwestern Mississippi. The Neshoba Sand Member is typically fine micaceous quartz sand containing 

some gray clay. It is locally glauconitic but is not 

known to be fossiliferous. The Neshoba Sand Member 

is considered by Stenzel (1952, p. 32) to be equivalent 

to the lower part of the Queen City Sand Member 

of the Mount Selman Formation. The Neshoba Sand 

Member is an aquifer in some areas in Mississippi.

The Holly Springs Sand Member (Lowe, 1913, 

p. 23-25) of the Tallahatta Formation in northern 

Mississippi was originally considered to be a formation 

of the Wilcox Group in Mississippi, Tennessee, and 

Kentucky. Foster (1940, p. 32, 53) restricts the name 

Holly Springs to beds in Lauderdale County, Miss., 

that are equivalent to the Tuscahoma Sand in adjoining Alabama. MacNeil (1946, p. 17) states that "the 

type Holly Springs formation of northern Mississippi, 

* * * is the nonmarine equivalent of the Tallahatta 

formation to the south. The name Holly Springs 

was accordingly abandoned in favor of Tallahatta for 

all of Mississippi." MacNeil (1947), however, uses 

the name Holly Springs Sand Member for the entire 

Tallahatta Formation of northern Mississippi. Brown 

(1947, p. 34) states that "the outcrops of sand around 

Holly Springs are exposures of the Meridian sand 

member of the Tallahatta formation * * * ."

The use of the name Holly Springs Sand Member 

probably should be discontinued because of the previous long association of the name with the Wilcox 

Group, but additional work is needed to determine the 

stratigraphic relation of this unit to other Eocene 

units in northern Mississippi.

Carrizo Sand. The Carrizo Sand (Owen, 1889, p. 70) 

in Texas, Louisiana, and Arkansas is equivalent to 

the Meridian Sand Member of the Tallahatta Formation of western Alabama and Mississippi. Like the 

Meridian Sand Member, the Carrizo varies in thickness 

because of its deposition on the irregular surface of the 

Wilcox sediments. The sand probably does not exceed 200 feet in thickness, and in many places it is 

reported to be absent.

The Carrizo Sand consists of fine to coarse lightgray to brownish-gray micaceous sand. It is an 

aquifer in the western part of the embayment.

'Mount Selman Formation. The Mount Selman 

Format ion (Kennedy, 1892, p. 45, 52-54), comprises 

in ascending order, the Reklaw (Wendlandt and Knebel,

1929, p. 1352), Queen City Sand (Kennedy, 1892, p. 50), 

and Weches Greensand (Wendlandt and Knebel, 1929, 

p. 1356) Members, or all strata above the top of the 

Carrizo Sand and below the base of the Sparta Sand. 

The Mount Selman Formation is equivalent to the 

Cane River Formation of Louisiana and Arkansas and 

to the Tallahatta Formation (except the Meridian 

Sand Member), Winona Sand, and Zilpha Clay of 

Mississippi. The Mount Selman Formation averages 

about 300 feet in thickness.

Overlying the Carrizo Sand and separated from it 

by a disconformity is the Reklaw Member of the Mount 

Selman Formation, a sequence of dark-colored stratified shales and sands that are commonly fossiliferous, 

micaceous, and glauconitic. Thin lenses of limonite 

normally are associated with the glauconite. The 

member is sandy in places, which makes it difficult to 

separate the Reklaw from the overlying and underlying units. The thickness of the Reklaw Member 

probably does not exceed 125 feet.

The Queen City Sand Member of tne Mount Selman 

Formation, overlying the Reklaw Member, consists 

predominantly of gray to grayish-brown fine to medium 

sand interbedded with layers of dark carbonaceous 

shale, silt, and impure lignite. The sands are crossbedded and lenticular. Beds or lenses of glauconite 

reportedly occur near the middle of the member. The 

thickness of the Queen City Sand Member in northeastern Texas is not known, but it probably is about 

200 feet.

The lower part of the Queen City Sand Member is 

considered by Stenzel (1952, p. 32) to be equivalent to 

the Neshoba Sand Member of the Tallahatta Formation. Various aspects of the geology of the Queen 

City Sand Member have been discussed by Smith 

(1958). The Queen City Sand Member is an important aquifer in northeastern Texas.

The Weches Greensand Member of the Mount 

Selman Formation overlies the Queen City Sand Member and consists predominantly of dark-green beds of 

glauconitic highly crossbedded, lenticular sand and of 

some thin strata of dark-gray to black glauconitic 

clay and shale. Limonite and siderite are concentrated sufficiently in places to make the unit of economic 

importance. The Weches Greensand Member is relatively thin; the unit probably is not more than 60 feet 

thick. It is equivalent to the Winona Sand and probably to Zilpha Clay of Mississippi.

Cane Hirer Formation. The Cane River Formation 

(Spooner, 1926, p. 235-236) in Arkansas and Louisiana 

includes from 150 to more than 500 feet of clay, sandy 

clay, marl, and thin beds of fine sand. Marine clay is 

predominant, and the beds are, in part, glauconitic and 

calcareous. The Cane River Formation includes all
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT

94" 93° 92° 91° 90° 89°

B19

Approximate limit of Cane River Formation 

or its equivalents

Contour interval 200 feet 

Datum is mean sea level

Compiled from data submitted by 

R. L. Hosman for Arkansas; C. E. 

Harris, Jr., and W. H. Walker for 

Louisiana; E. H. Boswell for Mississippi and E. T. Baker, Jr., for Texas

32°

FIGURE 7. Contour map showing configuration of the base of the Cane River Formation or its equivalents.

beds above the top of the Carrizo Sand and below the 

base of the Sparta Sand. It is correlative with the 

Mount Selman Formation and with the Tallahatta 

Formation (except the Meridian Sand Member), 

Winona Sand, and Zilpha Clay.

Figure 7 is a contour map showing configuration of 

the base of the Cane River Formation, the base of the 

Mount Selman Formation, and the base of the Basic 

City Shale Member of the Tallahatta Formation. The 

map is compiled for the southern part of the embayment, where these formations have been recognized.

The sands of the Cane River Formation are fine and 

relatively impermeable. In some areas these sands are 

important as aquifers.

Winona Sand. In typical outcrops the Winona Sand 

(Lowe, 1919, p. 73) is a highly glauconitic fossiliferous 

sand and clay. It has been mapped only in Mississippi. 

In Tennessee and northward, the nonmarine sands 

equivalent to the Winona Sand are included hi the 

undifferentiated Claiborne Group.

The Winona Sand ranges in thickness from less than 

10 feet near the Alabama State line to a maximum of 

about 50 feet in north-central Mississippi, where it is 

locally an aquifer.

Zilpha Clay The Zilpha Clay (Thomas, 1942, p. 34) 

crops out in Mississippi but has not been recognized 

in other parts of the region. The top of the Zilpha 

Clay is equivalent to the top of the Cane River Formation of Arkansas and Louisiana and to the top of the 

Mount Selman Formation of Texas.

The thickness of the outcropping Zilpha Clay ranges 

from a few feet to 75 feet (Thomas, 1942, p. 38). It is 

much thicker in the subsurface to the southwest. The 

Zilpha is a dark-gray clay that is carbonaceous, generally glauconitic, sparingly fossiliferous, and predominantly of marine origin. It is not an aquifer.

Sparta Sand. The Sparta Sand (originally defined by 

Vaughan, 1895, p. 225; restricted by Spooner, 1926, 

p. 235) crops out in Texas, Louisiana, Arkansas, and 

Mississippi. The Sparta has an average thickness in
B20 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

94" 93° 92" 91* 90° 89°

EXPLANATION

Approximate limit of Sparta Sand

0 50 100 MILES

Contour interval 200 feet 

Datum is mean sea level

Compiled from data submitted by 

R. L Hosman for Arkansas; C. E. 

Harris, Jr., and W. H. Walker for 

Louisiana; and E. H. Boswell for 

Mississippi

34

33' -

32

FIGURE 8. Contour map showing configuration of the top of the Sparta Sand.

outcrops of about 300 feet, but it thins to less than 100 

feet in southeastern Mississippi. It thickens considerably in the subsurface and may be as much as 1,000 

feet thick near the axis of the embayment at the southern limit of the region. The upper part of the "500- 

foot" sand of the Memphis area probably is Sparta 

Sand.

Figure 8 is a contour map showing configuration of 

the top of the Sparta Sand. It is compiled for the 

southern part of the region, where the sand has been 

recognized.

The Sparta is predominantly fluviatile sand containing subordinate amounts of sandy clay or shale. In 

Mississippi, the outcropping beds locally include ledges 

of orthoquartzite in the lower part of the unit, whereas 

in the upper part the sand is interbedded with light-gray 

clay. In the subsurface, lignite and other organic material are common. The Sparta Sand in Texas contains 

ferruginous sandstone ledges in some places.

The Sparta Sand is one of the most productive 

aquifers in the region.

Cook Mountain Formation. The Cook Mountain 

Formation (Kennedy, 1892, p. 54-57) crops out in 

Mississippi, Arkansas, and Louisiana. The formation 

is about 100 feet thick in the outcrop area, and it has 

a maximum thickness of about 200 feet in the 

embayment.

In eastern Mississippi, the Cook Mountain Formation was divided by Thomas (1942, p. 49) into the 

Archusa Marl Member at the base, the Potterchitto Sand 

Member, and the Gordon Creek Shale Member. These 

units have not been identified in the subsurface, where 

the formation is generally divisible into only two lithologic units. In Mississippi, Arkansas, and Louisiana 

the lower part of the Cook Mountain is glauconitic, 

calcareous fossiliferous sandy marl or limestone and 

seems to be equivalent to the Archusa Marl Member. 

The upper unit is sandy carbonaceous clay or shale, 

which is locally glauconitic.

The Cook Mountain Formation is not important 

regionally as a source of water.
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B21

Cockfield Formation. The Cockfield Formation 

(Vaughan, 1895, p. 220) crops out in Arkansas, Louisiana, and Mississippi. It has an average thickness 

in outcrop of about 250 feet in Mississippi and thickens 

in the subsurface to a maximum of about 600 feet.

The Cockfield Formation is fine to medium quartz 

sand and carbonaceous clay. The formation is very 

lenticular, but sand is fairly persistent in the lower 

part. Lignite is common in the subsurface.

The Cockfield Formation is the youngest Eocene 

artesian aquifer in the Mississippi embayment.

Jackson Group

The Jackson (Conrad, 1856, p. 257-258) crops out in 

Louisiana, Arkansas, Tennessee, and Mississippi. 

The Jackson Group is undifferentiated in Arkansas and 

northern Mississippi, but in Louisiana and central 

Mississippi it is separated into the Moodys Branch 

Formation and Yazoo Clay. The Jackson is a formation in Tennessee.

The truncated Jackson Group underlies extensive 

deposits of the Mississippi River alluvium in the southern part of the region. The occurrence of a fossil bone 

of Jackson age in the bluffs along the Mississippi River 

about 35 miles north of Memphis indicates that the 

Jackson sea probably extended considerably farther 

northward. Some of the clays and silts in Kentucky 

may represent deposition in the northern extension of 

the sea. The Jackson sea was the last extensive marine 

invasion of the Mississippi embayment.

The Jackson Group does not include an aquifer in 

the region.

Moodys Branch Formation. The Moodys Branch Formation (originally defined by Meyer, 1885, p. 435; 

described by Lowe, 1915, p. 75) is recognized in Mississippi and Louisiana. Normally 20 to 30 feet thick, 

it is a highly fossiliferous glauconitic sandy marl 

which unconformably overlies the uppermost beds of 

the Claiborne Group.

Yazoo Clay. The Yazoo Clay (Lowe, 1915, p. 79) 

is calcareous fossiliferous dark-gray to blue clay. Its 

thickness ranges from 350 to 500 feet where the entire 

unit is present. The Yazoo Clay in Mississippi was 

divided, in ascending order, by Murray (1947, p. 1839) 

into the North Creek, Cocoa Sand, Pachuta Marl, and 

Shubuta Members. The contact of the Shubuta 

Member with the overlying Forest Hill Sand is the 

Eocene-Oligocene boundary.

OLIGOCENE SERIES

The Oligocene Series comprises the Forest Hill Sand 

(Cooke, 1918, p. 187) and the Vicksburg Group (Conrad, 1848, p. 280-281). These units crop out in the 

extreme south-central part of the region and have an

aggregate thickness averaging about 200 feet. They 

thicken in the subsurface.

The Forest Hill Sand is an aquifer of local importance.

MIOCENE SERIES

The Catahoula Sandstone of Miocene age crops out 

in southern Hinds, Rankin, and Warren Counties, 

Miss. It was not studied in this investigation.

QUATERNARY SYSTEM

Deposits of Quaternary age cover much of the Coastal 

Plain surface and are assigned to the Pleistocene and 

Recent Epochs. The Quaternary sediments include 

sand, gravel, and clay occurring mostly as alluvial and 

terrace deposits. Loess covers much of the area east 

of the Mississippi River alluvial plain and caps Crowleys 

Ridge.

The sand and gravel deposits of the Mississippi 

River alluvial plain form the most important Quaternary ground-water reservoir. The thickness of the 

alluvium varies greatly, but generally ranges from 100 

to 200 feet. The lower part generally is composed of 

gravel and very coarse sand, whereas the upper part 

typically includes fine to medium sand and clay. Many 

large-capacity wells obtain water from the Mississippi 

River alluvium.

Alluvial deposits along other streams have been 

extensively developed in localities where they are 

capable of yielding large quantities of water.

STRUCTURE

The present Mississippi embayment is a syncline 

plunging to the south. The axis of the syncline roughly 

follows the present course of the Mississippi River. 

The trough is filled with sedimentary rocks ranging in 

age from Jurassic to Recent and has been extensively 

modified by various structural features (fig. 9). The 

character of the deposits was controlled by a depositional environment resulting, in part, from the structure.

Initial tectonic movements that resulted in the formation of the Mississippi embayment syncline may 

have been a part of the Appalachin revolution at the 

end of the Paleozoic Era. The uplift of the Appalachian Mountains was accompanied by other subcrustal 

movement, and the initial subsidence in the southwestern part of the embayment may have occurred at 

this time.

The major portion of the syncline was not yet in 

existence at the end of the Paleozoic Era. At the 

beginning of the Mesozoic Era the eastern part of the 

Ouachita Mountain system, the Ozark uplift, and the 

southwestern extremity of the Appalachian Mountain 

system occupied part of tne region. Siuce the Triassic 

Period, weathering of these uplifted areas has produced
B22 WATER RE SOURCES OF THE MISSISSIPPI EMBAYMENT

95° 94= 93" 92° 91°

37

36

Post-Paleozoic structural features 

Paleozoic structural features

0 50 100 MILES

LT^'-p^/ i I J^V-4^ I ~

sfiS^fcWj-^ K. 1 i > T ' '/ '

rfe^__j-._-j/ I J_ I _ I \ ^;k^Pf=±f-^e*^ t ^qrfgt^rt? j~^-! U --^ i i AT.ARAMA (^

-*--Y>V L FAULT ^ J ' L 

1 ,1^r | L<?0/V^/ I

-rilff / T'^vl .b^T

F¥T7 I \A^ /-'-

' LA5ABI4 up<ll-l(rT L^^^LOUISIANA >O^J"^

"TtrtW^ >^vt^

- ^ttrzb^EiiJL^

FIGURE 9. Structure map of the Mississippi embayment.

vast quantities of detrital material which was transported and deposited to form part of the complex 

sedimentary-rock assemblage in the present embayment. The sedimentation occurred concurrently with 

subsidence and inundation of the Gulf Coast geosyncline 

and the trough of the Mississippi embayment. The 

subsidence is presumed to have been caused primarily 

by subcrustal movement and sedimentary loading and 

also by compaction of the sediments.

Many of the rock units in the Mississippi embayment 

change from a clastic facies in the northern part of the 

region near the source of the sedimentary material, 

through an intermediate facies characteristic of continental shelves, to deeper marine deposits in the southern 

part of the embayment or in the Gulf Coast geosyncline. Most types of sedimentary rocks are represented 

in the region. The units thicken gradually downdip 

and abruptly through zones of increased subsidence. 

The maximum thickness of post-Paleozoic sediments, 

about 18,000 feet, occurs at the axis of the embayment 

in the extreme southern part of the region.

MESOZOIC ERA

TRIASSIC PERIOD

No direct evidence of a sedimentary basin during the 

Triassic Period has been observed. Any sediments 

of Triassic age were eroded or have not been identified.

JURASSIC PERIOD

During the Jurassic Period the southern part of the 

Mississippi embayment was a sedimentary basin, and 

deposits of Late Jurassic age occur in the subsurface. 

The northern limit of these sediments is near the 

southern flank of the buried eastern extension of the 

Ouachita Mountain system, a fact which indicates that 

the system was still positive enough to have considerable 

control on deposition. The character of the Jurassic 

sediments indicates that a large river in northern 

Mississippi was the source of material in the ArkansasMississippi area (Imlay, 1943, p. 1451, 1524). The 

areal configuration and thickness of the deposits indicate 

that the axis of the embayment was slightly east of the 

present trough. Also, the Sabine uplift area was a basin
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B23

and a center of Late Jurassic deposition (Imlay, 1956-, 

pi. 8).

CRETACEOUS PERIOD

The fact that Lower Cretaceous rocks extend farther 

north (Nunnally and Fowler, 1954) than the underlying 

Jurassic deposits indicates that subsidence continued 

into Early Cretaceous tune and that the boundary effect 

wnich the Ouachita Mountain system had on deposition 

decreased. In the extreme southern part of the embayment, a sufficient thickness of sediment had accumulated 

over the Jurassic sedimentary salt beds to start the 

intermittent upward movement of the salt plugs and 

folds which eventually formed salt domes; however, 

most of the upward movement seems to have occurred 

during the Tertiary Period.

During the Late Cretaceous Epoch, the sea reached its 

maximum northern limit for the Mesozoic Era. Upper 

Cretaceous sediments were deposited throughout the 

embayment, and subsidence and deposition continued 

at an accelerated though intermittent rate. Volcanic 

activity was common, as indicated by widespread 

volcanic material in Upper Cretaceous rocks. The 

Sabine uplif t is of early Late Cretaceous age. Near the 

end of Late Cretaceous tune the Monroe uplift create/1 a 

structural high across the original axis of the embayment, partially isolating the Desha basin.

The Desha basin occupies the part of the original 

embayment trough north of the Monroe uplift. The 

Jackson dome resulted from an igneous intrusion near 

the end of the Late Cretaceous, although some movement continued to occur at least until Oligocene tune. 

Several other smaller structural features of igneous or 

volcanic origin were formed, and the Mississippi embayment assumed its present size and shape by the end of 

the Cretaceous Period.

CENOZOIC ERA 

TERTIARY PERIOD

The Tertiary Period is characterized by a series of 

cyclic inundations and regressions by the sea. The 

maximum northern extent of inundation was probably 

during late Midway tune. There is evidence that uplift 

of the Appalachian Mountains continued intermittently 

at least into the Eocene (Todd and Folk, 1957); this 

uplift was accompanied by subsidence in the embayment 

due to subcrustal movement, loading, and compaction. 

Widespread faulting is reflected, in part, by flexure 

zones along the edges of continental shelves. Axes of 

deposition for most of the Tertiary units are similar, 

and so are the configurations of the surfaces of the units 

as shown on the contour maps (figs. 6, 7, and 8). The 

last widespread inundation by the sea occurred during 

Jackson tune at the end of the Eocene Epoch. The 

sea left evidence of its presence as far north as Tennessee

and may have extended considerably farther north. 

Since the end of Jackson time, most of the Mississippi 

embayment has remained above sea level.

QUATERNARY PERIOD

General subsidence and adjustment continued during 

the Quaternary Period. The initial uplift of the 

Kilmichael dome may have occurred as early as late 

Eocene, but the structure may be of Quaternary age. 

The alluvial fill of the Mississippi River valley was deposited and extensive terrace systems were formed 

during the Quaternary. Some diastrophism has occurred during historic time; the formation of Reelfoot 

Lake, for example, was the result of faulting associated 

with the New Madrid earthquakes of 1811-12.

PHYSIOGRAPHY

The Mississippi embayment is a part of the Atlantic 

Coastal Plain (Fenneman, 1938, p. 1) and lies within 

the Gulf Coastal Plain. The syncline forming the embayment is filled with sedimentary rocks, which crop 

out in a modified belted pattern (pi. 1). Differential 

erosion of these rocks has resulted in several physiographic districts typical of the Coastal Plain province. 

The embayment is separable into two general physiographic areas, the lowland of the Mississippi Alluvial 

Plain and the Coastal Plain uplands. Figure 10 shows 

the more important physiographic districts of the region.

The physiographic districts on the eastern side of the 

embayment are the Fall Line Hills, Black Belt, Pontotoc 

Ridge and Ripley Cuesta, Flatwoods, North Central 

Plateau, Buhrstone Cuesta, Jackson Prairie, Southern 

Pine Hills, and Loess Hills.

The Fall Line Hills occupy the 'periphery of the embayment from Alabama to southern Tennessee and 

constitute an area of rugged topography formed from 

the outcropping resistant sands of the Tuscaloosa 

Group, the McShan and Eutaw Formations, and the 

Coffee Sand. The district becomes indistinct in 

southern Tennessee, as the result of successive pinch 

out of progressively younger underlying geologic units.

The Black Belt is the topographic expression of the 

carbonate units of the Sehna Group. The district is 

characterized by gently rolling to nearly flat terrain 

and reaches its maximum width in western Alabama and 

central Mississippi. The district narrows abruptly in 

northern Mississippi and becomes indistinct in southern 

Tennessee.

The Ripley, Owl Creek, and Clayton Formations 

underlie the Pontotoc Ridge in northern Mississippi 

and southern Tennessee, and the Ripley Formation, 

Prairie Bluff Chalk, and Clayton Formation underlie 

the Ripley Cuesta in western Alabama. Between 

these districts, the Ripley is similar in lithology to the 

underlying Demopolis Chalk and the outcrop area is
B24 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

94° 93" 92° 91° 90° 89°

32

FIGURE 10. Physiographic map of the Mississippi embayment.

included in the Black Belt. Fenneman (1938, pi. 6) 

shows the Pontotoc Ridge extending a short distance 

into Tennessee. However, an extension of the ridge 

may form the divide between the Tennessee and Mississippi Rivers in northern Tennessee and Kentucky.

In western Alabama the Ripley Formation again 

becomes sandy, and the outcropping beds form the 

Ripley Cuesta. The relatively resistant limestone beds 

of the Clayton Formation are an important factor in 

the formation of the Pontotoc Ridge and the Ripley 

Cuesta.

The Flatwoods district is a level belt, as much as 10 

miles wide, which extends from Alabama through 

Mississippi into southern Tennessee. The district is 

mostly forested, because the clay soils, derived from the 

underlying Porters Creek Clay, generally are not 

suitable for crops. The Porters Creek Clay thins 

northward, and as a result the Flatwoods belt narrows 

in northern Mississippi and becomes indistinct in 

southern Tennessee.

The gulfward margin of the Flatwoods is bordered by 

the North Central Plateau. This district is underlain 

by the dissected outcropping Wilcox and Claiborne 

deposits, which are predominantly sandy. The topography is modified by extensive terrace and loess 

deposits. In southeastern Mississippi and southwestern 

Alabama the North Central Plateau includes a line of 

hills referred to as the Buhrstone Cuesta (Tallahatta 

Hills). This cuesta, underlain by the Tallahatta 

Formation, which includes highly resistant sandstone 

interbedded with the characteristic claystone of the 

formation, forms one of the most rugged districts of 

the Coastal Plain.

The North Central Plateau is bordered on the south 

by the Jackson Prairie, underlain by the clays of the 

Jackson Group, and characterized by gently rolling 

topography. A small area south of the Jackson Prairie 

is in the Southern Pine Hills.

A distinctly different physiographic feature, the 

Loess Hills (Bluff Hills), forms the western border of
GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B25

the uplands of the East Gulf Coastal Plain of Fenneman 

(1938). The Loess Hills superimposed on the North 

Central Plateau, the Jackson Prairie, and the Southern 

Pine Hills are the result of the unique erosional 

characteristics of loess. The loess, when eroded, forms 

vertical walls which overlie the steep slopes scoured by 

the Mississippi River along the eastern side of the 

alluvial plain. The resulting scarp, extending from 

Mississippi to Kentucky, is one of the most notable 

physiographic features of the Coastal Plain.

The physiographic districts on the western side of the 

embayment are the Lockesburg Wold, Saratoga Wold, 

Sulphur Wold, Black Prairie, and East Texas Timber 

Belt.

Fenneman (1938, fig. 28) shows the physiographic 

divisions for northeastern Texas on a section of the 

West Gulf Coastal Plain near the course of the Trinity 

River. These divisions are based on the type of 

underlying rock. Fenneman (1938, p. 103) states that

the Grand Prairie covers all Lower Cretaceous rocks except the 

basal (Trinity) sands which underlie the narrow belt of Western 

Cross Timbers. The Black Prairie covers the Upper Cretaceous 

with a like exclusion of basal (Woodbine) sands bearing the Eastern Cross Timbers, while the East Texas Timber belt is on the 

Tertiary.

The Western Cross Timbers, the Grand Prairie, and 

the Eastern Cross Timbers narrow northeastward and 

converge in southwestern Arkansas to form the Lockesburg Wold of Veatch (1906, p. 15). Dane (1929, p. 28) 

indicates that the Lockesburg Wold, or cuesta, actually 

includes two cuestas. One is formed on the basal 

gravel of the Woodbine Formation and the other on the 

basal gravel of the Tokio Formation.

South of the Lockesburg Wold is the Saratoga Wold 

(cuesta) of Veatch (1906, p. 15). The Saratoga Wold 

is a topographic ridge underlain by the Nacatoch Sand.

Farther south is the Sulphur Wold of Veatch (1906, 

p. 15). It is a dissected topographic ridge underlain 

by sandy units of the Wilcox Group in Arkansas.

The Black Prairie of northeastern Texas is underlain 

by Upper Cretaceous rocks and is similar to the Black 

Belt of the East Gulf Coastal Plain. This district 

apparently terminates at the alluvial valley of the Red 

River in northeastern Texas. It has not been extended 

into Arkansas.

South of the Black Prairie belt is the East Texas 

Timber Belt, which is underlain by Tertiary units. It 

extends through northeastern Texas into northern 

Louisiana and southwestern Arkansas.

The Mississippi Alluvial Plain is the result of aggradation by the Mississippi River and its tributaries. 

During the last stages of the evolution of the Mississippi 

embayment, the Mississippi River cut a deep valley

into the underlying rocks, mostly of Eocene age, at a 

time when the sea level was probably relatively much 

lower than it is at present. The general rise in sea 

level was accompanied by aggradation of the valley 

which, after a complex history (described in detail by 

Fisk, 1944) gradually assumed its present form. The 

alluvial plain is as much as 100 miles wide and about 

400 miles long in the Mississippi embayment. It is 

flat and slopes almost imperceptibly gulfward. Various 

physiographic features, such as natural levees, oxbow 

lakes, abandoned meanders, and alluvial fans, occur in 

the plain. An outstanding feature is Crowleys Ridge, 

the remnant of an old divide extending from southeastern Missouri to east-central Arkansas (fig. 10).

The Mississippi Alluvial Plain is divided into several 

basins, three of which are within the Mississippi embayment. The St. Francis Basin extends from the 

apex of the embayment to the Arkansas River; the 

Yazoo Basin occupies the part of the alluvial plain east 

of the Mississippi River from Memphis, Tenn., to 

Vicksburg, Miss.; and the Tensas Basin is in the part 

of the alluvial plain west of the Mississippi River and 

south of the Arkansas River.

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239-518.

Alabama Geological Survey, 1926, Geological Map of Alabama: 

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B26 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

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GENERAL GEOLOGY OF THE MISSISSIPPI EMBAYMENT B27

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 1956, Bluffport marl member of Demopolis chalk,

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B28 WATER RESOURCES OF THE MISSISSIPPI EMBAYMENT

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 1938, Stratigraphy of Upper Cretaceous series in 

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 1906, Geology and underground water resources of

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U. S. GOVERNMENT PRINTING OFFICE : 1968 O - 298-803