QUATERNARY GEOLOGIC MAP OF THE VICKSBURG

4° x 6° QUADRANGLE, UNITED STATES

QUATERNARY GEOLOGIC ATLAS OF THE UNITED STATES

MAP I-1420 (NI-15)

State compilations by

Drew F. Holbrook, William A. Gilliland, Kenneth V. Luza, David E. Pope,

E. Gerald Wermund, Robert A. Miller, William V. Bush,

Kathryn N. Jensen, and William D. Fishman

Edited and integrated by

Gerald M. Richmond, David S. Fullerton, and David L. Weide

1990

NOTE: This map is the product of collaboration of State geological surveys, universities, and the U.S. 

Geological Survey, and is designed for both scientific and practical purposes. It was prepared in two stages. 

First, separate maps and map explanations of the parts of States included in the quadrangle were prepared by the 

State compilers indicated on the inset diagram, Areas of Responsibility. Second, these maps were combined, 

integrated, locally supplemented, and related to a uniform map symbol classification. The map unit descriptions 

also were combined, supplemented, and coordinated with those of other maps of this series so that individual unit 

descriptions are applicable throughout both this map and all other maps of the series. Diagrams accompanying 

the map were prepared by the editors.

Differences in mapping or interpretation in different areas were resolved by correspondence to the extent 

possible. Most simply reflect differences in available information or differences in philosophies of mapping. 

Such differences serve to encourage further investigation.

Less than forty percent of the surficial deposits of the United States have been mapped and described. 

Traditionally, mapping of surficial deposits has been focused on glacial, alluvial, eolian, lacustrine, marine, and 

landslide deposits. Slope and upland deposits have been mapped in detail only in restricted areas. However, an 

enormous amount of engineering construction and many important problems of land use and land management 

are associated with regions that have extensive slope and upland deposits (colluvium, residuum, and saprolite, for 

example). These materials have many different physical characteristics. Therefore, an effort has been made to 

classify, map, and describe there deposits, based in large part on unpublished interpretations of individuals, 

published and unpublished subsoil data, and the distribution of bedrock parent materials. The classification is 

crude, but represents a first step toward a more refined and useful product.

For scientific purposes, the map differentiates Quaternary surficial deposits on the basis of a combination of 

criteria, such as lithology, texture, genesis, stratigraphic relationships, and age, as shown on the correlation 

diagram and indicated in the map unit descriptions. Some geomorphic features, such as sand dunes, are 

distinguished as map units. Erosional features, such as stream terraces, are not distinguished, and differentiation 

of sequences of alluvial deposits of different ages is rarely possible at a scale of 1:1,000,000. Most landslide 

deposits also are too small to be shown at this scale.

For practical purposes, the map is a surficial materials map, on which materials are distinguished on the basis 

of texture, composition, and local specific characteristics such as swelling clay. It is not a map of soils as soils 

are recognized and classified in pedology or agronomy. Rather it is a generalized map of soils as recognized in 

engineering geology, or of subsoils or parent materials from which pedologic and agronomic soils are formed. 

1
As a materials map it serves as a base from which a wide variety of derivative maps for use in planning 

engineering, land use, or land management projects can be compiled.

The map contains the following illustrations:

• An index map to the International Map of the World 1:100,000 topographic series showing the Quaternary 

geologic map of the Vicksburg 4°x 6° quadrangle and other published maps of the Miscellaneous 

Investigations Series (I–1420).

• An illustration showing the responsibility for State compilations.

• An illustration showing the correlation of map units.

• An illustration showing loess thickness and distribution in the map area

LIST OF MAP UNITS

HOLOCENE

asa ALLUVIAL SAND, SILT, CLAY, AND GRAVEL

as ALLUVIAL SILTY FINE SAND

asl ALLUVIAL SILT AND SAND

ac ALLUVIAL CLAY

aca ALLUVIAL CLAY

fl NATURAL LEVEE SILT AND CLAY

HOLOCENE AND LATE WISCONSIN

ed DUNE SAND

cbf BOULDERY SANDY COLLUVIUM

cbg CHERT FRAGMENT COLLUVIUM

cbh SANDSTONE BLOCK COLLUVIUM

cbi QUARTZITE BOULDER COLLUVIUM

cla SANDSTONE- AND SHALE-CLAST LOAMY COLLUVIUM

clf ACID SHALE-CHIP CLAY-LOAM COLLUVIUM

LATE PLEISTOCENE

asd ALLUVIAL FINE SAND AND SILT

acb ALLUVIAL CLAY AND SILT

asb ALLUVIAL GRAVEL AND SAND

asj ALLUVIAL SAND AND SILT

acc ALLUVIAL SILT AND CLAY

LATE PLEISTOCENE AND MIDDLE PLEISTOCENE

ela LOESS AND LOESSIAL COLLUVIUM AND ALLUVIUM

LATE PLEISTOCENE TO EARLY PLEISTOCENE

agb ALLUVIAL GRAVEL AND SAND

asg ALLUVIAL CLAY, SILT, SAND, AND GRAVEL

MIDDLE PLEISTOCENE

alj ALLUVIAL SILTY CLAY, SAND, AND GRAVEL

ash ALLUVIAL DELTA SAND, SILT, AND CLAY

EARLY PLEISTOCENE TO PLIOCENE(?)

agf ALLUVIAL CHERT-PEBBLE GRAVEL AND SAND

agc ALLUVIAL PEBBLE GRAVEL AND SAND

QUATERNARY AND TERTIARY

zsa LIMONITIC SANDY DECOMPOSITION RESIDUUM

zsb QUARTZ SAND DECOMPOSITION RESIDUUM

zsd SANDY DECOMPOSITION RESIDUUM

2
zse CLAYEY, FINE TO MEDIUM SAND AND FINE SANDY CLAY DECOMPOSITION 

RESIDUUM

zsh MEDIUM TO FINE SILTY SAND, SANDY SILT, AND SAND DECOMPOSITION RESIDUUM

zsp FINE SANDY, SILTY, CLAY DECOMPOSITION RESIDUUM

zld CLAYEY SILT DECOMPOSITION RESIDUUM

zca SANDY CLAY DECOMPOSITION RESIDUUM

zcb SMECTITIC CLAY DECOMPOSITION RESIDUUM

zcc FINE SILTY CLAY DECOMPOSITION RESIDUUM

zcg SAND, GRAVEL, SILT, AND CLAY DECOMPOSITION RESIDUUM

zch SILTY OR MICACEOUS SANDY CLAY DECOMPOSITION RESIDUUM

zrg SHALEY CLAY AND CHERTY CLAY DECOMPOSITION AND SOLUTION RESIDUUM

rcc CHERTY CLAY SOLUTION RESIDUUM

rcg DARK CLAY SOLUTION RESIDUUM

sca CLAY SAPROLITE

LIST OF MAP SYMBOLS

CONTACT

SHORELINE

PLEISTOCENE VOLCANIC ASH BED—Possibly belonging to Pearlette family of volcanic ashes derived 

from calderas in and near Yellowstone National Park

DESCRIPTION OF MAP UNITS

HOLOCENE

asa ALLUVIAL SAND, SILT, CLAY, AND GRAVEL—Light-gray, yellowish- to brownish-gray, or 

reddish-orange, coarse to fine sand and subangular to well-rounded pebble gravel; massive to well 

stratified. Locally includes interbedded or admixed silt and clay especially in flood plains of 

major drainages. Gravel is chert, quartz, and sandstone, derived from older deposits. Mapped 

areas include swamp and organic muck deposits in backswamps and on flood plains, and local 

colluvium along margins of valley floors. Thickness 3–30 m

as ALLUVIAL SILTY FINE SAND—Gray to light-brown and brown silty sand; poorly to well sorted, 

poorly to well stratified; contains intermixed and interbedded silt and clay. Comprises channel, 

overbank, and natural-levee deposits of the Mississippi and Arkansas Rivers. Overlies intermixed 

and interbedded gravel, sand, silt, and clay of Pleistocene age that become coarser with depth and 

ranges in thickness from 10 m to more than 70 m. Mapped areas include swamp deposits, muck 

of oxbow lakes, and scattered areas of dark-brown to black organic clay. Thickness 3–10 m

asl ALLUVIAL SILT AND SAND—Grayish-tan to brown, poorly sorted, irregularly bedded, locally 

clayey, silt, and fine to very fine quartz sand; scattered interbedded or intermixed chert-pebble 

gravel. Mapped only in Mississippi where it is derived mainly from older loess and loessial 

colluvium (ela). Mapped areas include organic muck and swamp deposits on flood plains. 

Thickness 5–10 m

ac ALLUVIAL CLAY—Gray to reddish-brown, poorly to well bedded, clay-dominant material 

representing overbank deposits of the Mississippi and Arkansas Rivers. Contains intermixed and 

interbedded fine sand and silt and sparse deposits of dark-brown to black organic clay. Mapped 

areas include swamp deposits and muck that accumulated in oxbow lakes. Overlies intermixed 

and interbedded gravel, sand, silt, and clay that coarsen with depth and is about 10–70 m thick. 

Thickness of alluvial clay 3–12 m; locally 20 m where deposit fills channels in underlying 

Pleistocene alluvial sand 

aca ALLUVIAL CLAY (Backswamp deposits of Saucier, 1974)—Light- to dark-gray, yellowish-gray, or 

brownish-gray clay, silty clay, and organic silty clay. Contains a few thin layers of medium to 

fine quartz sand and thin lenses of reworked fine chert-pebble gravel. Peat layers, abundant 

3
organic particles, and wood fragments are interspersed throughout. Deposits accumulated in 

abandoned river channels and overbank flood areas (backswamps) near natural levees of 

Mississippi River. Thickness 3–10 m; locally 20 m where deposit fills channels in underlying 

Pleistocene alluvium 

fl NATURAL LEVEE SILT AND CLAY—Brown to grayish-brown, light- to medium-gray silt and silty 

clay; includes small amounts of fine quartz sand. The clay and silt locally contain abundant plant 

fragments. Deposit moderately to highly oxidized; forms broad, natural levees 2–5 m high along 

present and former courses of Mississippi River. Thickness 1–6 m

HOLOCENE AND LATE WISCONSIN

ed DUNE SAND—Light-brown, fine to medium sand; includes some silt, clay, and organic matter. 

The dunes are mostly on late Pleistocene braided stream terraces of Saucier (1974) underlain by 

alluvial gravel and sand (asb) 

cbf BOULDERY SANDY COLLUVIUM1

—Tan to brown, dark-grayish-brown, or yellowish-brown fine 

sand, silt, and minor silty clay containing sandstone boulders; some boulder fields at surface. 

Developed on moderate to steep slopes underlain by highly folded and faulted sandstone and

shale. Thickness 0.5–1.5 m

cbg CHERT FRAGMENT COLLUVIUM1

—White to gray, angular to subrounded chert and novaculite 

fragments 7–22 cm in diameter in a gray to dark-grayish-brown, silty clay matrix. Mapped 

areas include bedrock outcrops and abundant talus material on moderate to steep slopes. 

Thickness 0.25–1.0 m

cbh SANDSTONE BLOCK COLLUVIUM1

—Orange to orange-brown, slightly silty to slightly clayey, 

well-rounded, medium to fine sand containing many angular to subround, boulder- to cobblesize sandstone blocks; local areas of orange sandy clay contain fragments of milky quartz. 

Developed on steep to moderate slopes. Mapped areas include many bedrock outcrops. 

Thickness 0.5–1.5 m

cbi QUARTZITE BOULDER COLLUVIUM1

—Dark-grayish-brown, reddish-orange, or tan, sandy to 

silty clay containing abundant milky quartz fragments and blocks of quartzite and either 

phyllite or sandstone 5–20 cm in diameter. Developed on steep to moderate slopes. Mapped 

areas include many rock outcrops. Thickness 0.5–1.5 m; locally in Arkansas may exceed 3 m 

cla SANDSTONE- AND SHALE-CLAST LOAMY COLLUVIUM1

—Very dark grayish-brown to 

yellowish-brown silty clay, silt, and sand containing angular to subangular sandstone and shale 

fragments. Developed on moderate to steep slopes. Mapped areas include sparse outcrops and 

patches of eolian sand. Thickness 0.5–1.5 m

clf ACID SHALE-CHIP CLAY-LOAM COLLUVIUM1

—Reddish- to greenish-brown or dark-grayishbrown sandy to silty clay containing shale chips and subangular to well-rounded clasts as much 

as 15 cm across. Clasts are chiefly sandstone, but locally are chert and quartzite. Developed 

on moderate to steep slopes. Mapped areas include rock outcrops and talus on steep slopes; 

small alluvial fans of sand and angular gravel on moderate slopes. Thickness 0.5–1.0 m

LATE PLEISTOCENE

asd ALLUVIAL FINE SAND AND SILT (Deposits of Deweyville terrace of Saucier, 1974, on Ouachita 

River)—Light-gray or light-brownish-gray to mottled red and brown, fine to very fine quartz

sand and silt, containing scattered lenses of clay and layers of quartzite and fine pebble gravel 

composed of chert. In southern Arkansas, the sand and silt underlies two low terraces; pebble 

gravel lenses include clasts as much as 5 cm across. Abandoned oxbow channels on the terrace 

surfaces are filled with interbedded silt and clay. Thickness 2–15 m

acb ALLUVIAL CLAY AND SILT (Deposits of Deweyville terrace of Bernard, 1950; Saucier, 1974)—

Light- to medium-gray, clay and silty clay. Poorly to well sorted, poorly to well bedded. 

Locally includes admixed or interbedded fine quartz sand. Thickness 3–5 m

asb ALLUVIAL GRAVEL AND SAND (Deposits of braided stream terraces of Saucier, 1974)—White to 

gray or brown, poorly to well-sorted, fine to coarse quartz sand and gravel; includes minor silt 

and clay. Forms a broad terrace along west side of Mississippi River flood plain in Louisiana and 

Arkansas; includes both glacial outwash and nonglacial alluvium; contains relict channels filled 

with interbedded silt and clay. Thickness 3–8 m; locally 10–40 m where deposit fills channels cut 

in underlying Pleistocene alluvial sand and gravel (asg) 

4
asj ALLUVIAL SAND AND SILT (Sand and silt facies of Prairie terrace of Saucier, 1974)—Light- to 

dark-brown, red, or reddish-brown, fine to coarse silty sand, locally interbedded with silt lenses 

and gravel lenses. Gravel, chiefly chert and quartzite, more abundant than in deposits of the 

Prairie terrace farther south. Locally covered by thin patches of loess. Mapped areas include 

organic silt and clay deposits of abandoned channels and oxbow lakes, and oxidized sand and silt 

deposits of natural levees (fl). Thickness 2–5 m; locally 10 m where deposit fills channels cut in 

underlying Pleistocene alluvial sand and gravel (asg) 

acc ALLUVIAL SILT AND CLAY (Silt-clay facies of Prairie terrace of Saucier, 1974)—Brown to red 

and dark-red clayey silt characterized by numerous, closely spaced, circular depressions and small 

silty clay mounds. Depressions range from 3 to 150 m in diameter and are filled with light- to 

medium-gray silty clay grading downward to red-brown silt containing abundant dark-red ironmanganese "buckshot" pellets. Silt matrix contains rare gravel lenses. Grades down into 

underlying Pleistocene alluvial sand and gravel (asg). Mapped only in Louisiana along edge of 

Mississippi River flood plain. Thickness 1.5–7 m; locally 50 m where it fills paleochannels cut in 

underlying Pleistocene alluvium

LATE PLEISTOCENE AND MIDDLE PLEISTOCENE

ela LOESS AND LOESSIAL COLLUVIUM AND ALLUVIUM—Yellow, brown to reddish-brown, or 

grayish-brown to yellowish-brown silt mixed with clay and fine sand; locally contains thin lenses 

of very fine to fine quartz sand. Near rivers, deposits are cut by ravines 20–30 m deep, forming 

extremely rugged terrain. In southeast Mississippi, east of mapped area, thin loess occurs locally 

on and is intermixed and interbedded with other mapped units. Thickness ranges from a 

maximum of 30 m along the Mississippi River to 3 m at eastern limit of mapped unit

LATE PLEISTOCENE TO EARLY PLEISTOCENE

agb ALLUVIAL GRAVEL AND SAND (Terrace gravel of the Arkansas River restricted to mountainous 

terrain in Arkansas and Oklahoma)—Light- brown, yellowish- to reddish-brown, and dark-red, 

medium to coarse sand; contains abundant pebbles and cobbles of chert. Terrace remnants are 

10–12 m above present flood plain of Arkansas River. Thickness 2–5 m

asg ALLUVIAL CLAY, SILT, SAND, AND GRAVEL (Undifferentiated alluvial terrace deposits of 

Deweyville, Beaumont, Lissie, and Willis age in Texas; undifferentiated terrace deposits in 

Arkansas and Oklahoma)—Light-brown to reddish-brown, fine to coarse sand and silt, pinkishorange and yellowish-tan mottled clay, and well rounded to subangular quartz and chert gravel; 

clasts 1–4 cm in diameter. Mapped areas include local colluvial deposits. Thickness 0.5–5 m

MIDDLE PLEISTOCENE

alj ALLUVIAL SILTY CLAY, SAND, AND GRAVEL—Reddish-brown to dark-gray silty clay; lenses 

of sand and scattered chert and limestone gravel in basal part. Underlies a sequence of river 

terraces and is mapped only in Oklahoma in northwestern part of the quadrangle. Deposit 

contains Pleistocene vertebrate fossils in places. Thickness 3–15 m

ash ALLUVIAL DELTA SAND, SILT, AND CLAY (Fine-grained channel facies of Bentley and 

Montgomery Formations of Fisk, 1938, 1940, in Louisiana)—Light-gray to brown or orangebrown, medium to fine sand, silt, and sandy clay; some interbedded lenses of gravel. In places, 

deposit characterized by channel-and-fill structures and graded bedding that indicate deposition in 

meander channels, point bars, and braided channels on landward part of delta plain. Locally, 

surface of deposit characterized by clusters of pimple mounds or mantled by low dunes of 

Holocene age. Thickness 5–15 m

EARLY PLEISTOCENE TO PLIOCENE(?)

agf ALLUVIAL CHERT-PEBBLE GRAVEL AND SAND (Gravel of Crowleys Ridge in Arkansas)—

Pale-buff, light-brown to dark-brown pebbles, cobbles, and a few boulders in a matrix of fine 

sand, silt, and clay; poorly sorted; unconsolidated; locally stained with iron or manganese oxide. 

Silt and clay increasingly abundant in upper part. Clasts mostly well rounded, a few angular; 

composed primarily of chert, sparse quartzite, sandstone, and claystone. Sand, chiefly quartz, 

grains of zircon, tourmaline, staurolite, and topaz, and minor kyanite and sillimanite indicate 

probable source in headwater area of ancestral Mississippi River. Deposit characterized by 

5
channel-and-fill cross-bedding; foreset beds dip mainly west or south. Thickness as much as 20 

m 

agc ALLUVIAL PEBBLE GRAVEL AND SAND (Citronelle Formation)—Light-gray to orange-brown, 

orange, or reddish-orange, gravelly, coarse to fine sand; includes lenses of moderate- to dark-red 

sandy silt and white to light-gray clay. Gravel consists of subangular to subround chert or quartz 

granules to medium-size pebbles, commonly in a loose, coarse sand matrix. The Citronelle 

Formation is considered middle Pliocene to possible early Pleistocene in age on the basis of fossil 

leaves found in Mississippi (Berry, 1916; Stringfield and Lamoureaux, 1957). A vertebrate fauna, 

collected from a dark-gray clay beneath oxidized sand typical of the Citronelle Formation in 

Alabama has been assigned a Hemphillian (middle Pliocene) age by F. C. Whitmore (Isphording 

and Lamb, 1971). Mapped areas include locally derived gravelly sand, alluvium, and colluvium. 

Thickness variable; as much as 60 m

QUATERNARY AND TERTIARY

zsa LIMONITIC SANDY DECOMPOSITION RESIDUUM2

—Dark-reddish-brown, brown, or yellowishbrown, fine to medium quartz sand and clay to silty clay. Sand is irregularly cemented to hard, 

limonitic masses; numerous limonite veins and nodules. Deposit grades down into sandstone, 

shale, and siltstone bedrock. Mapped areas include locally derived colluvium, alluvium, and 

bedrock outcrops. Thickness 1–15 m 

zsb QUARTZ SAND DECOMPOSITION RESIDUUM2

—Pale-gray to reddish-brown, slightly clayey 

coarse to medium quartz sand, commonly containing muscovite. Locally characterized by 

irregular, hard, limonite-cemented masses, nodules, and veins. Mapped areas include younger 

locally derived colluvium, bedrock outcrops, and broad, low sand dunes of late Pleistocene and 

Holocene age. Thickness 1–3 m

zsd SANDY DECOMPOSITION RESIDUUM2

—Very dark grayish-brown, olive-brown, yellowishbrown, or gray, fine sandy loam to silty clay loam containing angular sandstone fragments and 

shale chips; developed principally on flat to gently sloping terrain. May contain intermixed 

eolian silt or fine sand and colluvium. Thickness 0.5–2 m

zse CLAYEY, FINE TO MEDIUM SAND AND FINE SANDY CLAY DECOMPOSITION 

RESIDUUM2

—Brown to buff, clayey, fine to medium quartz sand and orange to yellowish-red, 

fine sandy, silty clay. In Louisiana, commonly contains small fragments of lignite. Thin where 

developed on layers of hard volcanic tuff in Texas. Mapped areas include colluvium and bedrock 

outcrops. Thickness 1–3 m

zsh MEDIUM TO FINE SILTY SAND, SANDY SILT, AND SAND DECOMPOSITION RESIDUUM2

—

Tan to light-brown silty fine sand with small amounts of reddish-brown silty to sandy clay; 

chiefly quartz sand in northern Arkansas. Thickness 0.5–2 m

zsp FINE SANDY, SILTY, CLAY DECOMPOSITION RESIDUUM2

—Light-brown to reddish-brown 

very fine sand, gray clay, reddish-brown silty clay, and some gravel. Clasts chiefly sandstone; a 

few are of limestone. Mapped areas include colluvium and bedrock outcrops. Thickness 0.5–2 m

zld CLAYEY SILT DECOMPOSITION RESIDUUM2

—Olive-brown to grayish-brown clay loam to silt 

loam containing small fragments of sandstone and chips of shale in lower part. Mapped areas 

include colluvium and bedrock outcrops. Thickness 1–1.5 m

zca SANDY CLAY DECOMPOSITION RESIDUUM2

—Pale-yellow, orange, reddish-orange, or greenishgray, mottled, poorly sorted, fine sandy clay; in places contains medium to coarse sand or pebbly 

sand, chiefly quartz. Mapped areas include local colluvium and bedrock outcrops. Thickness 1–2 

m 

zcb SMECTITIC CLAY DECOMPOSITION RESIDUUM2

—Light-brown to brown, reddish-brown, 

yellowish-gray or mottled pinkish-orange, clay, silty clay, silt, and fine sand, locally containing 

calcareous nodules. Clay is smectitic; expands when wet; shrinks and develops a crack structure, 

called gilgai when dry. Mapped areas include local colluvium and bedrock outcrops. Thickness 

commonly less than 1 m, locally 2 m

zcc FINE SILTY CLAY DECOMPOSITION RESIDUUM2

—Black to dark-gray or dark-brown silty clay; 

light brown to reddish brown where oxidized; contains areas of fine sand and chert-pebble gravel 

in Arkansas. Clay is strongly smectitic; expands when wet, shrinks and forms a crack structure, 

called gilgai, when dry. Mapped areas include local colluvium and bedrock outcrops. Thickness 

0.5–1 m, locally 2 m

6
zcg SAND, GRAVEL, SILT, AND CLAY DECOMPOSITION RESIDUUM2

—Dark-gray, olive-gray, 

grayish-brown to reddish-brown clay loam, silt loam, fine to medium sand, or clayey sandy 

gravel; contains both calcium carbonate concretions and limonite concretions. Sand chiefly 

quartz; gravel, 2–10 cm in diameter, is of novaculite, quartz, quartzite, and sandstone. Clay is 

mostly smectite; expands when wet and shrinks when dry. Mapped areas include local colluvium 

and bedrock outcrops. Thickness 0.5–2 m

zch SILTY OR MICACEOUS SANDY CLAY DECOMPOSITION RESIDUUM2

—Brown silty clay and 

micaceous, fine sandy clay, commonly limonite cemented. Lower part may locally contain 

fragments of lignite and petrified wood. Mapped areas include local colluvium and bedrock 

outcrops. Thickness 1–2 m

zrg SHALEY CLAY AND CHERTY CLAY DECOMPOSITION AND SOLUTION RESIDUUM2,3—

Yellowish- to reddish-orange, yellowish- to reddish-brown clay and minor amounts of sand and 

silt. Clasts chiefly of iron-stained, chalcedonic chert fragments and shale chips. Base is very 

uneven; residuum extends deeply into underlying bedrock along fractures. Mapped areas include 

locally derived sheetwash on steeper slopes, and bedrock outcrops. Thickness 0.5–2 m

rcc CHERTY CLAY SOLUTION RESIDUUM3

—Reddish-orange, grayish-brown to dark-brown clay and 

silty clay containing subangular to angular, white, tan, black, green, or gray, gravel- to cobblesize chert clasts. Contains slabs of sandstone, siltstone, and locally limestone or dolomite at or 

near the surface. Contact with underlying bedrock is an abrupt pinnacled, karst surface. Mapped 

areas include colluvium and bedrock exposures. Where colluvium overlies the residuum on steep 

slopes, both deposits tend to be unstable. Thickness 0.5–1.5 m, locally more than 5 m

rcg DARK CLAY SOLUTION RESIDUUM3

—Yellowish-gray, dark-gray to black, or dark-brown, fine, 

sandy clay containing scattered, very light gray, chalky, calcium carbonate nodules and marcasite 

concretions. Relatively high degree of plasticity; occurs in areas of low relief and rests in abrupt 

contact on underlying limestone bedrock. Mapped areas include small deposits of colluvium and 

bedrock exposures, the latter chiefly in areas of high relief. Thickness less than 1 m

sca CLAY SAPROLITE—Red to dark-brown clay saprolite developed on nepheline syenite. Clay 

contains residual angular, subangular, and rounded boulders and core stones. Includes some 

bauxite and areas of grus. Thickness 0.5–3 m

1

COLLUVIUM, for purposes of this map, is defined as material transported and deposited by mass-wasting 

processes. In this quadrangle the processes are chiefly creep, solifluction, mudflow, frost heave, landslide and 

sheetwash.

2

DECOMPOSITION RESIDUUM, for purposes of this map, is defined as material derived primarily by in-place 

chemical decay of clastic rock with no appreciable subsequent lateral transport.

3

SOLUTION RESIDUUM, for purposes of this map, is defined as material derived by in-place solution of 

carbonate rock or carbonate-cemented rock with no appreciable subsequent lateral transport.

SOURCES OF INFORMATION

ARKANSAS

Adams, G. I., and Ulrich, E. O., 1905, Description of the Fayetteville quadrangle [Arkansas-Missouri]: 

U.S. Geological Survey Geologic Atlas, Folio 119, 6 p.

Haley, B. R., Glick, E. E., Bush, W. V., Clardy, B. F., Stone, C. G., Woodward, M. B., and Zachary, D. 

L., 1976, Geologic map of Arkansas: U.S. Geological Survey map, scale 1:500,000. (Open-file 

copies of field maps, scales 1:24,000 or 1:62,500 are available at Arkansas Geologic Commission, 

Little Rock, Arkansas). 

McKnight, E. T., 1935, Zinc and lead deposits of northern Arkansas: U.S. Geological Survey Bulletin 

853, 311 p.

Purdue, A. H., 1907, Description of the Winslow quadrangle [Arkansas-Indiana Territory]: U.S. 

Geological Survey Geologic Atlas Folio 154, 6 p.

Purdue, A. H., and Miser, H. D., 1916, Description of the Eureka Springs-Harrison quadrangle [ArkansasMissouri]: U.S. Geological Survey Geologic Atlas, Folio 202, 22 p.

Saucier, R. T., 1974, Quaternary geology of the lower Mississippi Valley: Arkansas Archeological 

Survey Research Series 6, 26 p.

7
Saucier, R. T., 1978, Sand dunes and related aeolian features of the lower Mississippi River alluvial 

valley, in Hilliard, S. B., ed., Man and environment in the lower Mississippi Valley: Geoscience 

and Man, v. 19, p. 23–40.

U.S. Soil Conservation Service (in cooperation with Arkansas Agricultural Experiment Station), 1967, 

Soil association map, State of Arkansas: scale 1:1,000,000.

West, L. T., Rutledge, E. M., and Barber, D. M., 1980, Sources and properties of loess deposits on 

Crowley's Ridge in Arkansas: Soil Science Society of America Journal, v. 44, p. 353–358.

LOUISIANA

Bernard, H. A., 1950, Quaternary geology of southeast Texas: Baton Rouge, Louisiana State University, 

Ph.D. dissertation.

Berry, E. W., 1916, The flora of the Citronelle formation, in Shorter contributions to general geology: 

U.S. Geological Survey Professional Paper 98-L, p. 193–208.

Fisk, H. N., 1938, Geology of Grant and LaSalle Parishes, Louisiana: Louisiana Geological Survey 

Bulletin 10, 246 p.

Fisk, H. N., 1940, Geology of Avoyelles and Rapides Parishes, Louisiana: Louisiana Geological Survey 

Bulletin 18, 240 p.

Isphording, W. C., and Lamb, G. M., 1971, Age and origin of the Citronelle Formation in Alabama: 

Geological Society of America Bulletin, v. 82, no. 3, p. 775–780.

Saucier, R. T., 1974, Quaternary geology of the lower Mississippi Valley: Arkansas Archeological 

Survey Research Series 6, 26 p. 

Stringfield, V. T., and LaMoreaux, P. E., 1957, Age of the Citronelle Formation in the Gulf coastal plain: 

American Association of Petroleum Geologists Bulletin, v. 41, no. 4, p. 742–746. 

Woodward, T. P., and Gueno, A. J., Jr., 1941, The sand and gravel deposits of Louisiana: Louisiana 

Geological Survey Bulletin 19, 365 p.

MISSISSIPPI

Bicker, A. R., Jr., 1969, Geologic map of Mississippi: Mississippi Bureau of Geology, scale 1:500,000.

Bicker, A. R., Jr., and others, 1966, Claiborne County geology and mineral resources: Mississippi Bureau of 

Geology Bulletin 107, 174 p.

Brown, G. F., 1947, Geology and artesian water of the alluvial plain in northwestern Mississippi: Mississippi 

Bureau of Geology Bulletin 65, 424 p.

Brown, G. F., and Guyton, W. F., 1943, Geology and ground-water supply at Camp Van Dorn [Mississippi]: 

Mississippi Geological Survey Bulletin 56, 68 p.

Grim, R. E., 1936, The Eocene sediments of Mississippi: Mississippi Geological Survey Bulletin 30, 240 p.

Mellen, F. F., McCutcheon, T. E., 1940, Yazoo County mineral resources: Mississippi Geological Survey 

Bulletin 39, 132 p. 

Mellen, F. F., McCutcheon, T. E., and Livingston, M. R., 1941, Warren County mineral resources: Mississippi 

Geological Survey Bulletin 43, 140 p.

Moore, W. H., and others, 1965, Hinds County mineral resources: Mississippi Geological, Economic, and 

Topographic Survey Bulletin 105, 244 p.

Priddy, R. R., and McCutcheon, T. E., 1942, Tallahatchie County mineral resources: Mississippi Geological 

Survey Bulletin 50, 157 p. 

Saucier, R. T., 1967, Geological investigation of the Boeuf-Tensas Basin, lower Mississippi Valley: U.S. Army 

Engineer Waterways Experiment Station Technical Report No. 3–757.

Snowden, J. O., Jr., and others, 1968, Loess investigations in Mississippi: Mississippi Bureau of Geology 

Bulletin 111, 267 p.

Thomas, E. P., 1942, The Claiborne: Mississippi Bureau of Geology Bulletin 48, 96 p.

Vestal, F. E., 1950, Carroll County geology: Mississippi Geological Survey Bulletin 67, 114 p.

Vestal, F. E., 1956, Panola County geology: Mississippi Geological Survey Bulletin 81, 157 p.

OKLAHOMA

Burwell, A.L., and Ham, W.E., 1949, Cellular products from Oklahoma volcanic ash: Oklahoma Geological 

Survey Circular 27, 89 p. 

Gray, Fenton, and Galloway, H.M., 1969, Soils of Oklahoma: Stillwater, Oklahoma State University Agricultural 

Research Miscellaneous Publication, 65 p.

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Izett, G.A., and Wilcox, R.E., 1982, Map showing localities of the Huckleberry Ridge, Mesa Falls, and Lava 

Creek ash beds (Pearlette family ash beds) of Pliocene and Pleistocene age in the western United States 

and southern Canada: U.S. Geological Survey Miscellaneous Investigations Series Map I-1325, scale 

1:4,000,000. 

Marcher, M. V., 1969, Reconnaissance of the water resources of the Fort Smith quadrangle, east-central 

Oklahoma: Oklahoma Geological Survey Hydrologic Atlas HA-1, scale 1:250,000. 

Marcher, M.V., and Bergman, D.L., 1984 Reconnaissance of the water resources of the McAlester and Texarkana 

quadrangles, southeastern Oklahoma: Oklahoma Geological Survey Hydrologic Atlas HA-9, scale 

1:250,000.

Miser, H.D., 1957, Geologic map of Oklahoma: U.S. Geological Survey and Oklahoma Geological Survey, scale 

1:500,000.

TEXAS

Texas Bureau of Economic Geology, 1965, Geologic atlas of Texas, Tyler sheet; scale 1:250,000.

Texas Bureau of Economic Geology, 1966, Geologic atlas of Texas, Texarkana sheet; scale 1:250,000.

LOESS INDEX MAP

Thorp, James, and Smith, H.T.U., 1952, Pleistocene eolian deposits of the United States, Alaska, and parts of 

Canada: National Research Council Committee for the Study of Eolian Deposits, Geological Society of 

America, scale 1:2,500,000.

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