Ecs
Sparta Formation
White to light gray massive sands with interbedded clays; some thin interbeds of lignite or lignitic sands and shales.
Qal
Alluvium
Gray to brownish gray clay and silty clay, reddish brown in the Red River Valley, some sand and gravel locally.  Includes all alluvial valley deposits except natural levees of major streams
Qti
Intermediate Terraces
Light gray to orange-brown clay, sandy clay, and silt; much sand and gravel locally.  Surfaces show more dissection and are topographically higher than the Prairie.  Composed of terraces formerly design
Ecm
Cook Mountain Formation
Greenish gray sideritic, glauconitic clay in upper part may weather to brown ironstone; yellow to brown clays and fossiliferous marl in lower part may weather to black soil. Ironstone concretions near b
Qtp
Prairie Terraces
Light gray to light brown clay, sandy clay, silt, sand, and some gravel.  Surfaces generally show little dissection and are topographically higher than the Deweyville.  Three levels are recognized: two
Qnl
Natural Levees
Gray and brown silt, silty clay, some very fine sand, reddish brown along the Red River.  Shown only on past and present courses of major streams.
Water
Qth
High Terraces
Tan to orange clay, silt, and sand with a large amount of basal gravel.  Surfaces are highly dissected and less continuous than lower terraces.  Composed of terraces formerly designated as Willana, Citr
Ecf
Cockfield Formation
Brown lignitic clays, silts, and sands; some sideritic glauconite may weather to brown ironstone in lower part.
Qtd
Deweyville Terrace
Gray mixed with brown-to-red clay and silty clay; some sand and gravel locally.  Topographically higher that Holocene alluvium and lower than Prairie terraces.  Found along streams of intermediate size.
Qtp-l
Prairie Terraces - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meters of loess.  Also see detailed description for Qtp.
Qbs
Braided Stream Terraces
Light gray, tan, and brown fine to coarse sand, some clay, silt, and gravel.  Glacial outwash of ancestral Arkansas River.
Qbs-l
Braided Stream Terraces - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meters of loess.  Also see Qbs detailed description.
Ecr
Cane River Formation
Brown silty clay with basal glauconitic, fossiliferous silts which may weather to ironstone locally.
PEw
Wilcox Group (Undifferentiated)
Gray to brown lignitic sands and silty to sandy lignitic clays, many seams of lignite; some limestone and glauconite.  Includes small Carrizo Sand (Claiborne Group?) outcrops.
Pm
Midway Group (Undifferentiated)
Dark gray to black shale.  Only at surface in northwest Caddo Parish and at Prothro and Rayburns salt domes in Bienville Parish.
Misip
Ku
Upper Cretaceous
Fossiliferous limestone and marl.  Only at surface at Prothro and Rayburns salt domes in Bienville Parish.
Ej
Jackson Group (Undifferentiated)
Light gray to brown lignitic clays with interbeds of limonitic sands or lignite; near base, calcareous, glauconitic, and fossiliferous beds may weather to black soil.
Ej-l
Jackson Group - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meters of loess.  Also see detailed description of Ej.
Ov-l
Vicksburg Group - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meter of loess.  Also see detailed description of Ov.
Ov
Vicksburg Group (Undifferentiated)
Brown to gray lignitic clays with thin interbeds of lignite or micaceous sands; calcareous shale, petrified wood, and bluish fossiliferous clay locally.
Oc-l
Catahoula Formation - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meters of loess.  Also see detailed description of Oc.
Oc
Catahoula Formation
Gray to white sandstones, loose quartz sand, tuffaceous sandstone, volcanic ash, and brown sandy clays; petrified wood locally.
Mfcb
Carnahan Bayou Member
Yellow to gray siltstones, sandstones, and clays with thin tuffaceous beds; some lenses of black chert gravel; petrified wood locally.
Mfl
Lena Member
Gray calcareous clays which may weather to black soil, siltstones, tuffaceous clays, and some volcanic ash beds.
Mfd
Dough Hills Member
Gray to yellow silty clays; light gray calcareous clays which may weather to black soil; some siliceous silt and volcanic ash beds.
Mfw
Williamson Creek Member
White to gray silts, siltstones, silty clays, and sand beds; some lenses of black chert gravel.
Mfcc
Castor Creek Member
Gray to dark gray calcareous slays which may weather to black soil; lignitic clays and noncalcareous clayey soils.
Mfb
Blounts Creek Member
Gray to green silty clays, siltstones, and silts with abundant sand beds; some lignite and lenses of black chert gravel.
Qti-l
Intermediate Terraces - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meters of loess.  Also see detailed description of Qti.
Qth-l
High Terraces - Loess
Tan to reddish brown massive silt with some clay and minor amounts of very fine sand.  Stippled map units are those overlain by 1 to 9 meter of loess.  Also see detailed description of Qth.
Qdf
Delta Plain, Fresh Marsh
Gray to black clay of very high organic content, some peat.  Area of active and abandoned delta lobes of the Mississippi River.
Qds
Delta Plain, Saline Marsh
Gray to black clay of high organic content, some peat.  Area of active and abandoned delta lobes of the Mississippi River.
Qcf
Chenier Plain, Fresh Marsh
Gray to brown to black clay and silt of high organic content.  Area of accretion by longshore currents from major delta complex.
Qcs
Chenier Plain, Saline Marsh
Gray to brown to black clay and silt of moderate organic content.  Area of accretion by longshore currents from major delta complex.