Geologic units in Lauderdale county, Tennessee

Loess (Quaternary) at surface, covers 55 % of this area

Clayey and sandy silt, gray to brown, massive. Maximum thickness about 100 feet along bluffs of Mississippi River; thins eastward. (Minimum mapped thickness 4 feet.)

Alluvial deposits (Quaternary) at surface, covers 43 % of this area

Sand, silt, clay, and gravel. In flood plain of Mississippi River more than 100 feet thick; in smaller streams generally less than 20 feet thick.

Jackson (?) Formation (Tertiary) at surface, covers 2 % of this area

Sand, with layers of gray clay, silt, and lignite. Exposed only in bluffs along Mississippi River; thickness at least 60 feet.

Alluvium - Alluvial deposits in major stream channels or in mappable meanders of major streams (Holocene) at surface, covers 0.2 % of this area

Alluvial deposits in major stream channels or in mappable meanders of major streams - Includes alluvial deposits in natural levees in some areas.

High-level alluvial deposits (Quaternary-Tertiary) at surface, covers < 0.1 % of this area

Iron-stained gravel, sand, silt, and clay; variable in thickness but generally less then 60 feet thick.

Alluvium - Alluvial deposits of local streams or of overbank flow of major streams (Holocene) at surface, covers < 0.1 % of this area

Alluvial deposits of local streams or of overbank flow of major streams - In some areas includes deposits in abandoned meanders of major streams