Geologic units in Lonoke county, Arkansas

Alluvium - Alluvial deposits of local streams or of overbank flow of major streams (Holocene) at surface, covers 45 % 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

Terrace deposits (Late Pleistocene) at surface, covers 35 % of this area

Alluvial deposits on one or more terrace levels

Alluvium - Alluvial deposits in major stream channels or in mappable meanders of major streams (Holocene) at surface, covers 6 % 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.

Wilcox Group (Early Eocene) at surface, covers 5 % of this area

Wilcox Group

Midway Group (Paleocene) at surface, covers 2 % of this area

Midway Group

Atoka Formation - Middle part (Middle Pennsylvanian- Atokan) at surface, covers 2 % of this area

Atoka Formation - Middle part

Atoka Formation - Lower part (Middle Pennsylvanian- Atokan) at surface, covers 2 % of this area

Atoka Formation - Lower part

Atoka Formation - Upper part (Middle Pennsylvanian- Atokan) at surface, covers 1 % of this area

Atoka Formation - Upper part

Alluvium (Holocene) at surface, covers 0.7 % of this area

Alluvial deposits of present streams

Johns Valley Shale (Early Pennsylvanian- Morrowan) at surface, covers 0.7 % of this area

Johns Valley Shale