Geologic units in Faulkner county, Arkansas

Atoka Formation - Upper part (Middle Pennsylvanian- Atokan) at surface, covers 53 % of this area

Atoka Formation - Upper part

Atoka Formation - Middle part (Middle Pennsylvanian- Atokan) at surface, covers 21 % of this area

Atoka Formation - Middle part

Atoka Formation, undivided (Middle Pennsylvanian- Atokan) at surface, covers 14 % of this area

Atoka Formation, undivided

Alluvium (Holocene) at surface, covers 6 % of this area

Alluvial deposits of present streams

Atoka Formation - Lower part (Middle Pennsylvanian- Atokan) at surface, covers 5 % of this area

Atoka Formation - Lower part

Terrace deposits (Late Pleistocene) at surface, covers 0.9 % of this area

Alluvial deposits on one or more terrace levels

Johns Valley Shale (Early Pennsylvanian- Morrowan) at surface, covers 0.3 % of this area

Johns Valley Shale

Harthshorne Sandstone (Middle Pennsylvanian- Des Moinesian) at surface, covers 0.3 % of this area

Harthshorne Sandstone

Jackfork Sandstone (Early Pennsylvanian- Morrowan) at surface, covers < 0.1 % of this area

Jackfork Sandstone