Geologic units in Pulaski county, Arkansas

Jackfork Sandstone (Early Pennsylvanian- Morrowan) at surface, covers 28 % of this area

Jackfork Sandstone

Alluvium - Alluvial deposits in major stream channels or in mappable meanders of major streams (Holocene) at surface, covers 19 % 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.

Alluvium (Holocene) at surface, covers 7 % of this area

Alluvial deposits of present streams

Atoka Formation - Lower part (Middle Pennsylvanian- Atokan) at surface, covers 6 % of this area

Atoka Formation - Lower part

Alluvium - Alluvial deposits of local streams or of overbank flow of major streams (Holocene) at surface, covers 6 % 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

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

Wilcox Group

Terrace deposits (Late Pleistocene) at surface, covers 5 % of this area

Alluvial deposits on one or more terrace levels

Atoka Formation - Upper part (Middle Pennsylvanian- Atokan) at surface, covers 4 % of this area

Atoka Formation - Upper part

Atoka Formation - Middle part (Middle Pennsylvanian- Atokan) at surface, covers 4 % of this area

Atoka Formation - Middle part

Womble Shale (Middle Ordovician) (Middle Ordovician) at surface, covers 3 % of this area

Womble Shale (Middle Ordovician)

Midway Group (Paleocene) at surface, covers 3 % of this area

Midway Group

Pole Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician) (Late Ordovician to Middle Ordovician) at surface, covers 3 % of this area

Polk Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician)

Arkansas Novaculite (Early Mississippian to Late Devonian) at surface, covers 3 % of this area

Includes upper division (Mississippian), middle division (Mississippian and Devonian), and lower division (Devonian)

Stanley Shale (Early Mississippian) at surface, covers 2 % of this area

Stanley Shale - Includes Chickasaw Creek Chert equivalent of Harlton (1938) near top and Hatton Tuff Lentil and Hot Springs Sandstone Member near base

Igneous rocks (Cretaceous) at surface, covers 1 % of this area

Includes undifferentiated altered sedimentary rocks of Paleozoic age at Granite Mountain, Pulaski County, and Mufreesboro, Pike County. Acid to intermediate - Nepheline syenite complexes at Magnet Cove and Potash Sulfur Springs, stocks at Granite Mtn., explosion breccias, and dikes and sills (principally trachyte,tinguaite, phonolite, some ranging from syenite to diabase). Basic to ultrabasic - Lamproite pipes (Murfreesboro, Pike County) and dikes and sills (principally lamprophyres of fourchite, ouachitite, and monchiquite).

Claibourne Group (Middle Eocene) at surface, covers 0.5 % of this area

Claibourne Group

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

Johns Valley Shale

Blakely Sandstone (Middle and Lower Ordovician) (Middle Ordovician to Early Ordovician) at surface, covers 0.1 % of this area

Blakely Sandstone (Middle and Lower Ordovician)

Missouri Mountain Shale and Baylock Sandstone (Late Silurian) at surface, covers < 0.1 % of this area

The Baylock Sandstone is present only in the Cross, Cossatot, and Trap Mountains. Missouri Mountain Shale is mapped with Polk Creek Shale and Bigfork Chert in the area between Paron, Saline County, and Little Rock.