Geologic units in Pike county, Arkansas

Stanley Shale (Early Mississippian) at surface, covers 29 % 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

Jackfork Sandstone (Early Pennsylvanian- Morrowan) at surface, covers 22 % of this area

Jackfork Sandstone

Alluvium (Holocene) at surface, covers 10 % of this area

Alluvial deposits of present streams

Tokio Formation (Late Cretaceous) at surface, covers 9 % of this area

Tokio Formation

Trinity Group (Early Cretaceous) at surface, covers 9 % of this area

Trinity Group

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

Atoka Formation - Lower part

Johns Valley Shale (Early Pennsylvanian- Morrowan) at surface, covers 4 % of this area

Johns Valley Shale

Brownstown Marl (Late Cretaceous) at surface, covers 3 % of this area

Brownstown Marl

Arkansas Novaculite (Early Mississippian to Late Devonian) at surface, covers 2 % of this area

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

Dierks Limestone (Early Cretaceous) at surface, covers 2 % of this area

Dierks Limestone

Terrace deposits (Late Pleistocene) at surface, covers 1 % of this area

Alluvial deposits on one or more terrace levels

Woodbine Formation (Late Cretaceous) at surface, covers 0.7 % of this area

Woodbine Formation

Ozan Formation (Late Cretaceous) at surface, covers 0.7 % of this area

Ozan Formation

Missouri Mountain Shale and Baylock Sandstone (Late Silurian) at surface, covers 0.5 % 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.

De Queen Limestone (Early Cretaceous) at surface, covers 0.4 % of this area

De Queen Limestone

Igneous rocks (Cretaceous) at surface, covers < 0.1 % 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).