Geologic units in Garland county, Arkansas

Stanley Shale (Early Mississippian) at surface, covers 42 % 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

Womble Shale (Middle Ordovician) (Middle Ordovician) at surface, covers 13 % of this area

Womble Shale (Middle Ordovician)

Pole Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician) (Late Ordovician to Middle Ordovician) at surface, covers 12 % of this area

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

Blakely Sandstone (Middle and Lower Ordovician) (Middle Ordovician to Early Ordovician) at surface, covers 8 % of this area

Blakely Sandstone (Middle and Lower Ordovician)

Arkansas Novaculite (Early Mississippian to Late Devonian) at surface, covers 7 % of this area

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

Jackfork Sandstone (Early Pennsylvanian- Morrowan) at surface, covers 7 % of this area

Jackfork Sandstone

Mazarn Shale (Early Ordovician) at surface, covers 5 % of this area

Mazarn Shale

Missouri Mountain Shale and Baylock Sandstone (Late Silurian) at surface, covers 4 % 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.

Crystal Mountain Sandstone (Early Ordovician) at surface, covers 0.9 % of this area

Crystal Mountain Sandstone

Collier Shale (Early Ordovician) at surface, covers < 0.1 % of this area

Collier Shale

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).