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)
Polk Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician)
Blakely Sandstone (Middle and Lower Ordovician)
Includes upper division (Mississippian), middle division (Mississippian and Devonian), and lower division (Devonian)
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
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).