Geology Web Map
The geology of the map below represents geological mapping projects in the Ouachitas and Arkansas River Valley under the COGEO mapping program and in the West Gulf Coastal Plain under the STATEMAP program. You can zoom to a chosen county or quadrangle using the drop-down menus located above the map, and you can adjust the opacity of the surface geology layer using the opacity slider 
located at the top left corner of the map. For best printing results use either the Mozilla Firefox or Google Chrome web browsers.
ZOOM TO: County
ZOOM TO: 7.5' Quadrangle
Geology Web Map Legend
Inclined bedding - Showing approximate strike and dip
Overturned bedding - Showing approximate strike and dip
Contact - Existence certain, location approximate
Igneous Dike - Existence certain, location approximate
Normal Fault - Existence certain, location approximate
Normal Fault - Inferred or concealed
Tear Fault - Existence certain, location approximate
Tear Fault - Inferred or concealed
Thrust Fault - Existence certain, location approximate
Thrust Fault - Inferred or concealed
Overturned Thrust Fault - Existence certain, location approximate
Alluvium - Quaternary
Sand & Gravel - Quaternary
Stream Overbank - Quaternary
Terrace - Quaternary
River Terrace - Quaternary
Sand & Gravel - Tertiary
Gravel - Tertiary
Claiborne Group - Tertiary
Wilcox Group - Tertiary
Midway Group - Tertiary
Arkadelphia Marl - Cretaceous
Nacatoch Sand - Cretaceous
Saratoga Chalk - Cretaceous
Marlbrook Marl - Cretaceous
Annona Chalk - Cretaceous
Ozan Formation - Cretaceous
Brownstone Marl - Cretaceous
Tokio Formation - Cretaceous
Woodbine Formation - Cretaceous
Kiamichi/Goodland Formation - Cretaceous
Trinity Group - Cretaceous
De Queen Limestone - Cretaceous
Dierks Limestone - Cretaceous
Igneous Rocks - Cretaceous
Boggy - Pennsylvanian, Desmoinesian Series
Savanna - Pennsylvanian, Desmoinesian Series
McAlester - Pennsylvanian, Desmoinesian Series
Hartshorne Sandstone - Pennsylvanian, Desmoinesian Series
Upper Atoka - Pennsylvanian, Atokan Series
Middle Atoka - Pennsylvanian, Atokan Series
Lower Atoka - Pennsylvanian, Atokan Series
Johns Valley Shale - Pennsylvanian, Morrowan Series
Jackfork Sandstone - Pennsylvanian, Morrowan Series
Stanley Shale - Mississippian
Arkansas Novaculite - Devonian and Early Mississippian
Missouri Mountain Shale - Silurian
Blaylock Sandstone - Silurian
Missouri Mountain Shale / Polk Creek Shale - Silurian and Late Ordovician
Polk Creek Shale - Late Ordovician
Bigfork Chert - Middle and Late Ordovician
Womble Shale - Middle Ordovician
Blakely Sandstone - Middle Ordovician
Mazarn Shale - Early Ordovician
Crystal Mountain Sandstone - Early Ordovician
Collier Shale - Late Cambrian and Early Ordovician
Strip Mine