Bedrock Geology Units in Ohio

Code  Geological Period  Geological Units  Rock Types
(see footnote) 
Pm-Pd Pennsylvanian- Permian Dunkard Group 
Monongahela Group
sh, ss, ls, coal
Pp,a,c Pennsylvanian Conemaugh Group 
Allegheny Group 
Pottsville Group
sh, ss, ls, coal
M Mississippian Maxville Limestone     
Cuyahoga & Logan Formations 
Sunbury Shale 
Berea Sandstone 
Bedford Shale
ls, sh 
ss, cg, sh 

ss, sh 

Do,o  Devonian  Ohio Shale 
Olentangy Shale
 sh, ls
Dc,d  Devonian  Delaware Limestone 
Columbus Limestone 
ls, sh 
ls, dol
S-D Silurian- Devonian  Detroit River Group 
Lockport & Salina Groups   
Osgood Shale 
Dayton Formation
dol, ss 


O-S Ordovician- Silurian Brassfield Formation   
Cincinnati Group
ls, sh, ss 
 sh, ls

Rock types for each unit are listed from left to right in order of decreasing abundance.
Abbreviations are: cg, conglomerate; ss, sandstone; sh, shale; ls, limestone; and dol, dolostone.