Ohio Fossiliferous Bedrock Outcrop Geologic Time Line

Eon / Era / Period / Epoch / Date mya (Millions of Years Ago) / Counties with Fossiliferous Outcrops of this Age
Phanerozoic / Quaternary / Holocene / 0-.01 / Surficial material, no bedrock
Pleistocene / 0.1-2 / Surficial material, no bedrock
Tertiary / Neogene / Pliocene / 2-5 / No Known Outcrops in OH
Miocene / 5-24 / No Known Outcrops in OH
Paleogene / Oligocene / 24-37 / No Known Outcrops in OH
Eocene / 37-58 / No Known Outcrops in OH
Paleocene / 58-66 / No Known Outcrops in OH
Mesozoic / Cretaceous / 66-144 / No Known Outcrops in OH
Jurassic / 144-208 / No Known Outcrops in OH
Triassic / 208-245 / No Known Outcrops in OH
Paleozoic / Permian / 245-286
Carboniferous / Pennsylvanian / 286-320 / Lawrence, Scioto, Jackson, Gallia, Meigs, Vinton, Athens, Hocking, Washington, Morgan, Perry, Muskingum, Noble, Monroe, Guernsey, Belmont, Coshocton, Holmes, Tuscarawas, Harrison, Jefferson, Carroll, Stark, Columbiana, Mahoning, Trumbull, Geauga, Stark, Wayne, Portage, Summit, Medina, Licking, Knox
Mississippian / 320-360 / Scioto, Pike, Jackson, Vinton, Ross, Hocking, Pickaway, Fairfield, Perry, Licking, Muskingum, Coshocton, Knox, Morrow, Holmes, Richland, Ashland, Wayne, Crawford, Stark, Huron, Lorain, Medina, Summit, Cuyahoga, Portage, Lake, Geauga, Trumbull, Ashtabula, Mahoning
Devonian / 360-408 / Scioto, Adams, Pike, Ross, Pickaway, Franklin, Delaware, Morrow, Marion, Crawford, Wyandot, Huron, Seneca, Erie, Lorain, Cuyahoga, Lake, Ashtabula, Paulding, Defiance, Henry, Lucas, Fulton
Silurian / 408-438 / Adams, Highland, Clinton, Fayette, Greene, Madison, Clark, Champaign, Union, Delaware, Logan, Marion, Hardin, Wyandot, Hancock, Seneca, Sandusky, Wood, Ottawa, Lucas, Henry, Putnam, Allen, Auglaize, Shelby, Miami, Montgomery, Preble, Darke, Mercer, Van Wert, Paulding
Ordovician / 438-490 / Adams, Brown, Clermont, Hamilton, Butler, Warren, Clinton, Montgomery, Greene, Clark, Miami
570-2,500 / 505-570
2,500-3,800 / No Known Outcrops in OH / Hamilton, Butler, Warren, Montgomery, Greene, Miami, Clark, Clinton, Clermont, Brown, Highland, Adams
3,800-4,600 / No Known Outcrops in OH / No Known Outcrops in OH
Proterozoic / Precambrian / No Known Outcrops in OH
Archean
Hadean