Remains of aquatic, marine algae are found in Ohio's Paleozoic rocks but often these fossils are difficult to recognize and identify. Mound-shaped algal-sediment structures known as stromatolites or rounded ones known as oncolites, are found in some rocks in Ohio. They have been recognized from Silurian and Pennsylvanian rocks. Other, larger algae - seaweeds - have been found in Ordovician, Silurian, and Devonian rocks. Of particular note is a probable algal fossil known as Protosalvinia (formerly called Foerstia) that occurs in some abundance in a narrow zone in the Huron Member of the Ohio Shale. These fossils consist of shiny black, branched, lobed, or discoid structures preserved on bedding planes in fresh, unweathered shale.

References

1. Cross, A. T., Gillespie, W. H., and Taggart, R. E., 1996. "The Fossil Plants of Ohio: Introduction, Overview and Nonvascular Plants," in Fossils of Ohio, edited by R. M. Feldmann and Merrianne Hackathorn. Ohio Division of Geological Survey Bulletin 70, p. 370-395.