Paleontology and geology
During the Early Carboniferous (Mississippian), sediments from the eroding Appalachian Mountains to the east formed extensive marine deposits of muds and silts. Brachiopods are common fossils of this time. The Late Carboniferous brought the development of large deltaic systems>, a prevalence of both nearshore marine and terrestrial conditions, and only rare occurrences of oceanic conditions. Coal-forming swamp environments, present in many parts of eastern and southeastern Ohio, were an important part of these vast deltas. Fossils include lycopod trees and sphenopsid vines.