Understanding the Geology of Portage County as found in the Portage County Park District

The Portage County Parks District in Ohio, manages 12 public parks consisting of 1,300 acres and 14 miles of hike and bike trails, connecting communities across Portage County. This park system offers people great opportunities to experience and understand nature. Education has been a primary goal of Portage Parks, however, the parks lack geologic information that would be readily available for the public. Therefore, there is a greater need for a deeper understanding of how geology has shaped the topography of this county as found in the individual parks. To accomplish this goal, detailed field mapping of the parks was conducted and included a brief description of rock formations and glacial deposits. A geologic map of Portage County was constructed in ArcGIS consisting of multiple layers, including a digital elevation map produced using the microDEM program. Cross sections showing the subsurface geology were also constructed with the aid of ground water well data from the ODNR. This study shows that the rugged topography of the bedrock surface of the county is mostly concealed by a mantle of glacial deposits. Deep valleys cut by pre-Pleistocene and Pleistocene streams form a complex pattern buried beneath the glacial debris. Sediments filling the buried valleys are coarse sand and gravel while in other areas, the glacial deposits are tills of principally fine sand, silt, and clay. The bedrock units in Portage County range from Devonian to Pennsylvanian age and consist of mostly shales and sandstones deposited in ancient marine and delta environments.