Abstract Even before 1800, geological resources such as chert, iron, limestone, and coal were being utilized from the Pennsylvanian rocks of eastern Ohio and western Pennsylvania. These materials were of great interest to the early geologists of the region. This field trip discusses these products in the context of early grain milling, iron furnaces, and allied industries of Ohio and Pennsylvania in the late eighteenth and early nineteenth century, with a focus on two publicly accessible sites: McConnells Mill Park in western Pennsylvania, and Mill Creek Park in eastern Ohio. These parks contain publicly accessible gristmills and iron furnaces, and outcrops. We also provide new observations on cultural materials related to these industries, especially iron-furnace slag and millstones.

Core drilling in poorly exposed Lower and Middle Pennsylvanian strata of the Pottsville and Allegheny Groups in northeastern Ohio has led to a better understanding of the character and distribution of key Pennsylvanian marine units. Two unknown and three previously known marine and marine-influenced units are identified in strata of this area in the Pottsville Group. Distribution and facies maps of these marine units in northeastern Ohio suggest pre-Pennsylvanian erosional paleotopography and periodic movement on subsurface faults locally influenced depositional patterns. Additionally, the traditional placements of the Lowellville marine unit and the Quakertown coal in the stratigraphic column for Ohio appear to be in error. The new data suggest the need for an extensive revision of the geologic column for the Lower and Middle Pennsylvanian rocks in Ohio and the need to develop a more representative stratigraphic nomenclature and framework for these rocks. Core drilling referenced in this investigation was done as part of the recent statewide mapping and core-drilling program conducted by the Ohio Geological Survey.