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High-Resolution Subsurface Mapping of Depositional Cycles Within the Lower Part of the Huron Member of the Ohio Shale: Detailed Snapshots of Basin Development in Central and Eastern Ohio

Abstract

As part of the collaborative Midwest Regional Carbon Sequestration Partnership project, administrated by Battelle Memorial Institute and funded by the U.S. Department of Energy, the Ohio Department of Natural Resources, Division of Geological Survey evaluated the utility of strata in the Appalachian Basin for carbon utilization and sequestration. Research focused partially on developing a high-resolution stratigraphic framework for the numerous Upper Devonian black shale units in Ohio to help characterize their potential for carbon sequestration via adsorption of CO2 molecules onto organic particles. The lower part of the Huron Member of the Ohio Shale (Famennian Stage, Devonian System) is one potential target for carbon storage. It has a high average total organic carbon (TOC) concentration, but the distribution of TOC within the unit varies depending on both stratigraphic position and geographic location. Subdividing the lower Huron into chronostratigraphically meaningful units is useful for future work to precisely characterize the spatial distribution of TOC in the lower Huron, and to understand the geological factors that contributed to TOC deposition and preservation. The stacked gray and black shale layers of the lower Huron provide excellent markers for high-resolution correlation—they appear to be cyclical and were likely caused by glacio-eustatic sea-level variation. Eight high-frequency cycles superimposed on two third-order depositional sequences were identified in 789 wells across eastern Ohio using gamma-ray and bulk-density geophysical logs. Isopach maps created for each cycle illustrate that the location and size of depocenters within the study area changed during the deposition of the lower Huron. The close association of depocenter development and evolution with basement structural features indicates considerable structural control of basin bathymetry. On a broad scale, regional depositional strike became parallel to the Akron magnetic boundary and the Cambridge Cross-Strike Structural Discontinuity during cycles 4-8, indicating that these features localized movement during intervals of widespread basin subsidence. Several smaller, local-scale bathymetric characteristics appear to have been controlled by basement faults. A zone of thin strata in northwest Columbiana County during seven of the eight depositional cycles likely represents a bathymetric high caused by contractional overstepping between the Smith Township, Suffield, and Akron fault systems and the Highlandtown Fault. Subsidence along three unnamed basement faults in Belmont County appears to have led to the development of a sub-basin during cycles 5-8. The cycles likely represent the long eccentricity orbital variation, but additional chronostratigraphic data combined with orbital tuning is required to determine the duration of the cycles with more certainty.