Date of Award
Master of Science - Geology
Julie M. Bloxson
R. LaRell Nielson
The Utica shale is an extensive gas shale play within the Appalachian Basin, expanding from Quebec through New York, into Pennsylvania, West Virginia and Ohio. Currently a target for gas exploration, it is also the source rock for much of the Paleozoic reservoirs throughout the basin. However, the Utica-Point Pleasant lithology varies significantly across the Appalachian Basin which can make it challenging to characterize.
The Utica shale Play consists of the Trenton/Lexington Limestones, Point Pleasant Formation and Utica shale. The Point Pleasant Formation and Utica shale are often grouped together, especially in Ohio because they are difficult to visually distinguish from each other and their contact is not always marked by a change in log values. Here we show that chemostratigraphy reflects changes in depositional and facies characteristics of the Utica shale and Point Pleasant Formation.
For this study, two cores were analyzed using a handheld x-ray fluorescence (HH-XRF) spectrometer along with core descriptions, x-ray diffraction (XRD) and total organic carbon (TOC) data to interpret the depositional environment. Hierarchical clustering technique was used to identify five chemofacies which reflect the geochemical variability present in both cores. Six chemozones were identified and correlated using the chemofacies coupled with stratigraphic plots of selected major elements, trace metals and TOC. Detrital influx analysis revealed that the Utica-Point Pleasant interval in both cores were deposited in different water depths resulting in different amounts of terrigenous input. Paleoredox conditions revealed the Farley core was deposited in oxygenated bottom waters which account for the depletion of trace metals throughout the core. In the Tracker core, analysis showed that bottom-water conditions at the time of deposition varied between anoxic and euxinic. The Tracker core shares similar bottom-water conditions present in the Sebree Trough in Kentucky and is believed to have been deposited in an extension of the trough into northeast Ohio. The Farley core appears to have been deposited outside this trough and likely in the Utica-Point Pleasant basin. Overall the study supports the existence of different depocenters across the area with different conditions at the time of deposition.
Kemeh, Barbara and Bloxson, Julie M., "Geochemical Characterization of the Utica Shale Play using XRF-Based Chemostratigraphy in Ohio" (2021). Electronic Theses and Dissertations. 383.
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