The Organic Geochemistry And Trace Element Analysis Of The Sunbury Shale Of Ohio

Author : Aaron L. Evelsizor
Publisher :
ISBN 13 :
Total Pages : 125 pages
Book Rating : 4.:/5 (125 download)

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Download or read book Preservation of Organic Matter Within the Lower Huron Member of the Ohio Shale (Devonian), Scioto County, Ohio written by Aaron L. Evelsizor and published by . This book was released on 2020 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: A potential target for future unconventional hydrocarbon exploration including enhanced recovery of natural gas and CO2 sequestration, the lower Huron Shale Member of the Ohio Shale (Devonian) (`lower Huron’) is one of the most regionally extensive Devonian mudrocks in the Appalachian Basin. Understanding the paleodepositional conditions that aided in the preservation of organic matter in this unit is critical for assessing its viability as a potential hydrocarbon play. Multiple analyses were conducted on representative lithologies at a sampling frequency (n=16) of approximately every 7.8 ft (2.4 m) from a core located in Green Township, Scioto County, Ohio. Measurements include a high-resolution spectral gamma core scan of the entire lower Huron interval, and transmitted and reflected light and SEM imagery of thin sections. 13C values of the organic carbon and total organic carbon (TOC) measurements were taken on core subsamples (n=13), whereas powdered sample splits were utilized to determine mineral weight percent (from XRD measurements) and major and minor trace elements (from XRF/ICP-MS measurements). Mercury intrusion capillary pressure porosimetry was also used to determine porosity from whole-rock core fragments (n=7). Based on previously published data, 13Corganic values average -29.9 ± 1.13 and are indicative of distal marine facies. Lithologies are dominated by organic-rich laminated shale, and are composed predominantly of quartz, illite, mica, and significant amounts of preserved organic material inferred to have been derived from terrestrial plants and varied marine prokaryotes and eukaryotes. TOC and porosity average 6.7 ± 1.25 and 2.7 ± 0.69 percent, respectively, across the 124 ft (38 m) lower Huron interval. Chem-stratigraphy of trace-element redox proxies (V/V+Ni, V/Cr, Ni/Co) of both the study core and additional published datasets suggest sediment accumulation occurred under a range of oxic to dysoxic and even euxinic conditions in the regional study area, and across several mineralogically distinct lithotypes. Furthermore, significant trends in the relative degree of anoxia are positively correlated to existing published data acquired from equivalent strata located 50 mi (80 km) from the studied core, located in modern-day north central Kentucky and Washington, Ross, and Lorain Counties in Ohio. Organic matter deposition was influenced by fluctuations in siliciclastic flux caused by falling seal-level during regressive episodes and migrating depocenters, and by times of high productivity fueled by increased nutrient-rich terrigenous influx. Rapidly deposited material and subsequent O2 depletion appear to be the main drivers of organic matter preservation, which occurred primarily under alternating sub-oxic to euxinic conditions.