INTERACTIONS BETWEEN PROVENANCE, PALEOCLIMATE, AND PRODUCTIVITY IN THE DEVONIAN MILLBORO SHALE, NORTH-CENTRAL WEST VIRGINIA

Understanding the mechanisms that drive the production, transportation, and deposition of fine-grained sedimentary rocks in basins, including clay minerals and organic-matter, is important for understanding and predicting mudrock properties. Mudrocks are geologically significant due to the influence their formation has on the global carbon cycle that regulates the evolution of Earth’s biosphere and climate systems. The variability of mudrock properties is poorly understood because far fewer studies have attempted to constrain paleo-flux of clay and silt to sedimentary basins compared with coarser material, such as sand and gravel. To address this issue, our work is focusing on establishing the provenance of the Middle Devonian mud-rich sediments in the central Appalachian Basin through study of mudrock samples of the Millboro Shale. The Millboro Shale consists of both the Marcellus Shale and lower Mahantango Shale, which were recovered from the Marcellus Shale Energy and Environment Laboratory (MSEEL) project directed by West Virginia University in collaboration with Ohio State University and the U.S. Department of Energy.

Preliminary XRD analysis of 35 samples was performed to assess bulk mineralogy, determined using the reference intensity ratio (RIR) method. Results show the samples are mainly dominated by muscovite/illite (approximately 40-60%), quartz (~20-40%), and pyrite (~10-15%). These findings are consistent with previous XRD analyses performed on another well in Monongalia Co. by the Eastern Gas Shales Project in the 1970’s. Other minor minerals found in the samples include calcite, dolomite, albite, and barite. Thin-section petrography is needed to evaluate diagenetic versus detrital origin of these phases. Additional analyses to be completed include bulk-sample major-element XRF and Sm-Nd radioisotopic dating. The objective is to further constrain provenance evolution of fine-grained Middle Devonian sediments in the central Appalachian Basin.