Geochemistry and Depositional Environment of the Union Springs Member of the Marcellus Shale in Pennsylvania

Open Access
Bracht, Reed Owen
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 23, 2010
Committee Members:
  • James Terry Engelder, Thesis Advisor
  • Michael Allan Arthur, Thesis Advisor
  • Terry Engelder, Thesis Advisor
  • trace metals
  • Union Springs
  • Marcellus Shale
  • black shales
High resolution geochemical and lithologic analysis of the Union Springs Member of the Marcellus Shale in two cores from central and southwest Pennsylvania indicate that during the onset of deposition of organic-carbon rich sediments the clastic fraction of the sediments was relatively minor. Redox conditions in the sediment pore waters and at least a portion of the water column appear to have been euxinic, while phosphorous was being effciently recycled to the surface waters, thus fueling further productivity. Above this basal interval, the clastic fraction increased sharply and remained elevated relative to the basal portion for the remainder of Union Springs Member deposition. The sediment pore waters and water column became increasingly oxygenated and phosphorus recycling was less effcient. This upper portion of the Union Springs is characterized by considerably less organic-carbon enrichment. Additionally, Uranium-TOC (total organic content by weight percent) crossplots indicate the quantitative association between organic-carbon and uranium is site specific. Thus, a given predictive model for TOC based on spectral-gamma derived uranium concentrations may not be applicable to all regions of the basin, regardless of the spectral gamma logging tool's ability to accurately measure uranium concentrations.