2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 102-14
Presentation Time: 11:15 AM

NATURAL HYDRAULIC FRACTURING OF THE NEW ALBANY SHALE (DEVONIAN-MISSISSIPPIAN) IN THE ILLINOIS BASIN DURING PLEISTOCENE GLACIATIONS


PERSON, Mark, Dept of Earth & Environmental Science, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, MCINTOSH, Jennifer, Hydrology & Water Resources, University of Arizona, Tucson, AZ 85721, SCHLEGEL, Melissa, Geolgoical Sciences, Brigham Young University, S235 ESC, Provo, UT 84602, RUPP, John A., Indiana Geological Survey, Indiana University, 611 N. Walnut Grove Ave, Bloomington, IN 47405, ELLETT, Kevin, Indiana Geological Survey, Indiana University, 611 Walnut Grove Avenue, Bloomington, IN 47405, GABLE, Carl W., Los Alamos National Laboratory, EES-16, Los Alamos, NM 87545 and BOWEN, Brenda B., Department of Geology and Geophysics and Global Change and Sustainability Center, University of Utah, Salt Lake City, UT 84112

Within the Illinois Basin, freshwater extends down dip into the basin within the New Albany Shale (Devonian-Mississippian). The freshwater limit within the shale corresponds more or less to the southern limit of the pre-Wisconsin glaciation. In 2012, Schlegel used 4He analysis of pore fluids from New Albany to suggest that the freshwater was emplaced during the Pleistocene between about 0.5 to 1.5 Ma. We hypothesize that permeability in the New Albany Shale was enhanced by “natural hydraulic fracturing” caused by increased fluid pressures associated with glacial loading. Numerous open and calcite filled fractures within the New Albany Shales having aperture widths varying between 0.05 to 1 mm have been documented (Salehi et al. 2009). The influx of these melt waters into the New Albany Shale likely transported near-surface microorganisms to depths of 1-2 km, and led to the formation of economically significant quantities of microbial methane. Here we present results from a cross-sectional hydrodynamic-geomechanical model that includes a Mohr-Columb failure criteria for critically stressed faults. Permeability was increased by 1000 fold for all formations within the failure envelope. The region of enhanced permeability beneath the ice sheet facilitated the rapid transport of relatively fresh glacial meltwater to the south. Our model also produced salinity overturns with fresher water underlying more saline pore fluids; a phenomenon which has been observed across the Illinois Basin.

Session No. 102

T169. It's a Cold, Cold World: Permafrost and Glacial Hydrogeology
Monday, 20 October 2014: 8:00 AM-12:00 PM
110 (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.264
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