Master of Science, The Ohio State University, 2012, Geological Sciences
In 2011, Ohio State University began drilling wells for a geothermal heating and cooling system to upgrade several dormitories. The drillers encountered problems with collapsing boreholes and very high permeabilities at multiple depths within the Columbus Limestone, Salina Undifferentiated, and the Tymochtee and Greenfield dolomites. The driller reported two high permeability zones underlying the campus: one at 140-150 feet deep, and another at depths of 280 to 360 feet. The shallow zone corresponds to the depth of the Columbus Limestone and the deeper zone corresponds to the Salina Undifferentiated and the underlying dolomite units.
The upper permeability zone coincides with the known cave zone within the Delaware and Columbus limestones, which house the Ohio Caverns and the Olentangy Indian Caverns. More in-depth study of this zone's characteristics through quarry visits and core description reveals traditional continental or epigenetic karst features such as flow channels, dissolution along bedding planes, and missing core. This paleokarst zone was created by groundwater flow at or just below the water table and is a form of epigenic karst.
The depth of the lower permeable zone coincides with that of the Newburg Zone. Further study of the lower permeable zone based on core descriptions, quarry visits, geophysical logs, borehole video, and thin sections reveals evidence for extensive karstification in the form of vugs, dissolution chambers, enlarged fractures, spongerock, and missing core. The dissolution chambers are caves that have no evidence of flow passages leading in or out of them, suggesting that they are mixing chambers. These appear to be Silurian analogues to modern flank-margin caves that form on the flanks of carbonate islands where the fresh-water lens meets seawater. These flank-margin caves have been extensively described in tropical regions around the world. Based on the equatorial location of Ohio during the Late Silurian Period, the environmen (open full item for complete abstract)
Committee: E. Scott Bair PhD (Advisor); W. Berry Lyons PhD (Committee Member); William I. Ausich PhD (Committee Member)
Subjects: Environmental Geology; Geology