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Thesis Biniam Estifanos.pdf (6.49 MB)

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Geophysical Mapping of Concealed Karst and Conduits north of Bellevue, OH

Estifanos, Biniam H
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388079101

Abstract Details

2014, Master of Science, University of Toledo, Geology.
An Abstract of Geophysical Mapping of Concealed Karst and Conduits North of Bellevue, OH by Biniam H. Estifanos Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Geology The University of Toledo May 2014 The Bellevue region consists of thin glacio-lacustrine sediments underlain by a succession of Devonian and Silurian evaporites, carbonates and shales. These formations developed intrastratal karst due to dissolution of gypsum which was followed by subsequent collapse of the voids. This is manifested in surface expressions such as sinkholes, dolines, depressions and springs. However, there are also concealed karsts that lack surface expression. The objective of this study is to test the hypothesis that gravity can delineate subsurface mass deficit and to detect water table variations. The study also tests whether electrical resistivity can detect water table variations and delineate underground rivers that flow toward Sandusky bay. Two topographic depressions about 4 km2 and 2 km2 in area were the target of this study. A microgravity survey was carried out at State Route 269, Strecker and Southwest roads while, dipole-dipole electrical resistivity surveys were done at Strecker road, a field north of Strecker road west and Hale road. A total of 346 gravity measurements and 2 km of dipole-dipole electrical resistivity profiles were conducted. A total of nine gravity lows: four on State Route 269, another four at Strecker road and one at Southwest road were delineated. Their maximum amplitude ranges between -0.075 and -0.26 mGal. The gravity lows are associated with topographic lows. The volume of the void space was calculated from the negative residual gravity and it ranges between 0.12 and 0.69 km3 depending on the density of the infill material. At Strecker road, the dipole-dipole electrical resistivity delineated three 10-20 m wide throats of sediment filled-sinkholes and a low resistivity zone underlies the Columbus limestone. The microgravity survey also suggests these sinkholes are filled with a lower density material. Repeat measurements using both methods detected changes in water table elevation. The study showed that it is possible to map areas of mass deficit within the concealed karst and both methods can detect changes in water table elevation. However, outlining underground rivers from the dipole-dipole data was not successful.
Donald Stierman (Committee Chair)
Richard Becker (Committee Member)
James Martin-Hayden (Committee Member)
94 p.
Geology
Karst; Gravity; Electrical Resistivity; Bellevue; Sinkhole

Recommended Citations

Citations

  • Estifanos, B. H. (2014). Geophysical Mapping of Concealed Karst and Conduits north of Bellevue, OH [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388079101

    APA Style (7th edition)

  • Estifanos, Biniam. Geophysical Mapping of Concealed Karst and Conduits north of Bellevue, OH. 2014. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388079101.

    MLA Style (8th edition)

  • Estifanos, Biniam. "Geophysical Mapping of Concealed Karst and Conduits north of Bellevue, OH." Master's thesis, University of Toledo, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388079101

    Chicago Manual of Style (17th edition)

toledo1388079101
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This open access ETD is published by University of Toledo and OhioLINK.