Date of Award

4-2018

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. Alan E. Kehew

Second Advisor

William A. Sauck, Ph.D.

Third Advisor

Robb Gillespie, Ph.D.

Keywords

Geology, glacial, geophysics, horizontal to vertical spectral ratio (HVSR), tunnel valley

Access Setting

Masters Thesis-Open Access

Abstract

This study utilizes the Horizontal to Vertical Spectral Ratio (HVSR) technique to map bedrock topography in the Portage and Schoolcraft NW quadrangles, Kalamazoo Co., MI, looking for buried bedrock valleys. Glacial sediment-landform assemblages dominate the study area, due to multiple advances of the Laurentide Ice Sheet (LIS). Tunnel valleys, which are one type of buried valley, are eroded by subglacial meltwater and commonly filled with the coarser varieties of glacial outwash, making them potential aquifers. The HVSR technique measures the ratio of horizontal to vertical ground motion, excited by ambient seismic noise, resulting in a peak at the resonance frequency. I took 308 HVSR recordings of resonance frequency and used these values to calculate sediment thickness. This was accomplished with a calibration curve generated at 13 control wells, using the power law regression equation Z = af0b. The constants a and b are 101.36 and -1.46. Bedrock relief was determined to be 370 ft (112 m), including three bedrock valleys. One of these valleys is interpreted to be a Saginaw Lobe tunnel valley, due to its steep relief, surface expression, and orientation parallel to Saginaw Lobe flow direction. The two other valleys are interpreted to be the remnants of a pre-glacial drainage network. All three valleys contain several hundred feet of glacial drift, which may contain potentially valuable aquifers.

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