Date of Graduation

8-2017

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

Liner, Christopher L.

Committee Member

Manger, Walter L.

Second Committee Member

Liner, Robert T.

Keywords

Arkansas; Benton County; Geophysics; Lithostratigraphic; Near Surface; Pedro

Abstract

The roadcut on highway 412 near Pedro, Benton County, Arkansas (MArkUP site L15), has been of geological interest since its excavation in the 1980s. The roadcut is located within the Springfield Plateau and displays formations of Lower Mississippian age. The roadcut contains three mound-like features believed to be olistoliths. This thesis research work adds geophysical evidence to the geological exposure at the site. The purpose of this research is to answer the question of whether near surface seismic methods can be used to extend information at the Pedro outcrop below the ground surface. Specifically, can the top of the Middle Ordovician Everton contact be identified?

Seismic experiments were conducted by the University of Arkansas MArkUP team, investigating parts of the Middle Ordovician through Lower Mississippian succession, using a 48-channel Geode seismograph, sledge hammer source, and seismic acquisition software.

Interpretation of P-wave refraction events estimate that the top of the Middle Ordovician Everton occurs 69 feet below the natural ground surface from the top of the Pedro outcrop at the location of the largest mound, or approximately 31 feet below the surface of the base of the roadcut. Estimation of the Chattanooga-Everton contact involved data acquisition, processing to reduce noise, first arrival event picking and manual inversion to estimate layer depths and velocities. Ray Trace modeling confirmed inversion results and local stratigraphy was found to be consistent. The value of this study demonstrates that shallow seismic data can estimate buried contacts below outcrops and extend geological knowledge in northwest Arkansas.

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