Publication Date


Document Type


Committee Members

Ernest C. Hauser (Committee Chair), Doyle R. Watts (Committee Member), David F. Dominic (Committee Member)

Degree Name

Master of Science (MS)


This study focuses on northern Terre Haute, Indiana, where seven 2D seismic reflection time sections were collected by CountryMark and donated to Wright State University. Geologically, the area is on the eastern margin of the Illinois Basin. Two of these seismic lines display significant relief along a continuous, high-amplitude horizon approximately 180 milliseconds in two-way traveltime depth. This horizon was previously interpreted by CountryMark to be a Silurian reef core of the type common in this region of the Illinois Basin; however, other seismic lines within the data set display no relief. Furthermore, borehole logs within the area show no such relief at the equivalent depth of around 1700 feet. Therefore, the apparent structural high is an artifact within the two seismic lines, and can be called velocity pull-up. Various analyses were conducted to examine the causes of this velocity pull-up. The near-surface, within this region, contains many surfaces that may give rise to a velocity pull-up, including (1) the layer of weathered Pennsylvanian bedrock; (2) the Mississippian-Pennsylvanian Unconformity; and (3) an unconformity within Pennsylvanian section. It is possible that each of these surfaces could have enough relief to induce the observed velocity pull-up, and these possibilities were evaluated utilizing a combined analysis of Bouguer gravity, first-arrival traveltime tomography, passive seismic, and well log correlation. These multiple analyses show there is no Silurian reef core but a more complex velocity-inducing feature from a combination of the Mississippian-Pennsylvanian Unconformity and a shallower paleovalley fill.

Page Count


Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded


Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.