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Study of Rough Creek Graben Completed by KGS

The final report of a three-year study of the Rough Creek Graben has just been published by the Kentucky Geological Survey at the University of Kentucky. The graben is a deeply buried geologic trench or basin bounded by faults that extends from central Kentucky to southernmost Illinois. This study analyzed this crustal feature and the surrounding area, from the Nashville region up to the southern portions of Illinois and Indiana, for a total area of 67,311 square miles.

One of the goals of the project was to evaluate the possibility that there might be oil or gas resources in the deep geologic formations, particularly the Eau Claire Formation. This is why a dozen exploration companies, as well as the Kentucky Cabinet for Energy and Environment Cabinet, helped to fund the project.

"Unfortunately, we couldn’t confirm that there are oil and gas resources in the graben," says the principal investigator of the project, John Hickman, of the KGS Energy and Minerals Section. "We did identify four areas in the graben where geologic structures could theoretically trap oil or gas. But we can’t actually prove they are there without drilling additional wells."

The project succeeded, however, by taking a major step forward in understanding the geologic structure of the Rough Creek Graben and its surrounding region, according to Hickman. He gathered existing information from more than 1,700 wells in the region, analyzed samples stored in the KGS Well Sample and Core Library, interpreted more than 900 miles of reflection-seismic data, and incorporated data from other KGS research projects where possible. The results of his research are compiled in the new publication, "The Rough Creek Graben Consortium Final Report&" (Contract Report 55, Series XII, 2014).

"Before the project began, we noticed that there were data about the graben from drilling operations and research in the region,&" Hickman says. “But no one had done a cohesive analysis and interpretation of the data. We had more data than knowledge before the project. We hope we've reversed that, now that the project is complete."

His work, for instance, improved the understanding of the Eau Claire Formation in the region. "There is no outcrop of the Eau Claire in the region; it’s buried 7,300 to 16,000 feet deep, making it tough to gather reliable information on it. So, in my opinion, this project has increased our knowledge of the deep geology of the western part of the state." It also provided a better regional understanding of the continental plate beneath North America.
"The Rough Creek Graben Consortium Final Report" can be found at


Subsurface structure of the Eau Claire Formation across the Rough Creek Graben.
Warm colors (darker reds) indicate increasing depth (up to 14,000 feet below sea level). 
Major fault zones are indicated by bold red lines,
and seismic profile data are represented by bold gray lines.

These companies and agencies provided funding for the project: