GAMMA RAY AND STRATIGRAPHIC CORRELATION OF GEOLOGIC UNITS AT MCCHESNEY FIELD STATION

The objectives of this project were to: 1) gain hands-on experience with an air rotary drill rig and its parts by drilling at least one 250 ft. test hole at the Western Kentucky University McChesney Field Station; 2) correlate lithologies identified in the test holes with the same rock units exposed in nearby outcrops; 3) use gamma ray spectroscopy to characterize rock and sediment types down the test holes. A Standard Operating Procedure (SOP) was developed during this project and will be made available for current and future undergraduates to learn drilling procedures and better prepare for professional careers. The impetus for this project was to obtain experience in drilling techniques which are generally not covered by academic coursework.

This drilling and geophysical study was conducted at the McChesney Field Station, a 140-acre parcel of land along the Green River in northern Warren County, KY. The area is in the southeast portion of the Illinois Basin, exposing rocks of upper Mississippian and lower Pennsylvanian age. The test hole was drilled through five lithologic units using an air rotary drill rig made available by a local contractor. These units are (in order of increasing age): Big Clifty Sandstone, Haney Limestone, Hardinsburg Sandstone, Glen Dean Limestone, Tar Springs Sandstone, and the Vienna Limestone. A local well service company conducted downhole gamma ray readings, which measured the spectral variation of naturally occurring radiogenic potassium, uranium, and thorium isotopes emitted from the strata. These readings were used to produce E-Logs that show the characteristic gamma ray emission of each unit. A handheld gamma ray scintillometer was used to produce a vertical profile using outcrops exposed throughout the field area. The downhole readings were then correlated with the outcrop readings. Rock cuttings from the initial drilling were collected, examined, and archived for correlation to hand samples with the handheld scintillometer in and outside of the classroom. These will be available for future use correlating the units at the McChesney station with other locales (e.g. WKU Green River Biological Preserve approximately 30 miles to the east).