GENESEO, MARCELLUS, AND UTICA CORE DESCRIPTIONS AND ANALYSIS FROM THE RIDGE AND VALLEY OF CENTRAL PENNSYLVANIA; HOWARD TO MILL HALL QUADRANGLES, CENTRE AND CLINTON COUNTIES, PENNSYLVANIA

Since the increase of horizontal drilling practices for natural gas exploded in Pennsylvania, researchers have been trying to better understand methane-producing black shale source rock formations as opposed to reservoir rocks of conventional well targets. Characterizing these formations can prove difficult due to the lack of unweathered outcrop or having limited borehole data such as rock chips or geophysical logs for study.

The primary formations of interest include the Geneseo, Marcellus, and Utica. In 2015 a STATEMAP mapping project in the Beech Creek 7.5-minute quadrangle included the drilling of three cores for stratigraphic correlation across sections of minimal outcrop exposure. These cores covered all of the known methane-producing black shales: the Burket Member of the Harrell Formation (Geneseo), Marcellus Formation, Needmore Formation, Mandata Member of the Old Port Formation, and Antes Member of the Reedsville Formation (Utica, Point Pleasant). Sequence stratigraphy and formation transitions were captured through centimeter scale core descriptions and mapping correlation to successfully complete the focus of our research. Other tests run on each core included total organic carbon, vitrinite/bitumen reflectance, methane isotope analysis, and x-ray florescence. A full suite of geophysics was also captured on the Utica core hole.

Despite concerns about near-surface core in the ridge and valley having skewed results due to multiple orogenies affecting the thermogenic properties, most results were consistent with results from deep wells. The only inconsistency observed was from sampling procedures that may have allowed oxidation to influence methane isotope ratios. Further research needs to be done on near-surface or near-outcrop samples for methane isotope analysis and the associated oxidation effects. All of the descriptions, test results, and the cores themselves are available through the Pennsylvania Geological Survey core library. The data are open for use in further research and the core is available for additional testing in accordance with the Survey’s shared data and sampling procedures.