XRF ANALYSIS OF DEVONIAN TO MISSISSIPPIAN LITHOFACIES FROM DRILL CORE LYCO081_0341, LYCOMING COUNTY, PENNSYLVANIA

Core LYCO081_0341 was drilled in the Appalachian Plateau of Lycoming County, just north of Williamsport, PA as part of bedrock mapping in the Trout Run quadrangle through the STATEMAP program. The goal of this work was to document the lithofacies and depositional environments of the upper Catskill Formation (Devonian), the Huntley Mountain Formation (Devonian-Mississippian), and the lower part of the Burgoon Sandstone (Mississippian). In addition to the unit description and documentation of facies, this presented an excellent opportunity to utilize portable XRF (x-ray fluorescence) technology to acquire compositional data from the sandstone, siltstone and claystone in these formations that record fluvial deposition.

The XRF data were acquired with a Thermo Scientific Niton XL3t GOLDD+ XRF analyzer at a sample interval of approximately 1 ft. for the entire 1003.2 ft. length of the core. Samples were analyzed for approximately 120 seconds per sample. The results of the XRF analysis shows a strong correlation of the gamma-ray log with curves of the potassium and aluminum composition. These elements are in higher concentrations in intervals of siltstone and claystone and are associated with the occurrences of clay minerals. The distribution of silicon (Si) showed an inverse relationship to the gamma-ray log signature. Sandstone intervals showed higher Si than that of the finer-grained zones due to the increased amount of quartz. The occurrence of iron had a similar pattern to that of the gamma ray curve probably due to the presence of reddish siltstone and claystone in the fine-grained intervals. Calcium (Ca) concentrations were higher along the base of channel sandstones as calcite cements. Higher Ca within the finer-grained overbank deposits occurs in calcareous nodules in paleosols and in intraformational conglomerates that contain significant calcareous rip-up clasts. Minor elements such as uranium, thorium, copper, zinc, titanium and zirconium all had similar lithologic trends in that concentrations were lower in sandstone and higher in the siltstone and claystone intervals. This work suggests that portable XRF technology is suitable for the creation of synthetic logs that can be correlated with well log data.