INTRODUCTION: This study is a preliminary investigation of the geology of the Pennsylvanian-age rocks at McComish Gorge, the Old Burn Pit, the Pest Control Site, and the Mustard Gas Burial Grounds at the Naval Surface Warfare Center (NSWC), Crane Indiana. The purpose of this investigation is to better understand the geology of the Pennsylvanian-age aquifer bodies that lie beneath each site. More specifically, the purpose is to determine which rock units are potential aquifer bodies, and then to define their general geological and reservoir characteristics. This is being done as an aid to the U.S. Army Corps of Engineers in their site assessment and remediation efforts. Determining the size, shape, and structural dip of the aquifer bodies is also very important for subsurface ground water modeling. For the report on the Rockeye, Dye Burial Ground (DBG), and Demolition (DEMO) sites, this was accomplished by constructing detailed cross-sections, isopach maps, and structure contour maps (Barnhill, 1992). However, additional coreholes at McComish Gorge, the Old Burn Pit, the Pest Control site, and the Mustard Gas Burial Grounds are necessary for map and cross-section construction. Therefore, at present, the size and shape of aquifer bodies encountered in the deep borings from these four sites can, at this time, only be inferred based on previous experience with similar reservoir facies encountered at Rockeye, the DBG, and the DEMO sites. Five coreholes were examined for this report. These coreholes include WES-5c-01 (Old Burn Pit), WES-4c-01 (McComish Gorge), WES-9c-01 (Pest Control Site), and WES-1c-01 (Mustard Gas Burial Grounds). In addition, the Indiana Geological Survey Drill Hole #381 is included. This corehole, drilled for regional stratigraphic correlation purposes, is located near the Landfill Site. A description of the facies succession encountered in this corehole is included here because it may prove useful in planning a future coring program at the Landfill Site. A total of 818.5 feet of Pennsylvanian core taken from the five borings, was examined for this report. The longest core is from the Old Burn Pit (WES-5c-01) which contains 242.3 feet of Pennsylvanian section. The Pest Control Site corehole (WES-9c-01) recovered 132.5 feet of Pennsylvanian section, the Mustard Gas Burial Grounds corehole (WES-1c-01) recovered 126.5 feet of Pennsylvanian section, and the McComish Gorge corehole (WES-4c-01) recovered 98.8 feet of Pennsylvanian section. The Indiana Geological Survey drillhole #381 cored 218.4 feet of Pennsylvanian section.