GEOLOGICAL MAPPING OF LATE CRETACEOUS TO LATE EOCENE STRATA WITHIN THE INDIAN CREEK AREA, BUFFALO GAP NATIONAL GRASSLANDS, SOUTH DAKOTA

During the summer field season of 2012, it was recognized that a detailed geologic map of the Indian Creek area within the Buffalo Gap National Grasslands of South Dakota could be established. According to current knowledge, no detailed geologic map of the permitted field area has been published. Therefore, a preliminary map that includes members (Ahearn, Crazy Johnson, and Peanut Peak) of the Chadron Formation as well as the Chamberlain Pass and Pierre Shale Formations has been constructed. Each member and formation were located, measured, lithologically described, and compared to previous interpretations. Other collected data consisted of coordinates and elevations between stratigraphic boundaries. This information was acquired using a Trimble Geo XH with Terrasync 5.30 software. Once field data was transferred into ArcGIS 10.0, a map scale of 1:8000 was selected to show detail covering an area of 1.4 km². The data was overlaid with Digital Raster Graphs (DRG) and Digital Orthophoto Quarter Quadrangles (DOQQ). Contact lines of stratigraphic boundaries were digitized through coordinate points and correlated with surface topography to create a current geologic map. A detailed map of discernible stratigraphic units within the Indian Creek area will be a valuable tool for future paleontological and geological investigations. Since, more information is needed to cover the entire designated field area of 9 km², field work will continue in the summer of 2013 to obtain the necessary data for completion of this project.