DETERMINING MINERALOGY TO IDENTIFY STRATIGRAPHIC UNITS IN A HIGHLY-WEATHERED ZONE, GRAPE CREEK ECOLOGICAL PARK, CAÑON CITY, COLORADO

The famous Dakota Hogback of the Front Range, Rocky Mountains, borders the Cañon City Embayment on the western and northern margins. The hogback and associated valleys contain dramatic stratigraphic sections of Ordovician through Cretaceous sedimentary rocks uplifted and tilted during the Laramide Orogeny. Students from several geology field camps, including the Oklahoma State University (OSU) camp, measure these sections and map the area. This study examines section to the west of the hogback near Cañon City, Colorado. At the sample site, which is south of the Arkansas River in Grape Creek Ecological Park, we sampled a suspected fault zone consisting of highly weathered, poorly indurated powdery material and large displaced blocks of Fremont Dolomite. The weathered zone contains the contact of two formations that are possible sources for our samples: the Harding Sandstone, and the Fremont Dolomite. During the 2018 OSU field camp, three samples (A-C) were collected along a transect of the weathered zone, bagged and returned to camp. Once field camp concluded, these samples were transported to Oklahoma State University and x-rayed using a Philips Powder XRD to determine mineralogy. Samples were scanned from 5^o to 55^o 2θ, and cross referenced using XRD spectra of standards. Our initial hypothesis was that the samples would contain a mixture of dolomite and quartz weathered from the Fremont Dolomite and Harding Sandstone, respectively. However, quartz was negligible to absent compared to dolomite and therefore, we propose that the weathered area is a fault zone within the Fremont Dolomite.