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Field trip to the Permian and Cretaceous Rocks of the Callahan Divide area south of Abilene General Geology • As we go south from Abilene we go into the area of the Callahan Divide. Here we see mesas capped with Cretaceous resistant rocks as shown on the diagram in the next slide. Cross section of the local geology Limestone of the Fredericksburg Gp N Abilene Clear Fork Shale Antler Sand S Locality Sketch Map Rt277 Abilene Buffalo Gap Rd 3 1 Coron -ado’s Camp 2 Lake Abilene Rt. 89 Buffalo Gap Field trip stops Stop #1 • Shales of the Clear Fork Gp • Permian age • Probable environment of deposition floodplain Gps coordinates: N32deg 15.015min W99deg 53.576min Plant fossils in the reddish shales of the Clear Fork Gp Shales of the Clear Fork Gp, ruler is 1ft.long Shales of the Clear Fork Gp breaking down to a residual soil, green ruler is 1 ft. long Lake Abilene • This is a man made lake created in order to provide a reliable water supply for the city of Abilene Photo take from: N32deg 13.886min W99deg 53.479min Lake Abilene Another view of Lake Abilene Stop #2 • Antler Sand of the Trinity Gp • Cretaceous • Probable environment of deposition - beach environment GPS coord: N32deg 14.896min W99deg57.100min Antler Sand along the highway Antler Sand with GSA photo scale Another view of the Antler Sand with GSA photo scale Antler Sand with car for scale Stop #3 • Limestone unit of the Fredericksburg Gp • Cretaceous age • Probable Environment of Deposition shallow offshore marine GPS coord: N32deg 16.396min W99deg 56.777min Limestone of the Fredericksburg Gp Another photo of the Fredericksburg Gp limestone that sits on top of the Antler Sand Remember • Safety first and always on field trips • These slides and other information give an idea of the geology at various locations but the best way to get to know it is to really visit these sites in person - geologic observations in the field form the raw data on which the geosciences are based. • A Reference follows on next page. Reference • 1. Taylor, Howard, 1978,Occurrence, Quantity and Quality of Groundwater in Taylor County, Texas. Texas Department of Water Resources. Report 224. To return: • If on the web return to the main field trip webpage by clicking the green back button in the Explorer window.