Geology of the Western Llano Uplift, Fredericksburg to Mason, Texas

R. LaRell Nielson, Chris Barker

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This year's Texas Academy of Science Geology Field Trip will visit six interesting locations in the Texas Hill Country (Figure 01). At Bear Mountain quarry, former location of Balanced Rock, the contact between the Precambrian Bear Mountain Pluton and surrounding Cretaceous Edwards Group will be examined. Along Crab Apple Creek, south of Enchanted Rock, excellent exposures of the Hickory Sandstone provide the opportunity to study sedimentary structures and cross-bedding that represent the Sauk sequence deposited during the Cambrian Period (Figure 02). Next we will look at a Gypsum Mine and deposits of evaporites from the Cretaceous Kirschberg Lagoon (Figure 03 and 04). We will then take the back roads of the Llano Uplift to an interesting exposure of the Precambrian- Cambrian boundary represented by a nonconformity that shows the transgression of Cambrian seas (Sauk Sequence) across the eroded Precambrian Cherry Springs Pluton (Town Mountain). Next, we will stop at Comanche Creek south of Mason, Texas, to study complex folds in the Packsaddle Schist. These folds represent deformation of the Llano Uplift area during the Greenville Orogeny 1.2 Ga years ago. The last stop on the field trip will be at White’s Crossing near the Llano River, to ponder the origin and development of spectacular stromatolites exposed by uplift along faults in the area and down cutting of the Llano River. And finally, since no trip to the Llano Uplift is complete without a stop at a Coopers BBQ, we will have lunch at the Coopers in Mason, Texas.

Original languageUndefined/Unknown
JournalFaculty Publications
StatePublished - Mar 2 2013

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