Hill County Trinity Lithostratigraphy: Surface to Subsurface In Blanco and Hays Counties, Texas
Saturday, November 12, 2011
Fieldtrip Leaders/contributors: Brian B. Hunt, Alex S. Broun, Ronald Fieseler, Brian A. Smith, Doug Wierman, and Chock Woodruff (and perhaps a few others)
Destination: Northern Blanco and Hays Counties
Depart: 0800 from the Pickle Center parking lot at the East (Main) Entrance
Cost: TBD, sign-up at the first and second AGS meetings
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This trip is meant as a follow-up and compliment to the recent publication titled Hydrogeologic Atlas of the Hill Country Trinity Aquifer (Wierman et al., 2010), which AGS supported. Attendees will visit unique locations and a nearly continuous measured section of the Trinity Group centered along Flat Creek in northern Blanco and Hays Counties. This trip is a hands-on geologic fieldtrip with hammers, acid, and hand lenses encouraged. Participants will visit the Hammett Shale, and some unique exposures of the Cow Creek and Hensel on a private ranch. Then participants will walk from the top of the Cow Creek through a nearly continuous exposure of the Hensel, lower Glen Rose, and into the upper Glen Rose. The focus of discussion will be on the relationship of the Trinity Group rocks (as seen in outcrop) and how they influence groundwater availability in Hays County (Hill Country Trinity Aquifer). Geophysical logs and cuttings from boreholes will be presented during lunch as will other hydrogeological information.
Time allowing, additional stops could include Pedernales Falls to look at the Paleozoic and Hosston (lowest unit of the Trinity Group) and a road cut near the town of Blanco looking at the Trinity-Fredericksburg transition.
Participants will receive a guidebook containing maps and measured sections in addition to select plates (small) from the Hydrogeologic Atlas. This trip requires more than a mile of walking up hill along this unique exposure and some uneven and rough hiking along Flat Creek. Please bring your lunch and standard field gear (water bottle, hat, and sturdy hiking shoes or boots).