November President’s Prattle and Fieldtrip Recap

On Saturday October 20, 2007 AGS conducted a field trip to Westcave Preserve and Milton Reimers Ranch Park in western Travis County.  We experienced beautiful weather as we explored the geology and hydrology of those unique lands.  The trip was coordinated by myself, Chock Woodruff and Eddie Collins and attended by about 45 folks.

The trip began at Westcave Preserve with a tour by naturalist John Arhns.  John introduced the geology of the canyon and grotto area and explained the natural fauna of the preserve in great detail.  John explained the transformation over the years as nature (and their stewardship) reclaimed the stressed landscape.

From the preserve the group walked down to Hammetts Crossing where Raymond Slade reviewed the 1952 flood, which as he described it, was the “perfect storm and flood” with a rise of about ~70 ft at Hammetts Crossing!

The geology portion of the trip began with Eddie Collins as he reviewed the lower Cretaceous stratigraphy and walked us through the type section of the lower Cretaceous Sycamore Sand—a sequence of fining upward fluvial facies. The Sycamore Sand (Hosston Formation in subsurface) is part of the lower Trinity Aquifer—increasingly a target for groundwater production in the Hill Country.  One of the accomplishments of the field trip and guidebook was clarification of some of the confusion about the Sycamore and Hammett Shale at this exposure (See the paper by Collins in the guidebook).  Much discussion of the nature of the sediments ensued.

Lunch was in held under the oaks at Westcave—a poster presentation from Tom Hegemier discussed the watershed studies of the LCRA.  In particular Tom discussed some of the recent controversial developments impacting streams feeding Hamilton Pool. 

Our last talk at Westcave was a poster presentation by Al Broun (a preview of his GCAGS poster) in the beautiful exhibit hall.  Al discussed his subsurface geologic work of the Trinity and in recognition of his excellent (and unprecedented) detailed work Andrew Backus (Board President of the Hays Trinity Groundwater Conservation District) bestowed upon Al the “Orbitolina texana” award for excellence.

Next the fieldtrip moved to the climbing area on the Milton Reimers Ranch Park to view the next two formations above the Sycamore Sand. The Hammett Shale overlies the Sycamore Sand and is generally a confining unit for groundwater.  The Cow Creek Limestone is a very porous and permeable unit and principle aquifer of the Middle Trinity aquifer.  In the parking area Eddie Collins displayed 6 boxes of core taken in 1956 by the Shell Oil Co. investigators Lozo & Striklin at Hamilton’s Pool. The core serves as the type section for the Hammett Shale and overlying Cow Creek Limestone.  Participants then proceeded down into the climbing area to view the same stratigraphic units in outcrop.  The climbing area showed the cross-bedded, beach facies of the Cow creek, grading down into the more muddy facies of the lower Cow Creek, or upper Hammett Shale—depending on which reference in the literature you use.

Upon leaving Reimers Park the group stopped in a ditch along the road to view an exposure of mud (floodplain) and sand (channel) facies of the Hensel Sand.  The Hensel Sand overlies the Cow Creek and much discussion focused upon its function in recharge to the Cow Creek (see Woodruff paper). Janie Hopkins discussed the depositional setting of the Hensel and in particular the bizarre-looking calcretions (and other weird names) found in the muddy facies.

The last brief stop was to look at the Corbula Bed of the Glen Rose before heading back to Austin.  The famed Corbula bed divides the Lower and Upper Glen Rose and is used to delineate the upper Trinity Aquifer. 

It was a great trip with a wonderful group of folks. Our hope is that Guidebook #28 is a resource for years to come.  Many thanks to wonderful contributions by the authors and thanks to Steve Ruppel for getting the guidebook printed and Linda McCall for taking care of all the myriad of financial items that go along with these trips.

Fall 2007 Field Trip - Excursion to Westcave Preserve and Reimers Ranch
Trip Coordinator: Chock Woodruff

The AGS 2007 Fall Field Trip will be held on Saturday, October 20, 2007.
Cost: $60. Please sign up by the October 1 Meeting.
Departure: 8:00 a.m. from Sid Richardson Hall parking lot (Lot # 37) off Clyde Littlefield Drive at Red River, UT Campus Participants will provide their own lunch.

Previous Field Trips

Spring 2007 Field Trip - Uranium Mines in Karnes County

Trip Coordinator: Alan Cherepon

The AGS 2007 Spring Field Trip was held on February 17, 2007. The Karnes Uranium Mines offered a unique opportunity for Texas Geologists to study and see, close up, a soon to be inaccessible aspect of Texas Geology. The last of the "good" open pit uranium mines will be reclaimed by the middle or end of 2007. Aspects seen and explained included local stratigraphy of the Jackson Group and overlying Catahoula Formation, the unique mineralogy of the concretion zones, uranium geology and production history, hydrogeology, and environmental aspects of pre-open-pit mining law in Texas. The co-authors and co-leaders of the guidebook and trip include Alan Cherepon, past president, co-author, and coordinator of last year's trip for the AGS, former uranium geologist, resident of Karnes City, and author of a paper on the minerals of the area; Dr. William Galloway, UT Geology Professor Emeritus, author of numerous papers on uranium and depositional systems in Texas, involved in studies of the mine that was the focus of the trip, and leader of past field trips to the area; Jon Brandt, geologist with the Texas Railroad Commission, Surface Mining and Reclamation Division, familiar with the Texas uranium mine reclamation work, and the Texas Uranium Industry, mining and production records, and AGS member; and Mark Beaman, TAMU, who has conducted detailed research on local geology in and around the uranium mines. We'll post photos of the Field Trip soon.

Austin Geological Society's Spring 2006 Field Trip
"Volcanic Features of the Austin Area, Travis County, Texas. "

Trip Coordinator: Al Cherepon

The AGS Spring 2006 Field Trip was held on April 1, 2006. Two of the many highlights of the trip included access to Pilot Knob, and seeing the first lava tube or pillow structure yet identified in exposed volcanic features in the Austin area. The trip included a stop at McKinney Falls State Park. We'll post a summary of the trip soon.

Austin Geological Society's Spring 2005 Wine Field Trip
"Geology, Frontier History, and Selected Wineries of the Hill Country Appelation, Central Texas"

Here are pictures!

Saturday, April 23, 2005

Trip Leader: Dr. Pete Rose
Trip Coordinators: Craig Caldwell and Rima Petrossian

The 2005 Austin Geological Society Wine Field Trip was be held on Saturday, April 23, 2005. Dr. Pete Rose led a field trip to several of Central Texas' wineries, with an emphasis on the 'terroir', or the physical/environmental characteristics, of Central Texas wineries. The Wine Trip included visits to Becker Vineyards, Bell Mountain Vineyards, and Fall Creek Vineyards. Wine, cheese, and a delicious wine-appropriate lunch by In Good Taste Catering was served on the trip. We updated the popular AGS Publication No. 23; The Hill Country Appellation; A Geologic Tour of Selected Vineyards and Wineries of Central Texas: C.M. Woodruff, Jr., Peter R. Rose, and James W. Sansom, Jr.