Texas' faults exposed!

If you’re not a geologist you might have thought the headline referred to some Lone Star State-bashing, but it’s really all about a bit of the state’s geology that researchers can now see up close and personal.
The Southwest Research Institute, a San Antonio non-profit R&D organization, and four major oil companies have joined in a multi-year project to study a section of the Hidden Valley Fault near Canyon Lake in Comal County that was exposed following a 2002 flood.
It’s being billed as “an unprecedented natural laboratory for geologists” for studying faults found in limestone aquifers as well as petroleum reservoirs in Texas and around the world, according to David Ferrill, director of the Earth, Material, and Planetary Sciences Department of SwRI’s Geosciences and Engineering Division.

Texas inside-out.

From a SwRI press release:

“The flooding, brought on by 35 inches of rain in eight days, sent a wall of water more than seven feet tall over the 1,250-foot wide spillway and into a narrow valley behind Canyon Dam. The 70,000-cubic-feet-per-second torrent cut into the valley floor, removing thousands of cubic yards of soil, bedrock and limestone blocks.
When the floodwaters receded, what remained was a pristine gorge containing rocks that had not been exposed since dinosaurs roamed the Earth more than 65 million years ago.
Besides containing the best exposure of part of the Upper and Lower Glen Rose limestone formation available in Texas, the gorge also reveals a nearly continuous, 2,600-foot section of the Hidden Valley Fault. This fault is a fracture zone along which the Glen Rose Formation strata were displaced, or slipped nearly 250 feet downward, toward the Gulf of Mexico. Although the fault was known and had been studied in the 1960s when Canyon Dam was built, no one has had a clear view of it until after the flood of 2002.”

The Edwards Aquifer Authority and the U.S. Army Corps of Engineers provided some early funding to study the geologic structures of the Edwards and Trinity aquifers as seen at the gorge, but the oil companies involved are looking at the bigger picture.

“Because this fault is typical of thousands of miles of mapped faults in the Edwards and Trinity aquifers in the Balcones Fault Zone, the interplay of water and layering, faults and fractures in the Canyon Lake Gorge provides a remarkable opportunity to gain new insights into limestone aquifer behavior, Ferrill said.”

One might think after a century of oil and gas exploration and production in Texas we’d know all there is to know about geology here. But any oil company geologist would tell you to think again. Judging from all the new drilling rigs and reactivated wells one can find all around Texas, we’re far from done with exploration in the Lone Star state.