The Permian El Capitan reef complex in the Guadeloupe Mountains on the Texas-New Mexico border. After the flight from Dallas to El Paso we transferred to the tour bus for a geological field trip around West Texas.

As an undergraduate I wrote a long essay on carbonate reefs referring to the Guadalupian El Capitan as the prime ancient analogue of modern build-ups. It was a real buzz to actually visit it and hit the rocks with a hammer!