Postcard from the Permian Basin, West Texas and New Mexico

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Tennessee Tech earth science students and faculty find shade under the Carlsbad Caverns National Park entrance sign. Photo courtesy of Geoff Gadd.

What did West Texas and New Mexico look like during the Permian, 260 million years ago? That’s the question six Tennessee Tech earth science students attempted to answer on a nine-day field trip, May 23-June 1, 2013. Over the course of the spring semester, GEOL 4810 students Kolbe Andrzejewski, John Baird, Geoff Gadd, Joe Kalbarczyk, Jordan Sachs, and Paul Woods became experts on Permian depositional environments. Then, they headed west to find out what’s in them there western hills?

After two days of crossing the U.S., the group arrived at the Carlsbad KOA in New Mexico just in time for a desert thunderstorm with hail and high winds. It turned out to be the only precipitation students saw until the drive back east. Temperatures in the desert hovered in the 90s during the days and cooled off into the 60s at night.

As the trip progressed, the group explored a series of depositional environments from the Permian, including: (1) carbonate back-reef, reef, and fore-reef deposits; (2) carbonate and clastic slope rocks; (3) clastic deepwater formations; and (4) evaporite deposits. The group also made stops at Carlsbad Caverns to view karst features and the Permian Basin Petroleum Museum to learn about oil/gas exploration in the prolific reservoir system.

Field Trip Map

The five day field trip explored the Guadalupean Reef system, from the back-reef deposits (Day 1, blue route and stops) to the reef, slope and deepwater deposits (Day 5, purple route and stops).

To view the complete route map with geologic stops in Google Maps, click here.

DAY 1: Back-reef deposits

Led by Kolbe Andrzejewski, the first day of field work focused on facies and deposits of a back-reef environment. Stops 1 and 2 were located approximately 12 miles landward (northwestward) of the Guadalupean fault scarp, the modern-day expression of the ancient reef front. The group began by describing dolomite wackestones exposed in a dry desert riverbed known as Rocky Arroyo. At a second stop closer to the shelf edge, prominent dolomite outcrops contained  abundant algal stromatolites but few other fossils.

Algal stromatolites in a dolomitic wackestone.

Algal stromatolites in a dolomitic wackestone. Photo by Dr. W.

Tidal Channel

TTU student Paul Woods stands in front of a dolomite-filled sedimentary body, interpreted to be a tidal channel located in the back-reef environment. Photo by John Baird.

After lunching in the shade of the van, the group drove south of Carlsbad to Dark Canyon, where the carbonate facies were strikingly different. Located approximately 1 mile from the reef front, the rocks of Stops 3 and 4 were well-bedded pisolitic dolomite grainstones.

Pisolites in a dolomitic grainstone. Photo by John Baird.

DAY 2: The Reef – Guadalupe Peak Trail

The group got an early start on June 27th, and Day 2 was spent hiking Guadalupe Peak Trail in Guadalupe Mountains National Park. Although collecting rocks in the park was prohibited, folks had an opportunity to see spectacular rhombohedral calcite crystals along the hike. At the summit and on the descent, Geoff Gadd led discussions about reef and slope facies of the Guadalupe trail and ancient carbonate system.

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Paul Woods and Kolbe Andrzejewski enjoy a spectacular view of reef and slope deposits across the canyon. Photo by Dr. W.

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TTU student Paul Woods checks out the amazing calcite crystals along the hike. Photo by Dr. W.

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Panorama from the highest point in Texas, Guadalupe Peak at 8,750 ft. Photo by Kolbe Andrzejewski.

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Top of Guadalupe Peak, the highest point in Texas at 8,750 ft. Go Golden Eagles! Photo by a fellow hiker and courtesy of Geoff Gadd.

After a full day of hiking and investigating carbonate rocks, everyone was pretty hungry and ready to sample the local cuisine. Although skeptical at first, it was determined that the restaurant below did, indeed, have “The Best Mexican Food in Town”.

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What do geologists eat after hiking a Permian reef and the tallest point in Texas? The “Best Mexican Food in Town”, of course! Photo by Geoff Gadd.

DAY 3: Walnut Canyon and Carlsbad Caverns

On Day 3, students enjoyed a brief respite from the desert sun. The first stop of the day was located at the mouth of Walnut Canyon, on the road leading to Carlsbad Caverns.  Here, poorly bedded lime grainstones cropped out, complete with calcite-filled veins and joint sets.

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Is this a calcite-filled vein? Hmmm…
Photo by John Baird.

Also along the entrance highway, the group stopped for a glimpse of teepee structures in the carbonate beds and to admire abundant pisolite grainstones.

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TTU student Paul Woods checks out a breccia in the center of a carbonate teepee structure.

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Geoff Gadd patiently serves as a photo scale next to a teepee structure in the parking lot of Carlsbad Caverns. Photo by John Baird.

Folks enjoyed a quick lunch at Carlsbad Caverns prior to spending the afternoon underground. Jordan Sachs, an avid caver and TTU student, gave a thorough introduction on the local karst system and led group discussions, pointing out cave formations and features in the subsurface. A general consensus was reached that geologists love food, hence textural names for precipitating minerals like cave bacon and popcorn.

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TTU students opt to take the natural entrance into the cave. Photo by Dr. W.

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Cave formations of Carlsbad Caverns. Photo by Geoff Gadd.

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Cave formations of Carlsbad Caverns. Photo by Geoff Gadd.

DAY 4: McKittrick Canyon and the Permian Reef Geology Trail

Over the course of the first three days, students had worked their way from the back-reef to the carbonate reef environments of the Permian. On Day 4, Joe Kalbarczyk led the group up the Permian Reef Geology Trail, located in Guadalupe Mountains National Park. One of the most spectacular geo-trails in the world (how often can you actually hike up an ancient clinoform?!), brochures and a full guidebook are available on the geology of this route.

McKittrick Geology

At trail marker #4, Joe K. points out vertical changes in facies associated with deposition in a toe-of-slope environment. Burrowed wackestones overlie thin-bedded wackestones and alternating packages of packstone and wackestone. Photo by Dr. W.

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While hiking up the ancient slope, students keep a careful eye out for fossils and skeletal material in the wackestones and packestones. Photo by Dr. W. (Note to NPS: Don’t worry – – we didn’t collect rocks in the park!)

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Trilobite fossil identified by Paul Woods along the Permian Reef Geology Trail. Photo by Geoff Gadd.
Edit: Thanks to Brett Woodward for suggesting it may haven been an aberrant brachiopod!

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Skeletal packstone at trail marker #6; the interpreted depositional process is a slope-derived debris flow. Photo by Dr. W.

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Looking back to the south from the Permian Reef Geology Trail: point bars and a modern arroyo channel are visible along the floor of McKittrick Canyon. Photo by John Baird.

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TTU earth science students hike up McKittrick Canyon on the Permian Reef Geology Trail. Across the canyon, strata interpreted to be toe-of-slope, slope and reef deposits are visible. Photo by Dr. W.

At the top of the trail, students ate lunch on the nose of the ancient reef, looking southward into the basin.

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Hmm… perhaps the west Texas heat is starting to get to these Tennessee geologists…? Photo by Dr. W and courtesy of Geoff Gadd.

DAY 5: Evaporites, deepwater deposits and salt flats

The last field day was spent on the south side of the Guadalupe Fault scarp, exploring different types of basin fill that accumulated in the Permian. Led by Paul Woods, the first stop of the day was in the Castile Formation, which is characterized by couplets of gypsum and organic-rich micritic mud. These evaporites mark the transition from the Middle (Guadalupean) to Late (Ochoan) Permian; they are interpreted to record increasing salinity in the basin as it filled and became more and more dessicated. To the east, the Castile serves as an effective seal rock in the Permian petroleum system.

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Castile Formation couplets are characterized by highly irregular patterns of deformation, both brittle and ductile. Photo by John Baird.

At a second stop along Highway 180, boulder conglomerates outcropped approximately 7 miles from the ancient reef front. The giant clasts (some as large as a car!) contain carbonate lithofacies, which suggest they originated higher on the slope. Thus, they are interpreted to record mass transport processes, i.e. debris flows, that flowed into the basin.

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Boulder conglomerate, interpreted to be a Permian debris flow sourced from the slope. Photo by Dr. W.

The afternoon stops were spent south of the Guadalupe Fault scarp and looking back towards El Capitan and Guadalupe Peak. Deepwater clastic deposits of the Bell Canyon, Cherry Canyon and Brushy Canyon units were discussed and described by John Baird. The group identified incomplete Bouma sequences containing structureless sandstone, ripples and planar laminations.

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Partial Bouma sequences of deepwater deposits in the Brushy Canyon Formation. Thick beds are mostly structureless sandstone or siltstone, capped by ripple-laminated siltstones and planar laminated mudstones. Photo by Dr. W.

Salt Flat, an area along Highway 180, served as the final field stop of the trip. Here, the  group had time to observe modern evaporites, take in the West Texas vista, and contemplate the ancient Permian Basin System.

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TTU student Jordan Sachs sits on a modern evaporite deposit west of the Guadalupe Mountains. In the distance, El Capitan looms large, the geologic relict of an ancient Permian reef front. Photo by Kolbe Andrzejewski.

After five days investigating sedimentary rocks – clastics, carbonates, and evaporites – Tennessee Tech students and Dr. Wolak headed home to Cookeville. In Midland, TX, the Permian Basin Petroleum Museum offered an opportunity to review the geology through the lens of oil and gas exploration.

EPILOGUE

In addition to the spectacular geology and modern depositional environments, Tennessee Tech earth science students enjoyed a few other treats, including:

1.) Graffiti at Road Side BBQ in Memphis, TN

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Paul Woods adds a TTU Earth Sciences signature to graffiti-filled walls of the Road Side BBQ in west Memphis.

2.) Tarantula-viewing at the Carlsbad KOA entrance

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On the way into the field, students spot a gigantic black mass crossing the road. Photo by Dr. W.

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Desert tarantula in New Mexico. Photo by Geoff Gadd.

3.) High Desert Fashion, the Tennessee Way

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Kolbe Andrzejewski models appropriate ear cover in the sun-filled desert.

4.) Jumping for joy after a week in the field doing geology. Go Golden Eagles!

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Tennessee Tech students and Dr. Wolak catch some air in front of El Capitan and the Guadalupe Mountains of West Texas and New Mexico. Photo by John Baird and courtesy of Geoff Gadd.

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