Geologic Mapping of the Southern Flank of the Rosillos Laccolith, Brewster County, Texas

Big Bend Terrain

The Big Bend region of Trans-Pecos, Texas has a complex and unique geologic history, which has been of interest to geologists for almost a century. Although much is known about the geology of this region, there remains a great deal of work to be done before the geologic history of the region can be fully understood. The Rosillos Mountain Ranch is a privately owned ranch consisting of almost 25,500 acres and is contained within the boundaries of Big Bend National Park. There has been limited geologic mapping done on the ranch, and the mapping that does exist appears to be highly generalized and contains errors. The unmapped area is known to contain Cretaceous and Tertiary sedimentary rocks, expansive Quaternary alluvial fan deposits, and a complex igneous history as well.

Because of the immense size of the Rosillos Mountain Ranch and the extreme conditions of the Trans-Pecos region, traditional geologic mapping is somewhat of a cumbersome task. My thesis utilizes remote sensing technology to aid in the geologic mapping of such a vast area. Previously, there have been a series of remote sensing studies conducted in the Rosillos Mountains, but none have attempted to provide a geologic map of the area. The main objective of this study is to produce a more accurate geologic map of the southern flank of the Rosillos Mountains using remote sensing combined with more traditional field mapping techniques.


Progress (as of 11/1/98):

I spent numerous weeks in Big Bend this past summer conducting ground truthing of my remote sensing work and general field mapping. Things went well except for a few minor crisises. A field assistant, (I won't name names), and myself got the geology van stuck about 12 miles from the ranch house late one evening. The next day we made what I affectionately call the "Death March" in 110 degree heat. Another field assistant and myself got the geology van stuck on another trip in a sandy alluvial fan, but we just had a few miles to hike that time. If you ever need to field map in Trans-Pecos Texas, I would highly recommend demanding a 4X4 vehicle or horses. Besides those incidents (and a flat tire and intense rain in the desert), things went smooth. I'm in the process of preparing field maps and writing my thesis. I've discovered the motherload of unknown basalts, which I'm excited about. The TCU faculty will supervise my final field check in January. For futher details about my work, you can e-mail me or wait for the final product to be complete in May 1999.


Big Bend Sunset



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