The Solitario dome is one of the US Southwest’s most striking geologic features. The dome is a circular formation so large it can be viewed from space. At almost 16 km across, the dome is the uplift over one of the largest laccoliths in the world. It is located within the Trans-Pecos Magmatic Province in Presidio and Brewster counties, Texas, and comprises the northeast area of Big Bend Ranch State Park. Late Eocene to early Oligocene uplift of the Solitario dome generated coarse sediments comprising the Solitario Conglomerate (Tsg), an approximately 63 m thick mixed-clast formation outcropping to the west and the north of the dome. Tsg represents an alluvial fan network that is interpreted as the depositional product of major and minor pulses of uplift related to the igneous activity under the Solitario between 36 and 30 Ma (Henry and Davis, 1996). Near Fresno Canyon, immediately west of the dome, the Solitario Conglomerate outcrops in Arroyo Mexicano where it conformably overlies the Undifferentiated Chisos Group (47 to 34 Ma). The base of the conglomerate is composed chiefly of silicic igneous lithic fragments; up section, the silicic igneous clasts decrease in occurrence as Cretaceous limestone clasts become more abundant. At the top of the formation, clasts of Paleozoic cherts are present. This depositional sequence is consistent with the unroofing sequence of local strata uplifted by the Solitario dome. The variance in clast composition and sedimentary features between Arroyo Mexicano and Panther Canyon was unclear. The Solitario Conglomerate occupies an interval of 36 to 30 Ma. An ash layer was recently found within the conglomerate that could further constrain the timing of unroofing. This study analyzed clast compositions through the vertical section, noting first appearances of clasts and recording changes in clast sizes, thus reconstructing the uplift history of the Solitario dome.
|Commitee:||Kelsch, Jesse, Hall, Blaine, Measures, Elizabeth, Shiller, Thomas|
|School:||Sul Ross State University|
|School Location:||United States -- Texas|
|Source:||MAI 81/2(E), Masters Abstracts International|
|Subjects:||Geology, Sedimentary Geology|
|Keywords:||Alluvial fan, Big bend, Conglomerate, Fanglomerate, Oligocene, Solitario|
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