Petrography, northern Davis Mountains, Trans-Pecos, Texas

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dc.contributor.advisorNot available
dc.creatorRix, Cecil C.
dc.date.accessioned2018-04-09T15:04:24Z
dc.date.available2018-04-09T15:04:24Z
dc.date.issued1951
dc.description.abstractThe northern Davis Mountains are composed of Tertiary volcanic rocks of the group. This group, resting unconformably on southward dipping Cretaceous strata, contains a basal conglomerate and 1,500-2,000 feet of alternating beds of tuff and lava. Streams have cut steep-walled canyons in the outer margins of the mountains, and differential erosion between the tuffs and lavas has produced a stair-step profile. Landslides occur along the front as Toreva-blocks. The volcanic units of the McCutcheon group in the northern Davis Mountains are divided into six major mappable units consisting of three dissimilar flows, each underlain by tuff. The lavas are all rhyolites, the lowermost characterized by aegirite; the middle, by riebeckite and chlorite (?); and the upper, by riebeckite. The tuff units are rhyolitic and are classified as lithic, vitric, and crystal tuffs. The indices of refraction of natural glasses or fused igneous rocks vary inversely with the silica content. A standard silica-index of refraction curve is drawn for rocks from the alkalic province of the nearby Terlingua-Solitario district. Indices of refraction of artificial glasses of the Davis fountain rocks are referred to this curve to determine their approximate silica percentages. The igneous rocks of the Davis Mountains are similar in composition to igneous rocks in the Barrilla Mountains, the Big Bend, and the Buck Hill Quadrangle. The similarity of the rocks, indicated by the presence of soda-rich minerals, suggests that they were probably derived from the same parent magma.en_US
dc.description.departmentEarth and Planetary Sciencesen_US
dc.format.mediumelectronicen
dc.identifierdoi:10.15781/T22R3PD7F
dc.identifier.urihttp://hdl.handle.net/2152/64212
dc.language.isoengen_US
dc.relation.ispartofUT Electronic Theses and Dissertationsen_US
dc.rightsCopyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.rights.restrictionOpenen_US
dc.subject.lcshPetrology--Texas--Davis Mountains
dc.titlePetrography, northern Davis Mountains, Trans-Pecos, Texasen_US
dc.typeThesisen_US
dc.type.genreThesisen
thesis.degree.departmentGeological Sciencesen_US
thesis.degree.disciplineGeological Sciencesen_US
thesis.degree.grantorUniversity of Texas at Austinen
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Artsen_US

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