Browsing by Subject "Geology -- Texas -- Brewster County"

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A sketch of the geology of the Chisos country, Brewster county, Texas
(University of Texas at Austin, 1907) Udden, Johan August, 1859-1932
Geology of Agua Fria quadrangle, Brewster County, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1953) Moon, C. Gardley
The 15-minute Agua Fria quadrangle in southwestern Brewster County, Texas, is arid, sparsely vegetated, and includes diverse topographic features that result chiefly from complex structure and variation in rock resistance to erosion. The mountainous and more complicated southern part of the area has suffered much deformation by igneous intrusions and faulting. The Comanche series is represented by the Devils River limestone, Grayson marl, and Buda limestone. A disconformity separates it from the overlying gradational Gulf series which consists of the Boquillas,Terlingua, and Aguja formations. Because the Boquillas-Terlingua boundary problem is critical and unsettled, lithologic members and paleontologic zones in that section are described in considerable detail. A distinctive 50-foot rock unit, herein named the Fizzle Flat lentil, occurs about the middle of the Boquillas-Terlingua sequence. A widespread angular unconformity separates the Gulf series from the Tertiary Buck Hill volcanic series. Quaternary terrace gravels occur at different levels, and other alluvial deposits have been mapped. The Tertiary hypabyssal igneous rocks are alkalic and form stocks, laccoliths, plugs, sills, dikes, and bysmaliths or trap-door domes. Several lava flows are preserved in the southwest part of the quadrangle. Metamorphic effects generally are slight. The area is part of the Big Bend sunken block. Except where influenced by intrusive masses, a pattern of northwesterly normal faults establishes the structural trend of the area. Step faults are common. Most of the major faults are downthrown to the southwest with the huge intervening blocks tilted gently to the northeast. That much of the fault pattern was established during the Laramide revolution and that faulting recurred along the old lines of weakness fairly late in Tertiary time are postulated.
Geology of Cathedral Mountain quadrangle, Brewster County, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1955) McAnulty, William Noel, 1913-
Rocks exposed in the Cathedral Mountain quadrangle in the southeastern DavisMountains of Trans-Pecos Texas are assigned to the Word formation and to Capitan limestone in the Permian Guadalupe series; to the Maxon sandstone, Edwards limestone, Georgetown limestone, and Grayson (Del Rio) marl in the Cretaceous Comanche series; to the Buda limestone and Boquillas limestone in the Cretaceous Gulf series; and to the Buck Hill volcanic series in the Tertiary. Volcanic rocks up to 4600 feet thick cover most of the quadrangle. The volcanic succession, similar to that in Buck Hill and other quadrangles to the south, is divided into the Pruett tuff, Crossen trachyte, Sheep Canyon basalt, Potato Hill andesite, Cottonwood Spring basalt, Duff formation, and Rawls basalt. Vertebrate fossils indicate a late Eocene (Duchesne) age for the Pruett tuff (restricted to the lowermost tuff, sandstone, and conglomerate beds). The top of the Eocene is placed at a prominent disconformity between the Crossen trachyte and the Sheep Canyon basalt; it is suggested the overlying lava and tuff layers are Oligocene and younger (?). Some of the many intrusive bodies of alkalic microsyenite which are younger than the volcanic rocks have effected much local deformation of the layered rocks. Quaternary alluvium is present along streams and over valley flats. Northward across the quadrangle, the Crossen trachyte gains appreciable quartz, the Potato Hill andesite changes from highly porphyritic to nonporphyritic, and the Duff formation changes from dominantly rhyolite tuff to lava, tuff, and conglomerate (Decie member). Effects of five crustal disturbances mid-Mesozoic, late Cretaceous, pre-upper Eocene, and three in the late Cenozoic are apparent. Differential erosion of the intruded, folded, and faulted volcanic succession has roughened and diversified the landscape.
Geology of Hood Spring quadrangle, Brewster County, Texas
(University of Texas at Austin. Bureau of Economic Geology, 1954) Graves, Roy William
The Hood Spring quadrangle, in the central part of Brewster County, Texas, contains a segment of the southeast rim of the Marathon basin. It includes a part of the complexly folded and faulted Paleozoic rocks that occur in the center of the Marathon basin and also includes Cretaceous rocks exposed in the Maravillas scarp. This scarp has three stratigraphically separate cuestas that are formed by southeastward gently dipping beds. The southwestern corner of the quadrangle contains a faulted and folded segment of the Santiago Mountain range. Rocks of Cambrian (Dagger Flat formation), Ordovician (Marathon, Alsate, Fort Pena, Woods Hollow, and Maravillas formations), Devonian (Caballos novaculite), and Pennsylvanian (Tesnus formation)ages occur in the area of Paleozoic outcrops. A conodont fauna from the upper part of the Caballos novaculite indicates a Middle to Upper Devonian age for those beds. Most of the Cretaceous rocks exposed in the quadrangle belong to the Comanche series (Glen Rose, Maxon, Walnut-ComanchePeak, Edwards, Kiamichi, Georgetown, Grayson, and Buda formations) and are similar to equivalent age strata in central Texas. Gulf series rocks (Boquillas and Terlingua formations) have a restricted occurrence in the southwestern corner of the quadrangle contains a faulted and folded segment of the Santiago Mountain range. Tertiary intrusions include plugs, dikes, and sills of rhyolite, trachyte, and basalt which cut Cretaceous and Paleozoic rocks. These intrusives belong to the southern Trans-Pecos Texas suite of alkalic igneous rocks.
Geology of the Marathon region, Texas
(Geological Survey (U.S.), 1937) King, Philip Burke, 1903-