Browsing by Subject "Geology -- Texas"
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Item A carbon isotope and trace element analysis of Pennsylvanian rugose corals, North-Central Texas(Texas Tech University, 1989-12) Perkins, DianeCarbon and oxygen isotopes were analyzed to identify the process of algal symbiosis in Pennslyvanian rugose corals from the Graham Formation of north-central Texas. Because original oxygen and carbon isotopic compositions depend on the preservation of isotopic content during post-depositional diagenesis, trace element and petrographic analyses were used to determine the suitability of samples of Caninia, Lophophyllidum and the brachiopod Composita for analysis. Petrographic analysis of fossils from the Finis Shale indicate that these fossils have been subjected to four episodes of diagenetic cementation. Shell microstructures are partially preserved in Composita and Caninia. Recrystallization of the shell was more extensive in Lophophyllidum from the Finis Shale and Caninia from the Gunsight Limestone. Six episodes of cementation are recognized in Caninia from the Gunsight Limestone. Trace element analysis indicates that sodium and magnesium values are depleted and iron and manganese concentrations enriched in Caninia from the Finis Shale. Trace element analysis of Composita indicate that sodium, iron, manganese and strontium concentrations are within the observed range for Paleozoic brachiopods. Isotopic analyses of Caninia and Lophophyllidum exhibit 6 ^^C and 6 ^^0 values depleted compared to Composita and to the postulated range for carbonate precipitated in equilibrium with Pennsylvanian seawater. These findings suggest that an algal symbiont influenced the development of the coral skeleton.Item A Gravity and Magnetic Investigation of the Amarillo Uplift(Texas Tech University, 1969-05) Danbom, Stephen HNot Available.Item Item A petrographic comparison of the Lower Spraberry and the Dean Siltstones of the northern Midland Basin of West Texas(Texas Tech University, 1955-08) Tucker, Charles OdellNot availableItem A Provenance Study of the Triassic Deposits of Northwestern Texas(Texas Tech University, 1960-05) Kiatta, Howard WilliamContinental deposits of the Upper Triassic Dockum Group are exposed along the eastern escarpment of the Southern High Plains in northwestern Texas. Three formations are present: the Tecovas, the Trujillo, and the Chinle, generally representing the floodplain, stream channel, and floodplain environments respectively. Analyses of the sedimentary structures were made to determine the direction of the source of these beds. Mineralogical studies were conducted in an effort to establish the litho logic character of the source rocks. Results indicate that the provenance consisted chiefly of a terrene of sedimentary rooks to the east and southeast. Specific source areas are proposed and some pale geographic reconstructions are suggested.Item A Sedimentary Analysis of the Cox Formation of Trans-Pecos Texas(Texas Tech University, 1956-05) Priddy, Charles ParrishNot Available.Item A Study of the Silurian System and a Silurian Reef in West Texas and Southern New Mexico(Texas Tech University, 1971-05) Cronin, Thomas C.Not Available.Item Alteration of the Study Butte intrusive Terlingua, Brewster County, Texas(1967-06) Williams, Clifford RalphNot AvailableItem An Investigation of Primary Features Present in Recent Ephemeral Braided Stream Deposits, Southern High Plains, Texas(Texas Tech University, 1963-06) Kothmann, Sidney WinnardThe uniformitarian approach to the interpretation of ancient sedimentary environments has been employed for over a century, however it has only been within the last two decades that serious attention has been given this type of investigation. Textural studies have yielded much significant information, but no attempt has been made to investigate the textural aspects of individual sedimentary features. It appears that interest in the interpretation of primary sedimentary features as a guide to ancient environments is rapidly gaining momentum. This type of investigation has an advantage over a textural approach in that the data can be collected rapidly and interpretations rendered without returning to the laboratory Ephemeral braided stream deposits on the southern High Plains are characterized by numerous primary features, many of which are duplicated in other environments^ but the assemblage of features is seemingly unique^ Ripple marks that have been noted include cuspate or barchanoid current ripples, lobate current ripples, linear or transverse current ripple of linear or transverse wave ripples with parallel crests, rhombeid ripples, linear or transverse eolian ripples with parallel crests, linear or transverse eolian ripples with sub-parallel crests, ad eolian pinnate ripples. Other features include algal structures of various kinds, rill marks, scours graded bedding, chute-deltas> mud cracks, and clay chips and pebbles. The data collected during this investigation indicate that cuspate^ lobate^ and eolian ripples can be distinguished on the basis of inclination of foreset laminae and value of the obtuse angle between the foreset and backset laminae. Ripple index is not a criterion for distinguishing between eolian and fluviatile ripples in ephemeral braided stream deposits It is important to be able to identify the type of ripple mark in ancient sediments because early cuspate, linear or transverse current ripples, and rhombeid ripples are good indicators of true channel trend. An understanding of flooding in braided streams is important because most of the sedimentary features that are produced and topographic changes that occur are the result of flood stages. The role of eolian processes is important because (1) the wind reworks part of the material deposited by the water^ thus^ forming new ripples; (2) a considerable portion of bar growth is the result of lateral accretion produced by the wind; (3) other previously formed features are covered by wind blown sand and may thus be preserved. Cuspate, lobate^ and eolian ripple marks in a given locality can be distinguished on the basis of their textural characteristics^ The CM pattern of ephemeral braided stream deposits is similar to that of tractive currents as reported by Passega (1957)*Item Crustal xenoliths from Potrillo Maar: implications for evolution of continental crust beneath the southern Rio Grande rift(Texas Tech University, 2003-08) Chattopadhyay, IndraniThe mid-crustal xenoliths from Potrillo maar record a petrologic and geochemical history that has until now been unknown from the Potrillo volcanic field. The igneous and meta-igneous xenoliths are samples of one or more plutonic bodies that crystallized at depths from 7-14 km (middle to upper crust). The rock unit ranges in composition from hornblende biotite diorite to quartz monzonite and monzogranite; it is broadly alkalicalcic The initial Sr87Sr86 suggests that the source region is heterogeneous or that the parental magmas were contaminated by crustal material. At least three geochemical groups can be identified, primarily on the basis of silica content. There is considerable overlap between groups 1 and 2, and the boundary between these two groups cannot be distinguished graphically. The third group is granitic and is geochemically distinct from groups 1 and 2. A dioritic composition is thought to represent mafic parental magma. Its calculated liquidus temperature at 2% H2O and 4 Mpa pressure is 1172°C. The presence of fossiliferous limestone xenoliths indicates that the Potrillo maar eruption sampled rocks of late Paleozoic age. However, the age of marble and quartzite xenoliths are not known. The quartzite xenoliths are relatively undeformed, but isoclinal folding in some of the marble xenoliths suggests subsurface deformation that has not been observed in local surface exposures of metasedimentary rocks. One model proposed for the crust under the southern Rio Grande rift assumes that the marble is late Paleozoic in age. The fossiliferous limestones are late Paleozoic in age and are older than the plutonic rocks. The relative age of the deformed marbles in this model is not clear, it can be deformed with the plutonic rocks or due to an earlier regional extensional event. In the second model, marble is proposed to result from contact metamorphism in the aureole of a plutonic rock body at a depth of 7-14 km. The presence of marble and calc-silicate xenoliths in dioritic blocks is consistent with a correlation of the marble with surface exposures of the Castner Marble in the Franklin MountainsItem Depositional dynamics of the Queen Formation, New Mexico and Texas.(Texas Tech University, 1967-06) Williams, Karl W.Not availableItem Diversity of late Cenozoic gastropods on the Southern High Plains(Texas Tech University, 1975-05) Pierce, Harold GeorgeGastropods are often the only fossils found in late Cenozoic sediments on the Southern High Plains. By virtue of their conservatism and low rate of mobility, gastropods should be sensitive indicators of their environment, and the pluvial cycles of the late Cenozoic should have resulted in repeated local invasions and extinctions of species not presently living in this area. Recent advances in absolute age chronology through radiometric dating of volcanic ash beds have resulted in revision of the late Pliocene and early Pleistocene stratigraphic sequence throughout the Great Plains. Although intensively studied in other areas, earlier studies of the fossil gastropods of this area have been limited in scope, and conducted under the assumption of a single Pearlette ash datum. A detailed study of the fossil gastropod assemblages, collected by bulk sampling techniques, with concomitant study of the sedimentology and stratigraphy of selected localities was undertaken. It was found that for most stages of the late Cenozoic, index species and/or diagnostic assemblages existed. During the Wisconsinan stage, several stades could be identified by assemblages. Those stages in which diagnostic assemblages did not occur could be identified with reasonable certainty by a combination of sedimentology, stratigraphy and environmenta1 interpretations from the fossil assemblage. Statistical coefficients of correlation are used, but found to be more sensitive to similarity of environment than to relative age. The phylogeny of certain species are of use in determining the relative age of the assemblage. As environmental indicators, terrestrial gastropods are found to be useful and sensitive. Aquatic gastropods, insulated from the outside climate, are less sensitive but useful in confirmation of interpretations. One tolerant species, Pupoides albilabris, faithfully records long range climatic conditions in shell morphology. Environmental interpretations, based on the fossil gastropod assemblages, suggest revision of the commonly accepted late Cenozoic climatic cycles. The late Pliocene was slightly cooler and moister than the present, not warm and semiarid. The Yarmouthian stage was similar to the present, but somewhat moister, while the Illinoian pluvial was cool and differed from other pluvials in being dry and probably of short duration. At no time during the late Cenozoic was the Southern High Plains extensively forested, although riparian woodland, including scattered conifers, probably occurred during most pluvial maxima.Item Dust storm sediments of the Lubbock area, Texas(Texas Tech University, 1954-05) LaPrade, Kerby ENot availableItem Joint sets of the Llano Uplift, Texas(Texas Tech University, 1984-05) Alnes, Joel RRock units of the Llano Uplift of central Texas, which range in age from Precambrian through Cretaceous, display well-developed joint systems. A total of 3i88l joints at 40 exposures across the region are analyzed in the manner of Hoist and Foote (1981). From this analysis, three regional joint sets, with average median strikes of N46E, N88W, and N46W, respectively, are delineated in rocks of Precambrian through Pennsylvanian age. Rocks of Cretaceous age display a different and irregular pattern of jointing. Jointing of rocks of Precambrian through Pennsylvanian age apparently is of post-Atokan - pre-Cretaceous age and developed in response to regional stresses, while joints in the Cretaceous rocks appear to be a product of a different and very localized stress regimes. The fracture pattern in the rocks of Precambrian through Pennsylvanian age may be explained by strains induced by NW-SE stresses. These stresses are interpreted to be a product of converging plates during the Ouachita orogeny, which would date jointing as post-Atokan to Permian in age. Apparent abruptness of doming and faulting, followed by jointing of the region, suggests plate collision along the Ouachita tectonic belt.Item Micropaleontology of a part of the Lower Cretaceous in Kent Quandrangle, Texas(Texas Tech University, 1955-05) Hatley, Allen GradyMicropaleontologic and lithologic data obtained from several exposures of Finlay, Duck Creek and Fort Worth equivalents are recorded for comparison with similar information from other areas. Biostratigraphic and paleoecologlcal inferences have been made. Evidence obtained from ostracodes and foraminifera indicates that a Finlay equivalent, not Kiamichi, is present north of Kent. There is a lack of information on the Fredericksburg-Washita contact as it is not exposed within the area studied. For the most part the Duck Creek and Fort Worth equivalents were deposited in a sea of normal marine environment with depths of 5 to 60 fathoms, the only exception being in the upper portion of the Duck Creek equivalent whZere evidence indicates a slight restriction and possible regression of the sea.Item Origin of pisolites in Guadalupe Mountains, southern New Mexico and West Texas(Texas Tech University, 1964-05) Thomas, Carroll MorganNot availableItem Sedimentation of the Upper Salt Series of the Delaware Basin, Texas and New Mexico(Texas Tech University, 1940-05) Coon, Lester ANot availableItem Sedimentology of the outer Texas coast(1953-01) Blankenship, William Dave; Damon, Henry GordonThe Recent as represented on the Texas coast may be separated chronologically into the Ingleside, Alazan, and Post-Alazan or Present times. Each subdivision is associated with a major climatic fluctuation, the Ingleside and Post-Alazan with the “first and second climate optimums”, respectively, and the Alazan with the “Little Ice Age”. Characteristic of the Ingleside and Present times, and possibly of Alazan time, are the associated coastal barrier and lagoon systems. The physiographic features of the Present coastal barrier system forming the outer Texas coast, manifest a direct relation to the climatic characteristics of the Present, favoring onshore movement of sediments. The sediments carried by mainland streams to the bay systems, then moved through the barrier passes by tidal currents, and contributed to a southwestward moving longshore current. Wave transport and eddy action transfer the sediments to an inshore drift current, which is reversible in direction with the longshore component of the local wind. The direction of the inshore drift current affects directly the orientation of foreshore features: spits, bays between cusps, and the associated backwash channels and ripple marks. Three basic profiles representing calm, normal, and storm wind conditions result from secretion or removal of beach sediments. Hurricanes, occurring at any one locality on the Texas coast about once every 25 years, produce great waves that flood the barrier system in the region where the storm track crosses the coastline. A hurricane flood flattens low foredunes, breaks through gaps in higher foredunes, forms washover fans and temporary passes, and carries the material across the island channels, depositing the sediments in front of back dune fields and in the lagoon. The dry portion of the present wind regime (that free of precipitation) transports the Gulf beach sands inland over the barrier system. Precipitation, occurring more often with northerly winds than with southerly winds, reduces the effect of the former on sand movement. SE is the prevailing wind direction and also the resultant effective direction causing Aeolian movement of sand over the barrier system, producing an over-all resultant NW movement. Blowout tongues, barchans, and seif dunes of the barrier system, also the dune fields and wind-cut ridges and furrows of the mainland, have developed trends in agreement with the NW direction of Aeolian sand movement. The NW trends are superimposed on a sand sheet that centers at 27°N latitude on the mainland and extends W from Laguna Madre. The sand sheet was probably the product of a different wind regime because of its non-agreement with the present direction of sand movement. A gradual change of physiographic features southwestward along the coast is the direct result of the different degrees of sand movement corresponding with a climatic range from humid in the vicinity of Sabine Pass to semi-arid on northern Padre Island. Desert-type dunes, the seifs and barchans typical of the great ergs of the world, are found in the semi-arid portion of the Texas barrier system. Of the entire continental shores of the United States, only along the Texas shores do such dunes develop for no other shore in the United States approaches the same degree of aridity.Item Spectrochemical correlation of the Clay Creek salt dome formations(Texas Tech University, 1951-05) Burress, George ThomasNot availableItem Stratigraphy of the Ordovician Maravillas Formation(Texas Tech University, 1958-06) Wallis, Thomas IrvinStudy of the bryozoan fauna of the Ordovician Maravilllas Formation in trans-Pecos Texas indicates that the major portion of the formation is of Richmondian age. Exact correlation with the type Ordovician section appears somewhat uncertain, and the fauna is best considered as mixed. The twenty-six species described, including three which are new, are contained in twenty-two genera. More of the described species occur In the Fernvale Formation of the upper Mississippi Valley than In any other horizon. These include Anaphragma mirabile. Constellaria polystomella, Cyphotrypa wilmingtonensis. Phaenopora wilmingtonensis, and Sceptropora facula. Hallopora subnodosa and Rhombotrypa subquadrata are characteristic of those portions of the formation which contain bryazoans. A tentative occurrence chart is included, but further studies will undoubtedly produce many alterations in the chart.