Browsing by Subject "Paleontology--Texas"
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Item Fauna of the Glen Rose formation(1937) Whitney, Marion Isabelle, 1911-; Whitney, Francis Luther, 1878-1962Item The Georgetown formation of Central Texas and its North Texas equivalents(1927) Cuyler, Robert Hamilton; Not availableItem Late Cenozoic deposits of the Texas Coastal Plain between the Brazos River and the Rio Grande(1941) Weeks, Albert William, 1901-; Cuyler, Robert HamiltonItem Manual of suggested procedures to be employed by the state-wide paleontologic-mineralogic survey in Texas(Bureau of Economic Geology [University of Texas], 1939) Evans, Glen L. (Glen Louis), 1911-Item Stratigraphy, vertebrate paleontology and depositional history of the Ogallala Group in Blanco and Yellowhouse canyons, northwestern Texas(1985-08) Winkler, Dale A. (Dale Alvin), 1955-; Lundelius, Ernest L., 1927-The late Miocene Ogallala Group is up to 90 meters thick in exposures along the eastern escarpment of the High Plains in Crosby, Garza and Lubbock Counties, Texas. Two formations are mapped in this section. The lower formation can be divided into two members and is correlated with the early Clarendonian Land Mammal "Age". The upper formation contains early and late Hemphillian mammals. The geomorphic history of the area is reconstructed using depositional and biostratigraphic analysis of lithostratigraphic units. High-energy ephemeral streams first deposited sediment in valleys incised into Triassic and Cretaceous bedrock in early Clarendonian time. Later in Clarendonian time these fluvial sediments and areas of bedrock were covered by a blanket of eolian silty sand. In the late Clarendonian or early Hemphillian rivers began to downcut new valley systems. High-energy fluvial systems filled these incised valleys in the early Hemphillian. Ephemeral fluvial and eolian silty sand sheet deposits spread over most older bedrock highs on the High Plains in about the middle Hemphillian. Deposition ceased across the High Plains when fluvial input from the southern Rocky Mountains was cut off at the end of the Hemphillian. The caprock caliche formed at this time. Tectonic events in the Rocky Mountains appear to have controlled these geomorphic cycles in the study area and also to have influenced sedimentation in other areas. A significant break in sedimentation, seen in many areas of the central and western U.S., coincides with the Clarendonian/Hemphillian boundary. The faunal turnover at the Clarendonian/Hemphillian boundary in the Great Plains and the Rio Grande rift is probably accentuated by this hiatus. Vertebrate assemblages throughout the section are dominated by animals adapted to subhumid or semi-arid environments. Most of the ungulates are grazers. Ephemeral stream deposits, eolian silty sand sheets and caliche-rich paleosols also indicate subhumid or semi-arid conditions throughout the late Miocene. Faunal turnover and declines in diversity in the late Miocene are related to increasing aridity and possibly to a decrease in complexity of the savanna flora.Item A study of the Cretaceous Inocerami of Texas(1933) Cartwright, Weldon EmersonItem Trilobites of the Upper Cambrian Ptychaspid biomere, Wilberns Formation, central Texas(1968-06) Longacre, Susan Ann; Bell, William Charles, 1911-Trilobites collected during the past twenty years from the Morgan Creek, Point Peak, and San Saba members of the Wilberns Formation constitute the material basis for this paleontologic and statistical investigation. Eighty-nine species assigned to forty-five genera belong to zones of the upper Franconian and Trempealeauan Stages of the Upper Cambrian Croixan Series. New zonal names are proposed in the interest of a regionally applicable nomenclature. Although none of the zonal nomenclature is identical to that of the Cambrian Correlation Chart, the four zones recognized in central Texas are equivalent to the eight highest zones of the Chart. Stratigraphically lowest is the Franconian Taenicephalus zone, with a locally recognized Parabolinoides subzone at its base; this is equivalent to the Conaspis zone of the Correlation Chart. The Franconian Idahoia zone, with a locally recognized Idahoia lirae subzone at its base, is equivalent to the Ptychaspis subzone of the Ptychaspis-Prosaukia zone of the Correlation Chart. The sparsely fossiliferous Ellipsocephaloides zone corresponds to the Prosaukia subzone of the Ptychaspis-Prosaukia zone of the Chart. Almost two-thirds of the trilobite species occur in the Trempealeauan Saukia zone, which corresponds to the five highest zones of the Correlation Chart; local subzones, in ascending order, are the Saukiella pyrene subzone, the Saukiella junia subzone, the Saukiella serotina subzone, and the Corbinia apopsis subzone. The succession of ptychoparioid trilobite faunas contained within these zones make up the Ptychaspid biomere. The base of the biomere is at the base of the Taenicephalus zone; the top coincides with the lowest occurrence of the Ordovician trilobite fauna. Trilobite families that characterize the Ptychaspid biomere are the Ptychaspididae and the Parabolinoididae. Regression analyses of range data for all Saukia-zone taxa were used to compile a quantitative range chart. Differences between the quantitative chart and my intuitive range chart were not significant. Systematic descriptions include new species of Conaspis, Idiomesus, Euptychaspis, Keithiella, Saukiella, Prosaukia, Calvinella, and Westonaspis?; and one new variety of Orygmaspis.