This thesis examines six prominent Pecos River Style rock art anthropomorph attributes to determine if they are found in limited geographic districts of the Lower Pecos Region. Both Boyd (2003) and Turpin (2004) have suggested that spatially-segregated motif distributions exist in the rock art and that these patterns are important in understanding regional prehistoric hunter-gatherer lifeways during the Archaic Period. This study verifies that the feather hip cluster motif is geographically limited, identified only in the neighboring Seminole and Painted Canyon systems. As part of this spatial analysis, the previously undocumented principle of intersite stylistic traditions is introduced. Possible explanations for these anthropomorph attributes are also discussed. Finally, structural analyses of the six attributes are presented.

This thesis examines six prominent Pecos River Style rock art anthropomorph attributes to determine if they are found in limited geographic districts of the Lower Pecos Region. Both Boyd (2003) and Turpin (2004) have suggested that spatially-segregated motif distributions exist in the rock art and that these patterns are important in understanding regional prehistoric hunter-gatherer lifeways during the Archaic Period. This study verifies that the feather hip cluster motif is geographically limited, identified only in the neighboring Seminole and Painted Canyon systems. As part of this spatial analysis, the previously undocumented principle of intersite stylistic traditions is introduced. Possible explanations for these anthropomorph attributes are also discussed. Finally, structural analyses of the six attributes are presented.

An ash-flow sheet, to which the names Mitchell Mesa Rhyolite and Brite Ignimbrite have been applied, crops out prominently in Presidio and western Brewster Counties, Texas. Because of its great areal extent it is the most important unit for correlation in the Tertiary volcanic field of southern Trans-Pecos Texas, and it should bear a single name. Priority and widespread use in published literature support the name Mitchell Mesa. The ash-flow sheet is divisible into two cooling-units. The lower, a simple cooling-unit that grades locally into a compound cooling-unit, is a vitric-crystal rhyolitic ash-flow tuff with 15 to 25 percent opalescent alkali feldspar and bipyramidal quartz phenocrysts as long as 4 mm in a light brownish gray, grayish pink, or light gray vesiculated groundmass. The lower cooling-unit ranges in thickness from about 230 feet immediately north of Pinto Canyon to 2 feet at South Lajitas Mesa. The upper, simple cooling-unit is a vitric-lithic ash-flow tuff with as much as 20 percent lithic fragments in a very light gray to brownish gray groundmass containing about 10 percent non-opalescent alkali feldspar and quartz phenocrysts. The upper unit ranges in thickness from 60 to 100 feet. Its only outcrops are overlain by Petan Basalt north and northeast of Pinto Canyon. Except in a few places, the pyroclastic texture of the lower cooling-unit was obliterated by vapor-phase crystallization. Any tridymite and cristobalite originally present were subsequently converted to quartz. Four whole-rock chemical analyses of samples from widely separated localities are similar, showing only minor variations in K₂o and Na₂o. The alkali feldspar phenocrysts are richer in Na₂O and poorer in K₂O than the whole rock. Therefore the feldspar in the groundmass is more potassic than that in the phenocrysts. Foreign inclusions are most abundant in outcrops of Mitchell Mesa Rhyolite closest to the Chinati Mountains. Immediately north of the mountains, a separate ash-flow tuff is present beneath the Mitchell Mesa Rhyolite. This and other evidence leads to the conclusion that the Chinati Mountains area was the source of the ash-flow sheet. / text

Doct. Phil.--Anthropology--Texas A&M university, 1998. / Bibliogr. p. 193-214.

A one-dimensional, quasi-steady ablation model with finite rate surface chemistry and frozen equilibrium pyrolysis gases is developed and discussed. This material response model is then coupled to a film-transfer boundary layer model to enable the computation of heat and mass transfer to and from the ablating surface. A shock model is outlined, as well, and all three components are then coupled together to form a stand-alone ablation code. The coupled models in the code are validated with respect to arcjet experiments, and comparisons are drawn between the ablation code and the unsteady ablation code Chaleur, as well as other computations for a graphite ablator in an arcjet. The coupled code is found to compare very well to both the experimental results and the other calculations. It is also found to have unique computational capabilities due to the use of finite-rate surface chemistry. Finally, uncertainty propagation using the quadrature method of moments (QMOM) is discussed. The method is applied to a number of simplified sample problems, for both univariate and multivariate scenarios. QMOM is then used to compute the uncertainty in an application of the coupled ablation code using a graphite ablator. The results of this study are discussed, and conclusions about the utility of the method as well as the properties of the ablation code are drawn. / text

No description available.

Fault scarps cutting alluvial deposits define the present-day eastern boundary of Basin and Range faulting in Trans-Pecos Texas. These faults are found in the Salt Basin graben north of Van Horn, Texas, and its southerly extensions along Lobo Valley and Michigan Draw. Discontinuous and en echelon Quaternary fault scarps quickly die out to the south on the eastern side of the graben but become more continuous and develop larger displacements (up to 6 meters) along the west side of Salt Basin at the base of Sierra Diablo. The orientation of the more than one hundred Quaternary down-to-the-basin fault scarps and photolineaments appears to be controlled by pre-existing structural zones of weakness. The preferential alignment of Quaternary (Holocene?) fault scarps along the western side of the graben, the westward shifting of playa lakes and the preferred orientation of giant desiccation polygons show that the graben floor is subsiding more rapidly along the western margin. These faults also separate fresh from saline ground water. Four transverse structural lineaments crossing the northern portion of Salt Basin graben were mapped by P.B. King (1948, 1965) and M. Wiley (1970). A fifth zone, trending east-west between the Babb flexure and Bitterwell Mountain is proposed in this thesis. A tectonic origin is suggested by the orientation of the scarps and the proximity of the Mayfield fault scarps to the estimated epicenters of the 1931 Valentine earthquake. The frequency of small earth tremors felt by the residents of the basin and recorded by temporary seismograph stations indicate tectonic adjustments are presently occurring. / text

Increasing salinity has been a growing concern for users of waters from the Pecos River and the reservoirs it feeds in the Texas portion of the River's watershed. Irrigation water diverted from the river in the northern reach of this watershed is often only suitable for a limited number of crops, reducing harvesting options for local farmers. In the south, the Pecos feeds into the International Amistad Reservoir along the border with Mexico. During the 1990s, total dissolved solids concentrations in the reservoir rose as much as 10 mg/L per year and often approached the drinking water standard for potable water (1000 mg/L). Since this time, control efforts have focused on reducing the river's salinity, requiring the identification of salt sources. Hydrologic trend analysis and geochemical identification methods were used to determine these sources for the reach of the river between Red Bluff Reservoir and Brotherton Ranch. Between Red Bluff Reservoir and Coyanosa, flow diversions remove much of the flow that carries the salts, resulting in decreased salt loads, but also making the river more sensitive to evapotranspirative concentration. This sensitivity is evident in the river between Coyanosa and Girvin, where salinity begins to increase to the highest levels within the study area. However, salt loads increase here as well, indicating external salt sources as a contributor. The most substantial increase in bromide ions and the Br-/Cl- ratio appears between Grandfalls and Imperial, although no conclusion could be drawn regarding the identity of the source. The ratio continues to increase up to Girvin, where it appears that evapotranspirative concentration again has a significant effect. Here, several points drifted to the right of the groundwater mixing zones, plotting at values that were uncharacteristic of these sources.

The Middle-Ordovician Simpson group, deposited in a shallow epicontinental sea, is composed of a sequence of interbedded limestone, shale, and smaller amounts of sandstone. By means of electric and radioactivity logs the group is divided into eight zones traceable across Pecos County, except for its absence, over the Fort Stockton uplift area, caused by post-Simpson erosion. Each zone thins persistently eastward toward the Texas Peninsula, which separated the West Texas basin from the Oklahoma basin of deposition. A northwestward increase in sand content of each zone indicates that the source area for the sand was to the northwest. In Pecos County oil is produced from the Simpson at present in only a small north-central area. / text

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Samuel M. Wilson. Vita. Includes bibliographical references.