26 research outputs found
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Physical Environment at the King Ranch Training Site
The King Ranch training site of the Texas Army National Guard is a relatively pristine site that has suffered little physical abuse. Except for possible past overgrazing (as evidenced by the mesquite growth), the land has been used only as pasture. There is no record of major historical storms, but even a major hurricane would not damage the land. Surficial damages to the land surface and its vegetation are possible both when soils are saturated and during drought. Hurricanes are likely to make access to the site difficult; floodwaters from the Santa Gertrudis, Tranquitas, San Fernando, and Carreta Creeks would make U.S. Highway 77 impassable (Federal Emergency Management Agency, 1984). The fact that average annual precipitation is exceeded by evaporation indicates the potential for major drought. A drought would impact National Guard activities by limiting transportation because areas devegetated by traffic are attacked by wind deflation. During very dry periods, National Guard equipment and vehicles may potentially cause range fires.Bureau of Economic Geolog
Missourian Facies in the Possum Kingdom Vicinity, Palo Pinto County, Texas
The uppermost Keechie Creek, the Palo Pinto, the Wolf Mountain, and the Winchell Formations of the Missourian Series were mapped in the Possum Kingdom vicinity, Palo Pinto County, Texas. The Keechie Creek and Wolf Mountain Formations are dominantly terrigenous facies. The Palo Pinto Formation is an off-bank facies which crops out immediately updip of an equivalent subsurface limestone bank. Both the bank and off-bank facies of the Winchell Limestone crop out in the study area. Typical Missourian terrigenous facies includes mostly unfossiliferous silty clay shales intercalated with a small volume of fine-grained sandstones. Away from equivalent limestone banks the shales contain abundant clay-ironstone concretions. Near gradational contacts with limestone banks the silty clays become fossiliferous. Rarely, the terrigenous sandstones grade laterally into limestones. Limestone banks grade laterally into terrigenous and calcareous facies that are different from the bank facies itself. Typical bank facies consist of 2/3 limestone with a micritic matrix and 1/3 limestone with sparry matrix; only thin shale partings are present. The primary bank builders are platy algae in micritic limestones, osagiid-like algae in sparry limestones, and fenestrate bryozoans in both micritic and sparry limestones. Normal to the sedimentary strike of the algal-bryozoan banks the typical bank limestones grade into limestone-types which usually have a micritic matrix and contain increasing amounts of clay. In the same direction the volume of terrigenous facies increases. As much as 75 feet of bank limestones grade laterally into entirely terrigenous facies in one-quarter mile. The depositional environment of bank facies is inferred to have included: (1) slightly higher topography than surrounding terrigenous environments, (2) firm bottom sediments, (3) low turbidity in shallow marine water, and (4) abundant, loose faunal remains
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Analysis of Lineations in the Eagle Flat Study Area, Hudspeth County, Texas
The purpose of this study of the Eagle Flat study area, Hudspeth County, Texas, is to determine the density and orientation of lineaments as part of a characterization study of a proposed site for the Texas low-level radioactive waste repository. Because both the number and total length of lineations per unit area are low at the proposed site (north Paskin Ranch), the results of lineation analyses do not impact repository siting. The lineation study may, however, be a useful adjunct to other ongoing investigations of recharge, Quaternary faulting, geomorphology, and fissures.
The scope of this study is to examine the occurrence of lineations on aerial photographs and lineaments on Landsat imagery as they reflect topography and slopes, drainage, bedrock, soils, and geologic structure, as well as the degree to which analysis of linear elements contributes to understanding of both the geologic history of an arid area and the active geologic processes altering the ground surface. Lineations were identified on black-and-white, 1:22,000-scale, stereographic pairs of aerial photographs and transferred to 7.5-minute quadrangles, digitized, statistically analyzed (number, length, and azimuth) per unit area, and printed on maps that were hand-contoured. The study area was divided into 96 unit areas (4 mi2) for analysis. Thirty rectangular areas were selected to characterize the lineations associated with particular stratigraphic, structural, or geomorphic properties.
Histograms and scattergrams with straight-line curve-fitting of linear and geologic properties were computed to evaluate the characteristics of the lineations in the 30 selected areas. Five separate areas of Cretaceous outcrop have 26, 27, 28, 29, and 32 lineations per square mile; two Precambrian hills have 59 and 58/mi2. For straight-line curve-fitting of lineation lengths to age and type of bedrock, the R values display correlations of 0.918 to 0.982 for three Precambrian outcrop areas, 0.969 for Permian Hueco Limestone outcrop areas, and 0.886 and 0.873 in two Cretaceous outcrop areas. Azimuth R values are: 0.918, 0.950, and 0.988 (Precambrian), 0.823 (Permian), and 0.919 and 0.983 (Cretaceous). The best correlation of the number of lineations per grid and relief is 0.473, but 0.657 is the R factor of all selected slopes.
Lineations were interpreted on seven scenes of Landsat imagery containing the Eagle Flat study area. No lineations pass through or near the proposed site on Paskin Ranch; most lineations parallel structure and drainage.Bureau of Economic Geolog
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Physical Envoirnment of Camp Mabry, Austin, Texas
This report describes the physical attributes of Camp Mabry, in Austin, Texas, headquarters of Texas Army National Guard training. This is one of five reports completed on training sites; complementary reports describe training sites at Camp Bowie, Camp Swift, Fort Wolters, and King Ranch. The purpose of these five reports is to provide the natural physical data generally reported in an Environmental Assessment (EA) in conformity with the Environmental Protection Act and to present data applicable to an environmental training manual. The data are presented in text and maps; the maps show spatial layers that can be useful when a Geographic Information System (GIS) is later developed for training site management. Most of the data are collected from available sources in state and federal government reports and files.Bureau of Economic Geolog
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Physical Environment of Fort Wolters Military Reservation, Parker and Palo Pinto Counties, Texas
The purpose of this report is to describe the physical environment of Fort Wolters Military Reservation and to call attention to physical processes occurring on the base, to note availability of data, and to comment on potential limitations to land use. Fort Wolters (3,985 ac) is one of the training areas administered by the Texas Adjutant General for activities of the Texas Army National Guard. The Bureau of Economic Geology reviewed existing publications to identify essential baseline data (climate; geology, soil properties, hydrology, and present land condition) and made additional observations that will assist the Texas Adjutant General in preparing long-term environmental assessments mandated by the National Environmental Policy Act and U.S. Environmental Protection Agency regulations and environmental land management and land-condition monitoring plans required by the U.S. Army. This report also includes basic digital line graph (DLG) data sets for cultural features, hydrology, topography, and soils.
Fort Wolters is located in North-Central Texas in western Parker County and easternmost Palo Pinto County, about 3 mi northeast of the City of Mineral Wells. The area is within the subtropical subhumid climatic region of Texas, with an average annual precipitation of about 29 inches. Intense thunderstorms result in flashy surface runoff, causing erosion of unprotected soils, and flooding and siltation in area creeks. The principal bedrock geologic unit is the Pennsylvanian Mineral Wells Formation, which consists of shale with interbedded sandstone and limestone. Soils are mostly sandy loam and clayey loam. Because of the shaley nature of the Pennsylvanian strata, there are no major freshwater aquifers beneath the base. Limited amounts of fresh water are present in fractures in limestone and sandstone interbeds.Bureau of Economic Geolog
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Geological and Climatic Survey, Camp Bowie Military Reservation Brownwood, Texas
Camp Bowie, a Texas Army National Guard (TXARNG) training area located 6 miles south-southeast of Brownwood, Texas, and comprising 8,755 acres, is presently distributed as two parcels: an original reserve comprising 5,410 acres and a newly acquired adjacent tract to the southeast comprising 3,345 acres (Figure 1). The training area is used for vehicle maintenance and improving combat readiness in the TXARNG and is mandated for company and platoon-level training of reserve and active personnel in the use of armored vehicles and .50-caliber (nonexplosive) training devices. The area is of a size sufficient to implement the Army Training and Evaluation Program (ARTEP). The overall plan includes discontinuing agricultural use and allowing the land to return to a natural, if not original, physical state (Adjutant General's Department of Texas, 1992).
Physiographically, Camp Bowie is on a transition between rolling hills developed on Cretaceous rocks of the Grand Prairie province in the east and the generally lower-relief Osage Plains developed on much older rocks (Triassic, Permian, and Pennsylvanian) to the west (Sellards and others, 1932; Figure 2). These physiographic provinces have also been called Cross Timbers and Prairies, and Rolling Plains, respectively (Gould, 1975). The area is in the Colorado River drainage basin and includes many small intermittent creeks. Water from these streams eventually drains into Pecan Bayou to the east of the camp or Indian Creek to the west. Pecan Bayou and Indian Creek drain south into the Colorado River (Figure 1).Bureau of Economic Geolog
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The Feasibility of Locating a Texas Salt Test Facility
Differences in the geology of dome salt and bedded salt dictate that data and mining experience gained in one environment will not be fully applicable to the other. A test facility in a salt dome could be mined through a relatively thin section of elastic, a cap rock of evaporite minerals that may contain highly porous zones, and possibly 300 m (1,000 ft) of salt. The salt will probably be quite pure except for a few percent anhydrite, increasing in concentration toward the top of the salt stock (Balk, 1949; Muehlberger, 1959; and Dutton and Kreitler, 1980). Infrequent inclusions of the surrounding sediments may be found in dome salt that has been highly contorted and whose crystals show translational gliding as a result of salt dome emplacement (Muehlberger, 1959; Clabaugh, 1962; and Hofrichter, 1968).
Access to bedded salt will require mining through a sequence of predominantly terrigenous elastics and evaporites. The degree of consolidation, porosity, and permeability of these sediments will vary between horizons. The objective interval will be a required thickness of relatively pure salt. Crystallographic properties, water content, and elastic inclusions will be results of the original depositional environment rather than emplacement of a salt stock.
The feasibility of locating a Salt Test Facility in Texas has been studied and evaluated. Measured parameters are summarized in table 1. For primarily technical reasons, the most feasible Texas sites are the Gyp Hill salt dome in Brooks County or bedded salt in Loving County.Bureau of Economic Geolog
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Initial Report on the Geology of the Northeastern Part of the New Braunfels, Texas
This brief report describes initial progress on geologic mapping and paleontologic studies that are being conducted in the vicinity of New Braunfels, Texas. The primary objective of this work is to produce an accurate geologic map that will be printed on the new 1:100,000-scale map of the New Braunfels, Texas, 30 X 60 minute quadrangle, which is in preparation by the U.S. Geological Survey. A planimetric version has been printed, but the final topographic map is not yet available. Our initial mapping has been completed on 1:24,000-scale topographic maps and is intended for compilation at 1:100,000-scale. Partial funding for the second year of the study has been approved. Work during year two will continue the mapping into quadrangles adjacent to those mapped in year one. Paleontologic work by Dr. Will Elder will continue as part of the in-kind contribution by the U.S. Geological Survey to this effort. Dr. E. G. Wermund has described this project to several groups for whom the geology of this area is of interest. Draft copies of the mapping accomplished to date have been given to the Edwards Underground Water District, potentially for entry by them into a GIS, and copies will be made available to other interested parties as requested. In addition, the South Texas Geological Society has passed a resolution commending this initiative, supporting this new mapping effort, and offering the help of their membership.Bureau of Economic Geolog
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Secondary Natural Gas Recovery: Reservoir Heterogeneity and Potential for Reserve Growth through Infield Drilling: An Example from McAllen Ranch Field, Hidalgo County, Texas
Integrated engineering, geological, geophysical, and petrophysical analyses of McAllen Ranch field have delineated several controls on secondary recovery of natural gas. Barriers to the flow of natural gas within laterally continuous lower Vicksburg sandstone reservoirs can be demonstrated through finite-element modeling. These barriers are probably diagenetic in origin. In the B area of McAllen Ranch field, faults are unlikely to be the primary barriers to gas flow because faults were not inferred from analysis of high-quality three-dimensional seismic images between the key wells used in this study (Hill and others, 1991). Barriers result in incremental reserve additions when some reservoir domains contain no well completions. Areas containing potential incremental gas resources, identified through this analysis, were confirmed by subsequent recompletions in 1991. Three recompletions proposed by this project have proved successful. Our analysis of public domain production data indicates that new infield wells in the Vicksburg S reservoir have increased reserves 69 percent above an estimate made from analysis of 1980 public domain data. Additionally, more than 100 barrels per day of reserves has been added through new wells drilled between 1988 and 1991. Most of the McAllen Ranch Vicksburg S reserve increases are due to a geological reinterpretation that has stimulated infield step-out development of the Vicksburg S reservoir. Distributary-channel-fill sandstones are the most likely candidates to contain incremental reserves because they are laterally discontinuous and are predominant in areas where numerous reservoir sandstones are stacked.Bureau of Economic Geolog
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Preliminary Evaluation of the Eagle Flat Region Hudspeth County, Texas
Preliminary evaluation of the Eagle Flat region, as designated by the Texas Legislature, indicates several areas that may have geologic and hydrologic conditions favorable for further evaluation as potential siting areas for the Texas low-level radioactive waste repository. This determination is based on a review of available data regarding surface drainage, thickness and character of alluvial fill, depth to groundwater, and apparent presence or absence of such features as late Cenozoic faults, fissures, known natural resources, and evidence of erosion. Some general siting areas have been identified that contain several sections that appear to have favorable characteristics. Examples of apparently favorable general siting areas are east of Yucca Mesa, south of Eagle Flat Mountain, and north of Little Hills. Our preliminary assessment is that, of the three areas cited above, the Yucca Mesa location should be given priority consideration. Initial flooding and drainage analysis indicates that the Yucca Mesa site includes sufficient surface areas unaffected by flooding. There are no known fissures or late Cenozoic faults. Depth to groundwater may be in excess of 500 ft, and the water quality may be poor. Shallow alluvium may be somewhat finer grained than at other settings, and the surface appears to be relatively stable and devoid of major incision by existing drainages. Although each of these characteristics needs to be investigated by further work, the most critical unanswered question is the thickness of alluvial fill. Available gravity data, including recent work by The University of Texas at El Paso, indicates that 100 ft or more of alluvial fill may be present in the area. Other areas may be present that are of equal or similar merit, but the preliminary analysis and available information suggest that the Yucca Mesa location apparently has the most favorable characteristics of those general siting areas identified currently. Smaller potential siting areas, generally about 400 to 800 acres in size, also may exist locally throughout the region where alluvial fill may be of sufficient thickness and drainage characteristics may be appropriate. These smaller potential siting areas would require additional site-specific evaluation of surface drainage characteristics before drill testing could be recommended. Any potential siting area is unique and would require site-specific evaluation activities to assess its suitability for characterization.Bureau of Economic Geolog