Browsing by Author "Raney, J. A."

Now showing 1 - 20 of 41

1998 Annual Report - Year One: Geo-Environmental Characterization of the Delta del Orinoco, Venezuela
(1999) Raney, J. A.
The 1998 Annual Report for the project "Geo-Environmental Characterization of the Delta del Orinoco" describes the first year of work by the Bureau of Economic Geology (Bureau) at The University of Texas at Austin. The five-year project is funded by the Coordinación Desarrollo Económico de Oriente (DAO) of Petróleos de Venezuela, S.A. (PDVSA). PDVSA/DAO is supporting this work in the Orinoco Delta so that development of hydrocarbon resources and other projects for the benefit of the people of Venezuela can proceed with a minimum of adverse impacts in this ecologically diverse and sensitive area. Key to this effort is establishing an accessible baseline of environmental data and developing an understanding of the physical and biological dynamics of the delta system. This information is essential for anticipating the consequences of natural and human-induced changes in the environment of the Delta. The Bureau's role is to conduct technical studies, support collateral investigations by Venezuelan participants, assist DAO with technical coordination and program development, integrate the results of the various studies for public dissemination, and facilitate other technology transfer and institutional strengthening activities. Much was accomplished during 1998. Working concert with DAO, Bureau personnel assisted in the definition of related environmental studies, met with Venezuelan project participants to share initial results and coordinate planned activities, conducted joint field studies to collect data and observations, and helped DAO obtain international support for the investigations. Many of the issues encountered during 1998, such as many aspects of field logistics, were successfully resolved so that studies in subsequent phases of the project can proceed efficiently.
Analysis of Lineations in the Eagle Flat Study Area, Hudspeth County, Texas
(1992) Wermund, E. G.; Raney, J. A.
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.
Characterization of Mineral and Geothermal Resources in the Eagle Flat Region, West Texas
(1992) Seni, Steven J.; Raney, J. A.
The location and distribution of mineral and geothermal resources of the Eagle Flat study area have been described as part of the geologic characterization of the proposed site for the Texas low-level radioactive waste repository. Mineral localities were evaluated within the 400 mi2 (1,024 km2) Eagle Flat study area (Allamoore, Grayton Lake, Devil Ridge, Sierra Blanca, Bean Hill, and Dome Peak 7.5-minute topographic quadrangles) surrounding the proposed site. In order to more fully evaluate the regional trends and mineralogic associations, mineral localities were also characterized within a larger 900 mi2 (2,304 km2) reconnaissance area that includes 16 additional 7.5-minute quadrangles immediately surrounding the study area. The distribution and character of known mineral resources are important to the evaluation of the potential for economic mineral deposits on the siting area of the Texas low-level radioactive waste repository on the north Paskin Ranch. Excluding sand and gravel, which are ubiquitous in the basin, talc and possibly beryllium are the only known economic mineral deposits in the area. At the proposed site, basin-fill sediments in excess of 150 ft (45 m) thick probably preclude open-pit mining of talc or beryllium, and no favorable host rocks for talc are known to be present beneath the site. Beryllium is also highly unlikely because there are no drilling or geophysical data that indicate the occurrence of igneous intrusions beneath the basin-fill sediments of north Paskin Ranch. In addition, the site is located in a basin, not a highland, as is typical of intrusion-associated, Tertiary hydrothermal systems that occur elsewhere in the region.
Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas
(1991) Raney, J. A.; Seni, Steven J.; DuBar, Jules R.; Walter, T. G.
In a five-county area of South Texas, geopressured-geothermal reservoirs in the upper Wilcox Group are colocated with heavy-oil reservoirs in the overlying Jackson Group. In 1990, research at the Bureau of Economic Geology concentrated on evaluating the potential of using geopressured-geothermal water for hot-water flooding of heavy-oil reservoirs. Favorable geothermal reservoirs are defined by thick deltaic sandstones and growth-fault-bounded compartments. Potential geothermal reservoirs are present at a depth of 11,000 ft (3,350 m) to 15,000 ft (4,570 m) and contain water at temperatures of 350°F (177Â°C) to 383°F (195°C) in Fandango field, Zapata County. One potential geothermal reservoir sandstone in the upper Wilcox (R sandstone) is composed of a continuous sand body 100 ft (30 m) to greater than 200 ft (>61 m) thick. Fault blocks average 2 to 4 mi^2 (5.2 to 10.4 km^2) in area. Both heavy-oil (average API=19) and light-oil (average API=26) reservoirs in South Texas are present in sandstones of the Jackson Group Mirando trend. The updip pinch-out of strike-oriented sheet sandstones in the Jackson Group largely controls the distribution of Mirando-trend heavy-oil reservoirs. The lateral continuity of heavy-oil reservoirs minimizes reservoir compartmentalization, which could disrupt injected-fluid flow paths. Geologic and engineering research that still needs to be conducted includes (1) studies of the chemical compatibility between injected geothermal fluids and clay matrix of heavy-oil reservoirs, (2) detailed field studies of geometry and size of geothermal reservoirs, (3) detailed field studies of geometry and size of heavy-oil reservoirs, and (4) studies of changes in the temperature and chemistry of geothermal fluids when injected into heavy-oil reservoirs.
Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas: Colocation of Heavy-Oil and Geothermal Resources in South Texas
(1992) Seni, Steven J.; Walter, T. G.; Raney, J. A.
In a five-county area of South Texas, geopressured-geothermal reservoirs in the Eocene Wilcox Group occur below heavy-oil reservoirs in the Eocene Jackson Group. This colocation warrants consideration of the use of geothermal fluids for a thermally enhanced waterflood. Geothermal fairways comprise thick deltaic sandstones within growth-fault-bounded compartments containing geopressured water in excess of 250°F. Geothermal reservoirs occur at depths of 11,000 to 15,000 ft in continuous sandstones 100 to 200 ft thick. Permeability ranges from 1 to 150 md, and porosity from 12 to 24 percent. Updip pinch-out of shallowly buried (200 to 2,000 ft) barrier-bar/strandplain sandstones largely controls the distribution of heavy-oil reservoirs. Subtle structure, small faults, and sandbody pinch-outs form lateral barriers of the reservoirs. Structural, depositional, and diagenetic variations affect reservoir compartmentalization. The heavy-oil reservoirs are typically porous (25 to 35 percent), permeable (100 to 1,000 md), slightly clayey fine to medium sand. Calcite-cemented zones of low porosity (>5 percent) and permeability (0.01 md) compartmentalize reservoirs. Injection of hot (300°F), moderately fresh to saline brines will improve oil recovery by lowering viscosity and decreasing residual oil saturation. Matrix clays are smectites, which could swell and clog pore throats if injected waters were fresh. The high temperature of injected fluids will collapse some of the interlayer clays, thus increasing porosity and permeability. Reservoir heterogeneity resulting from facies variation and diagenesis must be considered when siting production and injection wells within the heavy-oil reservoir. The suitability of abandoned gas wells as geothermal production wells and their long-term well productivity also affect the economics of geothermally enhanced hot-water flooding.
Deforestation in Belize 1989/1992-1994/1996
(1996) White, William Allen, 1939-; Raney, J. A.; Tremblay, Thomas A.
Belize has extensive forest and associated woodland resources characterized primarily by tall, highly diverse broadleaf forests, and secondarily by pine forests, low scrubby woodland areas, and abundant mangroves (King and others, 1986, 1989, 1992; Zisman, 1992; Forest Department, 1993; and LIC, 1994). Among the environmental issues facing Belize are deforestation and the management of forest resources. Thousands of hectares of broadleaf forest have been cleared for agriculture and other purposes (Forest Department, 1993). Nevertheless, it is generally believed that the amount of deforestation that has occurred in Belize is much less than that which has occurred in other regions. The Ministry of Natural Resources of Belize, and its various components including the Land Information Centre (LIC), Forestry Department, and Lands and Survey Department, recognized the importance of assessing the current distribution of forest cover and determining the extent of deforestation in order to document the magnitude of the problem and to provide quantitative information to assist in managing these valuable natural resources.
Description and Quaternary History of the Campo Grande Fault of the Hueco Basin, Hudspeth and El Paso Counties, Trans-Pecos Texas
(1990) Collins, Edward W.; Raney, J. A.
The Hueco Basin of Trans-Pecos Texas and Chihuahua, Mexico, formed in response to Basin and Range extensional tectonism that began about 24 million years ago and continues to the present. The southeastern arm of the basin is asymmetrical with the thickest sediments deposited along the fault-bounded basin axis near the southwestern flank. Approximately 45 km long and striking northwestward, the Campo Grande fault is 12 km from the northeastern basin edge; it divides the downthrown, central part of the basin (>2,000 m of fill) from the shallower (175 m of fill) northeastern flank. Another major northwest-striking fault dips northeastward and bounds the southwestern basin margin in Mexico. The Campo Grande fault trend is composed of en echelon fault strands that are 1.5 to 10 km long and have strikes of N25° to 75°W. Dips are between 60° and 90° southwest. Displacements decrease near terminations of strands. Grooves on fault planes indicate mostly dip-slip movement. Fault scarps have been modified by erosion of the footwall and deposition on the hanging wall. Erosion-resistant caliche (stages IV to V) at the surface aids in preserving scarp heights of between 1.5 and 11.5 m and scarp slopes of 4° to 17°. Analysis of faulted upper Tertiary and Quaternary units indicates that successively younger units have less displacement. Maximum vertical offset measured across fault strands cutting the middle Pleistocene Madden Gravel (0.6 to 0.4 million years old), which caps the Camp Rice Formation, is about 10 m. Repeated arroyo incision and fluvial aggradation since the middle Pleistocene have developed Pleistocene terraces that are locally correlative and are mapped as parts of the regionally outcropping Ramey and Balluco Gravels. Holocene terraces also occur. Maximum throws across fault strands that cut Ramey terraces (0.4 to 0.1 million years old?) are 2.5 to 3 m, but some Ramey deposits overlie fault strands and are not faulted. Offset of Balluco (0.1 to 0.025 million years old?) and Holocene terraces has not been observed at fault strands that cut Ramey terraces. The average recurrence interval is 0.1 million years (maximum), and the last faulting episode was late Pleistocene. On the downdropped block of one fault strand, faulted calcic horizons (0.5 to 1.0 m thick; stage III) with vertical separations of 1 to 2 m indicate at least five episodes of movement, deposition, and surface stabilization during the last 0.6 to 0.4 million years. Maximum vertical offset during the last faulting event was about 1 to 1.5 m.
Description and Quaternary History of the Campo Grande Fault of the Hueco Basin, Hudspeth and El Paso Counties, Trans-Pecos Texas
(1989) Collins, Edward W.; Raney, J. A.
The Hueco Basin of Trans-Pecos Texas and Chihuahua, Mexico, formed in response to Basin and Range extensional tectonism that began about 24 million years ago and continues to the present. The southeastern arm of the basin is asymmetrical, with the thickest sediments deposited along the fault-bounded basin axis near the southwestern flank. Approximately 45 kilometers long and striking northwestward, the Campo Grande fault is 12 kilometers from the northeastern basin edge; it divides the downthrown central part of the basin (with over 2,000 meters of fill) from the shallower (175 meters) northeastern flank. Another major northwest-striking fault dips northeastward and bounds the southwestern basin margin in Mexico. The Campo Grande fault trend is composed of at least 17 en echelon fault strands that are 1.5 to 10 kilometers long, with strikes of N25° to 75°W. Dips range between 60 and 90° southwest. Displacements decrease near the terminations of strands. Grooves on fault planes indicate mostly dip-slip movement. Fault scarps have been modified by erosion of the footwall and deposition on the hanging wall. Erosion-resistant caliche (stages IV to V) at the surface aids in preserving scarp heights ranging from 1.5 to 11.5 meters and scarp slopes of 4 to 17°.
Eagle Flat Project, Hudspeth County, Texas
(1992) Raney, J. A.; Collins, Edward W.; Darling, Bruce Kelley, 1951-
The geomorphic, stratigraphic, and structural geologic studies are designed to characterize the geologic setting of the site and region. The results of these studies are required for the license application, to support design and geotechnical studies, and to construct the hydrogeologic framework. Various elements of the regional stratigraphy and structural setting have been described by many authors. Our studies will synthesize relevant portions of the previous work but focus on those issues that require more detailed characterization and analysis to evaluate the proposed site. Exposed bedrock geology, for example, was generally well mapped in the vicinity of the Faskin Ranch-Eagle Flat region by Underwood (1963), Albritton and Smith (1965), and King (1965). We have compiled the previous mapping on the six topographic maps (1:24,000) that cover the area designated by the Texas Legislature (fig. 1). Drilling, mapping, and geophysical studies associated with this project will add new information on the bedrock units beneath the basin-fill sediments and on the character of the basin-fill sediments themselves, particularly in the siting area.
Geologic and Hydrologic Studies of Sites Hu1A and Hu1B in Hudspeth County, Texas
(1987) Kreitler, Charles W.; Raney, J. A.; Mullican, William F.
The Bureau of Economic Geology, The University of Texas at Austin, conducted preliminary investigations of the geology and hydrology of northern Hudspeth County for the Texas Low-Level Radioactive Waste Disposal Authority. The Authority had previously identified two sites, HU1A and HU1B, as possible sites for an above-ground disposal facility for low-level radioactive wastes. Regional and site-specific investigations were conducted to characterize the geology and hydrology of HU1A and HU1B. The two sites are underlain by different bedrock lithologies covered by alluvium, which necessitated drilling for site-specific investigations. Because of the lack of exposed bedrock, studies of the regional geologic setting were used to infer the probable nature of the bedrock geologic environment at each site. Hydrologic studies were predominantly regional because of the limited data available at either site and the availability of water-level data and water samples from previously drilled wells in the region.
Geologic map of the New Braunfels, Texas, 30 x 60 minute quadrangle
(Bureau of Economic Geology University of Texas at Austin, 2000) Collins, Edward W.
Portion of a scanned and georeferenced version of Collins, E.W., 2000, Geologic Map of the New Braunfels, Texas, 30x60 Minute Quadrangle: University of Texas at Austin, Bureau of Economic Geology, Miscellaneous Map MM-39, scale 1:100,000.
Geologic Review of Proposed Dallas -Fort Worth Area Site for the Superconducting Super Collider (SSC)
(1987) Raney, J. A.; Allen, Peter M.; Reaser, Donald F.; Collins, Edward W.
In June 1987, the Texas National Research Laboratory Commission tasked the Bureau of Economic Geology at The University of Texas at Austin with reviewing and providing a brief report on the geology of the proposed site for the Superconducting Super Collider (SSC) in the Dallas-Fort Worth area. Additionally, they requested a surface geologic map of the site. An informal task force was assembled for this purpose, comprising Jay A. Raney (Coordinator and Structural Geology) from the Bureau of Economic Geology, Peter M. Allen (Environmental Geology and Stratigraphy) from Baylor University, Donald F. Reaser (Structural Geology and Stratigraphy) from The University of Texas at Arlington, and Edward W. Collins (Structural Geology) from the Bureau of Economic Geology. This report by the task force provides an explanatory note for the geologic map (Plate 1) of the proposed site near Waxahachie, Texas.
Geologic Review of Propsed Amarillo Area Site for the Superconducting Super Collider (SSC)
(1987) Raney, J. A.; Gustavson, Thomas C.; Caran, S. Christopher
In June 1987, the Texas National Research Laboratory Commission commissioned the Bureau of Economic Geology at The University of Texas at Austin to conduct a review and brief report on the geology of the proposed site for the Superconducting Super Collider (SSC) in the Amarillo area. They also requested a surface geologic map of the site. An informal task force was assembled for this purpose, including Jay A. Raney (Coordinator), Thomas C. Gustavson, and S. Christopher Caran from the Bureau of Economic Geology. This report is accompanied by the geologic map (Plate 1) of the proposed Amarillo area site in the Texas Panhandle.
Geology of Sierra Del Carmen, West Texas and Mexico: A General Geologic Framework to Support Mapping of Biologic (Botanical) Resources
(1996) Collins, Edward W.; Raney, J. A.
The purpose of this study is to provide geologic base maps to support the mapping of biological (botanical) resources in the Sierra del Carmen, Coahuila, Mexico, and adjacent areas in Big Bend National Park, Brewster County, Texas. Sierra del Carmen, which generally trends north-northwestward, includes the eastern part of Big Bend National Park and extends southerly into adjacent Coahuila. The range, which is within the Chihuahuan Desert, rises abruptly from the desert floor and has topographic relief that exceeds 2,000 m. The terrain is rugged, and the range is marked by numerous narrow and steep-sided canyons and valleys. The stratigraphic framework of the range is one aspect that controls the distribution of vegetation throughout the area. In general, different rock types can weather into soils of different composition, and the rocks and soils may contain different amounts of moisture. Thus, different plant species may be associated with specific rock lithologies. Geologic structures such as faults, folds, and fracture zones control the position of the rock units and influence landforms, drainage directions, and canyon development. Structures may also influence the concentration and retention of surface moisture. The geologic map of this region is intended to assist other scientists, students, and interested visitors in understanding the geology of this fascinating area and in interpreting the influence of the geologic framework on related sciences. The map emphasizes bedrock and surficial units that can be important controls on the distribution of plant communities.
Initial Report on the Geology of the Northeastern Part of the New Braunfels, Texas
(1991) Raney, J. A.; Baumgardner, Jr., Robert W.; Collins, Edward W.; Wermund, E. G.
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.
Late Cenozoic Faults of the Region Surrounding the Eagle Flat Study Area, Northwestern Trans-Pecos Texas
(1993) Collins, Edward W.; Raney, J. A.
The Eagle Flat study area is located along the southeastern edge of the southern Basin and Range-Rio Grande tectonic province in Trans-Pecos Texas. The desert region that encompasses the study area consists of the broad Diablo Plateau and a series of mountain ranges and adjacent intermontane basins that formed by extensional faulting that probably occurred in the last 24 mya. There has been no historical surface rupturing of faults in Trans-Pecos Texas, although earthquakes have occurred and faults that displace Quaternary (present to approximately 2 mya) deposits are present (fig. 1). Geologic investigations of faults active during the Quaternary provide important data (tables A-1 and A-2) for seismic risk studies of the proposed Eagle Flat low-level radioactive waste repository. Most of the Quaternary faults of Trans-Pecos Texas are between about 11 and 24.8 mi (18 and 40 km) long (table A-1). Many of the faults are sections of longer fault zones that are between 43 and 64 mi (70 and 105 km) long. Strikes of individual faults are variable, although most of the fault zones strike northwestward or northward. Faults dip between 50° and 89°. Fourteen Quaternary faults are within 31 mi (50 km) of the proposed repository.
Map and Data for Quaternary Faults in West Texas and Adjacent Parts of Mexico
(1996) Collins, Edward W.; Raney, J. A.; Machette, Michael N.
The "World Map of Major Active Faults" Project is compiling a series of digital maps for the United States and other countries that show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds; the companion database includes published information on these seismogenic features. This effort is sponsored by International Lithosphere Program (ILP) Project 11-2 and funded by the Earthquake Hazards Reduction Program (EHRP) through the U.S. Geological Survey. The maps and accompanying databases represent a key contribution to the new Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Disaster Reduction. This compilation, which describes surface faulting in West Texas and adjacent parts of Mexico, is the first of many similar State and regional compilations that are planned for the project. This compilation is presented as a traditional map product and printed catalog of data; however both should be available in digital form in the future. The database provides referenced data on a variety of geographic, geologic, and paleoseismologic parameters. The fault data were compiled by the senior authors (Edward W. Collins and Jay A. Raney, Texas Bureau of Economic Geology) as part of ongoing studies of active faulting in the West Texas area and adjacent parts of Mexico. The U.S. Geological Survey authors are responsible for organizing and integrating State and regional products under the national project, including the coordination and oversight of contributions from individuals and groups (Michael N. Machette, Project Chief), database design and management (Kathleen M. Haller), and digitization and manipulation of map data (Richard L. Dart).
Mineral Resource Assessment of Lands Administered by the Texas General Land Office in the Franklin Mountains, El Paso County, Texas
(1994) Raney, J. A.; Collins, Edward W.
The Franklin Mountains, with relief as great as 2,700 feet, bound the west edge of the northwest Hueco Basin. El Paso lies at the southern margin of the mountains where they terminate at the Rio Grande. The mountain range, a west-dipping, tilted fault block that trends northerly, is composed of a relatively continuous stratigraphic section of Precambrian through Permian rocks that are locally intruded by Tertiary igneous rocks (Harbour, 1972; LeMone, 1982, 1988). Quaternary alluvial-fan deposits have built up off the edge of the mountains into the adjacent basins (Raney and Collins, 1994a, b). Tertiary to Quaternary basin-fill fluvial and older lacustrine deposits rarely crop out. We have compiled the geology of the El Paso and North Franklin Mountain quadrangles, which are enclosed in the pocket at the back of this report.
Mineral Resource Assessment. Big Bend RanchState Natural Area, Presidio and Brewster Counties, Texas - Final Report
(1989) Henry, Christopher D.; Raney, J. A.; Rubin, Jeffrey N.; Standen, Allan R.
The Big Bend Ranch State Natural Area has a diverse geology reflecting nearly 600 million years of geologic evolution. Major geologic events include (1) deposition of elastic sedimentary rocks during the Paleozoic and their deformation (folding and faulting) at the end of the Paleozoic; (2) deposition of limestone and elastic rocks during the Cretaceous and their deformation during the early Tertiary; (3) intense extrusive and intrusive igneous activity during the middle Tertiary; and (4) major normal faulting during the late Tertiary. Almost all mineral potential of the area is associated with mid-Tertiary igneous activity. The only significant mineral production within the Ranch area was from the Fresno Mine in the western part of the Terlingua mercury district, one of the largest mining districts in Texas. This mine produced approximately 3500 flasks of mercury, mostly during World War II. Other production was minor and included some additional mercury from localities near the Fresno Mine, as well as silver-lead ore containing minor gold from a small mine in the Solitario.
Preliminary Evaluation of the Eagle Flat Region Hudspeth County, Texas
(1991) Raney, J. A.; Kreitler, Charles W.; Darling, Bruce Kelley, 1951-; Wermund, E. G.; Blount, Jonathan Gray; Randy Hill
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.