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ItemA numeric code for describing rocks in sedimentary basins(University of Texas at Austin. Bureau of Economic Geology, 1974) Wermund, E. G.; Caughey, Charles A.The purpose of this paper is to present a system of encoding rock data for multiple uses that include (1) mapping subsurface stratigraphy for economic exploration, (2) cataloging borings used in subsurface waste disposal, and (3) building a library of natural resource information. Regional surface and subsurface stratigraphic studies for exploration in sedimentary basins commonly require the handling of numerous columnar sections that display rock descriptions collected from both outcrop and borings. Data of the borings are core descriptions, logs of cuttings or ditch samples, and mechanical logs of physical properties such as self potential, resistivity, gamma, gamma-neutron, and others. It is not unusual in a regional problem for a geologist to use columnar data from 2,500 or more localities (Wermund and Jenkins, 1970; Galloway and Brown, 1972). One way of handling large stratigraphic data files is to describe the rocks in a computer-compatible format. Whenever lithofacies mapping or statistical analyses become a required means toward solving regional stratigraphic problems, a numerical encoding system to describe the rocks becomes valuable. Although there is a large literature on solving regional problems including various numerical (or lithofacies) mapping techniques, little has been written about methods for encoding rock data. At least, the writers are unaware of many published systems for encoding lithologic descriptions. There is considerable evidence (Galley, 1968) that the problem of disposing of man's wastes will increase in size and complexity and that waste disposal into deep wells will become more common than now. This will be especially true regarding disposal of radioactive wastes (Kubo and Rose, 1973). A catalog of possible deep disposal sites for which the lithologic sequence is encoded will be a valuable adjunct to decision making. Even for shallow pits at the surface which are more in demand the encoding of lithology will be useful. Related to the above needs, increased interest in the construction of environmental and natural resource inventories gives further impetus toward encoding rocks. This interest concerns ongoing active legislation to formulate land use policy and law. Government agencies at all levels, foreseeing their responsibilities in land management, actively discuss many kinds of classification and information systems, one of which is always a natural resources information system. Examples are land use classification (Anderson, Hardy, and Roach, 1972), the proposed nationwide RALI information system formulated by the U.S. Geological Survey (Clarke, 1973), and a Texas natural resources information system (Interagency Council on Natural Resources and Environment, 1973). Part of any natural resources information system requires the description of typical sections of rock in representative or critical geographic regions. If these natural resources systems are to be computer-compatible, then a lithologic encoding system will be an essential element. ItemA preliminary assessment of the geologic setting, hydrology, and geochemistry of the Hueco Tanks geothermal area, Texas and New Mexico(University of Texas at Austin. Bureau of Economic Geology, 1981) Henry, Christopher D.; Gluck, James K.The Hueco Tanks geothermal area contains five known but now inactive hot wells (50° to 71°C). The area trends north-south along the east side of Tularosa-Hueco Bolson astride the Texas-New Mexico border approximately 40 km northeast of El Paso. Because of its proximity to El Paso, geothermal water in the Hueco Tanks area could be a significant resource. Hueco Bolson is an asymmetric graben. Greatest displacement along boundary faults is on the west side adjacent to the Franklin Mountains. Faults, probably with less displacement, also form an irregular boundary on the east side of the bolson. Several probable faults may allow the rise of thermal waters from depth. Ground water in the central part of Hueco Bolson flows southward to the Rio Grande. However, four of the five hot wells occur in a ground-water trough along the eastern margin of the bolson. The trough may be bounded by one of the postulated faults serving as a barrier to ground-water flow. Data on permeability of potential reservoir rocks, including basin fill and fractured bedrock, suggest that they may be sufficiently permeable for development of geothermal water. The concentration of dissolved solids in the geothermal waters varies from 1,100 to at least 12,500 mg/L, but most waters show high concentrations. They are Na-Cl-(SO4) waters similar in composition to nonthermal waters in basin fill. The composition probably results from contact with evaporite deposits either in basin fill or in Paleozoic bedrock. Shallow reservoirs reach maximum temperatures of about 80° to 110°C. Available data are too limited to evaluate adequately the resource potential of geothermal water in the Hueco Tanks area. A complete exploration program, including geological, hydrological, and geochemical investigation, is recommended. ItemA revision of Taylor nomenclature, Upper Cretaceous, Central Texas(University of Texas at Austin. Bureau of Economic Geology, 1965) Young, Keith, 1918-2004Since the days of R. T. Hill (1901) two Upper Cretaceous lithic units have been used as formations but have remained unnamed. These two units have usually been called the "Lower Taylor Marl" and the "Upper Taylor Marl". If Taylor is used as a group, both of these formations belong in the Taylor Group. If one uses Hill's division system of classification, the "Upper Taylor Marl" belongs to the Taylor Division but the "Lower Taylor Marl" belongs to the Austin Division, since it is a claystone lithosome interfingering with the type Austin Chalk and is genetically part of the Austin. Schuchert (1943, p. 900) may have been aware of some of the problems and some of the confusion rising out of this nomenclatural muddle when he applied the term "unnamed formation" to the unit generally termed "Lower Taylor Marl". The "Lower Taylor" and the "Upper Taylor" are separated by the Pecan Gap Formation (Stephenson, 1918) so that the lithic sequence is claystone, chalk (or marly limestone), and claystone. In more detailed maps of the greater area of Austin, Texas, the Pecan Gap is omitted by faulting in some areas, leaving the two claystone formations in fault contact. To eliminate confusion, it is imperative that the two unnamed claystone units be named. ItemAsbestos in the Allamoore Talc District, Hudspeth and Culberson Counties, Texas(University of Texas at Austin. Bureau of Economic Geology, 1973) Rohrbacher, R. G.The Allamoore district of Hudspeth and Culberson counties, Texas, has become one of the most significant talc-producing areas of the United States. Exploitation of talc deposits in the district began in 1952 with a cumulative production of 120,000 tons through 1957 (Flawn, 1958). With continued growth, annual production exceeded 160,000 tons in 1968, making the district second only to New York State in national output, Moderate- to large-sized deposits have been developed with near-surface parts inexpensively extracted. Talc reserves are estimated in the tens of millions of tons. Long-fiber asbestos was first found in association with talc deposits of the Allamoore district in 1960 during exploratory drilling of what became the Buck claim, Small amounts of asbestos were noted in subsequent development of this large talc deposit. Later, small amounts of white asbestos were encountered in the T. & P. No. 1 mine and... at the Neal-Mann prospect (fig. 1). Early in 1971, Albert Gregory of Van Horn, Texas, discovered an asbestos deposit now known as the Diablo prospect. Subsequently, the Van Horn Soapstone and Talc Corporation was formed and preliminary exploratory work at the prospect indicated the possible presence of commercially exploitable amounts of asbestos. This evaluation of asbestos deposits is based on a current study of the stratigraphy, structure, and mineral deposits of the talc district. ItemBloating characteristics of east Texas clays(University of Texas at Austin. Bureau of Economic Geology, 1965) Fisher, W. L. (William Lawrence), 1932-; Garner, L. E.Incidence of bloating among approximately 600 clay samples from East Texas, ranging in age from Gulfian (Late Cretaceous) to Recent, correlates principally with clay mineralogy-and pH--together an indication of bulk composition--and to a lesser extent with texture, loss on ignition, and content of nonclay refractory minerals. Clay-mineral and pH data permit prediction of bloating with an accuracy of about 80 percent. Montmorillonitic and illitic clays are the best bloaters; bloating occurs in more than 80 percent of clays consisting of less than 30 percent kaolinite, more than l 0 percent illite, and between 20 and 90 percent montmorillonite. Only 10 percent of the high-alumina clays (more than 50 percent kaolinite) bloat; these generally are plastic and carbonaceous. Value of pH is an index of the amount of certain flux and gas-forming materials in clays; accordingly, bloating incidence generally increases with increase in pH. Incidence of bloating also increases slightly with decrease in grain size, increase in plasticity, increase in loss on ignition, and decrease in content of nonclay refractory minerals. ItemCalderas and mineralization: volcanic geology and mineralization in the Chinati Caldera complex, trans-Pecos Texas(University of Texas at Austin. Bureau of Economic Geology, 1981) Duex, Timothy W.; Henry, Christopher D.This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some (Albers and Kleinhampl, 1970) and denied by others (McKee, 1976, 1979). Steven and others (1974) have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, post-subsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chinati caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas. ItemCotton Valley (Upper Jurassic) and Hosston (Lower Cretaceous) depositional systems and their influence on salt tectonics in the East Texas Basin(University of Texas at Austin. Bureau of Economic Geology, 1984) McGowen, Mary K.; Harris, David W.Correct interpretation of the effect of basin infilling on salt mobilization is critical to understanding salt dome growth and stability. The size of salt structures in the East Texas Basin is determined by the original thickness of the underlying Louann Salt (Middle Jurassic). That is, salt structures distinctly increase in size toward the interior of the basin. Initial movement of salt apparently occurred in the marginal areas of the basin during Smackover (Late Jurassic) deposition. This movement seems to have resulted from downward creep induced by the loading of carbonate units and was enhanced by basinward tilting. During a major shift from carbonate to clastic sedimentation in the Late Jurassic, salt movement became more extensive. This salt migration was caused by uneven sediment loading of fluvial-deltaic systems in the Cotton Valley Group (Upper Jurassic) and the Hosston Formation (Lower Cretaceous). Erosion source areas on the west and north persisted throughout Cotton Valley and Hosston time. Clastics were delivered to the East Texas Basin by many small streams, rather than by one major stream, because a mature drainage system had not yet formed. The Cotton Valley Group, thought to be a fan-delta system, can be subdivided into three types of facies: prodelta deposits, delta-front deposits, and braided fluvial deposits. Fan deltas, supplied by braided streams, prograded from the north, northwest, and west. Dip-oriented sandstone trends dominate in the northwestern part of the basin and change basinward to northeast to southwest strike-oriented trends. During Hosston time, sedimentation in the northwestern part of the basin was predominantly fluvial. The depositional characteristics of sediments in this area are typical of braided streams. In the study area, parallel net-sandstone and sediment chucks are clearly defined in the distal part of the Cotton Valley but are not as well defined in the Hosston. This suggests that most deltaic sedimentation during Hosston time occurred basinward of the study area. A major transgression at the end of Hosston time resulted in the deposition of the Pettet Limestone. Apparently, the location of salt domes and salt anticlines was controlled by the position of the Smackover-Gilmer carbonate platform. This platform impeded local subsidence to the extent that fan-delta sediments of the Cotton Valley Group spread laterally across the shelf rather than stacked vertically. Sediment depocenters formed preferentially basinward of the platform, resulting in migration of the underlying salt into ridges that fronted the prograding sediment wedge. As the salt was depleted under these depocenters, subsidence slowed and thereby allowed the fan deltas to override the salt ridges. This resulted in a basinward progradation of deltaic depocenters and produced younger depocenters toward the interior of the basin. Further salt migration and differentiation of salt ridges produced the present complex array of salt domes and anticlines in the East Texas Basin. Seismic and gravity data clearly demonstrate the existence of these salt ridges and intervening sediment thicknesses. ItemCretaceous paleogeography: implications of endemic ammonite faunas(University of Texas at Austin. Bureau of Economic Geology, 1972) Young, Keith, 1918-2004Endemic ammonite faunas evolved from cosmopolitan faunas in a series of successive episodes over about 35 million years of the Cretaceous of the Gulf Coast of the United States. During basin-basin-margin tectonic adjustments the Cretaceous barrier reef was inundated or circumvented so that a cosmopolitan fauna entered the back-reef area. Gradual isolation of the fauna behind the barrier produced endemism. With the next basin adjustment the endemic fauna became extinct, and a new cosmopolitan fauna migrated into the back-reef area, likewise evolving into an endemic fauna in its turn. Six cosmopolitan-endemic cycles have been identified. Geological evidence suggests two or three additional cycles. ItemDepositional systems and oil-gas reservoirs in the Queen City Formation (Eocene), Texas(University of Texas at Austin. Bureau of Economic Geology, 1972) Guevara, Edgar H.; García, RobertoRegional surface and subsurface studies indicate that thick deltaic (Queen City Formation) and thin shelf (Reklaw and Weches Formations) sequences compose the stratigraphic interval between the top of the Carrizo Sand and the base of the Sparta Formation. In East Texas, the Queen City Formation accumulated as part of a high-constructive, lobate delta system; and in South Texas, as part of a high-destructive, wave-dominated delta system. In South Texas, principal facies are meanderbelt sand, lagoonal mud, stacked coastal barriers, and prodelta shelf mud facies. In East Texas, delta plain, delta front, and prodelta facies are dominant; and in Central Texas, the principal facies are strandplain sands originated by southwestward longshore drift of sediments from the high-constructive delta system. Facies distribution, composition, and size of the deltas in East Texas are similar to lobes of the Holocene high-constructive Mississippi delta system and to ancient deltas in the lower part of the Wilcox and m the Jackson Groups of the Gulf Coast Basin. Deltaic sediments of South Texas are comparable to Pleistocene high-destructive, wave-dominated facies on the Surinam coast, to the Holocene Rhone delta system, and to ancient deltas in the upper part of the Wilcox Group. Queen City deltas prograded gulfward over shelf muds and glauconites of the Reklaw Formation; they are overlain by comparable shelf facies of the Weches Formation. In East Texas, deltaic facies wedge out eastward. Terrigenous elastics of the high-destructive deltas extend southward into Mexico. Hydrocarbons are produced from thin strike-oriented sands downdip from the belt of maximum sand thickness of the high-destructive deltas in South Texas; only a minor amount of oil and gas has been obtained from delta front and distributary channel sands of the high-constructive deltas in East Texas. ItemDepositional systems and structural controls of Hackberry sandstone reservoirs in southeast Texas(University of Texas at Austin. Bureau of Economic Geology, 1984) Ewing, Thomas E.; Reed, Roneé S.Deep-water sandstones of the Oligocene-age Hackberry unit of the Frio Formation contain significant quantities of oil and gas and remain potentially one of the most productive exploration targets in southeast Texas. The Hackberry is a wedge of sandstone and shale containing bathyal fauna that separates upper Frio barrier-bar - strandplain sandstones from lower Frio neritic shale and sand. Major Hackberry sandstones lie atop a channeled unconformity that forms the base of the unit. Sandstones in a typical sand-rich channel at Port Arthur field grade upward from a basal, confined channel-fill sandstone to more widespread, broad, fan-channel deposits, Topmost are proximal to medial fan deposits and overbank turbidite deposits. The sequence suggests that Hackberry sandstones were laid down by an onlapping submarine canyon-fan complex deposited in canyons that eroded headward into the contemporaneous Frio barrier system. Regional maps and seismic interpretations outline a network of sand-filled channels extending from the barrier toward the southeast. The earliest structural activity of the Port Arthur area is lower Oligocene (Vicksburg) faulting associated with continental-slope sedimentation. Small growth faults of late Oligocene (Frio) age displace the Hackberry section less than 500 ft and extend upward into Miocene strata. Isopach and isolith maps indicate that the Orange, Port Neches, and Fannett salt domes were active uplifts during Frio and Anahuac (Lower Miocene) deposition. Near Spindletop dome, however, only a north-south-trending salt-cored ridge is present. The Hackberry channels are in part located in salt-withdrawal basins, but major channel axes extend across the uplifts. Time versus depth plots of water depth and sediment thickness indicate that most of the Hackberry Embayment in Texas could have been formed by normal subsidence during the later Oligocene if the embayment were cut off from its supply of muddy sediment. Thick, sandy, lower Hackberry deposits filled deep canyons eroded into the retreating shelf margin. The Hackberry contains two hydrocarbon plays. The updip play is relatively shallow and oil-rich and lies near the updip limit of deep-water deposition. Some of the fields in this play produce from barrier-bar - strandplain Frio sandstones erroneously correlated with the Hackberry. The downdip play is gas-rich and generally geopressured. The reservoirs lie either within or on the flanks of the major channel systems and are commonly bounded updip by small growth faults, Understanding the component depositional environments represented by the discontinuous and complex lithofacies of these sandstones will improve hydrocarbon exploration and production.