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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. ItemTexas mineral resources: problems and predictions(University of Texas at Austin. Bureau of Economic Geology, 1965) Flawn, Peter TyrellWhen a reference is made to the mineral resources of Texas, most people think of oil and gas, and some few also of sulfur. And, of course, it is true that of the whopping $4.4 billion dollars' worth of minerals produced in Texas in 1963, 92% was oil, gas, and natural gas liquids. In 1963, for the 29th year, Texas led the Nation as a producer of minerals. Value of mineral products was twice the value of agricultural products, equal to the value of manufactured products, and equal to about one-half the value of all retail trade. It is clear that the State has a mineral-oriented economy; it is true also that the mineral industry is distributed broadly throughout the State and not concentrated in several giant oil fields or very large mines--241 of 254 counties reported mineral production in 1963. But in addition to oil and gas, Texas produced 22 other minerals last year valued at $361.7 million dollars. There are indeed many States which would happily settle for this 8 percent of Texas' mineral production. Significantly, this is the segment of Texas' mineral industry growing most rapidly, and it is the segment that will continue to grow. ItemGeology in the state government of Texas(University of Texas at Austin. Bureau of Economic Geology, 1965) Flawn, Peter TyrellThis circular presents the history of "geological survey" in Texas from its beginning in 1858, through its intermittent early history, to . It also shows that any organization which carried the name "survey" was very short-lived in Texas. Whether this is because of early legislators' convictions that a survey was something that was organized to do a specific job and then terminated, or whether there were deeper causes for the ephemeral nature of the early surveys is a matter for more thorough historical research and analysis. ItemTexas minerals: trends in production(University of Texas at Austin. Bureau of Economic Geology, 1965) Fisher, W. L. (William Lawrence), 1932-Minerals play a vital role in the economy of an industrial State. In Texas, where annual production of minerals currently amounts to more than $4. 5 billion--twice the value of agricultural products, equal the value of manufactured products, and equal to half the value of all retail trade--mineral production is the principal part of the State's economic foundation. Analyses of past production trends and economic factors allow predictions of future trends in this vital and important segment of the Texas economy. Included herein are production graphs and brief annotations of production trends of principal or representative Texas mineral commodities. Period considered is 1950 through 1964, a period embracing significant post-war developments in the State and National economy. ItemFluorspar in Brewster County, Texas(University of Texas at Austin. Bureau of Economic Geology, 1967) McAnulty, William Noel, 1913-Since production of fluorspar began in northern Coahuila, Mexico, in 1950-51, thousands of tons of high-grade ore have been mined from numerous deposits situated 5 to 75 miles south of the Rio Grande. A large part of the fluorspar mined from these deposits has moved northward through Boquillas, Stillwell Crossing, and Heath Crossing to the railhead at Marathon, Texas. Consequently, Marathon has become one of the principal fluorspar shipping points in the world. Even though none of the nearly two million tons of fluorspar shipped from Marathon during the last 15 years came from a deposit in Texas, several occurrences of fluorite are known in southern Brewster County, Texas: the northern Mexico fluorspar province does not terminate abruptly at the Rio Grande. Deposits in Mariscal Mountain in Big Bend National Park are possibly equal in size and grade to deposits 5 to 10 miles southward across the Rio Grande in the San Vicente district. Potentially commercial deposits are known at several places in and around the Christmas Mountains (just outside the northwestern boundary of Big Bend National Park), and fluorite mineralization is widespread throughout the Terlingua quicksilver district. Cretaceous limestone formations which serve as host rocks for fluorspar deposits in northern Coahuila crop out extensively in Brewster County, Texas in the following areas: the Dove Mountain--Maravillas and Reagan Canyon country, on the flanks of the Marathon Dome, in the Sierra del Carmen--Santiago--Del Norte Range, in the Christmas Mountains--Corazones Peaks area, in the Terlingua quicksilver district, and in Mariscal Mountain in Big Bend National Park. But, in Brewster County, as in Coahuila, fluorspar deposits are found only in close proximity to rhyolite intrusions. The intrusive rocks in southeastern Brewster County are dominantly syenodioritic in composition and most of the intrusions north of the Christmas Mountains--Corazones Peaks area are trachytes and microsyenites. ItemUranium in Texas, 1967(University of Texas at Austin. Bureau of Economic Geology, 1967) Flawn, Peter TyrellThe uranium industry, born in boom in the late 1940's and early 1950's, fell upon hard times after about a decade of lusty growth as anticipated private markets failed to develop on schedule and the United States Atomic Energy Commission cut back and stretched out its purchase program. Exploration for uranium in the United States came to a halt. Mills closed down or operated on reduced schedules as contracts expired. But in 1965 there were signs of change as more and more announcements of construction of nuclear reactors for generation of electric power appeared in the newspapers, and by 1966, the discouraged uranium salesman found doors opening rapidly and smiles on the faces of his potential customers. The hoped-for private-sector market for uranium had become a reality. By September 1, 1966, a total of 47 reactors were either in operation, under construction, or firmly committed in the United States; of the total, orders for or commitments for 32 were made since February of 1965. The industry considered this sharply rising curve, looked at the nuclear fuel requirements, appraised the known reserves of uranium ore, and literally sprang into action. In the first half of 1966, only about half a million feet of exploratory drilling was completed; twice this was scheduled for the second half of the year and a million and a half feet has been budgeted for 1967. ItemDepositional systems in the Wilcox Group of Texas and their relationship to occurrence of oil and gas(University of Texas at Austin. Bureau of Economic Geology, 1967) Fisher, W. L. (William Lawrence), 1932-; McGowen, J. H.Regional investigation of the lower part of the Wilcox Group in Texas in outcrop and subsurface indicates seven principal depositional systems. These include: (1) Mt. Pleasant Fluvial System developed updip and in outcrop north of the Colorado River;(2) Rockdale Delta System, present primarily in subsurface, chiefly between the Guadalupe and Sabine Rivers; (3) Pendleton Lagoon-Bay System in outcrop and subsurface largely on the southern flank of the Sabine Uplift; (4) San Marcos Strandplain-Bay System, occurring in outcrop and subsurface mainly on the San Marcos Arch; (5) Cotulla Barrier Bar System in subsurface of South Texas; (6) Indio Bay-Lagoon System developed updip and in outcrop of South Texas; and (7) South Texas Shelf System, an extensive system entirely within subsurface of South Texas. The Rockdale Delta System, consisting of large lobate wedges of muds, sands, and carbonaceous deposits, is the thickest and most extensive of the lower Wilcox depositional systems. It grades updip to the thinner terrigenous facies of the Mt. Pleasant Fluvial System. Deposits of the Rockdale Delta System were the source of sediments redistributed by marine processes and deposited in laterally adjacent marine systems. Delineation of depositional systems and, more specifically, delineation of component facies of the various systems, permits establishment of regional oil and gas trends which show relationship of producing fields and distribution of potentially producing trends. ItemGlen Rose cycles and facies, Paluxy River Valley, Somervell County, Texas(University of Texas at Austin. Bureau of Economic Geology, 1968) Nagle, J. Stewart (James Stewart), 1889-1952Paleoenvironmental analysis of the alternating beds of the basal Cretaceous Glen Rose Formation in Central Texas indicates a cyclical alternation of subtidal through supratidal facies. These facies were reconstructed through detailed analysis of lithology, biota (including macrofauna, microfauna, ichnofauna, and macroflora), detrital shell dispersal, and primary sedimentary structures. Facies succession indicates that each cycle represents a subtidal to supratidal depositional regime transit; cycles are regressional, with the transgressional phase being poorly developed, if at all. This conclusion is in agreement with results of studies of the Holocene transgression, which reveal a regressional succession developed by progradation of shorelines. Some other formations show similar depositional regime transit cycles; hence the Glen Rose model may be widely applicable. Facies variations within and between cycles indicate (1) that there is no typical or ideal cycle, (2) that the cycles record successive sedimentation units within a marginal marine hypersaline lagoon or bay system, and (3) that depositional regime transit cycles have limited correlation value. Facies in the seven cycles in the lower Glen Rose, Paluxy Valley, include subtidal to supratidal flat deposits, marsh, flood plain, shoal patch reef, bay, marsh island, and shifting sand lobe deposits; the only typical aspect of the cycles is their general subtidal to supratidal succession. Mixed terrestrial, marginal marine, and marine faunas and floras within these facies tracts indicate that the lower Glen Rose in this area is a lagoonal or bay depositional system. Paucity of terrigenous elastics, abundance of evaporites, presence of serpulid-patch reefs, and relatively low diversity of faunas with an abundance of thick-shelled ostracods indicate that at least the earlier phases of the lagoonal system were hypersaline. Areal stratigraphic correlation of these depositional regime transit cycles is unwise because the cycles tend to proliferate downdip, and because units that could be used as key beds commonly are local in extent. These beds reflect similar depositional conditions which recur in homotaxial phases of different cycles; indeed potential key beds may change facies within a few miles, even when bed thickness remains nearly constant. Correlation by matching cyclesin sections less than a mile apart, however, is feasible. Several particulars are useful in recognizing position in the cycle. Burrow fillings change upwards from lime-mud to sparry calcite or dolomite--a reflection of diagenetic regime. Burrows with unlithified or partially indurated calcite mud and shells occur in subtidal sediments. Diagenetically modified burrows first appear in or above the zone of sorted and abraded shell, inferred to be the wave or beach zone. Diagenetic burrow modification is intrastratal; this plus the dense fabric with unaltered shells indicate early, soft sediment diagenesis. Paleoenvironmental evidence plus studies of the Recent support the idea that these diagenetic modifications are associated with exposure and solutional modification, dolomite by hypersalinity, sparry calcite by fresh water. Subtidal deposits contain articulated and unsorted shells, many in living position; nearshore wave zone or intertidal shells occur in beds of well-sorted and abraded detrital plates. Supratidal deposits abound in rollers or may contain abraded detrital plates in texturally inverted sediments. Supratidal marshes contain abundant remains of the plant Frenelopsis. Its tiny cells, thick epiderm, protected stomata, and poorly developed roots indicate it is a physiological xerophyte similar to Salicornia of present-day salt marshes. ItemGeometry and distribution of fluvial and deltaic sandstones (Pennsylvanian and Permian), North-Central Texas(University of Texas at Austin. Bureau of Economic Geology, 1969) Brown, L. F. (Leonard Franklin), 1928-Upper Pensylvanian and lower Permian rocks of the Eastern Shelf in North-central Texas are composed of 10 to 15 repetitive sequences including open shelf, deltaic, fluvial, and interdeltaic depositional systems. Sediments derived from the Ouachita Mountains and associated piedmont were transported westward across a narrow coastal plain. Fluvial and deltaic sandstone fac1es define a southwest paleoslopc of about 5 feet per mile. Sandstone facies are delta front sheets, distributary mouth bars, distributary and fluvial channels, and destructional bars. Sandstones displaying distributary patterns represent distal deposition in the upslope area. Belt sandstones, typified by uncommonly thick fluvial channel deposits, prograded far downslope. Composite patterns include distributary and belt sandstones representing complex progradational history. Rocks display one-half degree northwest regional dip; negative structure residuals outline a broad area within which 70 percent of the deltaic facies were deposited. Elongate sandstones are generally arranged parallel to paleoslope in vertically offset patterns controlled by differential compaction of fluvial and deltaic sands and interdistributary muds. Multistory sandstone bodies were deposited along narrow, structurally unstable belts which were periodically overloaded and later reoccupied by prograding deltas. Initial Cisco deltas followed a paleosurface grain controlled by underlying bank limestones; this orientation was maintained during deposition of 1,200 feet of Cisco strata. Each fluvial-deltaic system inherited its geometry from previous systems and, in turn, provided control for the next deltaic episode. Stratigraphic and structural mapping utilizing mud decompaction techniques confirms the roles played by compaction and structure in controlling the geometry of sandstone bodies. ItemSulfur in West Texas, its geology and economics(University of Texas at Austin. Bureau of Economic Geology, 1969) Zimmerman, James B.; Thomas, Eugene, 1904-Sulfur, along with salt, coal, and limestone, is one of the basic raw materials of the chemical industry. A nation's per capita sulfur consumption is a reliable index to its chemical production and a rough index to its standard of living. Sulfur, with its many properties, has literally hundreds of uses; most is used in the manufacture of fertilizers, fibers, papers, pigments, pharmaceuticals, and explosives.Sulfur or brimstone is one of the oldest elements known to man. It was used more than 4,000 years ago in rituals of sacrifice and as a bleaching agent for cotton. The Chinese, around 500 B.C., used sulfur as an ingredient in gunpowder. Arabian alchemists are thought to have discovered sulfuric acid in the 8th Century while trying to convert sulfur to gold. Sulfur became commercially important in 1791 with the development of the Leblanc soda ash process in France (Ambrose, 1965, p. 901). The sulfuric acid industry, which began in the United States near the end of the 18th Century, now uses about 87 percent of the total production. Sulfur plays an increasingly vital role in American industry and agriculture. The 1966 sulfur shortage motivated are evaluation of West Texas geologic and economic potential for sulfur production and a re-examination of its lengthy but spasmodic sulfur history. ItemResource capability units: their utility in land-and water-use management with examples from the Texas coastal zone(University of Texas at Austin. Bureau of Economic Geology, 1971) Brown, L. F. (Leonard Franklin), 1928-; Fisher, W. L. (William Lawrence), 1932-; Erxleben, A. W.; McGowen, J. H.A resource capability unit is an environmental entity--land, water, area of active process, or biota--defined in terms of the nature, degree of activity, or use it can sustain without losing an acceptable level of environmental quality. Units are established by recognizing elements of first-order environmental significance, whether dominantly physical, biologic, or chemical. These include (1) physical units (geologic substrate and soil units), where physical properties are of primary importance; (2) process units, such as beaches, washover channels, floodplains, escarpments, and dunes where active physical processes are dominant factors; (3) biologic units,such as reefs, marshes, swamps, and grassflats where biologic activity and habitation assume first-order significance; and (4) man-made units such as spoil heaps, dredged channels, canals, and made land where man's activity has resulted in important environmental modification. Capability of water systems is defined by the nature and distribution of sediment substrate, overall salinity patterns, circulation, tidal influence, depth variations, turbidity, fresh-water influx, distribution of biologic communities, and water chemistry. This report outlines (1) the nature of resource capability units, (2) the basic factors and properties exhibited by the units that define the limits of their use, and (3)the application of resource capability units to environmental management. Specific examples are shown for the 20,000 square miles of the Texas Coastal Zone, where a wide variety of resource units occur in an area of diverse human activities. 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. ItemMineral deposits in the West Chinati stock, Chinati Mountains, Presidio County, Texas(University of Texas at Austin. Bureau of Economic Geology, 1972) McAnulty, William Noel, 1913-The West Chinati stock, well exposed in San Antonio Canyon and immediately westward on slopes of the southwestern part of the Chinati Mountains, Presidio County, Texas, is a large stocklike body of porphyritic hornblende granite cut by numerous dikes and irregular-shaped plutons of rhyolite, rhyolite porphyry, microgranite, trachyte porphyry, diorite, and igneous breccia.Fissure veins developed in wide and long sheeted zones which strike E-W and N. 50" E. containpotentially commercial deposits of lead-zinc-silver fluorspar, minerals including galena (PbS), sphalerite (ZnS), argentite (Ag2S), cerargyrite (AgCl), and fluorite (CaF2). Minor amounts of chalcopyrite (CuFeS2) and oxidized copper minerals also occur in the fissure vein deposits. Marginal bodies of rhyolite, rhyolite porphyry, and trachyte porphyry contain disseminated copper mineralization and possibly host commercial porphyry-type copper deposits. 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. 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. ItemDepositional-episodes: their relationship to the Quaternary stratigraphic framework in the northwestern portion of the Gulf Basin(University of Texas at Austin. Bureau of Economic Geology, 1974) Frazier, David E.The stratigraphic record yields evidence that each episode of clastic silicate deposition has been of limited duration and that each has been preceded and followed by a significant hiatus. Evidence for alternations of deposition and nondeposition is readily apparent in the landward portions of Pleistocene deposits along the Gulf Coast, due to the glacio-eustatic changes in sea level; evidence of alternations, although elusive, exists also in the basinward portions of these deposits. The concept of depositional-episodes explains the significance and relationship of these alternating conditions throughout the basin. The strata attributed to each depositional episode are a composite of several discrete facies sequences and are referred to in this paper as a depositional-complex. Each facies-sequence represents either a single delta lobe within a deltaic progression, or one of the several repetitive sequences deposited in an interdeltaic environment. Each depositional-complex records and defines a depositional-episode and indicates three phases of development. Deposits of the initial phase record a stillstand of the sea during which each of the several rivers entering the basin prograde a succession of delta lobes and interdeltaic facies sequences across the shelf. The second phase of development (which is penecontemporaneous with the first) is recorded by the intercalation of clastic and organic flood-plain deposits which accumulate on the newly formed coastal plain, and by the deep-water hemipelagc basin sediments which are secondarily derived from unstable sediments deposited in the outermost shelf and uppermost slope environments. The terminal phase is evidenced by sediments deposited during a period of instability when a marine transgression either continuously or intermittently forces estuarine conditions on the rivers entering the basin. Throughout the terminal transgression, the finite zone of active deposition adjacent to the shoreline is shifted landward. Basinward of this active zone of deposition, hiatal conditions are imposed and at the instant of maximum transgression, when the depositional-episode is terminated, all points on the hiatal surface are synchronous. The bounding surfaces of depositional complexes represent natural stratigraphic breaks over the entire basin and are related to hiatal conditions imposed by marine transgressions. Within the Quaternary section, the repetitive alternation of depositional-episodes and significant hiatuses is due to the glacio-eustatic fluctuations of sea level: as a result, worldwide correlations of the Quaternary depositional complexes and hiatal surfaces may be possible. ItemPotential geothermal resources of Texas(University of Texas at Austin. Bureau of Economic Geology, 1974) Dorfman, Myron; Kehle, Ralph O.Geothermal energy is rapidly becoming recognized, both in the United States and abroad, as a viable source of energy which can supplement fossil fuels for electric power generation. Exploration and development of geothermal reservoirs is intensifying in the western United States and Mexico, and will continue to expand as petroleum supplies diminish and costs increase. Although geothermal energy is commonly perceived as a new and exotic energy source, it is neither. Steam has been used for electric power generation since 1904 in Larderello, Italy, and geothermal waters have been used for space heating and agricultural purposes in other parts of the world since 1890. Geothermal power generation began in the United States in 1960 at the Geysers, California, and new fields are under development in the Salton trough of southern California. Herein we will attempt to answer some of the basic questions about geothermal energy: what it is, how deposits are formed, and where these deposits are located. Special emphasis is placed on the potential geothermal resources of the Texas Gulf Coast and Trans-Pecos Texas. This discussion should provide the reader with an appreciation for both the problems and advantages of this unfamiliar form of energy as well as the potential it holds for supplying Texas with a portion of its future energy needs. ItemPhysiographic features and stratification types of coarse-grained point bars: modern and ancient examples(University of Texas at Austin. Bureau of Economic Geology, 1975) McGowen, J. H.; Garner, L. E.Primary sedimentary structures in modern point-bar deposits of the Amite River in Louisiana and the Colorado River in Texas are analogous to features observed in Eocene Simsboro and Pleistocene Colorado River deposits of the Texas Gulf Coastal Plain. Short-duration peak flow, channel pattern, average stream gradient of about 2 to 3 ft/mi, and bank stabilization by dense vegetation are major parameters controlling the depositional pattern of coarse sand and pebble gravel of the Amite and Colorado Rivers. Stratification is directly related to specific depositional features and consists of: large-scale trough-fill cross-stratification in the scour pool; trough-fill cross-stratification and foreset cross-stratification in the lower point bar; parallel laminae, large foreset cross-stratification, and trough-fill cross-stratification in the chute bar, parallel-inclined laminae, climbing ripple laminae, and mud drapes in the chute fill, and parallel inclined laminae, mud drape, and foreset crossstratification in overbank, floodplain deposits. Fundamental differences between point bars of bed-load streams (low suspended load/bed-load ratio) and mixed-load streams (high suspended load/bed-load ratio) are that upper point-bar sed iments with small trough sets and parallel-inclined laminae occur only in fine-grained (mixed load) fluvial deposits, and large-scale foresets of chute bars are common to coarse-grained (bed load) fluvial deposits but are not found in fine-grained fluvial deposits. Upward-fining sequences, characteristic of fine-grained fluvial deposits, are uncommon in sediments deposited by bed-load streams such as the Amite and Colorado Rivers. The Simsboro Sandstone consists mainly of scour-pool, lower point-bar, and chute-bar sediments. Chute-fill and floodplain deposits are preserved only in the highest stratigraphic sequence. Pleistocene Colorado River deposits display the same sequence of stratification types as the Simsboro but are composed of coarser material. ItemShoreline changes between Sabine Pass and Bolivar Roads: an analysis of historical changes of the Texas Gulf shoreline(University of Texas at Austin. Bureau of Economic Geology, 1975) Morton, Robert A.Historical monitoring between Sabine Pass and Bolivar Roads records the nature and magnitude of changes in position of the shoreline and vegetation line and provides insight into the factors affecting those changes. Documentation of changes is accomplished by the compilation of shoreline and vegetation line position from topographic maps, aerial photographs, and coastal charts of various vintages. Comparison of shoreline position based on topographic charts (dated 1882-83) and aerial photographs (taken in 1930, 1955-57, 1965, and 1974) indicates short-term changes of accretion and erosion along the Gulf shoreline between Sabine Pass and Bolivar Roads. Erosion produces a net loss in land, whereas accretion produces a net gain in land. Comparison of the vegetation line based on the aforementioned aerial photographs indicates short-term cycles of erosion related to storms (primarily hurricanes) and recovery during intervening years of low storm incidence. Long-term trend or direction of shoreline changes averaged over the 92-year time period of this study indicates that net accretion was 2,225 feet at Sabine Pass although there was no net change 2 miles west of Sabine Pass. Except for minor accretion associated with shoreline adjustment where the major change in orientation of the coast occurs west of Sabine Pass, net erosion dominated the shoreline from the preceding segment to approximately 3 miles east of Crystal Beach. Maximum net erosion was 2,900 feet or 31.5 feet per year; minimum net erosion was 100 feet or 1.1 feet per year. Net erosion for this segment over the 92-year time interval averaged 775 feet or 8.4 feet per year. Net accretion or equilibrium was recorded along the remaining beach westward from Crystal Beach to the east jetty at Bolivar Roads. Maximum net accretion for this segment, 2,575 feet, occurred just east of the east jetty; minimum net accretion for this segment was 25 feet. Because of limitations imposed by the technique used, rates of change are subordinate to trends or direction of change. Furthermore, values determined for long-term net changes should be used in context. The values for rates of net change are adequate for describing long-term trends; however, rates of short-term changes may be of greater magnitude than rates of long-term changes, particularly in areas where both accretion and erosion have occurred. Major and minor factors affecting shoreline changes include: (1) climate, (2) storm frequency and intensity, (3) local and eustatic sea-level conditions, (4) sediment budget, and (5) human activities. The major factors affecting shoreline changes along the Texas Coast, including the shoreline between Sabine Pass and Bolivar Roads, are relative sea-level rise, compactional subsidence, and a deficit in sediment supply. Changes in position of the vegetation line are primarily related to storms. Studies indicate that changes in shoreline and vegetation line between Sabine Pass and Bolivar Roads are largely the result of natural processes, perhaps expedited by man's activities. The only exceptions are accretion associated with the jetties at Sabine Pass and Bolivar Roads as well as erosion aggravated by the opening of Rollover Pass. A basic comprehension of these physical processes and their effects is requisite to avoid or minimize physical and economic losses associated with development and use of the coast. ItemMicrorelief (Gilgai) structures on expansive clays of the Texas Coastal Plain: their recognition and significance in engineering construction(University of Texas at Austin. Bureau of Economic Geology, 1975) Gustavson, Thomas C.Cracked pavements, undulating road surfaces, broken curbs, stairstep fractures of brick and stone building walls, and tilted power poles are common occurrences in areas underlain by cracking, expansive clay soils of the Vertisol order. These soils, which underlie 15 to 20 percent of the Coastal Plain of Texas, are composed predominately of montmorillonite and develop distinctive microtopographic features known as gilgaies. Relief between adjacent microknolls or ridges and microdepressions ranges up to 18 inches (45.7 cm). Cracks develop in these soils to depths of 60 inches (152.4 cm) and to widths of 4 inches (10.2 cm). Gilgai microtopography forms as montmorillonitic clay soils expand with the adsorption of water introduced via deep cracks, root holes, animal burrows, and normal gravity infiltration. Subsoil clay and dry clay soil which has fallen into cracks from the surface expand, causing subsoil material to move both laterally and upward. Areas of marked vertical movement produce diapirlike ridges of light-colored clay subsoil extending upward into dark surface soils. The subsoil diapirs underlie surface microknolls and microridges. Areas of gilgai microrelief are easily recognized from aerial photographs on which the scale is greater than 1:80,000. On slopes of less than 1 percent, the pattern is an irregular network of microridges. As slope increases, microridges and microdepressions become elongated downslope, resulting in a pattern of alternating linear ridges and troughs that are approximately parallel to slope direction. Towards the bases of slopes, gilgai microtopography becomes obscured by colluvium. As a consequence of large hydration pressures, vertical soil movements in areas of gilgai microrelief may place severe limitations on the construction of roads, buildings, power lines, buried transmission lines, and pipelines. Current engineering techniques for the mitigation of damage to highways and buildings include lime stabilization, ponding, and subgrading of highways .and use of steel reinforcing bars or post-tension cables in concrete-foundation slabs of buildings.