Browsing by Subject "geomorphology"

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3rd Annual Jackson School Research Symposium
(Jackson School of Geosciences, The University of Texas at Austin, 2014-01-25) Jackson School of Geosciences; The University of Texas at Austin
4th Annual Jackson School Research Symposium
(2015-02) Jackson School of Geosciences; The University of Texas at Austin
5th Annual Jackson School Research Symposium
(Jackson School of Geosciences; The University of Texas at Austin, 2016-02) Jackson School of Geosciences; The University of Texas at Austin
6th Annual Jackson School of Geosciences Student Research Symposium, February 4, 2017
(Jackson School of Geosciences; The University of Texas at Austin, 2017-02) Jackson School of Geosciences; The University of Texas at Austin
7th Annual Jackson School of Geosciences Student Research Symposium, February 3, 2018
(Jackson School of Geosciences; The University of Texas at Austin, 2018-02-03) Jackson School of Geosciences; The University of Texas at Austin
8th Annual Jackson School of Geosciences Student Research Symposium, February 2, 2019
(Jackson School of Geosciences; The University of Texas at Austin, 2019-02) Jackson School of Geosciences; The University of Texas at Austin
9th Annual Jackson School of Geosciences Student Research Symposium, February 15, 2020
(Jackson School of Geosciences; The University of Texas at Austin, 2020-02) Jackson School of Geosciences; The University of Texas at Austin
Anaylsis of Beach Morphology and Water Levels at Three Sites Along the Texas Gulf Shore
(1997) Morton, Robert A.
Integration of beach profiles and water-level measurements at three sites on a microtidal, wave-dominated coast reveals that tide-gauge records systematically underestimate the actual elevations and horizontal positions that water reaches on the beach as a result of wave runup. On low-gradient sandy beaches, natural morphological beach features, such as the erosional scarp and vegetation line, accurately reflect the positions of frequent maximum high-water levels, and the berm crest reflects the position of more frequent ordinary high-water levels, whereas tide-gauge records consistently predict lower maximum and average levels of beach flooding. The discrepancies between predicted and actual water positions on the beach have important scientific and legal implications. The scientific implications involve the need to map shoreline features that closely track the long-term trends in beach movement but are insensitive to short-term fluctuations in water level. Neither the instantaneous high-water line (wet beach-dry beach boundary) nor the berm crest satisfy this requirement, and therefore, they are not recommended for monitoring shoreline position either in the field or interpreted from aerial photographs unless there is no reliable alternative. The legal implications pertain to land ownership and property boundaries in the United States that currently are surveyed from tide-gauge records but were originally defined by common law on the basis of high-water levels that leave physical marks on the upland property. Because water levels are actually higher on the beach than predicted by tide gauges, land surveys based on a tidal datum allocate more littoral property to the upland owner than is justified by the physical facts or was intended by law. Consequently, the publicly owned state submerged lands encompass less of the beach than that area which is regularly flooded by marine water.
Biogeography of Cyprinodon across the Great Plains-Chihuahuan Desert region and adjacent areas
(Desert Fishes Council, 2021) Hoagstrom, Christopher; Osborne, Megan
Cyprinodon is renowned for localized endemism across the North American desert. Competing molecular studies have made elucidating timing of diversification across the desert controversial. Debate has focused on Mojave Desert species, with limited evaluation of other evidence. However, the Great Plains and Chihuahuan Desert harbor more taxonomic diversity and are geographically positioned between the Gulf of México (place of origin for the genus) and Mojave Desert, making them central to understanding the evolution of all desert Cyprinodon. This study is a detailed assessment of evidence from literature spanning geomorphology, climate, and biogeography vis à vis the mtDNA phylogeny for Cyprinodon. Conclusions of Late Miocene-Early Pleistocene diversification are supported across all major clades. Future studies that could improve understanding and address ongoing dilemmas are identified. Importantly, the geography of each clade corresponds to drainage configurations and their evolution through the proposed period of diversification. Eight hypotheses are presented to address major evolutionary events, with emphasis on exploring interpretive challenges within the phylogeny. Broadly, aridity within the Late Miocene apparently facilitated inland invasion of coastal Cyprinodon along the ancestral Brazos River and Río Grande. The following Pliocene warm, wet period enabled survival and range expansion through aridland drainages and into adjacent ones. Mio-Pliocene development of the Río Grande Rift and Gila River drainages, causing inter-drainage transfers, was crucial to range expansion. Development of other Gulf of California drainages (Colorado River, Río Yaqui) played peripheral roles. Climatic cooling in the Quaternary Period evidently caused range contractions for populations living at higher latitudes and elevations. Living Cyprinodon of the desert represent an incredible legacy of Pliocene range expansion memorialized by subsequent persistence of tenacious endemic populations. Human impacts now threaten this legacy.
The Chora of Chersonesos on the Black Sea: The 1998 Campaign
(Institute of Classical Archaeology, 1998) Carter, Joseph Coleman
The 1998 campaign season focused upon the site of Bezymyannaya, in the chora of Chersonesos. Thanks to a partnership with NASA, ICA was able to use remote sensing to map out much of the area, including the nearby necropolis. The report details ICA's first year of use of the new remote sensing technology and its significance for future excavation.
Formation of the Wink Sink, a Salt Dissolution Collapse Feature, Winkler County, Texas
(1982) Baumgardner, Jr., Robert W.; Hoadley, Ann D.; Goldstein, Arthur G.
The Wink Sink, located in Winkler County, Texas, formed suddenly on June 3, 1980. Within 24 hours, it expanded to a maximum width of 360 feet (110 meters) and reached a maximum depth of 110 feet (34 meters) by June 5. The volume of the sinkhole is estimated to be approximately 5.6 million cubic feet (158,600 cubic meters). Over the course of June 3 to June 6, a large area along the southern rim of the sink experienced subsidence of about 10 feet (3 meters) relative to the northern side. Further subsidence of 1.456 feet (44.4 centimeters) occurred along the southern rim between July 19 and December 12, 1980. The precursor to the sinkhole was likely a solution cavity that migrated upward due to successive roof failures, resulting in a collapse chimney filled with brecciated rock. The dissolution of salt in the Permian Salado Formation is believed to have created the solution cavity, with the Salado Formation's depth ranging from 1,300 to 2,200 feet (396 to 670 meters). However, data on the size and initial depth of the solution cavity are unavailable. Several dissolution zones are present within the Salado Formation in the region. Dissolution occurring in the middle of the Salado evaporite sequence may have been caused by groundwater flow along fractured anhydrite interbeds. Water could have come into contact with salt either through downward movement from overlying aquifers or upward movement from underlying aquifers under artesian pressure.
Geomorphic Processes of the Texas Panhandle
(1983) Baumgardner, Jr., Robert W.
Joints are fractures in a rock that exhibit no detectable displacement between one face of the fracture and the other. Previous work on the origin of joints has determined different mechanisms to explain fracturing. Some researchers have explained joints in terms of their relationship to tectonic deformation and major structural elements (Harris and others, 1960; Price, 1966; Stearns and Friedman, 1972). Others have shown that joints may develop independently from tectonic deformation and that joints may form in sedimentary rocks early in their history (Parker, 1942; Hodgson, 1961; Price, 1966; Cook and Johnson, 1970). Price (1974) investigated the development of joints and stress systems in undeformed sediments during the accumulation of a sedimentary series, its downwarping and subsequent uplift, and accompanying de-watering of the sediments. Joints can also result from unloading due to erosion (Chapman, 1958). The formation of joints in sedimentary rocks is dependent on three factors (Hobbs, 1967): (1) physical properties of both the fractured rock bed and the surrounding rock beds; (2) thickness of the rock bed; and (3) degree of tectonic deformation of the beds.
Late Cenozoic Geomorphic Evolution of the Texas Panhandle and Northeastern New Mexico: Case Studies of Structural Controls of Regional Drainage Development
(1984) Gustavson, Thomas C.; Finley, Robert J.
Salt dissolution has affected parts of the Upper Permian Salado, Seven Rivers, San Andres, Glorieta, and upper Clear Fork Formations beneath the Pecos River Valley in eastern New Mexico and beneath the Canadian River Valley and the Rolling Plains of the Texas Panhandle. Extensive dissolution of the salts of the Salado and Seven Rivers Formations has also occurred beneath the Southern High Plains. The cumulative thickness of salt lost to dissolution exceeds 150 m (500 ft) along the western, northern, and eastern margins of the Palo Duro Basin. Dissolution and subsidence occurred during the deposition of the Tertiary Ogallala Formation, but Ogallala deposition kept pace with subsidence. Following the end of Ogallala deposition in the late Pliocene, surface subsidence resulted in lacustrine basins along trends of relatively rapid dissolution. Preserved lacustrine sediments contain Blancan faunas, confirming minimum late Pliocene ages for the basins. Continued subsidence along trends of relatively rapid dissolution during the late Tertiary and early Quaternary resulted in a series of basins that diverted many of the streams flowing southeasterly across the Southern High Plains. As a result of subsidence, the headwaters of the ancestral Brazos River were diverted during the middle Pleistocene from a southeasterly drainage through the Portales paleovalley to a southerly drainage through the Pecos Valley. The present-day headwaters of the Canadian River are probably a former tributary of the Pecos-Portales-Brazos system that was diverted to the northeast along a subsidence trend caused by dissolution during the late Pliocene or early Quaternary.
Letter to H.B. Stenzel from Frank L. Doyle on 1951-03-04
(1951-03-04) Doyle, Frank L.
Modern Eolian Processes on the Southern High Plains
(1984) Machenberg, Marcie D.; Caran, S. Christopher
Eolian processes have substantially modified the landscape on the Southern High Plains within historic times. The maximum inferred rate of deflation was 18.9 mm/year at a site in Bailey County, Texas, a region of loose, sandy soils and frequent, seasonal dust storms. At least locally, agricultural practices have accelerated natural rates of erosion and deposition by winds. An extensive cover of windblown sand and silt mantles the gently sloping surface of the Southern High Plains. Eolian deflation and deposition are among the dominant geomorphic processes affecting this region throughout most of the Holocene and Pleistocene time. Historically, human activities have heightened the importance of wind action by disrupting the natural vegetative cover, thereby exposing the unconsolidated sediments. Agriculture, particularly dry-land cultivation, has been the principal form of land use in the area since the early 1900s or before (Webb, 1931). The effects of tilling practices on deflation are shown in Figure 1. The cultivated field on the right (east) is approximately 0.8 m lower than the range site on the left (west). This long, narrow field was cleared and probably brought into cultivation in the 1920s (C. D. Tunnell, personal communication, 1983). Its furrows run from north to south, along the field's long axis. The orientation of these furrows tends to maximize local deflation, as the furrows are parallel to the dominant winds. During the winter and early spring, some of the strongest winds are from the north, whereas the prevailing wind direction is southerly at other times of the year (Bomar, 1983). Other factors that enhance the erosional impact of the wind include antecedent dry conditions and frost heaving. Both are seasonal effects that increase the soil's susceptibility to removal during the frequent spring dust storms. After becoming entrained, soil aggregates from this field and others like it are transported from their source and redeposited as a broad sheet of eolian sediment.
Origin of the "Cup and Saucer"
(1981) Baumgardner, Jr., Robert W.
The "Cup and Saucer" feature, named due to its resemblance to those utensils (W. J. Brown, 1980, personal communication), is located in southern Mitchell County, Texas. It is situated on private property but can be easily observed about 400 ft (122 m) east of State Highway 163 between Sterling City and Colorado City, 3.4 mi (5.4 km) north of the intersection of that highway with FM2183. The feature lies on the eastern edge of the Hyman NE quadrangle (scale 1:24,000, 7.5-minute series, U.S. Geological Survey, topographic maps), 0.75 mi (1.2 km) south of Beals Mountain. The feature will be described according to the following conventions. The "saucer" portion, which dips concentrically toward the center, will be referred to as the "lower ring." The "cup" portion, located in the center of the saucer, will be called the "core." The outcrops south of the lower ring, also capped by rocks dipping toward the core, will be referred to as the "outer ring." This feature, long assumed to be a meteorite crater, exhibits characteristics that argue for another explanation. Firstly, the lower ring is capped with massive sandstone rocks that dip only gently (3°30' to 14°10') toward the core, which would not likely result from a violent meteorite impact. Secondly, abundant black stones scattered on the upper surface of the saucer are cemented with iron oxide but are neither fragments of a meteorite nor fused by the heat of an impact. Instead, they appear to be concretions formed in the vadose zone when the ring was still buried by younger sediments and the local water table was higher. Thirdly, if this feature were an ancient impact structure, the core would be composed of breccia created by the meteorite impact. However, the core is composed of friable fine-grained sandstone, volcanic ash, and fluvial gravels, none of which are brecciated.
Playa Basin Fills Near the Pantex Plant- Stratigraphic and Geomorphic Analysis
(1993) Hovorka, Susan D.
Playa basins on the Southern High Plains pond water and focus recharge to the Ogallala aquifer. Cores of the sedimentary fills of six of these basins near the Pantex Plant, northeast of Amarillo, have been examined to identify (1) the types of sediments beneath the floors of playa lakes, (2) the relative permeabilities of these sediments, (3) the geometries of playa lake clays and interbedded and interfingering facies, and (4) potential flow paths through the clays. This report focuses on core data rather than exposures because (1) core recovery was excellent, whereas most exposures have been degraded, (2) cores penetrate to greater depths than most exposures, (3) playas cored are close to the Pantex Plant, and (4) core data can be integrated with hydrologic and geochemical test results. Basin sediments have been examined by drilling 30-m-deep hollow-stem auger cores in a suite of playas and corresponding interplaya areas in a variety of geomorphic settings adjacent to the Pantex Plant (Fig. 1). To date, 41 cores totaling 766 m (2513 ft) of section from six playa basins adjacent to the Pantex Plant have been collected (Table 1). Playa basins were selected to examine a spectrum of geomorphologic characteristics and flooding histories. Playas examined are: (1) Seven Mile Basin located south of US 60 south of the Pantex Plant; (2) Wink playa basin located outside the west gate of the Pantex Plant; (3) TDCJ playa north of Pantex Lake; (4) Koesjan playa west of Pantex playa 5, (5) E. Vance playa, east of the east gate of the Pantex Plant, and (6) Finley playa in Armstrong County (Fig. 1). Seven Mile Basin is a large basin with a playa that has not been flooded during the past year. Wink, Koesjan, and TDCJ playas are average size playa basins with lakes that were flooded above the rim during the late summer of 1992, but playa lake levels dropped during the winter of 1993 and permitted coring of playa sediments. The E. Vance playa is in a composite of two basins and the Finley playa is in a shallow basin; both have been mostly dry during 1992-1993.
Quantifying downstream impacts of impoundment on flow regime and channel planform, lower Trinity River, Texas
(Geomorphology, 2005-07) Slattery, M.C.; Phillips, J.D.; Wellmeyer, J.L.
Sediment budgeting in the upper and middle basins of the Brazos and Trinity Rivers, TX: an assessment of methods and directions for future work
(TWDB, 2007-06) Slattery, M.C.
Shoreline Types of the Central Texas Coast: Matagorda to Corpus Christi Areas
(1998) Morton, Robert A.; White, William Allen, 1939-
The report details how the Bureau of Economic Geology (BEG) classified and mapped the shores of the central Texas coast, offering definitions of each shoreline type and providing examples that demonstrate how the physical attributes of shoreline habitats influence the impact of spilled oil. This information is crucial for the creation of Environmental Sensitivity Index (ESI) maps used in oil spill response and contingency planning. Shorelines were classified according to an ESI scheme established by Research Planning, Inc. (RPI) and the BEG, with rankings ranging from 1 to 10. Examples of each shoreline type are provided, along with explanations of common occurrences of multiple adjacent shoreline types. Mapping of shoreline types was conducted on U.S.G.S. topographic quadrangles (1:24,000) using recent vertical aerial photographs, low-altitude color video surveys from 1997, oblique color slides from 1992, and previous field experience. Ground spot checks were performed in May 1998 to verify the accuracy of the maps. The Matagorda to Corpus Christi region was chosen for the second phase of ESI mapping in Texas due to its diverse shoreline types, dense industrialization, environmentally sensitive wetlands, and significant volume of oil transportation through major shipping channels and the Intracoastal Waterway in the region.