I summarize the recent history of education reform and statewide testing in Texas, which led to introduction of the Texas Assessment of Academic Skills (TAAS) in 1990-91. A variety of evidence in the late 1990s led a number of observers to conclude that the state of Texas had made near miraculous progress in reducing dropouts and increasing achievement. The passing scores on TAAS tests were arbitrary and discriminatory. Analyses comparing TAAS reading, writing and math scores with one another and with relevant high school grades raise doubts about the reliability and validity of TAAS scores. I discuss problems of missing students and other mirages in Texas enrollment statistics that profoundly affect both reported dropout statistics and test scores. Only 50% of minority students in Texas have been progressing from grade 9 to high school graduation since the initiation of the TAAS testing program. Since about 1982, the rates at which Black and Hispanic students are required to repeat grade 9 have climbed steadily, such that by the late 1990s, nearly 30% of Black and Hispanic students were "failing" grade 9. Cumulative rates of grade retention in Texas are almost twice as high for Black and Hispanic students as for White students. Some portion of the gains in grade 10 TAAS pass rates are illusory. The numbers of students taking the grade 10 tests who were classified as "in special education" and hence not counted in schools' accountability ratings nearly doubled between 1994 and 1998. A substantial portion of the apparent increases in TAAS pass rates in the 1990s are due to such exclusions. In the opinion of educators in Texas, schools are devoting a huge amount of time and energy preparing students specifically for TAAS, and emphasis on TAAS is hurting more than helping teaching and learning in Texas schools, particularly with at-risk students, and TAAS contributes to retention in grade and dropping out. Five different sources of evidence about rates of high school completion in Texas are compared and contrasted. The review of GED statistics indicated that there was a sharp upturn in numbers of young people taking the GED tests in Texas in the mid-1990s to avoid TAAS. A convergence of evidence indicates that during the 1990s, slightly less than 70% of students in Texas actually graduated from high school. Between 1994 and 1997, TAAS results showed a 20% increase in the percentage of students passing all three exit level TAAS tests (reading, writing and math), but TASP (a college readiness test) results showed a sharp decrease (from 65.2% to 43.3%) in the percentage of students passing all three parts (reading, math, and writing). As measured by performance on the SAT, the academic learning of secondary school students in Texas has not improved since the early 1990s, compared with SAT takers nationally. SAT-Math scores have deteriorated relative to students nationally. The gains on NAEP for Texas fail to confirm the dramatic gains apparent on TAAS. The gains on TAAS and the unbelievable decreases in dropouts during the 1990s are more illusory than real. The Texas "miracle" is more hat than cattle.
Research Article| August 01, 1977 Stream-channel response to floods, with examples from central Texas VICTOR R. BAKER VICTOR R. BAKER 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar Author and Article Information VICTOR R. BAKER 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (8): 1057–1071. https://doi.org/10.1130/0016-7606(1977)88<1057:SRTFWE>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation VICTOR R. BAKER; Stream-channel response to floods, with examples from central Texas. GSA Bulletin 1977;; 88 (8): 1057–1071. doi: https://doi.org/10.1130/0016-7606(1977)88<1057:SRTFWE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The principle that most geomorphic work is accomplished by relatively frequent events of moderate intensity requires modification for application to stream channels in certain climatic and physiographic settings. Small drainage basins in regions of highly variable flood magnitudes appear to have a high potential for catastrophic response. Flash-flood potential for small basins can be regionally mapped by computing the standard deviation of the logarithms of the annual flood peaks. Highly right-skewed flood-frequency distributions indicate that a high potential exists in certain arid regions of the southwestern United States and in the seasonal subtropical-to-steppe climate region of central Texas. High-magnitude flood response is also promoted by physiographic factors, such as hillslope morphology, soils, rock type, and drainage density. The relative importance of overland flow, which produces intense flood peaks, versus interflow and ground-water flow, which produce more uniform streamflow, appears to integrate both the climatic and the physiographic influences on the potential for catastrophic floods.Another factor in realizing the climatic-hydrologic potential for catastrophic stream-channel response is the resistance of the channel itself to scour. Small limestone streams in central Texas show significant channel modification only during the rare high-magnitude floods characteristic of that region. This is mainly because of the high response threshold required to scour bouldery alluvium and dense valley-bottom vegetation. Effects of especially intense floods on such streams include the following: entrainment of jointed bed rock and boulders as much as 3 m in diameter, uprooting of trees that usually bind coarse-grained point bars, macroturbulent transport of boulders even over divides into adjacent drainages, local scour of chutes on meander bends, and passive boulder deposition on other preflood valley-bottom surfaces. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Understanding the nexus between energy and water -water used for energy and energy used for water -has become increasing important in a changing world. As growing populations demand more energy supplies and water resources, research aims to analyze the interconnectedness of these two resources. Our study sought to quantify the energy-water relationship in Texas, specifically the relationship between electricity generation and water resources as it pertains to policy and society. We examined the water requirements for various types of electricity generating facilities, for typical systems both nationwide and in Texas. We also addressed the energy requirements of water supply and wastewater treatment systems, comparing national averages with Texas-specific values. Analysis of available data for Texas reveals that approximately 595,000 megaliters of water annually -enough water for over three million people for a year -are consumed by cooling the state's thermoelectric power plants while generating approximately 400 terawatt-hours of electricity. At the same time, each year Texas uses an estimated 2.1 to 2.7 terawatthours of electricity for water systems and 1.8 to 2.0 terawatt-hours for wastewater systems -enough electricity for about 100,000 people for a year. In preparing our analysis, it became clear that substantially more site-specific data are necessary for a full understanding of the nature of the energy-water nexus and the sustainability of economic growth in Texas. We recommend that Texas increase efforts to collect accurate data on the withdrawal and consumption of cooling and process water at power plants, as well as data on electricity consumption for public water supply and wastewater treatment plants and distribution systems. The overarching conclusion of our work is that increased efficiency advances the sustainable use of both energy and water. Improving water efficiency will reduce power demand, and improving energy efficiency will reduce water demand. Greater efficiency in usage of either energy or water will help stretch our finite supplies of both, as well as reduce costs to water and power consumers.
The 2011 drought in Texas was unprecedented in its intensity. Beginning in October 2010, most of Texas experienced a relatively dry fall and winter, but the record dry March 2011 brought widespread extreme drought conditions to the state. The 12-month rainfall total for October 2010 through September 2011 was far below the previous record set in 1956. Average temperatures for June through August were over 2 °F above the previous Texas record and were close to the warmest statewide summer temperatures ever recorded in the United States. As the drought intensified, the previous year’s relatively lush growth dried out, setting the stage for spring wildfires. Conditions were so dry during the spring planting season across much of the state that many crops never emerged from the ground. Continued dry weather through the summer led to increasing hardship for ranchers, who generally saw very little warm-season grass growth while stock tanks dried up. By early fall, trees in central and eastern Texas were showing widespread mortality, and dry and windy conditions allowed forest fires to burn intensely and spread rapidly in Bastrop and elsewhere. Near-normal rainfall across Texas in October–December improved short-term conditions, but almost the entire state remained in drought. Citation: Nielsen-Gammon JW. 2012. The 2011 Texas Drought. The Texas Water Journal. 3(1):59-95. Available from: https://doi.org/10.21423/twj.v3i1.6463.
The Texas freeze of February 2021 left more than 4.5 million customers (more than 10 million people) without electricity at its peak, some for several days. The freeze had cascading effects on other services reliant upon electricity including drinking water treatment and medical services. Economic losses from lost output and damage are estimated to be $130 billion in Texas alone. In the wake of the freeze, there has been major fallout among regulators and utilities as actors sought to apportion blame and utilities and generators began to settle up accounts. This piece offers a retrospective on what caused the blackouts and the knock-on effects on other services, the subsequent financial and political effects of the freeze, and the implications for Texas and the country going forward. Texas failed to sufficiently winterize its electricity and gas systems after 2011. Feedback between failures in the two systems made the situation worse. Overall, the state faced outages of 30 GW of electricity as demand reached unprecedented highs. The gap between production and demand forced the non-profit grid manager, the Electric Reliability Council of Texas (ERCOT), to cut off supply to millions of customers or face a systems collapse that by some accounts was minutes away. The 2021 freeze suggests a need to rethink the state’s regulatory approach to energy to avoid future such outcomes. Weatherization, demand response, and expanded interstate interconnections are potential solutions Texas should consider to avoid generation losses, reduce demand, and tap neighboring states’ capacity.
This manual of the Texas flora is a monumental work and the authors, D. S. Correll and M. C. Johnston, as well as their collaborators, deserve the compliments of syste matists on its publication. A definitive treatment of a large and complex flora (174 families, 1216 genera, 4839 species and 576 subspecies and varieties in Texas) must depend to a considerable extent upon the labors of predecessors. There has been a long and active series of collectors and publishers interested in Texas plants, and they have pro vided an excellent basis for a comprehensive flora. How ever, the special research on the Texas flora by the authors, and their extensive field experience with it, have brought to this publication an important element of personal knowl edge. Fifty-six collaborators have provided the treatments of 20 families and of 38 separate genera. Both the authors and the collaborators are to be congratulated upon this productive cooperation. The book is well made up and the format and typography make it easy to use. An introduction provides a brief ac count of the principal vegetation regions in Texas. This is followed by a key to the families and the taxonomic treat ment of the flora, which encompasses 1700 pages. A brief appendix adds critical comments and some additional spe cies from data obtained during the course of publication. The list of Abbreviations of Authors' Names deserves special mention. It is in fact far more than the title states. It includes birth and death dates, and a variety of other information such as the principal professional position, or other occupation, major publications, groups or floras studied, and sometimes mention of other significant contri butions to botany. The inclusion of this information will
Combining shrewd applications of current cultural theory with compelling autobiography and elegant prose, Jose E. Limon works at the intersection of anthropology, folklore, popular culture, history, and literary criticism. A native of South Texas, he renders a historical and ethnographic account of its rich Mexican-American folk culture. This folk culture, he shows whether expressed through male joking rituals, ballroom polka dances, folk healing, or eating and drinking traditions metaphorically dances with the devil, both resisting and accommodating the dominant culture of Texas. Critiquing the work of his precursors John Gregory Bourke, J. Frank Dobie, Jovita Gonzalez, and Americo Paredes Limon deftly demonstrates that their accounts of Mexican-Americans in South Texas contain race, class, and gender contradictions, revealed most clearly in their accounts of the folkloric figure of the devil. Limon's own field-based ethnography follows, and again the devil appears as a recurrent motif, signaling the ideological contradictions of folk practices in a South Texas on the verge of postmodernity.
Shale-gas production using hydraulic fracturing of mostly horizontal wells has led to considerable controversy over water-resource and environmental impacts. The study objective was to quantify net water use for shale-gas production using data from Texas, which is the dominant producer of shale gas in the U.S. with a focus on three major plays: the Barnett Shale (~15,000 wells, mid-2011), Texas-Haynesville Shale (390 wells), and Eagle Ford Shale (1040 wells). Past water use was estimated from well-completion data, and future water use was extrapolated from past water use constrained by shale-gas resources. Cumulative water use in the Barnett totaled 145 Mm(3) (2000-mid-2011). Annual water use represents ~9% of water use in Dallas (population 1.3 million). Water use in younger (2008-mid-2011) plays, although less (6.5 Mm(3) Texas-Haynesville, 18 Mm(3) Eagle Ford), is increasing rapidly. Water use for shale gas is <1% of statewide water withdrawals; however, local impacts vary with water availability and competing demands. Projections of cumulative net water use during the next 50 years in all shale plays total ~4350 Mm(3), peaking at 145 Mm(3) in the mid-2020s and decreasing to 23 Mm(3) in 2060. Current freshwater use may shift to brackish water to reduce competition with other users.
PreviousNext No AccessSEG Technical Program Expanded Abstracts 1986Shear data in the presence of azimuthal anisotropy: Dilley, TexasAuthors: R. M. AlfordR. M. AlfordAmoco Production Co.https://doi.org/10.1190/1.1893036 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Permalink: https://doi.org/10.1190/1.1893036FiguresReferencesRelatedDetailsCited BySeparation of split S-waves in two nonorthogonal sets of vertical fracturesMengqi Li, Jun Lu, Yun Wang, Xueying Zhang, and Zongjie Li1 October 2021 | GEOPHYSICS, Vol. 86, No. 6Multiple Regression and Modified Faust Equation on Well Logging Data in Application to Seismic Procedures: Polish Outer Carpathians Case Study2 October 2021 | Energies, Vol. 14, No. 19Design, acquisition, and processing of three Permian Basin 3D VSP surveys to support the processing and interpretation of a large 3D/3C surface seismic surveyRichard Van Dok, Brian Fuller, and Ron Bianco1 September 2021Influence of eccentricity/tilted sonic logging tool on dispersive waveKosuke Kayama, Hitoshi Mikada, Junichi Takekawa, and Shibo Xu1 September 2021Research on the near-surface model building by shear wave in TD areaFeng Faquan, Deng Zhiwen, Ni Yudong, Wang Haili, Lan Yijun, Du Zhongdong, and Yu Baohua1 September 2021Combining vertical and radial-horizontal point-source data via 4C rotation in isotropic mediaJames Gaiser1 September 2021Shear-wave analysis of a time-lapse crosswell data setDavid Rampton and Mitchell J. 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Stewart, and Dhananjay Kumar21 January 2021 | GEOPHYSICS, Vol. 86, No. 1Shear-Wave Splitting: New Geophysics and Earthquake Stress-Forecasting27 May 2021Seismic field data displaying azimuthal anisotropy, 1986–2020Heloise Lynn12 October 2020 | Interpretation, Vol. 8, No. 4Reflection and transmission coefficient approximations for arbitrarily anisotropic mediaSong Jin and Alexey Stovas30 September 2020Logging-while-drilling cross-multipole measurements in anisotropic mediaChristoph Demmler, Tim Geerits, Baker Hughes, Olaf Hellwig, and Stefan Buske30 September 2020Modeling the effects of fracture density and saturation on S-wave radiation from horizontal sourcesJames Gaiser30 September 2020References20 August 2020Reflection and transmission approximations for weak contrast orthorhombic mediaSong Jin and Alexey Stovas9 January 2020 | GEOPHYSICS, Vol. 85, No. 2Crack‐Induced Shear‐Wave Orthorhombic Anisotropy: Modeling and Inversion of Shear‐Wave Borehole Measurements17 March 2020 | Journal of Geophysical Research: Solid Earth, Vol. 125, No. 3Shear-Wave Splitting: New Geophysics and Earthquake Stress-Forecasting27 January 2020Rock physics modelling for determination of effective elastic properties of the lower Paleozoic shale formation, North Poland7 September 2019 | Acta Geophysica, Vol. 67, No. 6Amplitude anisotropy of shear-wave splitting and fluid detection in thin-layer reservoir22 October 2019 | Acta Geophysica, Vol. 67, No. 6Crustal anisotropy from shear-wave splitting of local earthquakes in the Garhwal Lesser Himalaya10 September 2019 | Geophysical Journal International, Vol. 219, No. 3Frequency-dependent S-wave splitting parameters analysis: A case study from azimuthal PS data, Sanhu area of the Qaidam Basin, ChinaYun Wang, Chao Wang, Jianfeng Li, and Yuanyuan Yue9 October 2019 | GEOPHYSICS, Vol. 84, No. 6Theoretical study of cross-dipole acoustic wave propagation in a symmetrically partitioned isotropic modelChao Li, Xiao He, Yunhong Song, and Xiuming Wang10 August 2019Hybrid Polarimetric GPR Calibration and Elongated Object Orientation EstimationIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 12, No. 7Delineation of Damage Zones From 3 km Downhole Geophysical Logs in the Koyna Seismogenic Zone, Western India26 June 2019 | Journal of Geophysical Research: Solid Earth, Vol. 124, No. 63D passive wavefield imaging using the energy normDaniel Rocha, Paul Sava, Jeffrey Shragge, and Ben Witten26 February 2019 | GEOPHYSICS, Vol. 84, No. 2DETERMINATION OF AZIMUTHAL ANISOTROPIC MEDIA ELASTIC PARAMETERS FROM MULTIWAVE AVOA DATA BY NONLINEAR OPTIMIZATION METHOD29 January 2019 | Russian Journal of geophysical technologies, No. 2Identification of fractured carbonate vuggy reservoirs in the S48 well area using 3D 3C seismic technique: A case history from the Tarim BasinZongjie Li, Yun Wang, Zichuan Yang, Haiying Li, and Guangming Yu21 December 2018 | GEOPHYSICS, Vol. 84, No. 1Using Shear Wave Anisotropy Approach to Determine State of Stress Around the Wellbore from Advanced Acoustic Well Logging; Case Study from Southern Iraq11 November 2019Application of several converted-wave processing techniques in carbonate reservoirWei Yang, Xiaowei Wang, Donghui Bian, and Zhe Yang11 December 2018The Galperin source: A novel efficient multicomponent seismic sourceMauro Häusler, Cedric Schmelzbach, and David Sollberger12 September 2018 | GEOPHYSICS, Vol. 83, No. 6Simultaneous anisotropy inversion and type identification in the frequency domain for flexural waves in horizontal transverse isotropic mediaFuqiang Zeng, Wenzheng Yue, and Chao Li1 October 2018 | GEOPHYSICS, Vol. 83, No. 6Quaternion-based anisotropic inversion for flexural waves in horizontal transverse isotropic formations with unmatched sources: A synthetic exampleFuqiang Zeng, Wenzheng Yue, and Chao Li2 August 2018 | GEOPHYSICS, Vol. 83, No. 5High-Resolution Evaluation of Elastic Properties and Anisotropy of Unconventional Reservoir Rocks via Thermal Core Logging14 May 2018 | Rock Mechanics and Rock Engineering, Vol. 51, No. 9References and Bibliography27 February 2018Elastic-wave evaluation of downhole hydraulic fracturing: Modeling and field applicationsYuan-Da Su, Zhen Li, Song Xu, Chun-Xi Zhuang, and Xiao-Ming Tang13 November 2017 | GEOPHYSICS, Vol. 83, No. 1Understanding Stress Effects on Borehole Acoustic Waves for Unconventional Shale Reservoirs24 September 2018First Cross-Dipole Shear Wave Imaging Application for Intersecting a Mother Open-Hole from a Near-Parallel Side-Track Wellbore12 November 2018Fracture detection via correlating P-wave amplitude variation with offset and azimuth analysis and well data in eastern central Saudi ArabiaAli H. Al-Gawas and Abdullatif A. Al-Shuhail20 September 2017 | Interpretation, Vol. 5, No. 4Characteristics of waveforms recorded by azimuthally spaced hydrophones of sonic logging tool for incident plane wavesNobuyasu Hirabayashi, Naoki Sakiyama, and Toru Ikegami25 September 2017 | GEOPHYSICS, Vol. 82, No. 6Stress‐ and Structure‐Induced Anisotropy in Southern California From Two Decades of Shear Wave Splitting Measurements5 October 2017 | Geophysical Research Letters, Vol. 44, No. 19Characterization of naturally fractured Arbuckle Group in the Wellington Field, Kansas, using S-wave amplitude variation with offsetMenal Gupta, Kyle Spikes, and Bob Hardage9 November 2016 | Interpretation, Vol. 5, No. 1Crustal radial anisotropy beneath Cameroon from ambient noise tomographyTectonophysics, Vol. 696-697Prediction of coal seam details and mining safety using multicomponent seismic data: A case history from ChinaJun Lu, Xinghun Meng, Yun Wang, and Zhen Yang11 August 2016 | GEOPHYSICS, Vol. 81, No. 5Seismic and sonic wave attenuation of carbonate rocks in an onshore Abu Dhabi oil fieldFateh Bouchaala, Mohammed Ali, and Jun Matsushima1 September 2016Waveform analysis of borehole acoustic dipole data in transversely isotropic medium with a tilted axis of symmetrySatoshi Fuse, Hitoshi Mikada, and Junichi Takekawa1 September 2016Detection of near-surface hydrocarbon seeps using P- and S-wave reflectionsMathieu J. Duchesne, André J.-M. Pugin, Gabriel Fabien-Ouellet, and Mathieu Sauvageau14 July 2016 | Interpretation, Vol. 4, No. 3Numerical simulation of azimuthal acoustic logging in a borehole penetrating a rock formation boundaryPeng Liu, Wenxiao Qiao, Xiaohua Che, Xiaodong Ju, Junqiang Lu, Ruijia Wang, and Wenxing Duan20 April 2016 | GEOPHYSICS, Vol. 81, No. 3Stress‐induced seismic azimuthal anisotropy in the upper crust across the North West Shelf, Australia29 February 2016 | Journal of Geophysical Research: Solid Earth, Vol. 121, No. 2References24 May 2016Adopting Seismic Methodologies to Acoustic Logging Applications20 April 2016Seismic Wave Attenuation: Promising Attribute for Fluids, Fractures and Tar Mats Characterization in Abu Dhabi Oilfields7 November 2016Spatial variations of shear wave anisotropy near the San Jacinto Fault Zone in Southern California2 December 2015 | Journal of Geophysical Research: Solid Earth, Vol. 120, No. 12Data report: analysis of shear wave anisotropy in upper oceanic crust, ODP/IODP Hole 1256D2 November 2015Seismic Methodologies Adapted For Use In Acoustic Logging20 October 2015Azimuthal anisotropy: Distinguishing between unequal horizontal stress and vertical aligned macro-fractures, as demonstrated in thirty years of field data analysisHeloise Bloxsom Lynn*5 August 2014Statistical AVO intercept-gradient analysis of direct S-waves: A methodology for quantitative fracture characterizationMenal Gupta*, Kyle Spikes, Mehdi Far, Diana Sava, and Bob Hardage5 August 2014Direct shear wave polarization corrections across multiple offsets and anisotropic layersJacqueline Maleski and Robert Tatham5 August 20143D Alford rotation analysis for the Diamond M Field, Midland Basin, TexasOswaldo E. Davogustto Cataldo, Timothy J. Kwiatkowski, Kurt J. Marfurt, Steven L. Roche, and James W. Thomas23 April 2014 | Interpretation, Vol. 2, No. 2Research Note: Transverse isotropy estimation from dipole sonic logs acquired in pilot and production wells6 December 2013 | Geophysical Prospecting, Vol. 62, No. 2Reliability of the slowness and slowness-polarization methods for anisotropy estimation in VTI media from 3C walkaway VSP dataMehdi Asgharzadeh, Andrej Bóna, Roman Pevzner, Milovan Urosevic, and Boris Gurevich24 June 2013 | GEOPHYSICS, Vol. 78, No. 5Precision and stability in measurement of split PS-wave time delay and polarization azimuthR. Ross Haacke19 August 2013Piceance tight gas reservoir characterization using multicomponent seismic dataMichael Matheney, Tim Jenkinson, Andrew Shatilo, Rishi Bansal, and Kyle Lewallen19 August 2013High-precision estimation of split PS-wave time delays and polarization directionsR. Ross Haacke8 February 2013 | GEOPHYSICS, Vol. 78, No. 2Method to extract anisotropy parameters from MPAL logging dataCross-correlation-function method for separation of shear waves S1 and S2 in azimuthally anisotropic media and an example of its application with real dataT. Chichinina, I. Obolentseva, S. Gorshkalev, W. Karsten, and I. Korsunov25 October 2012Shear Wave Birefringence Analysis: an Integrative SchemeChangjun Zhang25 October 2012Corrections for polarization distortion in reflected shear-waves and possible extensions to the Alford Rotation at non-normal incidence angles and applicationsTerence Campbell and Robert H. Tatham25 October 2012Analysis of Different Well Log and Seismic Data for Estimating Shear Wave Polarization DirectionNaser Tamimi and Paritosh Singh25 October 2012Bibliography20 July 20123D, 9C seismic modeling and inversion of Weyburn Field dataHerurisa Rusmanugroho and George A. McMechan18 June 2012 | GEOPHYSICS, Vol. 77, No. 4A microelectromechanical system digital 3C array seismic cone penetrometerRanajit Ghose23 April 2012 | GEOPHYSICS, Vol. 77, No. 3Estimation of horizontal stress magnitudes and stress coefficients of velocities using borehole sonic dataTing Lei, Bikash K. Sinha, and Michael Sanders23 April 2012 | GEOPHYSICS, Vol. 77, No. 3Separating P- and S-waves in an affine coordinate system12 December 2011 | Journal of Geophysics and Engineering, Vol. 9, No. 1References25 February 2013Estimation of azimuthal anisotropy from VSP data using multicomponent S-wave velocity analysisRoman Pevzner, Boris Gurevich, and Milovan Urosevic19 November 2011 | GEOPHYSICS, Vol. 76, No. 5Algebraic processing technique for extracting frequency-dependent shear-wave splitting parameters in an anisotropic medium16 July 2011 | Applied Geophysics, Vol. 8, No. 2Seismic reservoir characterization: how can multicomponent data help?10 March 2011 | Journal of Geophysics and Engineering, Vol. 8, No. 2Shear wave analysis of multi‐offset VSP data from the West Texas OverthrustA. Sayed, A. Catoi, R. Rufino, A. Fryer, M. McClay, D. Bafia, J. Sheldon, and B. McCormick8 August 201110. References21 March 2012Shear-Wave Splitting: New Geophysics and Earthquake Stress-Forecasting27 August 2014Fifty years of seismic anisotropy studies in RussiaRussian Geology and Geophysics, Vol. 51, No. 10Seismic anisotropy in exploration and reservoir characterization: An overviewIlya Tsvankin, James Gaiser, Vladimir Grechka, Mirko van der Baan, and Leon Thomsen14 September 2010 | GEOPHYSICS, Vol. 75, No. 5Seismic azimuthal impedance anisotropy in the Barnett ShaleKui Zhang, Bo Zhang, J. Tim. Kwiatkowski, and Kurt J. Marfurt21 October 20104. Chapter 4: Development GeophysicsColin MacBeth, Sankar Muhuri, William L. Abriel, William Haworth, Mark Chapin, Peter Swinburn, Raphic van der Weiden, Dieter Skaloud, Sola Adesanya, David Stevens, Chris Varley, Jacob Wilkie, Eric Brentjens, Martijn Blaauw, Liz Ross, Kevin King, Gerard Bodewitz, Hajo van Hasselt, Greg Stone, Wim Twigt, Wim Swinkels, Andrew James, Tony Addis, Chris Parsons, Robert Meij, Sarah Bell, Alexei Trofimov, Patrick Jackson, Valery Cholovsky, Edwin Lamers, Syrie Crouch, Rusty (John) Gilbert, Yuhong Liu, William Abriel, Rachel Preece, Dongjun (Taller) Fu, E. Charlotte Sullivan, Kurt J. Marfurt, Jose Luis Masaferro, Ruth Bourne, Jean-Claude Jauffred, P. Avseth, T. Mukerji, A. Jørstad, G. Mavko, T. Veggeland, M. K. MacLeod, R. A. Hanson, C. R. Bell, S. McHugo, Jan H. Kommedal, Susan Fowler, John McGarrity, C. R. Bates, D. R. Phillips, R. Grimm, H. Lynn, B. Blonk, R. W. Calvert, J. K. Koster, and G. van der Zee21 March 20122. AnisotropyIlya Tsvankin, James Gaiser, Vladimir Grechka, Mirko van der Baan, and Leon Thomsen21 March 2012A review of a quarter century of International Workshops on Seismic Anisotropy in the crust (0IWSA–12IWSA)10 September 2008 | Journal of Seismology, Vol. 13, No. 2Comments on 'Global anisotropic phase velocity maps for higher mode Love and Rayleigh waves' by Visser, Trampert & KennettGeophysical Journal International, Vol. 177, No. 1Converted-wave splitting estimation and compensationJames L. Simmons30 December 2008 | GEOPHYSICS, Vol. 74, No. 1Non‐converted shear wave VSP imaging of tight gas sands in Rulison Field, ColoradoPrajnajyoti Mazumdar and Thomas. L. Davis14 October 2009Estimating interval shear-wave splitting from multicomponent virtual shear check shotsAndrey Bakulin and Albena Mateeva4 August 2008 | GEOPHYSICS, Vol. 73, No. 5Compressive stress field in the crust deduced from shear-wave anisotropy: an example in capital area of China26 August 2008 | Science Bulletin, Vol. 53, No. 18Using seismic attributes to detect vertical fractures: A physical model studyRobert W. Wiley, Byron C. Golden, Peter H. Wilson, and Scott W. Peters15 December 2008Azimuthal anisotropy characterization with multicomponent virtual shear sources at Rulison Field, ColoradoPrajnajyoti Mazumdar, Albena Mateeva, and Andrey Bakulin15 December 2008Estimating interval shear‐wave splitting from multicomponent virtual shear checkshots15 December 2008Fracture detection by using full azimuth P wave attributes11 September 2007 | Applied Geophysics, Vol. 4, No. 3Forward modeling of fracture-induced sonic anisotropy using a combination of borehole image and sonic logsRomain Prioul, Adam Donald, Randy Koepsell, Zakariae El Marzouki, and Tom Bratton4 June 2007 | GEOPHYSICS, Vol. 72, No. 4Comment on the Reply on "Theta map: Edge detection in magnetic data" ()Colin M. Sayers27 November 2006 | GEOPHYSICS, Vol. 72, No. 1Anisotropy processing without matched cross‐dipole transmittersS. Bose, B. K. Sinha, S. Sunaga, T. Endo, and H. P. Valero14 September 2007Reliable small‐percentage azimuthal anisotropy evaluation from a new wireline cross‐dipole sonic tool: Field Examples from US, Mexico and UkraineT. Plona, H‐P. Valero, S. Bose, J. Walsh, E. Wielemaker, and P. Saldungaray14 September 2007A multiscale study of the mechanisms controlling shear velocity anisotropy in the San Andreas Fault Observatory at DepthNaomi L. Boness and Mark D. Zoback28 August 2006 | GEOPHYSICS, Vol. 71, No. 5Characterization of layered anisotropic media from prestack PS-wave-reflection dataJason E. Gumble and James E. Gaiser11 September 2006 | GEOPHYSICS, Vol. 71, No. 5Vector imaging of converted wave data in laterally uniform media with VTI anisotropyCharlie Jing, Thomas A. Dickens, and Graham A. Winbow1 August 2006 | GEOPHYSICS, Vol. 71, No. 4Surface-consistent deconvolution using reciprocity and waveform inversionRobbert van Vossen, Andrew Curtis, Andreas Laake, and Jeannot Trampert10 March 2006 | GEOPHYSICS, Vol. 71, No. 2Slowness‐frequency‐projection logs: A QC for accurate slowness estimation and formation property identificationT. Plona, T. Endo, E. Wielemaker, J. Walsh, and H. Yamamoto6 October 2006Fracture detection by P and C wave anisotropy from multi‐azimuth VSPQinglin Liu, John Owusu, and Jaafar Alnemer6 October 2006A new modular sonic tool provides complete acoustic formation characterizationV. Pistre, T. Plona, B. Sinha, T. Kinoshita, H. Tashiro, T. Ikegami, J. Pabon, S. Zeroug, R. Shenoy, T. Habashy, H. Sugiyama, A. Saito, C. Chang, D. Johnson, H. P. Valero, C. J. Hsu, S. Bose, H. Hori, C. Wang, T. Endo, H. Yamamoto, and K. Schilling7 December 2005Vector imaging of converted wave data in laterally uniform media with VTI anisotropyCharlie Jing, Thomas A. Dickens, and Graham A. Winbow7 December of for fracture characterization: E. and R. Van December in the detection and of and December estimation of fracture from A. Li, and December rotation method for fracture with and December March 2012A review of shear-wave splitting in the anisotropic Vol. No. anisotropy from dipole shear logs in oceanic January | Vol. No. to using P-wave 3D seismic and Brian J. May | GEOPHYSICS, Vol. No. fracture detection by the polarization properties of P. Van Paul L. D. and May | GEOPHYSICS, Vol. No. in shear-wave polarization and time February | Geophysical Prospecting, Vol. No. of in a transversely isotropic January | Geophysical Prospecting, Vol. No. characterization from October | Geophysical Prospecting, Vol. 51, No. review of shear wave splitting in the Journal International, Vol. No. of walkaway VSP data for the Vol. No. characterization of vertical as March | Geophysical Prospecting, Vol. 51, No. for sonic logs: Application to seismic well Vol. No. of for GPR from polarization and amplitude offset January | Vol. No. seismic Vol. No. prestack by wavefield Vol. 67, No. seismic Vol. 67, No. shear-wave splitting in fractured July | Geophysical Prospecting, Vol. No. modelling and time-lapse effects of in a fractured Journal International, Vol. No. wavefield inversion to from multicomponent seismic and George A. March | GEOPHYSICS, Vol. 67, No. of Alford rotation to Vol. No. years of vertical in VSP Vol. No. and Vol. No. prestack by wavefield and Kurt J. January case study for fracture characterization: of and Van January case study for fracture characterization: processing of Van Dok, James Gaiser, and John January Reservoir March Vol. No. seismic for near surface from central and of Applied Geophysics, Vol. 44, No. sources for shear-wave surveys in December | Geophysical Prospecting, Vol. No. of for media December | Geophysical Prospecting, Vol. No. and sonic logs in a Vol. No. 2The 3D shear the field in Reservoir data and anisotropy December | Geophysical Prospecting, Vol. No. detection in a carbonate reservoir using a of seismic A. Vladimir Grechka, and J. February 2012 | GEOPHYSICS, Vol. No. of azimuthal anisotropy from shear‐wave Vol. No. and attributes using prestack azimuth E. January of the of and the for P and S waves in rocks multiple fracture Journal International, Vol. No. of P with offset and azimuth in anisotropic Vol. No. of the of azimuthal anisotropy from P seismic Vol. No. characterization: how can anisotropy January | Vol. No. the of to Journal International, Vol. No. for E. Gaiser, Paul J. Fowler, and R. February case example of near-surface for multicomponent Prospecting, Vol. 44, No. seismic Journal International, Vol. 124, No. cross‐dipole reciprocity and February of of azimuthal anisotropy from seismic J. and Ron E. February data and polarization with in multicomponent and February for multicomponent data in presence of azimuthal February of azimuthal anisotropy from shear‐wave Tsvankin, and Michael C. February in fracture from surface converted J. February and of the flexural waves in an anisotropic borehole C. H. and M. February for seismic anisotropy using Prospecting, Vol. No. in isotropic and anisotropic formations and Prospecting, Vol. No. anisotropy analysis from direct and converted wave VSP data using and Michael J. February corrections for multicomponent surface seismic February estimation of for and and February converted Part 2, application to a fractured J. and February VSP Prospecting, Vol. No. ANISOTROPIC Prospecting, Vol. No. OF ANISOTROPIC Prospecting, Vol. No. to crack of in and Peter C. February OF Prospecting, Vol. No. OF Prospecting, Vol. No. 4A of shear-wave splitting in the can of and Journal International, Vol. No. of in fracture using multicomponent shear-wave surface seismic as a to horizontal in the Journal International, Vol. No. detection using surveys and vertical seismic at the Borehole Journal International, Vol. No. of shear-wave amplitude offset studies in anisotropic Journal International, Vol. No. shear-wave for anisotropy using offset synthetic Journal International, Vol. No. for anisotropy using of shear-wave Journal International, Vol. No. analysis of shear-wave Journal International, Vol. No. analysis of shear-wave case Journal International, Vol. No. anisotropy analysis from shear Journal International, Vol. No. OF A OF Prospecting, Vol. No. Prospecting, Vol. No. OF OF Prospecting, Vol. No. propagation of interpretation of April 2007 | Geophysical Journal International, Vol. No. in the the between and November | Journal of the Vol. No. wave inversion for fracture February of and fractured January | Journal of Geophysical Vol. No. fracture anisotropy in the An January | Journal of Geophysical Vol. No. study of seismic anisotropy and the fracture system at the Borehole January | Journal of Geophysical Vol. No. A Prospecting, Vol. No. OF Prospecting, Vol. No. wave splitting in the Seismic as possible January | Journal of Geophysical Vol. No. Technical Program Expanded Abstracts of of R. M. data in the presence of azimuthal anisotropy: Dilley, Technical Program Expanded Abstracts
BACKGROUND: A panel consisting of academic psychiatrists and pharmacist administrators of the Texas Department of State Health Services (formerly Texas Department of Mental Health and Mental Retardation), community mental health physicians, advocates, and consumers met in May 2004 to review new evidence in the pharmacologic treatment of bipolar I disorder (BDI). The goal of the consensus conference was to update and revise the current treatment algorithm for BDI as part of the Texas Implementation of Medication Algorithms, a statewide quality assurance program for the treatment of major psychiatric illness. The guidelines for evaluating possible medications, the criteria for selection and ranking, and the updated algorithms are described. METHOD: Principles from previous consensus conferences were reviewed and amended. Medication algorithms for the acute treatment of hypomanic/manic or mixed and depressive episodes in BDI were developed after examining recent efficacy and safety and tolerability data. Recommendations for maintenance treatments were developed. RESULTS: The panel updated the 2 primary algorithms (hypomanic/manic/mixed and depressive) based on clinical evidence for efficacy, tolerability, and safety developed since 2000. Expert consensus was utilized where clinical evidence was limited. Prevention of new episodes or prophylaxis treatment recommendations were developed based on recent data from longer-term trials. Maintenance recommendations are provided as levels versus a specified staged algorithm, as for acute treatment, due to the relatively limited database to inform treatment. CONCLUSIONS: These algorithms for the treatment of BDI represent the recommendations based on the most recent evidence available. These recommendations are meant to provide a framework for clinical decision making, not to replace clinical judgment. As with any algorithm, treatment practices will evolve beyond the recommendations of this consensus conference as new evidence and additional medications become available.
Abstract A bar on the Brazos River near Calvert, Texas, has been analyzed in order to determine the geologic meaning of certain grain size parameters and to study the behavior of the size fractions with transport. The bar consists of a strongly bimodal mixture of pebble gravel and medium to fine sand; there is a lack of material in the range of 0.5 to 2 mm, because the source does not supply particles of this size. The size distributions of the two modes, which were established in the parent deposits, are nearly invariant over the bar because the present environment of deposition only affects the relative proportions of the two modes, not the grain size properties of the modes themselves. Two proportions are most common; the sediment either contains no gravel or else contains about 60% gravel. Three sediment types with characteristic bedding features occur on the bar in constant stratigraphic order, with the coarsest at the base. Statistical analysis of the data is based on a series of grain size parameters modified from those of Inman (1952) to provide a more detailed coverage of non-normal size curves. Unimodal sediments have nearly normal curves as defined by their skewness and kurtosis. Non-normal kurtosis and skewness values are held to be the identifying characteristics of bimodal sediments even where such modes are not evident in frequency curves. The relative proportions of each mode define a systematic series of changes in numerical properties; mean size, standard deviation and skewness are shown to be linked in a helical trend, which is believed to be applicable to many other sedimentary suites. The equations of the helix may be characteristic of certain environments. Kurtosis values show rhythmic pulsations along the helix and are diagnostic of two-generation sediments.
BACKGROUND: This article describes the development of consensus medication algorithms for the treatment of patients with major depressive disorder in the Texas public mental health system. To the best of our knowledge, the Texas Medication Algorithm Project (TMAP) is the first attempt to develop and prospectively evaluate consensus-based medication algorithms for the treatment of individuals with severe and persistent mental illnesses. The goals of the algorithm project are to increase the consistency of appropriate treatment of major depressive disorder and to improve clinical outcomes of patients with the disorder. METHOD: A consensus conference composed of academic clinicians and researchers, practicing clinicians, administrators, consumers, and families was convened to develop evidence-based consensus algorithms for the pharmacotherapy of major depressive disorder in the Texas mental health system. After a series of presentations and panel discussions, the consensus panel met and drafted the algorithms. RESULTS: The panel consensually agreed on algorithms developed for both nonpsychotic and psychotic depression. The algorithms consist of systematic strategies to define appropriate treatment interventions and tactics to assure optimal implementation of the strategies. Subsequent to the consensus process, the algorithms were further modified and expanded iteratively to facilitate implementation on a local basis. CONCLUSION: These algorithms serve as the initial foundation for the development and implementation of medication treatment algorithms for patients treated in public mental health systems. Specific issues related to adaptation, implementation, feasibility testing, and evaluation of outcomes with the pharmacotherapeutic algorithms will be described in future articles.
Abstract The Mississippian Barnett Shale serves as source, seal, and reservoir to a world-class unconventional natural-gas accumulation in the Fort Worth basin of north-central Texas. The formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce. At present, production is mainly confined to a limited portion of the northern basin where the Barnett Shale is relatively thick (&gt;300 ft; &gt;92 m), organic rich (present-day total organic carbon &gt; 3.0%), thermally mature (vitrinite reflectance &gt; 1.1%), and enclosed by dense limestone units able to contain induced fractures. The most actively drilled area is Newark East field, currently the largest gas field in Texas. Newark East is 400 mi2 (1036 km2) in extent, with more than 2340 producing wells and about 2.7 tcf of booked gas reserves. Cumulative gas production from Barnett Shale wells through 2003 was about 0.8 tcf. Wells in Newark East field typically produce from depths of 7500 ft (2285 m) at rates ranging from 0.5 to more than 4 mmcf/day. Estimated ultimate recoveries per well range from 0.75 to as high as 7.0 bcf. Efforts to extend the current Barnett play beyond the field limits have encountered several challenges, including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth. Patterns of oil and gas occurrence in the Barnett, in conjunction with maturation and burial-history data, indicate a complex, multiphased thermal evolution, with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas in portions of the basin where paleotemperatures were especially elevated. These and other data imply a large-potential Barnett resource for the basin as a whole (possibly &gt;200 tcf gas in place). Recent assessment by the U.S. Geological Survey suggests a mean volume of 26.2 tcf of undiscovered, technically recoverable gas in the central Fort Worth basin. Recovery of a significant portion of this undiscovered resource will require continued improvements in geoscientific characterization and approaches to stimulation of the Barnett reservoirs.
This article uses two dominant traditions in the organizational study of schools—the neoinstitutional and faculty workplace approaches—to explain an urban elementary school’s response to the Texas Accountability System. The findings indicate that teachers, guided by an institutional logic, sought to create the appearance of test score improvement by using a constellation of “educational triage” practices. Educational triage was manifest in the diversion of resources to students believed to be on the threshold of passing the Texas Assessment of Knowledge and Skills (“bubble kids”) and to “accountable” students (those affecting the school’s accountability rating). Teachers also attempted to remove any liabilities to the school’s rating by referring these students for special education. To explain why teachers participated in educational triage, the author shows how the equation of good teaching with high test scores by the institutional environment and the district reconstituted both teacher professional identities and teacher-teacher relationships.
In 1984, the Texas Legislature funded a four-university, interdisciplinary effort to identify feasible sites for location of a very high-energy physics lab in Texas and to evaluate the comparative advantages of one site versus another. Six feasible sites were identified and a comparative site analysis was made by applying Data Envelopment Analysis (DEA), incorporating project cost, user time delay, and environmental impact data. In addition, for the efficient sites, the price weights for user time delay and environmental impact, given normalization on project cost, were analyzed and arguments were developed to bracket these pairs of price weights into an “assurance region” for the preferred site(s). The South Dallas site was found to be preferred for a wide range of conditions, while the North Houston site was sensitive to the method of indexing the impact of the environment. The method appears to be applicable to a wide range of siting problems faced by not only government, but also industry.
Abstract Shale-gas resource plays can be distinguished by gas type and system characteristics. The Newark East gas field, located in the Fort Worth Basin, Texas, is defined by thermogenic gas production from low-porosity and low-permeability Barnett Shale. The Barnett Shale gas system, a self-contained source-reservoir system, has generated large amounts of gas in the key productive areas because of various characteristics and processes, including (1) excellent original organic richness and generation potential; (2) primary and secondary cracking of kerogen and retained oil, respectively; (3) retention of oil for cracking to gas by adsorption; (4) porosity resulting from organic matter decomposition; and (5) brittle mineralogical composition. The calculated total gas in place (GIP) based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf/section (5.78 × 109 m3/1.73 × 104 m3). We estimate that the Barnett Shale has a total generation potential of about 609 bbl of oil equivalent/ac-ft or the equivalent of 3657 mcf/ac-ft (84.0 m3/m3). Assuming a thickness of 350 ft (107 m) and only sufficient hydrogen for partial cracking of retained oil to gas, a total generation potential of 820 bcf/section is estimated. Of this potential, approximately 60% was expelled, and the balance was retained for secondary cracking of oil to gas, if sufficient thermal maturity was reached. Gas storage capacity of the Barnett Shale at typical reservoir pressure, volume, and temperature conditions and 6% porosity shows a maximum storage capacity of 540 mcf/ac-ft or 159 scf/ton.
Along the Texas-Mexico border, the prevalence of neural tube defects (NTDs) among Mexican-American women doubled during 1990-1991. The human outbreak began during the same crop year as epizootics attributed to exposure to fumonisin, a mycotoxin that often contaminates corn. Because Mexican Americans in Texas consume large quantities of corn, primarily in the form of tortillas, they may be exposed to high levels of fumonisins. We examined whether or not maternal exposure to fumonisins increases the risk of NTDs in offspring using a population-based case-control study. We estimated fumonisin exposure from a postpartum sphinganine:sphingosine (sa:so) ratio, a biomarker for fumonisin exposure measured in maternal serum, and from maternal recall of periconceptional corn tortilla intake. After adjusting for confounders, moderate (301-400) compared with low (< or = 100) consumption of tortillas during the first trimester was associated with increased odds ratios (ORs) of having an NTD-affected pregnancy (OR = 2.4; 95% confidence interval, 1.1-5.3). No increased risks were observed at intakes higher than 400 tortillas (OR = 0.8 for 401-800, OR = 1.0 for > 800). Based on the postpartum sa:so ratio, increasing levels of fumonisin exposure were associated with increasing ORs for NTD occurrences, except for the highest exposure category (sa:so > 0.35). Our findings suggest that fumonisin exposure increases the risk of NTD, proportionate to dose, up to a threshold level, at which point fetal death may be more likely to occur. These results also call for population studies that can more directly measure individual fumonisin intakes and assess effects on the developing embryo.
To refine estimates of source strengths from agricultural wetlands and to study the process of methane production and emission, this study was carried out in rice fields at the Texas A&M University Agricultural Research and Extension Center, Beaumont, Texas, during the summer of 1989. It focussed on two fields on different soil types (Lake Charles clay and Beaumont clay) and spanned a period from shortly after permanent field flooding (June 6, 1989) until field draining prior to harvest (August 28, 1989). Integrated methane emission over 75 days ranged from 4.5 to 15.9 g m −2 . Aboveground biomass, net primary production, and root biomass were determined. Methane emission was strongly related to aboveground biomass in one of two fields studied. Laboratory incubations of soil cores show that methane production by soil bacteria is highest near the soil surface in the rice row and decreases with depth and distance from the plant. Much of the seasonal increase in total methane production is due to increasing activity at intermediate depths and distances from the plants. The temporal and spatial distribution of methane production was found to be related to root biomass. Seasonally integrated emission was 42% of methane production in both fields. Soil pore water methane and plant stem gas composition are related to the distribution in the soil of methane production and root biomass. Methane production ceased with field draining prior to harvest, even following prolonged anaerobic incubation. Methanogenesis rapidly resumed with added acetate substrate.
For the Texas‐Louisiana coast west of 92.5°W, long series of data from near Freeport, Texas, together with shorter series from other locations, show strong response of coastal current to wind stress in agreement with coastal jet concepts. We infer from coastal winds, scattered current measurements, and distributions of sea‐surface salinity and geopotential that a cyclonic gyre elongated along the shelf is the dominant feature of the prevailing shelf circulation. The inshore limb of the gyre is the coastal jet driven by wind with a west or southward (downcoast) component which prevails along much of the coast except in July‐August. Because the coast is concave, the shoreward prevailing wind results in a convergence of coastal currents, which marks the downcoast extent of the gyre. Corresponding to the convergence is a seaward flow which forms the southwest limb of the gyre. A prevailing countercurrent (north or eastward flow) along the shelf break includes the outer limb of the gyre. The eastern, shoreward‐flowing limb of the gyre corresponds to divergence along the coast centered near 92.5°W. The convergence at the western or southern end of the gyre migrates seasonally with the direction of the prevailing wind, reaching south of the Rio Grande mouth in fall and the Cameron offing in July. The gyre is normally absent in July, but reappears in August‐September when a downcoast wind component develops.
Abstract Sandstones and shales of the Wilcox Group (lower Eocene) in southwest Texas were examined by X-ray powder diffraction, electron microprobe, and petrographically to interpret their diagenetic history. Samples analyzed are from depths of 975 to 4650 m, representing a temperature range of 55 degrees C to 210 degrees C. No consistent trend of depositional environments is recognized with increasing depth, and mineralogic changes observed are interpreted as diagenetic. Major mineral distribution patterns are (1) disappearance of discrete smectite at temperatures &gt;70 degrees C, (2) gradation of mixed-layer illite/smectite to less expandable (more illitic) illite/smectite over the entire temperature range, (3) disappearance of kaolinite from 150-200 degrees C accompanied by an increase in chlorite, and (4) replacement of calcite cement at about 117 120 degrees C by ankerite. Calculations based on data of Hower and others (1976) indicate that the stability of smectite layers may be a function of composition. Smectites with high ratios of octahedral (Fe + Mg)/Al appear to resist conversion to illite until temperatures high enough to produce ordering are attained. A diagenetic model is proposed which involves the breakdown of detrital K-feldspar and of some smectite layers in illite/smectite to convert other smectite layers to illite. Silica and calcium released by the illitization of smectite is transferred from shales to sandstones to produce quartz overgrowths and calcite cements at temperatures as low as 60 degrees C. Iron and magnesium released by the illitization reaction are transferred from shales to sandstones at temperatures &gt;100 degrees C and react with kaolinite to produce high-alumina chlorite and/or with calcite to produce ankerite.