Geochemistry of bottom sediments -- Matagorda Bay system, Texas

UT Librarie

The Gulf shoreline of Texas : processes, characteristics, and factors in use

UT Librarie

Depositional Setting of the Triassic Dockum Group, Texas Panhandle Eastern New Mexico

The upper Triassic Dockum Group accumulated in relict Paleozoic basins defined in Texas by the Amarillo Uplift on the north and the Glass Mountains on the south. These basins were reactivated during the late Paleozoic or early Mesozoic by tectonic activity that was probably related to the opening of the Gulf of Mexico. As basins subsided and some relict positive elements were uplifted, sedimentation rates increased. More than 2,000 ft (610 m) of terrigenous elastics, derived chiefly from Paleozoic sedimentary rocks, accumulated within the basin. Source areas were in Texas, Oklahoma, and New Mexico; sediment transport was from the south, east, north, and west. The Dockum Group accumulated in a variety of depositional environments including: (1) braided and meandering streams; (2) alluvial fans and fan deltas; (3) distributary-type lacustrine deltas (high-constructive elongate deltas); (4) ephemeral and relatively long-lived lakes; and (5) mud flats. Alternation of wet and dry climate caused cyclic sedimentation in the Dockum. The main control on climate was most likely tectonism. During wet periods, lake level was relatively stable. Meandering streams supplied sediment to high-constructive elongate deltas in the central basin area of Texas and New Mexico, whereas braided streams and fan deltas were dominant depositional elements along southern and northern basin margins. Lake area and depth decreased when dry conditions prevailed. Under these conditions, base level was lowered, valleys were cut into older Dockum deposits, and small fan deltas were built into ephemeral lakes; evaporites, calcretes, silcretes, and soils developed upon emergent surfaces ranging from floors of ephemeral lakes to delta platforms.Bureau of Economic Geolog

Uranium Resource Evaluation Amarillo Quadrangle Texas

Uranium resources of the Amarillo Quadrangle, Texas, were evaluated, using criteria established for the National Uranium Evaluation (NURE) program, to a depth of 1500 m (5,000 ft) using available surface and subsurface information. No surface uranium occurrences were reported in the literature. Areas of anomalous radioactivity, interpreted from an aerial radiometric survey, and geochemical anomalies, interpreted from hydrogeochemical and stream-sediment reconnaissance, were investigated. No uranium occurrences were located during a detailed rock sampling program. Areas of uranium favorability in the subsurface were evaluated using driller's log descriptions and gamma-ray well logs. On the basis of subsurface data, five areas of uranium favorability were delineated within the quadrangle. Two areas in the Triassic Dockum Group are in sand-rich facies. Two areas are in thick arkosic alluvial fan and fluvial facies of Early Permian and Pennsylvanian age. Early Permian arkosic strata cover the greatest area. One favorable area along and northeast of the Amarillo Uplift is characterized by abundant gamma-ray log anomalies that are concentrated in Wolfcampian (Early Permian) and older strata. Geologic units considered unfavorable are all Pleistocene strata, all the Tertiary Ogallala Formation, most of the Triassic Dockum Group, all post-Wolfcampian Permian strata, and parts of Lower Permian (Wolfcampian) and Pennsylvanian rock units. Recommendations for improving the reliability of this evaluation include drilling test holes for detailed subsurface information.Bureau of Economic Geolog

Geologic approaches to the determination of long-term coastal recession rates, matagorda peninsula, Texas

The degree to which human modifications in the coastal zone have increased or decreased coastal erosion rates is difficult to determine owing to the short time period for which shoreline-position data are available. This limitation is circumvented in areas where long-term recession rates can be determined from geologic data. Three such areas from Matagorda Bay have been examined to determine the temporal variation in recession rates over the past several thousand years. Preliminary results indicate that recession rates over the past century may be 30% to 40% greater than those of prehistoric time. Although additional data are needed, it is suggested that accelerated rates result from human modification of the coastal zone, and that in the future increased recession rates can be anticipated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46765/1/254_2006_Article_BF02380504.pd

Environmental geologic atlas of the Texas coastal zone : Port Lavaca area

UT Librarie

Teacher Tasks for Mathematical Insight and Reorganization of What it Means to Learn Mathematics

The mathematics-for-teachers tasks we discuss in this chapter have two qualities: (1) they offer teachers opportunities to experience the pleasure of mathematical insight; and (2) they aim to disrupt and reorganize teachers\u27 views of what it means to do and learn mathematics. Given that many future and inservice elementary teachers fear and dislike mathematics, it is perhaps not too far-fetched to suggest that there is a need for “math therapy.” We believe that a form of mathematics therapy may involve new and different experiences with mathematics. Such experiences, considered broadly to include questions or prompts for mathematical exploration, draw attention to deep mathematical ideas and offer the potential of experiencing the pleasure of significant mathematical insight. In our work with teachers we have developed and used a variety of mathematics tasks as opportunities for experiential therapy. The tasks aim to challenge some of the mathematical myths that future teachers believe to be true and are typically assumed by them in mathematics classrooms. The tasks have potential to disrupt teachers\u27 view of mathematics, and to start the process for reorganizing their thinking about what mathematics is and what it means to do and learn mathematics. In this chapter we describe and discuss four of the mathematics tasks which involve non-routine mathematics problems that we use in our mathematics-for-teachers program. This program is offered annually to our 440 future elementary school (K-8) teachers, who generally lack confidence in mathematics and often fear and/or dislike the subject. It is also offered to inservice teachers through a series of mathematics-for-teachers courses. A student response summarizes the effects of our approach

Analysis of the FGF gene family provides insights into aquatic adaptation in cetaceans

Cetacean body structure and physiology exhibit dramatic adaptations to their aquatic environment. Fibroblast growth factors (FGFs) are a family of essential factors that regulate animal development and physiology; however, their role in cetacean evolution is not clearly understood. Here, we sequenced the fin whale genome and analysed FGFs from 8 cetaceans. FGF22, a hair follicle-enriched gene, exhibited pseudogenization, indicating that the function of this gene is no longer necessary in cetaceans that have lost most of their body hair. An evolutionary analysis revealed signatures of positive selection for FGF3 and FGF11, genes related to ear and tooth development and hypoxia, respectively. We found a D203G substitution in cetacean FGF9, which was predicted to affect FGF9 homodimerization, suggesting that this gene plays a role in the acquisition of rigid flippers for efficient manoeuvring. Cetaceans utilize low bone density as a buoyancy control mechanism, but the underlying genes are not known. We found that the expression of FGF23, a gene associated with reduced bone density, is greatly increased in the cetacean liver under hypoxic conditions, thus implicating FGF23 in low bone density in cetaceans. Altogether, our results provide novel insights into the roles of FGFs in cetacean adaptation to the aquatic environment.ope

Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

Timing and Tempo of Early and Successive Adaptive Radiations in Macaronesia

The flora of Macaronesia, which encompasses five Atlantic archipelagos (Azores, Canaries, Madeira, Cape Verde, and Salvage), is exceptionally rich and diverse