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Plano, TX, United States

Hall S.A.,Red Rock Geological Enterprises | Miller M.R.,Geo Marine Inc | Goble R.J.,University of Nebraska - Lincoln
Bulletin of the Geological Society of America | Year: 2010

The Bolson sand sheet occurs in the Tularosa Valley, New Mexico, and the Hueco Bolson, Texas and consists of two principal eolian sand units. Optically stimulated luminescence (OSL) dating provides a new chronology of the sand sheet that relates as well to the formation, preservation, and visibility of the local archaeological record. The lower sand (unit Q2) (44.8 ± 2.9 ka) and the upper sand (unit Q3) (22.2 ± 1.6-5.2 ± 0.3 ka) have a combined thickness of less than 2 m. The Q2 sand is characterized by a red Bt paleosol, and the Q3 sand has a weak calcic paleosol with stage I carbonate morphology. Elevated amounts of airborne silt were incorporated in the Q3 sand during the period 24-14.5 ka, representing higher amounts of dust in the atmosphere during glacial and lateglacial time. Multiple OSL ages from the Q3 sand indicate a slow net sedimentation rate of 0.06-0.09 mm/yr, similar to other OSL-dated sand sheets in the region; sand deposits in dune fields have higher accumulation rates. The McGregor A horizon soil, radiocarbon-dated to younger than 0.5 ka, occurs at the top of the sand sheet and likely formed with desert grassland vegetation. Thousands of recent mesquite coppice dunes (unit Q4d) mantle the sand sheet, and two are dated to the twentieth century by OSL and 137Cs. Archaeological sites that postdate 3000 B.C. are concentrated, sometimes together, on the surface of the sand sheet, while sites that predate 3000 B.C., although rare, may be buried within the Q3 eolian sand. The Q2 sand is too old to contain archaeological sites, although site features may intrude into the sand. Previous chronologies of the sand sheet are based on radiocarbon dates of charcoal from archaeo logical sites, on radiocarbon dates of soil carbonate, and on soil-geomorphology correlations with Rio Grande Valley alluvium. The optical chronology does not support these various correlations. We recommend that the alluvial names Isaacks' Ranch, Fillmore, and Organ no longer be applied to the Bolson sand sheet. © 2010 Geological Society of America. Source

Precht W.F.,Dial Cordy and Associates | Deslarzes K.J.P.,Geo Marine Inc | Hickerson E.L.,National Oceanic and Atmospheric Administration | Schmahl G.P.,National Oceanic and Atmospheric Administration | And 2 more authors.
Marine Geology | Year: 2014

Fossil elkhorn corals, Acropora palmata, were discovered at the Flower Garden Banks (FGB) on the shelf-margin off the Texas coast in 2006. Radiocarbon dating revealed an A. palmata-dominated community aged 10,157-6838. cal BP. The Acropora reefs correspond in time to an interval of warmer-than-present sea-surface temperatures (SSTs) during the Holocene thermal maximum (HTM). The subsequent demise of A. palmata in the middle Holocene was a consequence of the inability of the shallowest reef facies to keep pace with rising sea level following complete submergence of the banks, possibly coupled with decreasing SSTs following the HTM. In 2007, the first fossil staghorn corals, Acropora cervicornis, were discovered at the FGB. Based on radiocarbon dating of these corals to 1027-211. cal BP, it appears that populations of A. cervicornis flourished in deeper waters (~. 25-32. m depth) on the edges of the banks until the peak of the Little Ice Age (LIA) when they died, presumably from cold-water exposure. The recent return of A. palmata to reefs of the FGB associated with increasing sea temperatures appears to be both an echo of the past and a harbinger of the future. © 2014 The Authors. Source

Lauder K.D.,University of Dundee | Lauder K.D.,Lloyds Register | Brown M.J.,University of Dundee | Bransby M.F.,University of Dundee | And 2 more authors.
Canadian Geotechnical Journal | Year: 2012

Pipeline plough behaviour has been investigated by means of reduced scale physical model testing. A testing programme was devised to investigate the influence of permeability, relative density, and plough depth on the associated tow force measured during ploughing over a range of velocities in saturated granular material. An increase in tow force with velocity was found during all of the tests and the results have been compared to previously developed analytical models. A new empirical equation has been developed to describe the change in tow force with velocity for a variety of model siliceous sand conditions. Application of this new approach to full-scale ploughing requires consideration of scaling effects and the use of appropriate input parameters determined to replicate field conditions. Source

Finley T.G.,University of Arkansas at Little Rock | Finley T.G.,University of Wisconsin - Madison | Finley T.G.,Geo Marine Inc | Sikes R.S.,University of Arkansas at Little Rock | And 2 more authors.
Zoo Biology | Year: 2011

Endangered giant pandas (Ailuropoda melanoleuca) are bears (Family Ursidae), within the order Carnivora. They specialize on an herbivorous diet of bamboo yet retain a gastrointestinal tract typical of their carnivorous ancestry. The evolutionary constraints of their digestive tract result in a low extraction efficiency from bamboo (<40% in reported studies). The goal of this study was to determine the energy digestibility of bamboo by giant pandas used in digestibility trials and through subsequent analyses with bomb calorimetry. Seven digestibility trials were conducted (three with bamboo-only diets and four with supplemental diets). Energy digestibilities ranged from 7.5-38.9% for mixed diets and 9.2-34.0% for bamboo-only diets. The bamboo-only trials summarized here represent, to our knowledge, the first empirical data available for energy digestibility on a bamboo diet for giant pandas. © 2010 Wiley-Liss, Inc. Source

Dudzinski K.M.,Geo Marine Inc | Brown S.J.,Geo Marine Inc | Lammers M.,Hawaii Institute of Marine Biology | Lucke K.,University of Kiel | And 7 more authors.
Journal of the Acoustical Society of America | Year: 2011

Deployment of any type of measuring device into the ocean, whether to shallow or deeper depths, is accompanied by the hope that this equipment and associated data will be recovered. The ocean is harsh on gear. Salt water corrodes. Currents, tides, surge, storms, and winds collaborate to increase the severity of the conditions that monitoring devices will endure. All ocean-related research has encountered the situations described in this paper. In collating the details of various deployment and recovery scenarios related to stationary passive acoustic monitoring use in the ocean, it is the intent of this paper to share trouble-shooting successes and failures to guide future work with this gear to monitor marine mammal, fish, and ambient (biologic and anthropogenic) sounds in the ocean-in both coastal and open waters. © 2011 Acoustical Society of America. Source

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