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Articles 241 - 246 of 246

Full-Text Articles in Earth Sciences

Timing And Extent Of Late Quaternary Paleolakes In The Trans-Pecos Closed Basin, West Texas And South-Central New Mexico, David Wilkins, Donald Currey Apr 1997

Timing And Extent Of Late Quaternary Paleolakes In The Trans-Pecos Closed Basin, West Texas And South-Central New Mexico, David Wilkins, Donald Currey

David E. Wilkins

The Trans-Pecos Closed Basin is a hydrographically closed region covering 20,000 km centered on Salt Basin, 160 km east of El Paso, Texas. Geomorphic and limnetic evidence have been used to identify four major highstands for Lake King during the last glacial maximum (LGM). Additional geomorphic features from a second, recently identified, paleolake, Lake Sacramento, have been found in the Beargrass subbasin, a nested subbasin approximately 75 km northwest of Salt Basin. Radiocarbon ages of the organic material in Lake King sediments date four abrupt climate changes and rapid lacustrine transgressions during the LGM with a quasi-periodicity of 2000 yr. …

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Direct Dating Of Deformation; U-Pb Age Of Syndeformational Sphene Growth In The Proterozoic Laramie Peak Shear Zone, Phillip G. Resor, Kevin R. Chamberlain, Carol D. Frost, B Ronald Frost, Arthur W. Snoke Jun 1996

Direct Dating Of Deformation; U-Pb Age Of Syndeformational Sphene Growth In The Proterozoic Laramie Peak Shear Zone, Phillip G. Resor, Kevin R. Chamberlain, Carol D. Frost, B Ronald Frost, Arthur W. Snoke

Phillip G Resor

In this paper, we show that deformation can be dated by combining mesoscopic and microscopic structural observations with an understanding of metamorphic mineral reactions and U-Pb ages of newly grown sphene (titanite). This approach can be used on a variety of rock types that have been deformed at a wide range of metamorphic conditions. In an example from the Proterozoic Laramie Peak shear zone of southeastern Wyoming, a single period of syntectonic sphene growth in sheared mafic dikes is documented both by a strong spatial relationship between deformation and metamorphism and by sphene microtextures. U-Pb analyses of sphene separates give …

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The In Situ Passive Acoustic Measurement Of Shingle Movement Under Waves And Currents: Instrument (Tosca) Development And Preliminary Results, George Voulgaris, Michael Wilkin, Michael Collins Jul 1995

The In Situ Passive Acoustic Measurement Of Shingle Movement Under Waves And Currents: Instrument (Tosca) Development And Preliminary Results, George Voulgaris, Michael Wilkin, Michael Collins

George Voulgaris

An instrumented platform (TOSCA) is described for monitoring coarse-grained sediment transport in high (wave and tidal) energy environments. The system consists of a number of sensors which measure: instantaneous current velocities at three levels; sea surface elevation; and self-generated noise (SGN) caused by intercollision of particles in transit. SGN is related to transport rates, on the basis of laboratory calibration; this, in turn, allows a correlation with simultaneous near-bed shear stress to be established. During the field measurements, PC-based real-time data transmission is realised through the use of a (buoyed) radio telemetry system.

TOSCA has been deployed in eastern Christchurch …

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Thermochronology And Thermobarometry In Lithotectonic Zones In Eastern New England, Andrea Koziol, Robert Wintsch Apr 1991

Thermochronology And Thermobarometry In Lithotectonic Zones In Eastern New England, Andrea Koziol, Robert Wintsch

Andrea M. Koziol

Eastern New England is now recognized to consist of a number of exotic terranes joined to ancestral North America along large faults. However, the timing of the accretion of these terranes is in a state of flux. This project will gather thermometric and barometric data from both sides of these terrane bounding faults and together with existing age determinations will assess the possibility of major Alleghenian motion, not previously recognized. Results have the potential to provide a major re-interpretation of the timing of terrane accretion in New England.

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Acquisition Of An Electron Probe Microanalyzer, Andrea Koziol, Robert Wintsch, Michael Dorais, Edward Ripley, Enrique Merino Dec 1990

Acquisition Of An Electron Probe Microanalyzer, Andrea Koziol, Robert Wintsch, Michael Dorais, Edward Ripley, Enrique Merino

Andrea M. Koziol

This award will provide half of the funds needed for the acquisition of an electron microprobe. This new electron microscope will primarily serve the needs of the Geology faculty and graduate students in the Department of Geological Sciences at The University of Indiana. The University of Indiana is committed to provide the additional funds to make this acquisition possible. Seven Geology Department faculty and their students have been identified as primary users. Six other faculty expect to be less frequent or occasional users. This large group of faculty and their students pursue research in diverse areas (e.g. thermodynamic links between …

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The Vcl Hypothesis Revisited: Patterns Of Femoral Morphology Among Quadrupedal And Saltatorial Prosimian Primates, Robert Anemone Dec 1989

The Vcl Hypothesis Revisited: Patterns Of Femoral Morphology Among Quadrupedal And Saltatorial Prosimian Primates, Robert Anemone

Robert L. Anemone

The descriptive and functional morphology of the postcranium of the vertical clinging and leaping prosimians is of great interest in both adaptational and phylogenetic studies of extant and extinct primates. An analysis of patterns of femoral morphology among quadrupedal and saltatory living prosimians indicates the presence of at least two, and possibly three, distinct femoral adaptations to the demands of an arboreal, saltatory existence. Osteological measurements were taken on 277 postcranial skeletons representing eight prosimian families, with skeletal trunk length (Biegert and Maurer, Folia Primatol. 17:142–156, 1972) used as an estimator of body size in both bivariate and multivariate (discriminant …

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