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Texas A&M University (2017)

System Controls on the South Texas Sand Sheet

Barrineau, Clifton Patrick

Titre : System Controls on the South Texas Sand Sheet

Auteur : Barrineau, Clifton Patrick

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 2017

Résumé
Semi-stabilized dune systems are important indicators of Quaternary drought variability across central North America. The South Texas sand sheet (STSS) is the southernmost relict dune system in central North America and is exposed to higher evapotranspiration and moisture variability than similar landscapes farther north. This study uses multi-scale analysis of LiDAR data, geophysical surveys, optically stimulated luminescence dates of core samples, and X-ray fluorescence analysis to identify historical periods of desertification across the STSS. These data suggest long-term relationships between climate, ecological disturbances, geological framework, and desertification. Aeolian activations dated at ca. 75, 230, 2000, 4100, and 6600 yr bp correspond to periods of persistent regional drought, changes in sediment supply, and anthropogenic disturbances of native ecology. From these results it appears that regionalized activation in semi-stabilized dune systems is controlled primarily by climatic variations that reduce the overall moisture available for maintaining vigorous vegetation growth, while localized activation patterns depend more on stresses related to site-specific morphodynamics as well as human activity. With enhanced aridity forecast for much of central North America through the 21st century, understanding the specific thresholds of desertification is an important step towards building a conceptual model of desertification in semi-stabilized dune landscapes.

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