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Universität Potsdam (2015)

The role of wind and water in shaping earth’s plateaus

Rohrmann Alexander

Titre : The role of wind and water in shaping earth’s plateaus

Die Rolle von Wind und Wasser bei der Bildung von Hochplateaus der Erde

Auteur : Rohrmann Alexander

Université de soutenance : Universität Potsdam

Grade : Doctoral Thesis 2015

Résumé partiel
The overarching goal of this dissertation is to provide a better understanding of the role of wind and water in shaping Earth’s Cenozoic orogenic plateaus - prominent high-elevation, low relief sectors in the interior of Cenozoic mountain belts. In particular, the feedbacks between surface uplift, the build-up of topography and ensuing changes in precipitation, erosion, and vegetation patterns are addressed in light of past and future climate change. Regionally, the study focuses on the two world’s largest plateaus, the Altiplano-Puna Plateau of the Andes and Tibetan Plateau, both characterized by average elevations of >4 km. Both plateaus feature high, deeply incised flanks with pronounced gradients in rainfall, vegetation, hydrology, and surface processes. These characteristics are rooted in the role of plateaus to act as efficient orographic barriers to rainfall and to force changes in atmospheric flow.
The thesis examines the complex topics of tectonic and climatic forcing of the surface-process regime on three different spatial and temporal scales : (1) bedrock wind-erosion rates are quantified in the arid Qaidam Basin of NW Tibet over millennial timescales using cosmogenic radionuclide dating ; (2) present-day stable isotope composition in rainfall is examined across the south-central Andes in three transects between 22° S and 28° S ; these data are modeled and assessed with remotely sensed rainfall data of the Tropical Rainfall Measuring Mission and the Moderate Resolution Imaging Spectroradiometer ; (3) finally, a 2.5-km-long Mio-Pliocene sedimentary record of the intermontane Angastaco Basin (25°45’ S, 66°00’ W) is presented in the context of hydrogen and carbon compositions of molecular lipid biomarker, and oxygen and carbon isotopes obtained from pedogenic carbonates ; these records are compared to other environmental proxies, including hydrated volcanic glass shards from volcanic ashes intercalated in the sedimentary strata.

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