Neotectonics and Climatic History of the Central Andes: High-Resolution Seismic Reflection Imaging of the Salar de Uyuni

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9815062McGearyThis research involves the acquisition of a set of high-resolution seismic reflection profiles across the Salar de Uyuni in the Altiplano of Bolivia. This salar is the largest salt flat in the world and is a conspicuous remnant of the late Pleistocene Lake Minchin-Tauca. The project has two major objectives: (1) to produce a stratigraphic and paleoclimate record for Pleistocene deposits within the southern basin of the Altiplano by imaging interbedded layers of lake marls and salar salt down to depths of 300-500 meters and (2) to document the extent to which the Quaternary lake stratigraphy is affected by neotectonic deformation in the form of either isostatic rebound or active faulting across the 100-km wide salar. The seismic profiles will reveal depths to significant stratigraphic boundaries, which are expected to chiefly reflect the alternating marl and salt layers that were seen in the only deep (120 m) core that has been recovered from beneath the salar. The marl is deposited during stable phases of deep lake cycles (approximately 100-m water depth) and the salt is deposited during terminations of deep lake cycles, when lake level is low or falling. The present salar surface is flat to within 1 m over a 100 by 100-km area. Lateral variations in depth to the tops of buried salt units will mostly reflect isostatic response to lacustrine water and sediment loads, and an unknown component of neotectonic deformation. One of the significant puzzles these data will address is the discordant indicators of regional tilting associated with the uppermost salt unit, which thickens to the east, and the highest Lake Minchin shoreline, which tilts down to the west.