Collaborative Research: Geodetic Constraints on the Tectonic Processes Operating at the East Flank of the Central Andean Plateau

University Of Hawaii, Honolulu

Investigators

Abstract

A team of scientists from Ohio State University and the University of Hawaii is constructing a dense GPS network over the entire eastern flank of the Andean Plateau within Bolivia and northernmost Argentina in order to address a variety of questions about orogenic wedge processes and Andean plateaus margin kinematics. The project will to study contemporary patterns of deformation in the Andean Plateau, and focus on its eastern flank, which is comprise of the Eastern Cordillera, the Interandean Zone, and the Subandes. To better understand orogenic wedge processes they research team will: (1) determine whether a strong eastern flank velocity gradient is a signal of a slipping-locked transition zone on the basal decollement or of out-of-sequence thrusting; (2) measure differences in the width of the active wedge north and south of the Santa Cruz bend and determine its relationship to the differences in rainfall (as a proxy for erosion) on either side of the bend; (3) assess mechanisms by which active shortening is transferred from the deeper, inboard portions of a plateau to the shallower outboard wedges. Andean plateau kinematics will be elucidated by: (1) determination of the kinematic framework of the east flank of the Andean plateau; (2) measurement of the variation of active shortening along-strike; (3) assessment of the influence of paleogeography and foreland basin stratigraphy on crustal displacement and foreland shortening; (4) examination of the relationship between the absence of Paleozoic sediments in the foreland basin of the Chapare region and the Cochabamba Shear Zone; (5) exploration for evidence of extrusion tectonics in the main physiographic transition or topographic ramp above the northern Subandes. Orogenic plateaus have formed throughout much of geological history, and because they are produced by massive crustal thickening accompanied by large scale crustal melting, their formation plays an important role in the evolution of continental crust. The best prospect for understanding the mechanisms responsible for plateau orogenesis is the study of active continental plateaus, such as the plateau in the central Andes. Current theories for the development of this high plateau suggest either a slow two-stage uplift process or a rapid uplift scenario. This study will provide data that will contribute to the resolution of this controversy as well as improve understanding of the active processes along the plateau's eastern margin. This project should lead to a deeper understanding of the way that mountain belts and topographic plateaus deform. The research should improve understanding of the generation of earthquakes in the highly populated regions flanking high mountains.