Multi-Scale Imaging of the Andean Subduction Zone from the Crust of the Northern Andes to the Nazca Slab's Descent Into the Lower Mantle from Seismic Tomography

Abstract

The Nazca-South America subduction zone spans >7,000 km of the South America margin. It is characterized by the subduction of the oceanic Nazca plate beneath continental South America and is responsible for the largest ongoing tectonics recorded in the overriding plate of a convergent margin, including the Andean Mountain belt. The subduction zone is often described as a natural laboratory to study the fundamentals of subduction and as a modern analog to other Cordilleran-style tectonics (e.g., the North American Cordillera). Models which compare the two often focus on the down-going plate and its role in driving processes in the overriding plate and its effects on the mantle. This dissertation explores the relationship between the morphology of the downgoing Nazca slab, the surrounding mantle, and its influence on the overriding plate using seismic tomography. The first two chapters focus on the large-scale morphology of the subducting slab from 90 to 1450 km depth with increasing detail in the second chapter. The final chapter focuses on the crust and connection between subducted bathymetric features of the slab and the development of the forearc and volcanic arc architecture.