Investigating the Geological and Biogeographical Cenozoic History of the Amazon-Andes Region

Abstract

The Amazon-Andes region of tropical South America plays host to the world’s largest river, its highest biodiversity and one of its highest mountain chains, as well as a long and complex history. As such, it represents an ideal location to study the interplay between geology, climate and biodiversity. In this thesis I first present a statistical analysis of the usefulness of paleocurrent data in reconstructing that complex history, using high-resolution topographic data from the Shuttle Radar Topography Mission to develop and test a river network model of the modern Amazon River watershed, followed by new zircon geochronology provenance data from the Alter do Chão Formation in Brazil, with implications for hypothesized Miocene drainage reversal in Amazonia. I then present potentially the first attempt to utilize phylogenetic data to inform our understanding of the uplift history of the Andes, using a simple biogeographic model of vicariant speciation along with phylogenetically-established dates for isolation events to compare varying simulations of Andean uplift over the past 10 million years.I will conclude (1) that paleocurrent analysis is likely of very limited use in watershed-scale investigations, while highlighting the complexity of river flow patterns within a large basin such as the Amazon, and (2) that the topography found at the modern day Huancabamba Depression likely did not reach its current elevation earlier than ca. 3 million years.