Patterns of Andean growth in the Ecuadorian Andes

Abstract

Reconstructing the topographic evolution of mountains helps to understand the geodynamic processes that shape the Earth's surface. The Napo Uplift (NU) occupies the frontal Andes in northeastern Ecuador and is related to slip along a deep mega-thrust system. Thermochronometry and sedimentary provenance data reveal that exhumation west of the NU, in the Cordillera Real in Ecuador, occurred since late Cretaceous (Spikings et al., 2010). However, surface uplift in the region is less well-constrained. Here we aim to evaluate spatial trends in rock uplift by (1) acquiring new apatite fission track (AFT) and (U-Th)/He data in basement and sedimentary rocks of the NU with various degrees of thermal resetting, and (2) performing thermo-kinematic modeling of thermochronological data to quantify the rates of tectonic deformation. The purpose of the scholarship for a Research Internship Abroad in the University of Rennes revolves around the direct quantification of Uranium content and other multi-elemental data in apatites analysis using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). This technique allows for the simultaneous acquisition of U-Pb and multi-elemental geochemistry data, such as Cl, rare earth element, and other trace elements commonly used in AFT and provenance analysis (Chew and Spikings, 2015). In addition, AHe analysis will also be acquired using a facility recently established at Géosciences Rennes. Finally, geochronological and geochemical detrital data will be used to identify populations using a method recently developed by Prof. Gallagher and his group whereby individual populations are independently modeled to estimate the thermal history of both, the sedimentary rock and its source area (Wildman et al., 2020). Acquiring and interpreting thermochronological data with these techniques will allow for a better characterization of the provenance and thermal histories of the Ecuadorian Andes. (AU)