T174 Future Directions in Tectonics and Lithospheric Processes: A Session for Early Career Researchers (Posters)

Tuesday, 11 October 2022
9:00 AM - 1:00 PM
Exhibit Hall F

DECONVOLVING MULTIPLE SUBSIDENCE MECHANISMS IN RETROARC CORDILLERAN GEODYNAMICS THROUGH BASIN ANALYSIS OF THE ALTIPLANO BASIN

Paper number: T174-4
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

Synorogenic basins provide a spatio-temporally extensive perspective on lithosphere-scale processes that drive vertical crustal movement. High-resolution basin analysis in the central Andes informs the ongoing debate on the role and relative importance of upper- versus lower-plate processes at continental subduction margins, a particular problem where flat-slab subduction is involved. Stratigraphy of the Altiplano region spans Late Cretaceous–Cenozoic central Andean orogenesis. While recent sedimentology and paleoaltimetry data have improved the four-dimensional picture of vertical crustal movement in the northern Altiplano (southern Peru and NW Bolivia), limited chronostratigraphy for Paleogene non-marine strata has precluded a comprehensive subsidence analysis for the entire Altiplano.

We report U-Pb detrital zircon geochronology from newly measured/remeasured stratigraphic sections and integrate these data with published chronostratigraphy. Preliminary tectonic subsidence analysis of nine locations spanning the Altiplano Basin from ~13°S to 25°S shows variation in the timing, rate, and magnitude of basin development. Across these latitudes, stratigraphy records Late Cretaceous subsidence followed by a Paleocene decrease in subsidence rates. A subsequent N to S-progressing onset of rapid Paleogene subsidence in the northern and central AP can be partially attributed to coeval crustal shortening and tectonic loading-induced flexure. Subsidence rates decrease for the northern Altiplano by ~24 Ma but remain high for the central Altiplano until <10 Ma. Geohistories generally do not conform to idealized subsidence curves for particular drivers, suggesting superposition of mechanisms such as lithospheric flexure, extensional/transtensional faulting, lithospheric densification, and/or dynamic topography. This ongoing work will extend coverage of age constraints on central and southern Altiplano strata (SW Bolivia) for a more complete picture of basin-forming tectonic-geodynamic processes in cordilleran systems.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-381108

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.