Cenozoic Basin Development and Environmental Change in the Peruvian Altiplano and Implications for Uplift Mechanisms

University Of Houston, Houston TX

Investigators

Abstract

Surface elevation is a first-order reflection of the geodynamic mechanisms that create and sustain large mountain belts and plateaux. One family of models for surface uplift predicts uplift spatially and temporally associated with crustal thickening during mountain building processes. In these models, surface uplift keeps pace with shortening of the crust. Another family of models predicts that surface uplift is the result of removal of a dense subcrustal load accumulated during crustal shortening. Uplift in these models significantly post-dates upper crustal shortening. This project aims to test these end-member models in the best modern analog for an oceanic-continental subduction system: the Central Andean Plateau. Successfully discriminating between these models has implications for the timing and pace of sedimentary basin formation in modern and ancient settings. Because foreland basins host important hydrocarbon reserves, determining which model best describes their formation has potential implications for hydrocarbon exploration. Surface elevation also impacts the global climate system and provides barriers to migration that promote the development of new biological species. This project will promote full participation of women and minorities in science, technology, engineering and mathematics (STEM) fields by supporting at least one female graduate student and at least one minority undergraduate student. The principal investigator and his graduate students will contribute to STEM education by supporting geoscience outreach to local middle school and homeschool students and by supporting the TerraElm middleschool outreach program. Funds from this project will support the education of the next generation in a globally competitive STEM workforce through undergraduate and graduate training. Finally, it will support international collaborations between US and Peruvian scientists. This project will investigate the timing and mechanism of surface uplift of high elevation terranes in the archetypal ocean-continent subduction setting of the southern Peruvian Central Andean Plateau. Outstanding questions have prevented a systematic identification of the mechanism of basin formation and its relation to exhumation and surface uplift in the Peruvian Central Andean Plateau. Insufficient chronological data prevents a detailed reconstruction of the timing and tempo of sediment accumulation in the Peruvian Central Andean Plateau. In this study, the principal investigator will develop a detailed chronology of deposition based on multiple intercalated volcanic strata in Neogene deposits and syndepositional volcanic zircons in Paleogene strata. A regional reconstruction of sediment provenance, dispersal systems, and basin geometry through time awaits application of multiple independent techniques will also be produced. The principal investigator will use detrital geochronology coupled with sandstone petrology, conglomerate clast composition, and paleocurrent data to track sediment sources through time. Detrital (Uranium-Thorium)/Helium thermochronology will be used in combination with detrital Uranium-Lead geochronology to track the locus of exhumation through time. Changes in depositional environments and climate are predicted to accompany surface uplift, and this will be demonstrated by documenting changes in depositional environment and climate using a combination of hydrogen and oxygen stable isotopic compositions with paleotemperatures derived from carbonate clumped isotope paleothermometry and by observations of changing sedimentary lithofacies associations. The project will also employ a novel paleoelevation proxy: delta-D values of the waters of hydration of volcanic glass to aid in reconstructing the paleoelevation of the Peruvian Central Andean Plateau.