49-3 Interplay of tectonics and climate archived in intra-arc basin strata of the late Cenozoic central Andes of southern Peru

Session: Exploring Feedbacks Between Tectonics and Climate on Lithospheric Evolution Using Multidisciplinary Approaches

Presenting Author:

Kurt Sundell

Authors:

Sundell, Kurt¹, Eden, Ryan², Styron, Richard³, Villarreal, Dustin⁴, Usnayo Perales, Whitney Paola⁵, Saylor, Joel⁶, Göğüş, Oguz⁷, Finney, Bruce⁸, Lapen, Thomas⁹, Cardenas, Jose¹⁰, Carlotto, Victor¹¹

(1) Idaho State University, Pocatello, Idaho, USA, (2) University of California, Santa Barbara, Santa Barbara, CA, USA, (3) Global Earthquake Model Foundation, Pavia, Italy, (4) University of Houston, Houston, TX, USA, (5) Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru, (6) University of British Columbia, Vancouver, BC, Canada, (7) Istanbul Technical University, Istanbul, Turkey, (8) Idaho State University, Pocatello, ID, USA, (9) University of Houston, Houston, TX, USA, (10) Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru, (11) Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru,

Abstract:

Intra-arc basins are valuable stratigraphic archives that link tectonic processes driving topographic development to surface processes shaping the landscape. Disentangling complex records of tectonic activity intertwined with climatic effects remains challenging. This is exemplified in the central Andes, where the timing of surface uplift and its control on moisture sourcing, meteoric water, and paleoenvironment remains debated. Disagreements largely stem from interpretations of the timing and rates of surface uplift, with estimates in the Western Cordillera being especially disparate. Some suggest the transition from low-to-moderate elevation (1000–2500 m) to near-modern elevation (>4000 m) took place rapidly in the early to middle Miocene, whereas others suggest it took place earlier and slower during the Paleogene; whether arid-hyperarid conditions along the Pacific coast are a product of this topographic development is similarly debated. We present a multidisciplinary study of intra-arc basin strata in the Western Cordillera of southern Peru including lithofacies characterization, detrital zircon U-Pb geochronology of sandstones, stable isotopic analysis of lacustrine limestones, and Hf isotopic geochemistry of zircon. Basin strata show a shift from fluvial to lacustrine-evaporitic depositional environments recorded in the ~2.6 km-thick siliciclastic-carbonate basin fill of the Tincopalca Basin. Detrital zircon U-Pb geochronology yields age distributions dominated by syndepositional volcanism with new maximum depositional ages bracketing deposition between 28 and 21 Ma. A decrease in lacustrine carbonate δ¹⁸O from ~0‰ to -9‰ at 22–21 Ma, synchronous with lithologic evidence for basin closure, can be explained by (1) prior attainment of high elevations in the Eastern Cordillera and attendant westward penetration of isotopically depleted eastern moisture, and/or (2) attainment of sufficient elevation in the Western Cordillera to block enriched western moisture. Zircon initial Hf in the Western Cordillera increase from -8 to 0 at 25–18 Ma, consistent with basin subsidence driven by the formation and removal of a lithospheric instability. New results placed in the context of published regional stratigraphic and isotopic data are consistent with lithospheric instability formation driving basin subsidence at 28–20 Ma. Instability removal slowed subsidence during a transition to depleted eastern moisture, coeval with increasing zircon initial Hf at 20–17 Ma and concomitant rapid surface uplift at 18–16 Ma. Lacustrine basin ponding and aridification followed after 16 Ma in a deepening central Andean rain shadow.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10292

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