49-1 Catchment-wide Constraints on Long-term Erosion, Deformation, and Weathering to Resolve Tectonic and Climatic Controls in the Sierras Pampeanas (Argentina)

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

Presenting Author:

Julie Fosdick

Authors:

Fosdick, Julie C.¹, Mota, Arielle², Mooney, Jordan³, Mistry, Trisha⁴, Sinoplu, Ozan⁵, Biddle, Julian⁶, Milanesio, Delfina⁷, Palmero, Lucía⁸, Armas, Paula⁹, Otamendi, Juan¹⁰, Ouimet, William B.¹¹, Callahan, Russell¹²

(1) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (2) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (3) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (4) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (5) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (6) Department of Earth Sciences, UConn, Storrs, CT, USA, (7) CONICET-ICBIA, Departamento de Geología, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina, (8) CONICET-ICBIA, Departamento de Geología, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina, (9) CONICET-ICBIA, Departamento de Geología, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina, (10) CONICET-ICBIA, Departamento de Geología, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina, (11) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA, (12) Department of Earth Sciences, University of Connecticut, Storrs, CT, USA,

Abstract:

Quantifying tectonic and climatic controls on orogenic erosion is crucial for understanding lithospheric evolution and changes in surface environments during mountain-building. In thick-skinned deformational settings, complex faulting, topographic growth, and orographic precipitation gradients further obscure tectonic and climatic signals of erosion and weathering. We present detrital apatite (U-Th)/He thermochronology (dAHe), geomorphic analysis, and mud-sized fraction geochemistry from the Sierras Pampeanas of Argentina to quantify catchment-wide rock cooling, weathering intensities, and exhumation patterns. Data from modern catchments draining three basement-cored uplifts with varying climatic and tectonic activity show distinct differences in detrital cooling age spectra and weathering intensity. Results from predominantly granitic Sierra de Velasco yield older dAHe dates (327–91 Ma) and low long-term erosion rates (0.01–0.02 mm/yr) in the leeward catchments compared to younger dates (196–5 Ma) and higher erosion rates (0.11 mm/yr) from the wetter windward catchment. A pronounced ca. 25 Ma dAHe age mode suggests accelerated late Paleogene cooling and exhumation. While the windward catchment has the highest weathering intensity, young dAHe dates suggest rapid catchment denudation driven by steepened topography generated via deformation. Cerro Bola, a west-verging anticlinal uplift of Paleozoic shallow-marine and continental strata, yields 21–3 Ma dAHe dates with detrital modes at 20 Ma, 9 Ma, and 5 Ma. High catchment-wide weathering intensity may reflect compositional controls from recycled/sedimentary input. Bedrock samples yield dAHe dates 10.8–1.4 Ma, suggesting post-depositional reheating of Carboniferous strata, followed by Late Miocene–Pliocene cooling. We report the first thermochronologic constraints on the onset of Cerro Bola uplift and exhumation. High weathering intensities despite the catchment’s location in an arid climate suggests compositional effects from recycled strata. Sierra del Espinal, located in an arid climate, exposes predominantly Proterozoic metamorphic rocks and yields 120–12 Ma dates and the lowest weathering intensity of all catchments. Taken together, the multimodal thermochronology age spectra from the three basement-cored ranges suggest: 1) abundance of young (<10 Ma) dAHe dates validate a thermochronologic signature of Mio–Pliocene exhumation, 2) older Cenozoic cooling ca. 25–20 Ma that supports recent evidence for Paleogene topographic development across parts of the Sierras Pampeanas, and 3) preservation of relict Paleozoic–Mesozoic thermotectonic events. We leverage catchment-wide datasets in combination with morphological analysis for capturing orogenic exhumational signatures where bedrock transects are limited.

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

doi: 10.1130/abs/2025AM-9796

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