301-9 Exploring Geometric and Kinematic Linkages between Fold-thrust Belt and Basement-cored Structural Systems in the southern Central Andes: Insights from geo/thermochronolgy data and thermal history modeling

Session: Geochronology (Posters)

Poster Booth No.: 150

Presenting Author:

Liliana Binetti

Authors:

Binetti, Liliana¹, Mackaman-Lofland, Chelsea A.², Capaldi, Tomas N.³, Odlum, Margo⁴, Weeks, Chloe⁵, Ortiz, Gustavo Federico⁶

(1) Department of Earth, Environmental, and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA, (2) University of Tennessee, Knoxville, TN, USA, (3) Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA, (4) Scripps Institution of Oceanography, University of California San Diego, San Diego, CA, USA, (5) Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA, (6) Universidad Nacional de San Juan, San Juan, USA,

Abstract:

The southern Central Andes are the product of overriding plate deformation, uplift, erosion, and basin evolution during a Miocene-Recent transition to flat-slab subduction. Deformation generated a thin-skinned fold-thrust belt that accommodated the majority of retroarc shortening, as well as distinct thick-skinned (e.g., crystalline basement-involved) reverse fault systems that (1) contributed to shortening and topographic relief development along the retroarc hinterland flank, and (2) produced basement-cored uplifts that partition the distal foreland. Complex thin- and thick-skinned structural systems at the western (hinterland) and eastern (distal foreland) fold-thrust belt margins remain poorly understood, but host significant modern seismic activity along emergent and subsurface faults. This work assembles new and published structural, sedimentological, and geo/thermochronological constraints from retroarc hinterland to distal foreland domains to quantify the timing and magnitude of deformation and examine geometric and kinematic interpretations. Published sedimentological and geochronological data for synorogenic basin segments spanning the present-day hinterland to distal foreland positions record upward-coarsening, nonmarine sediment accumulation, with age-thickness inflections indicative of rapid flexural subsidence starting at ~14–17 Ma in proximal basin segments, ~8–11 Ma in medial depocenters, and ~5 Ma in distal retroarc locations. Apatite (U-Th)/He thermochronology (AHe) data obtained from new (N=9) and published (N=31) samples from thin-skinned thrust sheets, synorogenic basin fill, and crystalline basement uplifts are partially to fully reset with respect to sample deposition or emplacement. Samples from Neogene basin fill, some thin-skinned Paleozoic thrust sheets, and westernmost crystalline basement uplifts yield ~1–20 Ma AHe dates with low (<5 Myr) intrasample dispersion, indicative of rapid exhumational cooling during eastward-propagating shortening along thin- and thick-skinned structures. Other Paleozoic thrust sheet and crystalline basement samples produce AHe dates characterized by high (>20–80 Myr) intrasample dispersion with clear date-eU and/or -grain size relationships; for these samples, thermal history models reveal protracted Mesozoic-early Cenozoic residence at ~40–90°C, with cooling to surface conditions permitted between ~2 and 50 Ma. These data provide preliminary constraints on the magnitude of burial reheating during retroarc basin accumulation, the timing of exhumational cooling during crustal shortening, and a framework for exploring links among deformation, rock exhumation, uplift, and subsidence during complex thin- and thick-skinned structural interactions.

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

doi: 10.1130/abs/2025AM-7874

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