Foreland basin evolution in response to thin-skinned vs. basement-involved (Laramide-style) deformation: a case study from the southern Central Andes, Argentina (28-29°S)
Abstract
Retroarc deformation above the Argentina-Chile flat-slab subduction segment (28-33°S) is characterized by type examples of (1) thin-skinned thrusting along the eastern flank of the high Andes (Precordillera fold-thrust belt), and (2) basement uplifts that expand >700 km towards the craton (Sierras Pampeanas structural domain). The Precordillera and Sierras Pampeanas intersect near the flat- to normal-slab transition zone at ~29°S, providing an excellent location to study structural interactions and basin architecture in response to thin- and thick-skinned deformation. We integrate new geo- and thermochronological data for bedrock and Neogene foreland basin fill with structural, stratigraphic, and sediment provenance results to reconstruct development of the broken foreland basin system. Zircon U-Pb maximum depositional ages and published magnetostratigraphic ages constrain synorogenic deposition in the La Flecha depocenter from ~23 to <9 Ma. Detrital zircon age distributions record sediment contribution from the hinterland cordillera during distal foreland basin accumulation and eolian sedimentation at ~23-19 Ma, followed by decreased hinterland signals, introduction of Precordillera-derived components, and a shift to predominantly fluvial deposition by ~19 Ma. Coarsening-upward facies cycles and the reintroduction of hinterland provenance signatures in upper fluvial-alluvial deposits reflect eastward migration of the Precordillera thrust belt and recycling of foreland basin strata. Updated correlations with the adjacent Vinchina basin further confirm thickening and coarsening of the fluvial and alluvial succession to the north, compatible with the onset of exhumation, thrust loading, and sediment contribution from the basement-involved Toro Negro range as early as ~19-16 Ma. Bedrock apatite (U-Th)/He results for basement uplifts separating the modern La Flecha and Vinchina depocenters yield disperse ages consistent with long crustal residence times; however, the youngest cooling ages and uppermost facies trends suggest basin partitioning after ~9 Ma. Finally, late Miocene-Pliocene (~4-9 Ma) cooling ages for the basal La Flecha deposits, coupled with regional thermochronology results, suggest foreland basin exhumation occurred nearly synchronously from ~27 to 30°S.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T14C..01M
- Keywords:
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- 5475 Tectonics;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 8102 Continental contractional orogenic belts and inversion tectonics;
- TECTONOPHYSICS;
- 8108 Continental tectonics: compressional;
- TECTONOPHYSICS;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS