Refining the paradigm of fold-and-thrust belt and foreland basin systems: A review of current thinking and new ideas in the Southern Patagonian Andes and Magallanes-Austral Basin
Abstract
The Patagonian-Fuegian Andes fold-and-thrust belts and Magallanes-Austral Basin constitute an orogen-basin pair that both exemplifies and defies conventional behavior in retroarc foreland basin systems. Situated along the southwestern margin of the South American Plate, the orogen developed in response to the onset of plate convergence and subsequent changes in plate boundary configurations, including opening of an oceanic backarc rift basin, tectonic separation from Antarctica, birth of the Scotia Plate, and multiple asthenospheric slab window formations producing a narrow fold-and-thrust belt, prolonged phase of Late Cretaceous deep marine sedimentation, and abundant unconformities within the shallow to non-marine Cenozoic basin infill. The resulting stratigraphy is unique along the Andean foreland and lends insight into how narrow orogens - and their genetically linked foreland sedimentary basins - evolve along complex plate boundaries. Key questions include: (1) To what extent do changing plate boundary processes affect growth and erosional decay of fold-and-thrust belts? (2) Along the attenuated margins of continental plates, how do orogens build up emergent topography above sea level and what are the impacts on erosion processes, deformation behavior, basin subsidence, and sediment dispersal? This presentation reviews current thinking and new ideas in the Magallanes-Austral Basin, and highlights recent work showing feedbacks between deep tectonic underthrusting and subsequent rapid exhumation of hinterland thrust sheets during the culmination of underfilled foredeep subsidence. New sedimentary provenance data from the Cenozoic basin infill document (1) the continued uplift and subsequently progressive isolation of hinterland thrust sheets, and (2) the compositional evolution of the magmatic arc from intermediate to more mafic magma generation. Upsection changes in sediment composition and volcanic sources within the arc, along with stratigraphy, subsidence patterns, and unconformities, suggest a strong impact on foreland basin evolution from the formation of multiple asthenospheric slab windows beneath the South American Plate and associated changes in stress regime.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T51B..08F
- Keywords:
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- 1165 Sedimentary geochronology;
- GEOCHRONOLOGYDE: 8169 Sedimentary basin processes;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS