The origin of the San Jorge Gulf Basin in the context of the Mesozoic-Cenozoic evolution of Patagonia. (January 2020)

• Record Type: Journal Article
• Authors: Folguera, A.; Fernández Paz, L.; Iannelli, S.; Navarrete, C.; Echaurren, A.; Gianni, G.; Butler, K.L.; Horton, B.K.; Litvak, V.; Encinas, A.; Orts, D.
• Is Part Of: Journal of South American earth sciences. Volume 97(2020)
• Publication Date: 2020-01
• Subjects: San Jorge Gulf Basin -- Patagonia -- Rollback -- Flat subduction zone -- Magmatic shifting -- Flare-ups -- Synorogenic rifting; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2019.102422
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The retroarc region of central Patagonia recorded three contractional stages (Late Triassic, Late Cretaceous, and Miocene) coincident with eastward broadening of arc magmatism. Inboard arc migration may be linked to shallowing of the subducted slab, subduction erosion of forearc regions, or a combination of both. Contractional episodes were followed by slab rollback, producing a series of extensional depocenters and magmatic belts across Patagonia at ~170-130 Ma, ~55-22 Ma and ~5 Ma. These rollback events weakened Patagonian crust through fracturing, mantle upwelling, and magmatic injection, favoring inception and propagation of subsequent contractional episodes. Phases of slab rollback and retroarc extension are reflected in εHf and εNd isotopic trends, with more juvenile trajectories corresponding to mantle upwelling into a broad asthenospheric wedge during slab retreat. Periods of crustal shortening are recorded by evolved εHf and εNd isotopic trajectories, demonstrating modified mantle sources. Mesozoic-Cenozoic extensional basins of Patagonia, such as the Chubut Basin, Cañadón Asfalto Basin, Río Mayo-Aysén Basin, Pilcaniyeu and Auca Pan-El Maitén magmatic belts/volcanogenic basins, and the Traiguén Basin were generated during episodes of slab rollback. In contrast, the extension-related San Jorge Gulf Basin constitutes an east-west-trending anomaly developed in an interval of the Cretaceous when the rest of western Patagonia experienced shortening. During this time, crustal evolution trends shifted from juvenile to more evolved and the arc expanded toward the continental interior most likely under a flat-slab regime. The San Jorge Gulf Basin is linked to Neocomian extensional structures in an intracratonic basin later influenced by compressional stresses linked to subduction zone in the west and incipient opening of the south Atlantic to east. Highlights: The evolution of the Northern Patagonian Andes comprises shallow slab subduction, slab-rollback and flare-up events. Eastward arc broadening and flare-ups coincided with modification of the asthenospheric source during slab shallowing. Westward arc retreat coincided with asthenospheric rejuvenation as indicated by more juvenile isotopic trajectories. San Jorge Gulf Basin is an extensional basin in Patagonia that is not associated with extension during slab resteepening.