Provenance constraints for the Jurassic Cañadón Asfalto basin, Central Chubut, Argentina

HAUSER, NATALIA; CABALERI, NORA; VOLKHEIMER, WOLFGANG; MATTEINI, MASSIMO; PIMENTEL, MARCIO; ARMELLA, CLAUDIA; GALLEGO, OSCAR F.; MONFERRAN, MATEO; SILVA NIETO, DIEGO; PAEZ, MANUEL; DANTAS, ELTON

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Simposio; V Simposio Argentino del Jurásico; 2013

Museo Paleontológico Egidio Feruglio

During the Mesozoic, rifting and extensive magmatism occurred throughout South America, due to the opening of the Atlantic Ocean. The Early Jurassic Cañadón Asfalto, is one of the most important basin, recording the deposition of continental sediments with paleontological record coeval with basic volcanism during syn-rift and post-rift phases. In order to constrain the provenance pattern of detrital sedimentary rocks, new U-Pb ages on zircons from two sedimentary layers were obtained. Sandstone from the Sierra de La Manea (La Manea-1), in the eastern part of the Cerro Condor sub-basin, which was attributed to the Cretaceous in previous studies, indicate an unimodal distribution with ages between 171 and 206 Ma with a main peak at 178 Ma. The second analyzed sample (tuff sandstone CAF-6), represents the post-rift stage from the Fossati sub-basin, and shows a bimodal zircon distribution with two populations at 164-186 Ma and 277-305 Ma. Maximum depositional ages (MDA) for the Sierra de La Manea sandstone, and for the Fossati sandstone are 173±6 Ma and 176±1 Ma respectively. The Cañadón Asfalto basin itself and its basement represent the provenance areas for La Manea and Fossati sandstones. The Carboniferous-Permian zircons from the Fossati rocks are derived from the western metamorphic and magmatic belt of the Patagonia basement (Mamil Choique Formation), outcropping to the south of the Fossati depocenter, in the Sierra de Pichiñanes, suggesting that it was exposed to erosion at ~158 Ma. The Jurassic MDA for La Manea sandstone is not conclusive and its stratigraphy position remains ambiguous.