The Late Oligocene ? Early Miocene marine transgresssion of Patagonia: paleogeographic and tectonic implications

FLORENCIA BECHIS; FELIPE PÉREZ; RICARDO RIFFO; SVEN NIELSEN; VERÓNICA OLIVEROS; ANDRÉS FOLGUERA; PATRICIO ZAMBRANO; FRANCISCA TAPIA; DARÍO ORTS; JOSÉ CUITIÑO; VICTOR A. RAMOS; ALFONSO ENCINAS; KENNET FINGER; PABLO BERNABÉ; LUIS BUATOIS; VÍCTOR VALENCIA; LIZET DE GIROLAMO DEL MAURO

Santiago

Simposio; Primer Simposio de Tectónica Sudamericana; 2016

Asociación Tectónica Sudamericana

The most important Cenozoic marine transgression in Patagonia occurred during the late Oligocene?early Miocene when marine waters of Pacific and Atlantic origin flooded most of southern South America including the present Patagonian Andes between ~41° and 47°S. The age and correlation of the different marine formations deposited during this period is debated. However, recent studies based principally on U-Pb geochronology and Sr isotope stratigraphy indicate that these units were all accumulated during the late Oligocene?early Miocene. The marine transgression flooded a vast part of southern South America and, according to paleontologic data, permitted, for the first time in the history of this area, the transient connection between the Pacific and Atlantic oceans. Marine deposition started in the late Oligocene?earliest Miocene (~26?23 My) and was probably caused by a regional event of extension related to a major plate reorganization in the Southeast Pacific. Progressive extension and crustal thinning allowed a generalized marine flooding of Patagonia that reached its maximum extension at ~20 Ma. It was followed by a phase of compressive tectonics that started around 19?16 My and led to the growth of the North Patagonian Andes. The youngest (~19?15 My) marine deposits that accumulated in the eastern Andean Cordillera and the extra-Andean regions are coeval with fluvial sinorogenic deposits and were probably accumulated under a compressive regime.