Stratigraphy and geochronology of the Naupa Huen Formation: implications for the North Patagonian Foreland

Abstract

The Naupa Huen Formation represents a sedimentary fluvial unit distributed across the North Patagonian Foreland and has been assigned to the late Oligocene – Early Miocene based on fossil content and stratigraphic relations. These observations have led to the correlation of the unit with continental synorogenic volcaniclastic deposits of the tectono-stratigraphic cycle configured the Patagonian Broken Foreland (PBF) during the Early to Middle Miocene Andean contractional regime. However, the stratigraphic and sedimentary characteristics, and the predominantly epiclastic composition of the Naupa Huen Formation, contrast with the depositional synorogenic features and volcaniclastic composition of other units preserved in the Neogene depocenters of the PBF. To understand the tectono-stratigraphic framework under which the Naupa Huen Formation was deposited, a stratigraphic and geochronological analysis using U-Pb LA-ICP-MS dating on detrital zircons was conducted. The results obtained in this study constrain the Naupa Huen Formation to the early Eocene – earliest Miocene, suggesting that its deposition corresponds to a tectono-stratigraphic cycle preceding the configuration of the PBF in the Early to Middle Miocene contractional regime, as previously proposed. Although the results presented have enabled the evaluation of possible stratigraphic correlations with different Paleogene units of the Patagonian Foreland, additional studies of this nature are necessary to further deepen the understanding of Cenozoic sedimentation in this region.