Cenozoic tectonic plate interaction registered in a South Atlantic passive margin basin (southern sector, Pelotas Basin)

The South Atlantic present-day configuration is the result of remarkable paleogeographic and paleoclimate events that occurred during the Cenozoic. These tectono-climatic events include opening and closing ocean gateways, hyperthermal events, climate changes, and the rise of the Andean Mountain Chain. This work aims to define how these events affected the evolution of the Pelotas Basin in the southern Atlantic Ocean passive margin regarding their sedimentary and geomorphic records. To reach this objective, a multiproxy and multiscale analysis based on subsurface data and regional information using seismic interpretation, backstripping, and numerical modeling was performed to identify the influence of climatic, eustatic, and tectonic triggers. Our results point that the interaction between Naszca, South America, and Antarctic tectonic plates are the root to explain the Cenozoic events registered in the South Atlantic passive margins. The Andean Mountain Chain Uplift on the west side of South America and their retroarc foreland system, the forebulge and back-bulge provinces conducted a strong tectonic control over the Pelotas Basin. On the other hand, the climatic control resulting from the Drake Passage widening and consequent development of the Antarctic Circumpolar Current changed the contour currents dynamics. In response to these tectonic-induced climatic changes, the Pelotas Basin records over the Cenozoic: a) depocenter change, b) alterations in oceanic currents described through contourite deposits, and c) formation of a huge fan-like feature (Rio Grande Fan) during an accelerated increase in the sedimentation rate and consequent gravitational collapse driven by overpressure occurred in undercompacted shales.