Seismic stratigraphy of the Cretaceous post-rift in Punta del Este Basin (offshore Uruguay) and its implications for deep-water reservoirs

Abstract

The formation of Punta del Este Basin is associated with the fragmentation of West Gondwana and consequently the opening of the South Atlantic Ocean during the Early Cretaceous. The basin comprises the Cretaceous depocenter of the Uruguayan continental margin (UCM). This study provides a seismic stratigraphic analysis of the sedimentary interval of the Cretaceous post-rift in the basin by defining its seismic facies, depositional sequences, shelf-edge trajectories, and palaeophysiographic settings. All depositional sequences of the Cretaceous post-rift represent intense basinward progradation marked by two depositional trends. The Lower Cretaceous sedimentary interval exhibits a dominant flat-to-descending shelf-edge trajectory, with migration up to 37 km. Deposition occurred over an irregular physiography with proximal NW–SE and distal WSW–ENE trends controlled by the characteristics of the volcanic margin. Basin geometry has strong implications for understanding the deposition of a deep-water turbidite system in the UCM, with a strong analogy to the recent discovery of Venus well in the Orange Basin, offshore Namibia. Towards the Late Cretaceous, the NW–SE depositional trend was controlled by a NE-SW slope break, indicating deposition over the South and North highs. A low-angle ascending shelf-edge trajectory was observed, with migration up to 16 km.