Seaward-dipping reflectors in the continental margin of Uruguay

Abstract

The Uruguayan Continental Margin (UCM) is of volcanic-rifted type, as revealed by conspicuous wedges of seaward-dipping reflectors (SDR). They are interpreted as mainly volcanic flows extruded in subaerial to submarine setting, accomodated by NE antithetic faulting, as a result of Gondwana fragmentation and subsequent opening of the South Atlantic during the Early Cretaceous. Detailed mapping of the SDR wedges in the MCU allowed to identify a more complex morphology than previously recognized. In the southerwestern sector (distal Punta del Este Basin), there are two to three wedges of strongly curved reflections, proximaly dislocated by faul reactivation. In the central sector, dominated by hypertension, SDRs are absent. In the northeastern sector (Pelotas Basin), there are several wedges of rather straight, only distally curved reflections. In both the Punta del Este and Pelotas basin boundaries, SDRs are heavily faulted due to the influence of the Río de la Plata Transfer System (RPTS). Where not faulted, in strike lines southern SDR wedges are flat (i.e. they dip purely seawards) in constrast to northern SDRs, which dip towards the northeast besides dipping seawards (i.e. overall they dip eastwards).