A refined model of Early Cretaceous South Atlantic–Southern Ocean gateway evolution based on high-resolution data from DSDP Site 511 (Falkland Plateau)

Abstract

The Falkland Plateau is a key region for Early Cretaceous oceanography and climate, as its bathymetry controlled water mass and sediment exchange between the emerging South Atlantic and Southern Ocean basins. Changes in large-scale deep water circulation, induced by the evolution of marine gateways in the Falkland Plateau region, in turn, affected regional organic carbon burial dynamics with wide implications for the global carbon cycle and the formation of petroleum source rocks. In this study, we reconstruct the Early Cretaceous depositional environment on the Falkland Plateau based on new high-resolution sedimentological and geochemical data from DSDP Site 511. These proxy records are used to refine temporal constraints on the gateway opening. The record from Site 511 documents a long-term transition from a restricted outer shelf basin in the Neocomian (i.e. Berriasian–Hauterivian) to an open marine environment in the Albian. Pronounced changes in sediment source and flux, redox conditions, organic carbon burial, and ecology occurred in the Late Aptian and Early Albian, related to the opening of the shallow Falkland Plateau Gateway and the deep Georgia Basin Gateway, respectively. In both cases, the opening was preceded by a succession of paleoenvironmetal changes, which are interpreted to reflect partial opening and progressive widening/deepening of both gateways. These early stages of gateway evolution commenced in the Early Aptian and Late Aptian, respectively, several million years before a full intermediate/deep water connection between the South Atlantic and Southern Ocean basins was established.