Seismic stratigraphy and tectonic evolution of the Falkland/Malvinas Plateau, Revista Brasileira de Geociencias

ABSTRACT A new perspective on the geology of the FalklandlMalvinas Plateau (South Atlantic) is derived from a detailed synthesis of 14,000 km of mainly unpublished single-channel and multichannel seismic data, aided by red~-haul descrip~ons and DSDP data. The Plateau is a foundered co~plex of continental blocks that were differentiaUy rifted during the opening of the South Atlantic in the Middle Jurassic to Early Cretaceous. Up to 7 km of synrift, transitional, and hemipelagic sediments have been deposited since the Middle Jurassic, largely under the control of a northern marginal fracture ridge. Three major structural lineations outline basement geometry. They are: 1. a NE-SW tectonic trend marking the eastern edge of the Plateau; 2. the Falkland Escarpment marginal fracture ridge to the north and nearby grabens that are parallel or subparallel to the approximately E-W Falkland Fracture Zone; and 3. the western edge of the Maurice Ewing Bank running NW-SE that is related to extensive rifting and volcanic activity in the central Falkland Basin. The complicated geometries of these structural trends are related to triple-Junction tectonics when the South American, African, and Antarctic blocks moved apart in the Late Jurassic/Early Cretaceous. We estimate that the Plateau had been lengthened by at least 400 km in an east-west direction, before the initiation of drift at about anomaly MlO time. From the acoustic stratigraphy we have defined four widespread depositional sequences. Three of these have been sampled by DSD