POST-DRILLING ANALYSIS OF THE NORTH FALKLAND BASIN - PART 1: TECTONO-STRATIGRAPHIC FRAMEWORK

Six wells were drilled in the extensional North Falkland Basin in 1998. The wells encountered a Devonian to Cenozoic stratigraphy dominated by thick Mesozoic syn- and post-rift successions. Although most previously published models predicted that the succession would most likely be of marine origin, it is in fact predominantly terrestrial; marine conditions did not become established in the basin until the Late Cretaceous. The oldest rocks recorded are Devonian and these were penetrated in only one well. The overlying succession comprises: a fluvio-lacustrine, early syn-rift interval of ?mid-Jurassic to Tithonian age; a late syn-rift fluviolacustrine interval of Tithonian to Berriasian age; a rift-sag transitional unit of Berriasian to Valanginian age; an early post-rift lacustrine unit of Valanginian to early Aptian age; a middle post-rift, transgressive unit of Aptian to Albian age; a late post-rift, terrestrial to marine unit of Albian to early Palaeocene age; and a post-uplift thermal subsidence unit of Palaeocene to Recent age. Much of the sediment appears to have been derived from volcanic and/or metamorphic A terranes, probably located to the north or NW of the basin. As well as the volcanic material which occurs in the ground mass and as lithoclasts in many of the units, some volcaniclastic rocks and minor amounts of ashfall tuffs are observed, particularly within the late syn-rift succession.