The Falkland Islands and the early fragmentation of Gondwana: implications for hydrocarbon exploration in the Falkland Plateau

Abstract

During the early breakup of Gondwana, the Falkland Platform became detached from southern Africa as a separate microplate. At this time the Falkland Plateau Basin developed between the Falkland Platform and the Maurice Ewing Bank. Significant extension occurred within this basin with accompanying high heat flow. This heat flow will have thermally overmatured any Late Jurassic to Mid-Cretaceous source rocks present within the basin while still beneath a thin sedimentary cover. This early overmaturation is confirmed by anomalously high thermal maturity levels and vitrinite reflectivity gradients from DSDP sites on the Maurice Ewing Bank. It is envisaged that only restricted hydrocarbon source potential remained for subsequent generation during later Cretaceous and Tertiary burial. Source rock analysis of the Permian Black Rock Member (Port Sussex Formation) in East Falkland shows it to have once had significant hydrocarbon generating potential, although now destroyed by metamorphism. Some potential may still remain in southernmost East Falkland. In contrast, thermal maturities in West Falkland are still within the oil window such that these Permian shales remain a viable source rock.