Print this pageThe Structure of the North Malvinas Basin, South Atlantic Ocean
PINCHIN, JOHN, MENNO DINKELMAN, JIM ROSS, MATEO TURIC, ANTONIO NEVISTIC, and DEAN GRIFFIN
Following the recent petroleum license awards, oil exploration is now underway in the North Malvinas Basin. This basin is located due north of the Malvinas Islands in water depths of 100 m to 500 m.
The North Malvinas Basin has been created by two successive episodes of rifting. Early to Middle Jurassic rifting was related to crustal extension northeast of the Samfrau Subduction Zone at the southern margin of Gondwana The Late Jurassic to Early Cretaceous rifting episode preceded the break-up of Gondwana and subsequent seafloor spreading in the South Atlantic.
The two rifting events created two different structural trends. The older (Early Jurassic) trend is northwesterly, comprised mainly of narrow half-graben structures in the south and the southwest ofthe basin. The younger (Late Jurassic) rifting episode created broada north-trending structures the largest of which is named the "Northern Graben" and which contains the thickest sedimentary section. The late rifting episode was followed by Early to Late Cretaceous basin-wide sag, the effects of which are mostly seen in the Northern Graben. This period of subsidence was briefly interrupted during the Turonian by mild compression and basin inversion which produced a central anticlinal trend in the Northern Graben. The Post-Rift stage was followed by Tertiary subsidence and down-to-the-northeast tilting, as the area developed into a passive margin of the South Atlantic Ocean.
The basin contains over 10,000 m of Jurassic to Tertiary sedimentary rocks deposited in syn-rift, post-rift (sag) and shelfal tectonic settings. Petroleum prospectivity is thought to be good in the late syn-rift and the early post-rift sequences. Early to Mid Cretaceous fluviodeltaic sediments are expected to provide the target for the first exploration well in the basin, and which may be drilled in late 1997 or early 1998.