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Structural Framework and Hydrocarbon Potential of Ross Sea, Antarctica

Alan K. Cooper, Frederick J. Davey

The 400 to 1,100-m deep continental shelf of the Ross Sea is underlain by three major sedimentary basins (Eastern basin, Central trough, and Previous HitVictoriaNext Hit Land basin), which contain 5 to 6 km of sedimentary rock of Late Cretaceous(?) and younger age. An additional 6 to 7 km of older sedimentary and volcanic rocks lie within the Previous HitVictoriaNext Hit Land basin. Eroded basement ridges of early Paleozoic(?) and older rocks similar to those of onshore Previous HitVictoriaNext Hit Land separate the basins. The three basins formed initially in late Mesozoic time during an early period of rifting between East and West Antarctica.

The Eastern basin is a 300-km wide, asymmetric basement trough that structurally opens into the Southern Ocean. A seaward-prograding sequence of late Oligocene and younger glacial deposits covers a deeper, layered sequence of Paleogene(?) and older age. The Central trough, a 100-km wide depression, is bounded by basement block faults and is filled with a nearly flat-lying sedimentary section. A prominent positive gravity anomaly, possibly caused by rift-related basement rocks, lies along the axis of the basin.

The Previous HitVictoriaNext Hit Land basin, unlike the other two basins, additionally contains a Paleogene(?) to Holocene rift zone, the Terror Rift. Rocks in the rift, near the axis of the 150-km wide basement half-graben, show extensive shallow faulting and magmatic intrusion of the sedimentary section. The active Terror Rift and older basin structures extend at least 300 km along the base of the Transantarctic Mountains.

Petroleum hydrocarbons have not been reported in the Ross Sea region, with possible exception of ethane gas found in Deep Sea Drilling Project cores from the Eastern basin. Model studies indicate that hydrocarbons could be generated at depths of 3.5 to 6 km within the sedimentary section. The best structures for hydrocarbon entrapment occur in the Previous HitVictoriaTop Land basin and associated Terror Rift.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.