Abstract: Masirah Graben, Oman: A Hidden Cretaceous Rift Basin?

Weldon Beauchamp, A. C. Ries, M. P. Coward, J. A. Miles

The Masirah graben is located east of the Huqf Arch, roughly parallel to the southern coast of Oman. Based on seismic data, well data and surface geology, it is proposed that this graben represents a Cretaceous rift basin hidden beneath thrusted Tertiary allochthonous sediments. The eastern side of the northeast trending Huqf anticlinorium is bounded by an extensional fault system which is downthrown to the southeast, forming the western edge of the Masirah graben. This graben is limited to the east by a large wedge of oceanic sea floor sediments and crust, stacked as imbricate thrusts. These sediments/ophiolites were obducted onto the southern margin of the Arabian plate upon the collision of the Indian/Afghan plates at the end of the Cretaceous. This sequence was stable until furthe rifting of the Arabian Sea/Gulf of Aden in the Late Tertiary. Wells drilled in the Masirah graben in the south penetrated reservoir quality rocks in the middle to Lower Cretaceous carbonates. These Mesozoic sediments represent a probable syn-rift sequence overlying a thick pre-rift sequence composed of Infracambrian sediments. Analysis of oil extracted from pre-rift Infracambrian sediments penetrated by wells in the Masirah graben suggests an origin from a Mesozoic source rock.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994