Extension across the Indian-Arabian plate boundary: the Murray Ridge

Seismic reflection profiles from the Murray Ridge in the Gulf of Oman, northwest Indian Ocean, show a significant component of extension across the predominantly strike-slip Indian-Arabian plate boundary. The Murray Ridge lies along the northern section of the plate boundary, where its trend becomes more easterly and thus allows a component of extension. The Dalrymple Trough is a 25 km wide, steep-sided halfgraben, bounded by large faults with components of both strike-slip and normal motion. The throw at the seabed of the main fault on the southeastern side of the halfgraben reaches 1800 m. The northwest side of the trough is delineated by a series of smaller antithetic normal faults. Wide-angle seismic, gravity and magnetic models show that the Murray Ridge and Dalrymple Trough are underlain by a crystalline crust up to 17 km thick, which may be continental in origin. Any crustal thinning due to extension is limited, and no new crust has been formed.