Geological evolution of the southeastern Red Sea Rift margin, Republic of Yemen

Slow subsidence of up to 1 km occurred over the area during a 100 m.y. period before rifting. There was a major episode of flood volcanism between ca. 30 and 20 Ma, and important extensional faulting began after the eruption of the volcanic rocks and ceased before middle to late Miocene sediments and volcanic rocks were deposited unconformably on top of rotated fault blocks on the coastal Tihama Plain. Volcanism was accompanied by emplacement of subvertical dike swarms, which generally strike parallel to the Red Sea coastaline. Major faults indicate northeast-southwest-directed extension. Large granitic sheets and plutons intruded the volcanic rocks. Approximately 30 km of extension has taken place across a 75-km-wide zone in 6-8 m.y. The proto-Red Sea Rift was caused by regional plate stresses that exploited lithospheric weakening caused by the Afar plume. Appreciable doming only occurred after the main episode of volcanism, which suggests that magmas extruded before maximum thermal expansion of the lithosphere took place. -from Authors