Oligocene regional denudation of the northern Afar dome: Pre- and syn-breakup stages of the Afro-Arabian plate.

A regional truncation surface developed during the Oligocene in the northern Red Sea and southern Levant as a result of the combined effects: (1) the formation of an ~3000 km x 1500 km crustal dome affecting the northeastern sector of the Afro-Arabian continent above the Afar plume, and (2) widespread fluvial erosion that truncated the northern edge of this dome. The regional truncation surface separates two main stratigraphic divisions: (1) middle Eocene--early Oligocene prerift clastics preserved below the regional truncation surface and (2) late Oligo cene--Holocene Red Sea Supergroup deposited after the regional truncation surface developed. The prerifting sequence is composed of two major units: (1) Eocene marine intraformational debris flows (Themed clastics), and (2) fluviolacustrine continental conglomerates, most of them monomictic (Mahatardi Conglomerate). The Red Sea Supergroup is composed of polymictic conglomerates, which include fragments of older rock units, down to the Precambrian. The reconstructed regional truncation surface and its subcrop map shed new light on the initial stages of the Afro-Arabian breakup, indicating two principal phases: (1) an Oligocene slow crustal doming, with reactivation of preexisting faults and the development of the regional truncation surface, all triggered by the upwelling of the Afar plume; and (2) late Oligo cene--early Miocene rifting of the Red Sea and Suez rift, which refaulted the region, including the initiation of the Dead Sea Transform along a preexisting suture line. This two-stage model indicates the mutual genetic relationship between the early Oligocene phase of tectonic development following the penetration of the Afar plume and the post-Oligocene rifting and continental breakup of the Afro-Arabian continent. [ABSTRACT FROM AUTHOR]