Deepwater Sedimentation in a Proximal, Rift-Margin Setting: Observations of Syn-Rift Strata, Northern Red Sea

Abstract

The Midyan Peninsula of the northern Red Sea, Saudi Arabia, includes a thick rift-related sequence of sediments deposited in a series of deep half grabens formed during the opening of the Red Sea, beginning in the Oligocene. The syn-rift sequence tracks the different stages of basin development from an initial terrestrial fluvial and alluvial sediment influx of the Al Wajh Formation, an evaporitic marine stage of the Yanbu and Musayr Formations, a subsequent deep-water rift-climax unit of the Burqan Formation, and ultimately to post-rift alluvial fill. This study focuses on the Early Miocene Burqan Formation, a deep-water, syn-rift unit dominated by deposits of sediment gravity flows. The Burqan Formation is a key reservoir and source unit for the region, including fields on the Midyan Peninsula and immediately offshore, but relatively little work has been done regarding its sedimentology. The exceptional exposure of the Burqan Formation on the Midyan Peninsula offers the opportunity to investigate depositional geometries, facies trends, and stratigraphic architectures in a proximal, rift-margin setting. The Burqan turbidites can be traced northward to the basin margin, where they interfinger with angle-of-repose breccias deposited along the northern fault scarp, and to the northwest, where they transition into thick, steep, conglomerate and sandstone beds that may represent fan deltas. Shelves were non-existent to very narrow. The basinal sandy turbidites are quite remarkable in containing boulder-sized clasts many kilometers out into the basin within a setting dominated by the deposition of thick-bedded turbiditic sandstones. We speculate that the sediments were fed into these rift-margin basins by dense, catastrophic floods across the fan deltas and that the basinal turbidites, even with very coarse debris, may have originated as hyperpycnal flow events.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015