The Northern Red Sea - a model for rifting leading to continental break-up
- The Australian School of Petreoleum and Energy Resources, Adelaide University, South Australia 5000 (email@example.com)
The Gulf of Suez and the Northern Red Sea form the northwestern sector of the Afro-Arabian rift system. Studies of outstanding outcrops of rift fault systems and syntectonic strata integrated with sub-surface data together with thermo-chronological studies indicate that the Gulf of Suez - Northern Red Sea rift system initiated at around the Oligocene to Miocene transition (24 to 23 Ma). A regional NW-SE trending Oligocene-Miocene (~23 Ma) alkali basalt dike swarm and basalt flows near Cairo, appears to mark the onset of crustal-scale extension and continental rifting. These dikes and scarce local flows, are interbedded with the oldest siliciclastic syn-rift strata (Aquitanian Nukhul Fm.), and are associated with the oldest recognized extensional faulting in the Red Sea. Bedrock thermochronometric results from the Gulf of Suez and both margins of the Red Sea also point to a latest Oligocene onset of major normal faulting and rift flank exhumation and large-magnitude early Miocene extension along the entire length of the Red Sea rift. The early phase of rifting produced complex, discontinuous fault patterns with very high rates of fault block rotation, distinct sub-basins with alternating regional dip domains separated by well-defined accommodation zones. Sedimentary facies were laterally and vertically complex and dominated by marginal to shallow marine siliciclastics of the Abu Zenima, Nukhul and Nakheil Formations. Neotethyan faunas appeared throughout all of the sub-basins at this time. During the Early Burdigalian (~20 Ma) tectonically-driven subsidence accelerated and was accompanied by a concordant increase in denudation and uplift of the rift shoulders. The intra-rift fault networks coalesced into through-going structures and extension became progressively more focused along the rift axis. This reconfiguration resulted in more laterally continuous depositional facies and the moderate-to-deep marine deposits of the Rudeis, Kareem and Ranga Formations.
At the early Middle Miocene (~14 Ma) onset of the left-lateral Gulf of Aqaba transform fault system marked dramatic changes in rift kinematics and sedimentary depositional environments. The Gulf of Suez became isolated from the active northern Red Sea rift, with a switch from orthogonal to oblique rifting and to hyperextension in the northern Red Sea. The previous open marine seaway was replaced by an extensive evaporitic basin along the entire length of the rift from the central Gulf of Suez to Yemen/Eritrea. In Egypt these evaporites are ascribed to the Belayim, South Gharib, Zeit and Abu Dabbab Formations. Evaporite deposition continued to dominate until the end of the Miocene (~5 Ma) when a subaerial unconformity developed across most of the basins. With the onset of seafloor spreading in the southern Red Sea, Indian Ocean marine waters re-entered through the Bab el Mandab in the earliest Pliocene and re-established open marine conditions. In the northern Red Sea well and seismic data demonstrate that continental crust extends at least several tens of kilometers offshore. The northern Red Sea is a highly extended non-volcanic rift and true, laterally integrated sea-floor spreading has not yet developed.
How to cite: McClay, K., Bosworth, B., Khalil, S., Ligi, M., and Stockli, D.: The Northern Red Sea - a model for rifting leading to continental break-up, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7102, https://doi.org/10.5194/egusphere-egu21-7102, 2021.
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