Neogene tectonic and stratigraphic events in the Gulf of Suez rift area, Egypt

Abstract

The Gulf of Suez Neogene (syn-rift) section contains at least five datable intra-basinal unconformities or stratigraphie hiatuses. These events and associated changes in sedimentary sequences seen in the basin can be related to changes in Suez rift subsidence, Miocene eustasy, and the tectonic effects of adjacent Red Sea and Dead Sea rifting. The first hiatus spans Oligocène to earliest Miocene time and separates syn-rift from pre-rift strata throughout the region. This erosional event resulted from regional emergence during the Oligocene and the initiation of Suez rifting. A second hiatus, from ~ 21-19 Ma, separates the poorly dated, shallow-marine Nukhul Formation of Aquitanian to early Burdigalian age from the overlying upper bathyal shales of the middle Burdigalian to Langhian (NN3–5) Rudeis Formation. This hiatus resulted from both a brief lowstand in early Burdigalian sea level and increased Suez rift-related tectonism. This event climaxed with the rapid tectonic subsidence that established deep-marine conditions by 19 Ma. A third major event occurs within the Rudeis at ~ 17 Ma (NN4, N7) and marks the initiation of uplift of I he rift shoulders and margins, and decelerated subsidence, or even minor uplift, in the axial trough. Hiatuses are seen over paleohighs e.g. tilted fault blocks, whereas coarse elastics are deposited in more basinal areas in submarine fans and as turbidites. A fourth unconformity, at ~ 14 Ma, separates the Middle Miocene Kareem Formation from overlying anhydrites and open marine shales of the Belayim Formation. Minor tectonic uplift throughout the Suez region resulted from this event, and a sill was established between the Mediterranean and Suez basins, allowing cyclic anhydrite-marl deposition from ~ 14 to 11 Ma. This “post-Kareem event” may be the sedimentary response to initiation of movement along the Dead Sea-Aqaba transform. A sharp drop in sea level at ~ 11 Ma restricted the Suez basin even more, and marked the initiation of massive halite precipitation in the central and southern Suez, well south of the sill area. A final major Neogene event occurs at the Miocene-Pliocene boundary, and is marked by a major unconformity caused by tectonic uplift. This tectonic pulse is related to initiation of Red Sea sea-floor spreading, and acceleration of sinistral motion along the Dead Sea-Aqaba transform at ~ 5 Ma. This event establishes the marine connection with the Red Sea and the sedimentary environments seen in the Gulf of Suez today.