Rift dynamic based on a stratigraphic architecture and paleogeographic basin-scale study: Example of the Gulf of Suez (Egypt)

Rift basin geology is a major issue because of its economic importance for petroleum industry as well as its related scientific challenges such as the relationship between deep and surface processes. A major limitation to go further is the calibration of theoretical concepts to real data observations at basin-scale and with high resolution time lines.

We propose a high resolution basin-scale (~300 x 1OO km) study ofthe pre-salt to salt sedimentary fill from the Gulf of Suez (Egypt) based on outcrop and subsurface data (279 wells, 31 sedimentological sections). The stratigraphic architecture has recorded five main stages of rift evolution, from rift initiation to finally tectonic quiescence recorded by salt deposits.

Rift initiation (ca. l-4 Myr duration): the Suez rift was initiated at the end ofthe Oligocene along the NNW-SSE trend of the Red Sea with evidences of active volcanism. Continental to lacustrine deposits are only preserved in isolated depocenters.

Rift widening (ca. 3 Myr duration): the rift was propagated from south to north (Aquitanian), with first marine incursions from the Mediterranean Sea. The rift was subdivided into numerous depocenters controlled by active faults. Sedimentation was characterized by small carbonate platform and associated sebkhra deposits to the south and shallow open marine condition to the north with mixed sedimentation organized into an overall transgressive trend. Rift climax (ca. 5 Myr duration): the rift was then flooded during Burdigalian times. The faults were gradually connected and reliefs on the rift shoulders were high as evidenced by a strong increase of the uplift/subsidence rates and sediment supply. Sedimentation was characterized by very large Gilbert-type deltas along the eastem margin and associated submarine fan and turbidite along the basin axis. Isolated carbonate platforms and reefs mainly occurred in the Southern Basin and along tilted block crests.

Flexuration to rift narrowing (ca. 4 Myr duration): during the Langhian times, the basin recorded several falls of relative sea level and bathymetry in the rift axis was progressively reduced. The former reliefs induced during the rift climax were quickly destroyed. During Serravalian times, the rift basin recorded several disconnections with the Meditemmean and Red seas as evidenced by massive evaporites in major fault controlled depocenters.

Tectonic quiescence to flexuration (ca. 7 Myr duration): the Tortonian is then characterized by the deposition of very thick salt series (>lOOO m) which has recorded a period ofmaximum restriction for the Suez rift. The basin was still subdivided into several sub-basins bounded by major faults. The basin was totally and permanently disconnected from the Mediterranean Sea, and possibly connected to open marine condition via the Red Sea. The Messinian is also characterized by a thick salt series, but the evaporite typology and sedimentary systems distribution suggest a more humid climate than during Tortonian times.

Rates and fluxes derived from this basin-scale study can be used to implement and test numerical models, as well as better understand other rift systems.