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Interaction Between Lithospheric Stretching and Asthenospheric Secondary Convection: Application to Suez Rift Evolution

I. Moretti, P. Y. Chenet

Modeling of geodynamic rifting processes by lithospheric stretching does not adequately account for some rift features, such as the abrupt uplift of the rift shoulders. Using a thermomechanical model dealing with a non-Newtonian crust and mantle rheology, I. Moretti and C. Froidevaux suggested that the numerous continental rifts evolved from upward propagation of an asthenospheric thermal anomaly; an extensive regional stress would have caused these convective phenomena, as well as crustal thinning.

Between 23 and 17 Ma, the Suez rift, as determined by tectonic subsidence studies, had an initial period of rapid subsidence over the entire width (80 km) of the rift. The subsidence nearly stopped between 18 and 13 Ma, probably as a result of the decreased extensional rate. The rift trough tends to narrow progressively, and active subsidence was restricted to the present-day Gulf of Suez (40-50 km) while the onshore areas began to uplift. This evolution has been modeled assuming an initial lithospheric stretching phase of a few million years of duration and a continuous asthenospheric upwelling away from the rift axis.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.