Thermal history of the eastern margin of the Gulf of Suez .1. Reconstruction from borehole temperature and organic maturity measurements

The Gulf of Suez is a Tertiary continental rift associated with prominent flank uplift. Despite numerous studies which focused mainly on the western and central parts of the graben, the thermo-mechanics controlling the tectonic evolution of the Gulf of Suez is still enigmatic. We have integrated borehole temperatures and organic maturity measurements in the eastern margin of the Gulf of Suez, in order to study rift-related paleothermometry and the present-day thermal regime. The data obtained suggest that the present thermal regime represents the maximum heat flow and temperatures for the sedimentary section in the basin. Furthermore, lateral distributions of geothermal gradient and heat flow in the Gulf of Suez do not correlate, mainly because of extensive variability in lithology and thermal conductivity. Rift-related heat flow increases systematically and subparallel to the rift axis, from about 60 mW/m(2) in the Darag subbasin in the north to about 80 mW/m(2) in the Ras Garra area in the south. Both values are higher than 45 mW/m(2), the average heat flow assumed for the pre-rift stage and the characteristic level for the present-day heat how away from the rift. The north to south increase in heat flow probably reflects the southward increase of extension as well as lateral transfer of heat flow from the Red Sea. This latter conclusion is supported by the fact that heat how in the southern Gulf of Suez recorded by the paleothermometric reconstructions and borehole temperature data is somewhat higher than that estimated by model calculations for the extension derived from structural and subsidence reconstruction.