Uplift and Subsidence of the Suez Rift: Constraints from Fission-Track Analysis and Sediment Backstripping

Michael S. Steckler, Gomaa I. Omar, W. Roger Buck

The Gulf of Suez is a Neogene rift that has evolved as one arm of the Sinai triple junction. The basement uplifts flanking the rift are larger than can be explained by uniform lithospheric extension. The timing of the regional heating required by the uplift has important implications for hydrocarbon maturation for the Gulf of Suez and rifts in general. The local geology indicates that the uplift did not predate rifting. Therefore, a regional subsidence and two-dimensional backstripping of the rift sediments were undertaken in conjunction with fission track analyses of the basement uplift. The initial rift deposits (Nukhul Formation) indicate slow extension during the earliest Miocene. The extension rate increased at the beginning of the deposition of the Rudeis Formation t approximately 19 Ma as the Gulf of Suez entered its main phase of rifting. By the end of the deposition of the Kareem Formation (approximately 14-15 Ma), most of the Africa-Arabia separation had transferred to the Gulf of Aqaba-Dead Sea transform. In order to determine the onset of the rift flank uplift relative to the rift history, 55 apatite fission track analyses were performed on samples from the basement of the eastern desert, on the western side of the rift. Apatite fission tracks record the thermal history of the samples for temperatures up to 125°C. Apparent ages range from 382 to 11 Ma representing samples that have undergone various degrees of track annealing. Track length distributions clearly show the fading of tracks acquired prior to uplift in more deeply buried samp es and the accumulation of long unannealed tracks subsequent to unroofing. The pattern of the track length vs. age distribution indicates that major uplift began simultaneously with the main phase of rifting at 19-20 Ma.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.