M. A. Younes*
*Geology Department, Faculty of Science, Alexandria University, Alexandria, Egypt.
Active oil seepages in the Gebel El-Zeit area (southern Gulf of Suez, Egypt) occur in fault zones on the western flank of the East Zeit Basin. Gas chromatography-mass spectrometry indicates that these oils are rich in tricyclic terpanes and extended hopanes with few diasteranes. These characteristics are typical of oils derived from marine siliciclastic source rocks; an input of terrestrial angiosperms material as indicated by the very high oleanane index of 32.65% and the low gammacerane index of 6.28%. The molecular maturity parameter C29 a a a cholestane [20S/(20S+20R)] index is <0.5 indicating that these oils were generated at relatively low thermal maturities. The seepage oils resemble Miocene crude oils in the East Zeit Basin which are believed to be generated from Lower Miocene Rudeis Shale. Burial history modelling of source rock indicates that oil generation from this unit began at around 3-4 Ma at vitrinite reflectance measurements of Ro%=0.60-0.85. This implies extensive lateral and vertical migration has taken place for the generated oil to reach the surface. Alternatively, the seepage oils may be sourced by leakage from pre-existing accumulations.