GEOPHYSICS LETTERS

Ghalib M. et al. 61Faraun seismic sequence on the grid o. the available seismic data intosegments, which represent the lateral extent of the various seismic faciesunits. The segments ar-' then transferred to a shoot point map withappropriate description )f names of seismic facies units or theirinterpreted lithology. The resuJting map represents the distribution of theseismic facies units or their interpreted lithology, as represented on Fig.(13). THs figure represents the distribution of the interpreted lithology tothe seismic fades units within Hammam Faraun sequence in ShoabGharib, Ras Fanar, and Ras Gharib oil fields. The figure also representsthe widely distribution of Nullipore rock in Shoab Gharib area (as apatch reefs), which may be an extension of the Ras Gharib reefs. Thefigure also represents Ras Fanar reefs as a narrow elongated build-up,aligned NW -SE (Gulf of Suez trend).4- Depositional history of Nullipore rock:Figure (13) represents the distribution of the interpreted carbonatebuild-up (reefs) in Ras Gharib and Shoab Gharib area, as patch reefs andrepresents the elongated shape of the reefs in Ras Fanar area. Theinterpreted seismic sectioH:;and the time structure contour maps of thetop and bottom of the Hammam Faraun sequence Figs. (14) and (15)show that, Ras Fanar reefs were deposited over an elongated pre-Miocene high, approximately of the same water depth, which result in areef barrier like-shape. Shoab Gharib reefs were deposited on a domalfeature (topographic high) with a wide range of water depth. Then, thecarbonate build-ups are close and related to the structural highs and hightopographic areas that related to the rifting of the Gulf of Suez. Theconjunction between the preceding characters represents the depositionalhistory of the Nullipore rock as follows:The origin (depositional history) of the Nullipore rocks in the studiedarea is related to the structural configuration resulting from the rifting ofthe Gulf of Suez in the pre-Miocene time. This leads to the occurrence ofa number of horst blocks, step blocks, with grabens and marineembayments in between. This structural configuration leads to theexistence of areas with free sea' water circulation connected with theopen sea, which is the top surface of the horst blocks and topographichigh areas (structural high areas). The above areas are adjacent to closedareas (grabens and marine embaymeIlts)with little or no-circulation. In