Exploration Implications of Neotectonic Fault Pattern, Gulf of Suez: ABSTRACT

Detailed topographic mapping of the Ras Issaran area along the west bank of the Gulf of Suez reveals Quaternary faulting along preexisting trends, cross-fault reversals, and tectonically controlled sedimentation. The neotectonic fault systems of the region were identified and mapped by altimetry of selected bedrock units and Quaternary gravel surfaces. The relict gravel surfaces are tilted gulfward, bowed near faults, displaced across faults, and show fault-induced drainage changes, evidenced by truncation and rerouting of wadis. Although the current major fault scarps on the high Quaternary surface have migrated back from the original bed-rock faults, the configuration and magnitude of the Quaternary faults are clearly visible. This has important implications for the int rpretation of subsurface data. In particular, ability to detect subsurface structures, reversed faults, and significant fault trends is enhanced by knowledge of the modern fault patterns. Tectonic activity in the Ras Issaran area is dominated by movement occurring on two major sets of normal faults. The primary End_Page 468------------------------------ set consists of NW-trending, gulf-parallel faults which define major horst and basin systems. Breaking these are roughly NE-trending cross-faults. Paralleling the coast is a NW-SE trending horst segmented by cross-faults. Relative dissection and weathering of the relict gravel surfaces indicate the most recent uplift of the area occurred sequentially from northwest to southeast in three major segments. As uplift shifted along structure, motion on intervening cross-faults reversed. Bed-rock facies changes indicate gulf-parallel faulting has continued from the Miocene along preexisting trends to the present day. Miocene and Pliocene reefal concentrations at the crest of the horst give way to thinly laminated limestone down structure and deeper water marls, evaporites, or clastics off structure. Local fault-associated arching also influenced deposition, resulting in thickening Pliocene clastic fill off the crest of the uplift. In the adjacent basins, ongoing sedimentation encouraged growth faulting. In general, the NE-SE cross-faults did not influence sedimentation to the same extent as the gulf-parallel fault system. Detailed mapping of the neotectonic fault system indicates a continuation of past structural movement through the Quaternary. These fault patterns and their effects on local sedimentation provide a model for subsurface projection of Neogene facies variations. As oil concentrations are intimately related to local structures in the Gulf of Suez, detailed knowledge of Quaternary fault movements combined with seismic interpretation, can significantly aid in understanding the sedimentology and structural features of potential oil reservoirs. End_of_Article - Last_Page 469------------