Evolutionary Model
1. Basement and pre-extension deposits are affected by planar and Antithetic Crustal extension faults with almost the same thickness and degree in both hanging/foot wall, unless some blocks were eroded. 2. Syn-extension section begins to fill the resulted fault blocks in wedge shape with variation in thickness along faul sides (still see fault effect). 3. Post-extension deposition is the last stage almost with constant thickness without fault effect to be seen.
Detached Extension Fault System
These involve only the shallow upper crust (in ductile sediments deposited above Basement). Some detachment faults have large transitional displacements. The Pro-gradation delta system, Niger delta , passive continental margins, and West African margin are some examples.
Gulf of Suez Rift Evolution on three stages:
1. From late Oligocene to early Miocene initial rift was divided by accommodation zones (Galala - Zenima, Morgan , and Brother) into 3 distinct asymmetrical half-graben sub-basins, each bounded on one side by a major border fault system (Fig c) 2. Middle Miocene continental rifting extended until 35 km in southern Gulf of Suez (NE-SW extension) (Fig b). 3. On late stage rift was affected by Strike – slip movement on Levant - Aqaba transform plate boundary (Fig a) This evolution divided Gulf of Suez to three distinct asymmetrical sub-basins, each of them is bounded on one side by a major NW-SE trending border fault system (Amal - Zeit province, Belayim Province and Darag Basin). Sub-basins are divided by complex accommodation zones. We can note clearly fault polarities and strata dip directions are reversed across accommodation zones.
Criteria of Detached faults
1. Listric faults detachment in post rift section underlain by base- ment and may involve extension faults. 2. Rollover Anticline and crustal collapse graben which have sigmoidal synthetic and planar antithetic faults. 3. In case of oil potential these rollover anticlines can be possible location for oil accumulation.
Stratigraphic sequence of Eastern Gulf of Suez is divided as following:
Evolutionary Model
1. Basement affected by extension faults, overlain by Pre-exten- sion deposits which include detachment layer mainly Salt or Evaporate deposits. 2. Syn-extension deposits rapid development due to huge volume of deposition (Gulf of Mexico-7km/million years) which creates large District faults on detachment layer with rollover anticline on hanging wall. 3. Post-extension deposited the same as Crustal Extension fault system.
1.Basement: The crystalline basement (Precambrian granites and gneisses). Basement fractures control the position of transferring faults in the overlying sequences. 2.Pre-Rift: Three mega sequences a. Esna Shale and Eocene. b. Limestones; Nezzazat Group. c. Sudr Chalk; Nubia Sandstones. 3.Syn-rift: Two mega sequences a. Evaporites, Post-Evaporites b. The Nukhul and Rudeis formations
Hydrocarbon reservoirs exist in both the pre-rift and syn-rift strata. The principal source rock is the Upper Cretaceous Sudr Chalk. Major Fields such as the October and July Fields.
References:
1. Prof. Ken Mc Cally, 2014. Lectures and Assessment exercise, University of London. 2. Khalil, McClay, 2002, extension fault –related folding, nort western Red sea, Egypt journal of structural Geology 24(2002) 743-762 Reviewed by Mr. Hisham Ali, Exploration Manger, Tri-Ocean Energy
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