Three-Dimensional Characteristics of Rift-Initiation Depositional Sequences and Controls from Their Origin: Abu Zenima and Nukhul Formations, Nukhul Fault Zone, Suez Rift, Egypt

Robert Gawthorpe, Frank Rarity, Paul Wilson, and Dave Hodgetts
Earth, Atmos and Env Sci, University of Manchester, Manchester, United Kingdom

During the early stages of rifting, basin physiography is controlled by the interaction of antecedent drainage and the growth of fault segments. In contrast, in rift climax times subsidence largely outpaces sediment supply and depocentres are under-filled. Thus it is expected that sequences and reservoir architectures are likely to be significantly different in initiation and climax stages of rift evolution. We present an integrated sedimentological, structural and digital outcrop study of rift initiation, continental to shallow marine deposits, located in the hangingwall of the 10 km long Nukhul Fault, Suez Rift, Egypt.

The earliest rift-related continental deposits of the Abu Zenima Formation are dominated by incised valleys cutting across the Nukhul Fault at high angles. Towards the end of Abu Zenima deposition, structural control on deposition and erosion becomes apparent as tectonically-enhanced sequence boundaries are developed in some fault footwalls. Isopachs of Abu Zenima sequences reflect the early segmented nature of the Nukhul fault zone and activity on associated faults and folds. The overlying Nukhul Formation is dominated by tidal channel and tidal flat deposits. During Nukhul deposition, the Nukhul Fault became a major control on palaeoflow, with tidal-channel palaeocurrents oriented sub-parallel to the Nukhul Fault. Erosion on key stratal surfaces is most pronounced along the axis of a fault parallel, hangingwall syncline offset approximately 500 m from the Nukhul Fault. There is a deepening upward trend within the Nukhul Formation, interpreted to reflect increasing displacement on major fault zones.

Our results indicate complex and evolving controls on depositional sequences associated with fault growth, which may explain different fluid contacts and lack of connectivity of Abu Zenima and Nukhul formation reservoirs in fields in the Gulf of Suez.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas