Internal structure and deformation of an accommodation zone in the northern part of the Suez rift

Abstract

Detailed structural study of the eastern (onshore) part of the Gharandal accommodation zone that separates the northern (SW-dipping) and central (NE-dipping) half grabens of the Suez rift helped\decipher the internal structure and deformation of accommodation zones of continental rifts. This 60 km-wide zone is affected by pure normal faulting. The NE-dipping faults of the northern half graben extend southward into the accommodation zone where they interfinger with SW-dipping faults extending from the central half graben. These two sets of rift-parallel faults form several horsts and grabens in the accommodation zone. Areas dipping parallel to the northern or southern half grabens form several intermixing dip domains in the accommodation zone. Smaller-scale accommodation of dip between these dip domains proceeds by the development of rift-parallel folds (twist zones). In contrast to the southern accommodation zone of the Suez rift, the internal structure of the Gharandal accommodation zone is believed to be representative of accommodation zones in regions (a) unaffected by prerift structures lying at high angles to the rift; and (b) experiencing relatively small extension. Accommodation zones in areas having pre-rift structures lying at high angle to the rift have relatively narrow width and are characterized by transverse, strike-slip faults. Strike-slip movement on these faults is related to the torsional strain resulting from the opposite tilt directions and transport of fault blocks of adjacent half grabens.