--> Structural Evolution of Extensional Phanerozoic Rift Blocks: El Hamrawein Area, Northwest Red Sea, Eastern Desert, Egypt

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Structural Evolution of Extensional Phanerozoic Rift Blocks: El Hamrawein Area, Northwest Red Sea, Eastern Desert, Egypt

Abstract

The Hamrawein surrounding area, located at the northwestern part of the Red Sea (between Quseir and Safaga) is geologically significant because it can be used as a model for rift blocks development in Phanerozoic sedimentary succession between Pre-Cambrian basement rocks. Detailed field mapping revealed that the structural styles of the area are represented by block-faulting related to the Red Sea rift. The area can be broadly divided into two elongated blocks; Western and Eastern blocks, based on structural style, fault polarity and stratigraphic units. The rocks in the two blocks have a regional NE dip with several NW-SE trending faults. Faults are the main structure and subsequent by folding. Major faults are mainly normal with different trends (NW, NNW, NS and NE trends). The Nakheil Fault represents the major fault of the area where extends mainly in a NW direction and separate the basement rocks to the east from the different sedimentary units to the west. Rift-parallel folds play also an important role in the deformation of the study area. Structural analysis suggests the presence of three main phases of deformation (D1, D2 and D3) which affected the study area during the Mesozoic/Cenozoic. The proposed structural model based on the origination of two sets of extensional faults in the Pre- Cambrian basement rocks, which may be related to the Late Triassic- Early Jurassic (Pre- Cretaceous) rifting phase of extensional faulting. This tectonic phase (D1) started in Pre- Cretaceous time and led to the formation of isolated fault-bounded sub- basins (grabens and horsts) in the study area. This phase was followed by the deposition of the Cretaceous- Early Eocene formations (Pre-rift group) and the pre-existing extensional faults become deep seated faults. In the Oligocene time, the first stage of opening of the Red Sea occurred causing reactivation of the pre-existing faults and the formation of the Western block with the deposition of Oligocene rocks in the Western block (D2). Due to the continuous opening stage of the Red Sea, the Pre-Cambrian rocks are uplifted forming high lands and Red Sea basement belt. This led to the formation of Eastern block and the main rift fault (RF). Due to the opposite extensional forces forming normal faults and the presence of two adjacent blocks (Rifts) with the dragging along extensional faults, lead to the development of some folds (mainly synclines). Finally in Post Early Miocene, new pulses of extensional faults affect the Eastern block of the study area and accompanied by the deposition of recent Syn-rift group sediments in the Eastern block (D3).