Sandstone dykes as evidence of localized transtension in a Transpressive Regime, Bir Zreir Area, eastern Sinai

The Bir Zreir area, NE Sinai, is part of the 40‐km‐wide eastern Sinai shear zone stretching along the western margin of the Gulf of Elat. Sinistral movement along faults comprising this shear zone is consistent with the regional NNW‐SSE compression in which the Dead Sea transform fault was formed. In the Bir Zreir area, sandstone dykes within NE striking fault breccias were developed within the Precambrian crystalline basement. These breccias, up to 200 m in width, resulted from transpression along the NE striking faults in response to sinistral movement along the NNE striking major faults. Paradoxically, the sandstone dykes developed by infilling of transtensional open fissures which share the NE trend of the breccia zones. The source rock for the dykes is Nubian Sandstone unconformably overlying the basement. The depth beneath the unconformity to which the sandstone collapsed is 500–600 m. Local NW‐SE transtension along parts of the NE striking faults enabled the formation of fissures and their infilling by sand and sandstone blocks of various sizes as dykes. The infilling occurred despite the regional NNW‐SSE compression which prevailed in the study area. A kinematic model is developed which combines sinistral movement and clockwise rotation of rigid blocks between the faults with resultant local NW‐SE transtension along the northern segment of the NE trending strike‐slip faults.