Abstract

Fabric development and block rotation related to flexural slip were examined in sedimentary strata draped over a basement normal fault at the western margin of the Dead Sea rift in southern Israel. In addition to documenting differences in deformation style as a function of lithology, this study focuses on the progressive development of flexural-slip horizons and fabric development in extensional settings. Deformation in the intercalated shale, siltstone, carbonate, and gypsum beds of the Turonian Ora Formation is dominated by extension, bedding-plane slip, and block rotation, which occur at different scales and magnitudes throughout the approximately 12 m section. Extension appears as boudinage in carbonate beds and fibrous sigmoidal gypsum veins in shale, whereas strong foliation, highly deformed gypsum veins, and asymmetric folds characterize slip and adjacent drag zones. Magnitude of extension in individual beds is directly related to relative magnitude of adjacent bedding-plane–slip horizons, implying a common origin. Initial flexural slip was lithologically controlled, with displacement occurring along numerous narrow zones throughout shale and siltstone horizons. Continued top-to-the-west bedding-plane slip, however, led to antithetic block rotation within competent beds, which in turn resulted in the termination of slip along zones abutting block-bounding faults. As block size increased during progressive development of flexural slip, so did the spacing between active slip zones. Therefore, rigid block rotation within subhorizontal simple shear zones provided the mechanism for concentrating flexural slip along several major detachments during extension of the Ora Formation above a basin-bounding normal fault.

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