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Fault-zone architecture in sandstone

We focus on deformation features in two study areas: (1) Capitol Reef National Park, Utah, and (2) southern Israel (Negev). The features include deformation bands, deformation zones and slip surfaces. Our work in Capitol Reef National Park, Utah, is summarized in the following paper:

  • Katz, Y.,Weinberger, R, and Aydin, A. (in press). Geometry and kinematic evolution of Riedel shear structures, Capitol Reef National Park, Utah ,J. Struct. Geol. (Download PDF file)

    • Here we describe our work in southern Israel. The field data has been collected and analyzed in an attempt to identify and evaluate the factors governing the deformation processes, and to address questions concerning the distribution, orientation and age of the associated stress field. The study area is located on the slopes of Har Amir., 10 km north of the city of Elat, where Cambrian and Lower Cretaceous sandstone formations are well exposed. Over twenty deformation zones were inspected, measured and mapped. The data reviles two main strike directions, NW and NNW, and suggested a substantial normal dip-slip offset component. Both deformation zones and slip surfaces may expand up to 0.5 m wide and hundreds of meters long. The former is associated with offset of up to a few decimeters and the latter with up to tens of meters. Deformation bands are observed within the proximate vicinity of the larger-scale deformation zones. Over a hundred of deformation bands were measured and many more were mapped to a scale of 1:20.

    Several main features were observed: (a) Preferred strike directions – over 70% of the measured deformation bands strike to either NW or NNW. (b) Moderate to steep dipping fractures – the majority of the deformation band dips range within the magnitude of 60 to 90 degrees>. (c) Consistent offset components – inspection of field relationship between deformation bands striking NW and those striking NNW exhibit consistent offset trends. When the NNW-trending bands offset the NW-trending bands the displacement is sinistral, while an offset of the NNW-trending bands by the NW-trending bands is dextral. (d) Pebble fracturing – in places, pebbles caught into deformation zones show extended fracturing. A fractured pebble usually retains its original shape, and the cracks orient subparallel to the plane of the deformation band. (e) 'Twisted ladders'- a structure consisting of two sub-parallel straight deformation band/zone segments connected by antithetic 'rungs'. This structure appears in different scales. Albeit the variety of sizes, it is noticeable that the structure proportions remained constant. (f) 'Fan-like' structures – deformation zones that disperse into an opening fan-like structure as approaching another deformation zone and terminate at the intersection.

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    This study is part of Yoram Katz's dissertation. We are collaborating with Atilla Aydin, and Vladimir Lyakhovsky,.