Structural setting of Jabal Abu Ghurrah area, Wadi Fatima, west-central Saudi Arabia

Abstract

Detailed field mapping and structural study of J. Abu Ghurrah area indicate that the uppermost Precambrian sediments and volcanics of the Fatima Formation were deformed by NNW-SSE tangential compression. The styles of deformation include flexural-slip folding forming a large ENE to NE plunging, overturned syncline and low-angle thrusting in a hinterland dipping duplex. The floor thrust of the duplex is a decollement between the 150 meter thick andesite sill and the underlying limestone beds of the middle Fatima member. The roof thrust of the duplex has the largest displacement among the mapped thrusts. The duplex was formed by continued shortening of the areas as the thick andesite sill of the middle Fatima member acted as a rigid and brittle beam that resisted folding and failed by low-angle thrusting. Layer-parallel shortening by minor folding and thrusting is also common in the area and represents an early phase of deformation.