INTERNAL GEOMETRY AND ORIGIN OF THE HUBAT STRUCTURAL CULMINATION, OMAN MOUNTAINS

The Hubat structure is a doubly plunging antiform affecting an allochthonous succession of Mesozoic sedimentary rock (the Hawasina Complex) overlain by the Haybi Complex and the Semail Ophiolite. It is cored by a well exposed imbricated nappe of the Hamrat Duru Group. Detailed investigations of the Hamrat Duru Group led to the recognition of a main phase of imbrication, followed by a phase of meso- and macroscopic folding with axes at a high angle to the strike of the imbricates, parallel to their assumed transport direction. Thrust relationships displayed in this area indicate that the floor thrust of the Semail Ophiolite is younger than the emplacement of the lower units and therefore 'out-of-sequence'. This culmination may have originated either as a result of a post-emplacement regional compressive event of Tertiary age or during the emplacement of allochthons above an oblique ramp during the late Cretaceous orogeny.