Structure and deformational history of the Hawasina Complex in the Sufrat ad Dawh Range, western foothills of the Oman Mountains, Eastern Arabian Peninsula

Barrette, Paul Dominique (1985) Structure and deformational history of the Hawasina Complex in the Sufrat ad Dawh Range, western foothills of the Oman Mountains, Eastern Arabian Peninsula. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Semail ophiolite dominates the geological framework of the Oman Mountains and represents the southern extension of a discontinuous belt of ophiolites emplaced oh the eastern edge of the Arabian continental margin In the Late Cretaceous. Its obduction led to the telescoping and emplacement of shelf, slope and basinal sedimentary sequences of Mesozoic age, corresponding to the Hajar Supergroup, the Sumeini Group and the Hawasina Complex, respectively. -- The Sufrat ad Dawh Range is underlain by units of the Hawasina Complex, namely the Hamrat Duru Group and the Wahrah, Al Ayn and Haliw formations. The deformational style in this area is dominated by a regular hinterland-facing imbricate thrust stack. Two sets of imbricate thrust faults are recognized. The faults of the predominant set dip northwards, and are generally parallel to bedding. In the Wahrah nappe, they define an impressive array of connecting, rejoining and diverging splays with minor folding. This set of faults is folded on a macroscopic scale along E-W trending axes, and these folds are, in turn, truncated by steeply northerly-dipping reverse faults belonging to the second set. This second set defines a large-scale re-imbrication system, systematically repeating the Hawasina tectonostratigraphy. Open folding along N-S trending axes occurs in the southern part of the Sufrat ad Dawh Range. -- The tectonic evolution of the Hawasina Complex in the Sufrat ad Dawh Range is divided into three stages. The first stage is an early Imbrication event related to the telescoping of the Hawasina sequenced into separate nappes, and to the tectonic superposition of these nappes in the stacking order generally displayed in the Oman Mountains. The second stage corresponds to the folding of the nappes at distinct intervals across the strike of the allochthons, and with additional shortening In the N-S direction, to the disruption of the limbs of these folds and re-imbrication of the Hawasina nappes. The last stage results either from inhomogeneous compression in the E-W direction, or blending of the nappes over a N-S oriented ramp at depth. 'The timing of deformation cannot be ascertained and several alternatives are presented. The re-imbrication is thought to extend at depth beneath the shelf carbonate sequences of the Hajar Supergroup.

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