Updoming, rifting and continental margin development during the Late Palaeozoic in northern Oman

Abstract

Abstract Subsurface data from northern interior Oman and new surface data from the Oman Mountains imply that the north Oman passive continental margin developed in the Permian. Late Carboniferous and Permian updoming of an area roughly overlapping the present Oman Mountains is indicated by the northward thinning of the continental clastics of the Haushi Group (Late Carboniferous and Early Permian) in the sub-surface. Well correlations show the thinning as cutouts at internal unconformities proving contemporary uplift along a roughly E-W strike. Deep water sedimentation off northern Oman commenced already in the early Late Permian. Permian deep water sediments of the Hawasina nappes consist of reef-derived sediment gravity flow deposits, cephalopod limestones and radiolarites that were deposited in a slope and basin floor environment north of a coralgal reef tract. Mafic volcanics underlying these deposits show locally tholeiitic characters suggesting that incipient drifting of the Hawasina ocean occurred as early as the Late Permian. Penecontemporaneous flooding of the Arabian shield occurred on an almost unfaulted substratum even in areas close to the inferred shelf edge. The interpretation of these data in terms of models for continental rifting suggests that north Oman developed on the little faulted side of an asymmetrical rift produced by Permo-Carboniferous low-angle normal faulting of the lithosphere.