Evolution of the Arabian continental margin in the Dibba Zone, Northern Oman Mountains

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Abstract
The Dibba Zone, Northern Oman Mountains, documents the history of an oblique-rifted (transtensional) segment of the Arabian passive margin. Unmetamorphosed Palaeozoic, pre-rift (Ordovician to ?Devonian) successions, exposed in rifted continental slivers (Oman Exotics), record stable siliciclastic and carbonate platform deposition. Early Permian rifting of the Neo-Tethys initiated a carbonate platform in the Musandam Peninsula, while shallow marine bioclastic carbonate and quartzose sediments accumulated in the subsiding axial zones (Asfar Fm., Jebel Qamar Exotics). During final continental break-up, in the Late Triassic-Early Jurassic, a carbonate platform in the Musandam Peninsula was bordered by an escarpment-bypass margin with a turbiditic apron to the southeast (Zulla Fm.). Rifted continental slivers underwent mass-wasting, giving rise to detached blocks, or olistoliths that slid into organic-rich muds and turbiditic sands (Kub Melange). During the Jurassic, the subsiding Musandam carbonate platform was bordered by a steep slope (Sumeini Gp.) and redeposited carbonates accumulated on the continental rise (Guweyza Limestone Fm.). A switch to mainly siliceous accumulation, from Late Jurassic to Early Cretaceous (Tithonian-Berriasian Sid’r Fm.) ensued, mainly in response to tensional faulting, combined with eustatic sea level rise. Following re-establishment of the platform, carbonate sediment was again shed into the basin in the Early Cretaceous (Nayid Fm.). During Cenomanian time, tholeiitic and alkaline basalt extrusions formed seamounts that locally built-up into shallow water (99–92 Ma). Platform deposition halted in the Turonian ( c. 90 Ma), with flexural upwarp and erosion, followed by subsidence and slumping of shelf edge and upper slope sediments into a syntectonic foredeep, accumulating siliceous sediments and redeposited lithoclastic carbonates (Riyamah unit, Muti Fm.). Associated with emplacement of the Semail ophiolite, the passive margin successions were then imbricated by foreland-progagating thrusts (76–65 Ma), modified by the effects of possible oblique convergence, sidewall ramping and late-stage (dorsal) culmination collapse. Following erosion in the Campanian-Maastrichtian (Juweiza Fm.), platform deposition was reestablished in Palaeocene-early Oligocene. Renewed compression after mid-Eocene resulted in folding and reverse faulting of the Dibba Zone and thrust culmination of the Musandam shelf carbonates, driven by incipient continent-continent collision in the Zagros area.