The Jurassic–Cretaceous depositional and tectonic evolution of the southernwestern margin of the Neotethys Ocean, Northern Oman and United Arab Emirates

Abstract

The concept that the autochthonous, parautochthonous and allochthonous Permian-Cretaceous sequences in the United Arab Emirates (UAE) and Oman record the transition from platform, slope to basin sedimentation within the southern part of Neotethys has been fundamental to the interpretation of the geological history of the region. The results of a major geological mapping programme of the UAE, carried out by the British Geological Survey for the Federal Government of the UAE, coupled with the detailed examination of key sections within northern Oman has led to a re-evaluation of the geological evolution of this region. This detailed study has led to a greater appreciation of the sedimentology and depositional setting of the sediments laid down along the northeastern Arabian continental margin during the Jurassic to Cretaceous, allowing a more refined model of Neotethys Ocean basin evolution to be established. The model charts the progressive breakup of the Arabian continental margin and closure of Neotethys during the mid to late Cretaceous and is divided into three main stages: Stage 1 -Initial rifting and formation of the Neotethys Ocean, followed by a prolonged period of stable, passive margin sedimentation which extended from the Permian to Late Jurassic times; Stage 2 -Uplift and erosion of the shelf margin during the Late Jurassic to Early Cretaceous, coincident with increased carbonate-clastic sedimentation in the outer ramp, distal slope and basinal areas; Stage 3 -Increased instability during the Late Cretaceous leading to the breakup of the platform margin and foreland basin sedimentation accompanying the obduction of the Oman-UAE ophiolite. Data obtained for the upper part of the platform and platform margin to slope successions has revealed that the topography of the "shelf"-slope-basinal margin was more subdued than previously thought, with this more gentle ramp margin morphology persisting until early to midCretaceous times when the platform margin started to become unstable during ophiolite obduction. The thrust-repeated allochthonous sedimentary rocks of the Hamrat Duru Group were deposited on the outer platform margin/lower slope rise to basinal plain of this basin margin and includes the dismembered remains of two turbidite fan systems which fed carbonate-rich detritus into deeper parts of the ocean. A re-evaluation of the chert-rich sequences, previously equated with deposition on the abyssal plain of Neotethys, has led to the conclusion that they may record sedimentation at a much shallower level within a starved ocean basin, possibly in a mid-ramp (above storm wave base) to outer ramp setting. A marked change in basin dynamics occurred during the mid-Cretaceous leading to the development of a shallow ramp basin margin in Oman with terrestrial to shallow marine sedimentary rocks interdigitating with red siliceous mudstones. By contrast, the contemporaneous succession in the Dibba Zone of the UAE indicates considerable instability on a steep shelf break. This instability is recorded by t...

Synchronous Seafloor Spreading and Subduction at the Paleo‐Convergent Margin of Semail and Arabia

“…In the northern Oman and Emirates Mountains, shelf slope marginal basin ramp sedimentation is dominantly represented by the Sumeini Group, toward a basin dominated through Triassic and Jurassic by radiolarian chert crosscut by intraplate alkaline volcanism, basin open on the Neotethyan Ocean (Glennie et al, ; Lippard et al, ; Searle et al, ; Styles et al, ). This ramp persists till late Cenomanian marked by foundering of the platform margin, preceded nevertheless by its increasing instability (uplift and erosion) during Late Jurassic‐Early Cretaceous (Philips et al, ; Searle et al, ).…”

“…The tectono‐metamorphic evolution of the Arabian margin during Cretaceous, as well as the sedimentary record chart a progressive breakup of the Arabian continental margin and closure of Neotethys during Middle to Late Cretaceous (Philips et al, ; Searle et al, ). As pointed in the sedimentary record (see section 3.4), the episode of starved sedimentation in Hamrat Duru Basin following an ~300‐km inland retreat of the continental slope is assigned to foundering of the Hamrat Duru continental basement, initiated at the end of Jurassic (Béchennec et al, , ).…”