Geological and seismic evidence for the tectonic evolution of the NE Oman continental margin and Gulf of Oman

Abstract

Late Cretaceous obduction of the Semail ophiolite and underlying thrust sheets of Neo-Tethyan oceanic sediments onto the submerged continental margin of Oman involved thin-skinned SW-vergent thrusting above a thick Guadalupian–Cenomanian shelf-carbonate sequence. A flexural foreland basin (Muti and Aruma Basin) developed due to the thrust loading. Newly available seismic reflection data, tied to wells in the Gulf of Oman, suggest indirectly that the trailing edge of the Semail Ophiolite is not rooted in the Gulf of Oman crust but is truncated by an ENE-dipping extensional fault parallel to the coastline. This fault is inferred to separate the Semail ophiolite to the SW from in situ oceanic Gulf of Oman crust to the NE. It forms the basin margin to a “hinterland” basin formed atop the Gulf of Oman crust, in which 5 km of Late Cretaceous deep-water mudstones accumulated together with 4 km of Miocene and younger deep-water mudstones and sandstones. Syndepositional folding included Paleocene–Eocene folds on N-S axes, and Paleocene to Oligocene growth faults with roll-over anticlines, along the basin flank. Pliocene compression formed, or tightened, box folds whose axes parallel the modern coast with local south-vergent thrusts and reversal of the growth faults. This Pliocene compression resulted in large-scale buckling of the Cenozoic section, truncated above by an intra-Pliocene unconformity. A spectacular 60-km-long, Eocene(?) to Recent, low-angle, extensional, gravitational fault, down-throws the upper basin fill to the north. The inferred basement of the hinterland basin is in situ Late Cretaceous oceanic lithosphere that is subducting northwards beneath the Makran accretionary prism.

Oligocene/Early Miocene E/W‐Shortening in the Oman Mountains Related to Oblique Arabia‐India Convergence

“…to NW/SE-oriented folds within the post-obductional formation in the Muscat-Seeb area and the Permian rocks of the Saih Hatat Dome have been reported by LeMétour et al (1986a),,Villey, Le Métour et al (1986b),Mann et al (1990), Miller et al (2002,,Kajima, Ishii, Otake, and Goto (2012),,Scharf et al (2016),Searle (2019),Hansman et al (2021), andLevell et al (2021), and are summarized in Figure6. The respective folds deform stratigraphic units up to the mid-Eocene limestone of the Seeb Formation.…”

“…(2021), and Levell et al. (2021), and are summarized in Figure 6. The respective folds deform stratigraphic units up to the mid‐Eocene limestone of the Seeb Formation.…”

“…The age of these faults is unknown. Note that the large NNE‐oriented anticline as continuation of the Jabal Akhdar/Jabal Nakhl is late Eocene in age, based on seismic data (Levell et al., 2021).…”

“…(2020); (n)—Levell et al. (2021). Thin black lines represent undifferentiated faults, taken from Béchennec et al.…”

“…2021) presented seismic and well data from offshore northereastern Oman. A pre-late Eocene NNE-trending major fold has been reported by Levell et al (2021). This fold occurs in the NNE-ward projected extension of the Jabal Akhdar/Jabal Nakhl (JN).…”