The post-Campanian tectonic evolution of the Central Oman Mountains: Tertiary extension of the Eastern Arabian Margin

Abstract

This paper documents the structural history of the central Oman Mountains after the obduction of the Semail ophiolite onto the eastern margin of the Arabian continent during the Late Cretaceous (Santonian/Campanian). The post-obduction history is recorded by a Late Campanian/Maastrichian-Tertiary sedimentary cover to the mountain belt. These sediments have been deformed within an extensional tectonic regime which is continuous northeastwards into the Gulf of Oman hinterland basin and southwestwards away from the SW foothills.Large-scale down-to-the-basin normal faults have been recognized on the Batinah Coastal Plain NE of the mountain belt. Localized block-faulting and roll-over folds are associated with major faults that separate the Late Campanian to Tertiary sediments from older basement rocks of the Oman Mountains and with Late Cretaceous thrusts reactivated as normal faults. To the SW of the mountains, large NW-SE striking folds are thought to be gravity structures developed above a decollement in Late Cretaceous shales.

Tertiary and quaternary marine terraces and planation surfaces of northern Oman: Interaction of flexural bulge migration associated with the Arabian-Eurasian collision and eustatic sea level changes

“…Small to medium earthquakes occasionally shake the region (Deif et al, 2013). Convergence between the northern Oman margin and the Zagros-Makran wedge was re-established by Eocene times (Mann et al, 1990). Tertiary structures in the central Hajar Mountains have been attributed to gravity tectonics (Glennie, 2005), down-to-basin normal faulting (Mann et al, 1990), or passage of a flexural bulge related to the Arabia-Eurasia collision (Kusky et al, 2005) as supported by gravity data (Ravaut et al, 1997).…”

“…Convergence between the northern Oman margin and the Zagros-Makran wedge was re-established by Eocene times (Mann et al, 1990). Tertiary structures in the central Hajar Mountains have been attributed to gravity tectonics (Glennie, 2005), down-to-basin normal faulting (Mann et al, 1990), or passage of a flexural bulge related to the Arabia-Eurasia collision (Kusky et al, 2005) as supported by gravity data (Ravaut et al, 1997). Kusky et al (2005) were able to show from a comprehensive program of mapping late faults, drainage networks, topography, and terraces that Tertiary-Quaternary structures and geomorphic features are related to the contemporaneous subduction and imminent collision with the Makran to the north.…”

Kinematics of Post-obduction Deformation of the Tertiary Ridge at Al-Khod Village (Muscat, Oman)

“…indicates NE directed extension (stops 9 & 10). Similar striking extensional structures were identified along the northern and southern margins of the Gulf of Aden in Oman [36,37], in Yemen [38], Socotra Island [39] and in the Oman Mountains, including the Tertiary Ridge [9]. These extensional structures are associated with Oligocene rifting of the Gulf of Aden [8] or are gravity-driven, facilitating tectonic transport away from the Oman Mountains and towards the Gulf of Oman [9].…”

“…This may have resulted in the formation of SE-NW-directed extensional structures in the Arabian Plate, including the Oman Mountains. On the other hand, the extensional structures may be related to flexural bulging [7] and gravitational collapse structures [9]. The latter could possibly explain a tectonic transport of the postobductional sedimentary cover toward the NE, towards the Gulf of Oman.…”

“…Whereas many studies have concentrated on the regional extensional deformation (e.g., [7,9,10 and sources therein]), very little has been published on post-Cretaceous compressional structures, the work by [8] being a notable exception. They determined a late Oligocene/early Miocene to Pliocene compressional phase with two episodes of different stress directions: E-W to NE-SW (early Miocene) and N-S to NNE-SSW (Pliocene).…”