Sedimentary aspects of the Eo-Alpine cycle on the northeast edge of the Arabian Platform (Oman Mountains)

Abstract

The northeast edge of the Arabian Platform in the Oman Mountains is represented by the autochthonous unit that crops out in the two windows of Jabal Akhdar and Saih Hatat, beneath and in front of the Hawasina and Samail nappes.The Eo-Alpine orogenic cycle began in the Late Permian with extension on the margin of Gondwana and ended in the Campanian with the formation of a subduction-obductiontype mountain range, the Oman Mountains of the Late Cretaceous. During this cycle, long periods of stable shelf sedimentation were interrupted by tensional tectonic episodes, often accompanied by volcanism and subsidence of the platform, passing into the bathyal domain.Deposition during the Permian to Campanian occurred during five main sedimentary cycles. In the Late Permian (Murghabian), a widespread marine transgression covered the edge of Gondwana in a tensional setting. The 'Fusulinid Sea' transgression was followed by the deposition, lasting until the Triassic, of a thick regressive sequence, the Akhdar Group, which was terminated by emergence and weathering in a continental environment. The next sedimentary cycle, represented by the Sahtan Group, began in the Pliensbachian, when the Oman Mountains area formed an inner carbonate shelf, and ended in the early Tithonian. The entire margin of the platform was profoundly affected, in the late Tithonian, by extension, listric faulting and foundering into the bathyal domain, with deposition of the Kahmah Group (Maiolica-type deposits: calpionellid-bearing micrite), and rapid retreat of the continental slope by about 250 km. Renewed carbonate shelf deposition then prograded SSW-NNE across the foundered part, though this was still incomplete when the latest Aptian-Albian transgression took place. At the Cenomanian-Turonian boundary, the shelf underwent profound reorganization with the development of the Muff (intrashelf) Basin, in which the Aruma Group was deposited, and the Masqat-Musandam High which provided the detritus filling the Muti Basin on the continentward side and the Hawasina Basin on the oceanic side. Fragments from the advancing nappe were redeposited in the Muti Basin only from the Campanian on, and it was only during this period that a flysch trough became superimposed on part of the Muti Basin. The closure of the Muti Basin was affected with the emplacement of the nappes on the platform and the subsequent deposition of cover formations over both nappes and the autochthon from the late Maastrichtian onward.

Linking process, dimension, texture, and geochemistry in dolomite geobodies: A case study from Wadi Mistal (northern Oman)

“…1). Here, Permian to Cretaceous platform sediments unconformably overlie Neo-Proterozoic to Cambrian basement (Rabu et al, 1990).…”

Influence of climate and dolomite composition on dedolomitization: insights from a multi-proxy study in the central Oman Mountains

“…The lowgrade greenschist-facies Late Proterozoic rocks in the Jebel Akhdar dome are unconformably overlain by weakly metamorphosed middle Permian to Cenomanian carbonates. The carbonates, forming a succession 2.5 km thick, were deposited on the subsiding southern passive margin of the Tethyan ocean (Hanna 1990;Rabu et al 1990;Mann et al 1990;Pratt and Smewing 1993;Masse et al 1997Masse et al , 1998Hillgärtner et al 2003). This succession is known as the Hajar Supergroup and includes, from bottom to top, middle-Late Permian fusulinid limestone (Saiq Formation), Triassic calc-dolomites (Mahil Formation), Jurassic limestone and siliciclastic red beds (Sahtan Group), and lower Cretaceous-Cenomanian limestone (Kahmah and Wasia Groups; Saddiqi et al 2006).…”

“…This succession is known as the Hajar Supergroup and includes, from bottom to top, middle-Late Permian fusulinid limestone (Saiq Formation), Triassic calc-dolomites (Mahil Formation), Jurassic limestone and siliciclastic red beds (Sahtan Group), and lower Cretaceous-Cenomanian limestone (Kahmah and Wasia Groups; Saddiqi et al 2006). The Jurassic-Cretaceous limestone is disconformably topped by the Turonian-Santonian clastic marls and olistostromes (Muti Formation or lower Aruna Group), which correspond to foredeep deposits (Robertson 1987;Rabu et al 1990) and generally form the footwall of the Tethyan nappes. Post-nappe, shallow-water sediments were deposited over the ophiolite front in the foredeep as early as in the late Maastrichtian and continued during the Tertiary (Saddiqi et al 2006).…”

Extent, duration, and nature of the Permian-Triassic superanoxic event

“…Most of these sections still require detailed facies and biostratigraphic analysis, but some general observations can be made. The shallowest environments are recorded in the Upper Saiq and lower Mahil Formations and record deposition in the shallow subtidal to supratidal settings of the Arabian platform (e.g., Rabu et al, 1990). Unfortunately, pervasive dolomitization has affected the entire Wordian to Upper Triassic record, and little facies or faunal information has been gleaned.…”