Supersequence and composite sequence carbonate platform growth: Permian and Triassic outcrop data of the Arabian platform and Neo-Tethys

Abstract

Permian and Triassic carbonate platforms of the Arabian Peninsula (Gondwana) and seamounts of the Neo-Tethys (Hawasina and Batain basins) are characterized by distinctive supersequences (second order, duration 5–20 million years, my) and composite sequences (third order, duration 0.5–5 my). The presented sequence stratigraphic framework will be compared with existing sea level curves to discuss the validity of different regional oscillations during the dispersal of Pangea. The carbonate succession of the Haushi and Akhdar Groups of the Arabian platform is composed of four Permian (P1–P4) and four Triassic supersequences (Tr1–Tr4). Isolated platforms of the Hawasina and Batain basins comprise two Permian supersequences and one Triassic supersequence. In contrast to the continuous development of the Arabian shield, carbonate platform growth of the seamounts was restricted to the Guadalupian–Lopingian and to the Middle–Upper Triassic, and ceased after drowning events. Composite sequences exhibit a well-developed stacking pattern during the Guadalupian–Lopingian (Saiq Formation). Lowstand systems tracts (LSTs) occur during the Cisuralian (Gharif Formation, Haushi Group) and Triassic (Mahil Formation, Akhdar Group). Open-marine depositional environments prevail during transgressive systems tracts (TSTs) with diverse biota including rugose and scleractinian corals, chaetetids, bryozoans, and crinoids. Highstand system tracts (HSTs) exhibit a twofold pattern: During the transgressive phase of supersequences, composite sequence highstands are dominated by reef or level-bottom communities with corals. Cyclic platform deposits or monotonous mud- and wackestone accumulated during the turnaround or late second-order highstand of a supersequence. Correlation of maximum flooding surfaces with published data suggests that supersequences P1, P2, and Tr4 can be traced across the Arabian platform into the Neo-Tethys basins, while supersequences P3, P4, and Tr1–Tr3 resulted from local tectonic events at the margin of the Arabian platform (Hulw half-graben). The presented sea level curve corresponds therefore to the Tethyan sea level curve during the Cisuralian and Guadalupian, but differs significantly during the Lopingian, as a result of the dispersal of Pangea. The Middle and Upper Triassic sea level curve from Oman is again in good correlation with published data. The Permian and Triassic sequence architecture on the Arabian plate and adjacent Neo-Tethys was predominantly triggered by the global warming after the Permian–Carboniferous glaciation, the initial rifting of Neo-Tethys, and subordinately by eustatic sea level changes.