199 Abstracts of Khuff Sequence Workshop, Part I 11717 The Arabian Plate and the IGC Programme 572 (Permian–Triassic extinction and recovery): Results from the Muscat - Gutech (German University of Technology in Oman) ield meeting (February, 2010) Aymon Baud (BGC, <aymon.baud@unil.ch>), Michaela Bernecker (German University of Technology in Oman, <michaela.bernecker@gutech.edu.om>), Leopold Krystyn (Vienna University, Austria), Sylvain Richoz (University of Graz), Oliver Weidlich (Wintershall), Benoit Beauchamp (University of Calgary, Canada), Fabrice Cordey (Lyon University, France), Stephen Grasby (Geological Survey of Canada) and Charles Henderson (University of Calgary) Summary The Permian–Triassic transition has been surveyed in the Oman Mountains and new detailed sections have been presented (Baud and Bernecker, 2010), from autochthonous shallow-water units (Saih Hatat and Al Jabal al-Akhdar) to slope deposits in the Jabal Sumeini area (Wadi Maqam units), from distal tilted block (Wadi Wasit) to oceanic deep-water deposits (Buday’ah). Middle Permian Transgression At the dawn of the Wordian (Middle Permian), the “Fusulinid Sea” transgressed over most of Oman with the exception of Jabal Ja’alan and the Huqf-Dhofar High. This transgression enabled the establishment of a vast carbonate platform in Al Jabal al-Akhdar, a 700 m-thick succession of cyclic shallow-marine carbonate, the Saiq Formation (Middle and Late Permian, basal Triassic (Baud et al., 2001a, b, 2005; Richoz et al., 2005; Richoz, 2006)). A similar succession occurs in Saih Hatat (Le Métour, 1988; Weidlich and Bernecker, 2003; Chauvet, 2007), in the Musandam (Bih Formation; Maurer et al., 2009), as well as in Interior Oman and in the Haushi area (Khuff Formation; Angiolini et al. 1998, 2003). Clearly, for us, this transgression was the result of the break-up of the Neo-Tethyan rift and the associated thermal subsidence. Following the peak of the thermal subsidence in the Wordian–Capitanian, a stable carbonate platform became established on the Arabian Peninsula. The Saiq, Khuff and Hagil formations show a strong regressive tendency at the end of the Guadalupian (Middle Permian), with restricted environment facies and a reduced biophase, mainly associated with a global fall in sea level at this time and climate changes (Isozaki, 2009). During the Lopingian (Late Permian), the subsidence as recorded in the Saiq mega-cycle B (up to 300 m of shallowing-upward cycles) was still well active. The most striking effect of the climax of the Neo-Tethyan extension was the formation of a continental slope (Sumeini) and a basin (Hawasina) that constituted with the adjacent Arabian Platform, the southern continental passive margin of the Neo-Tethys Ocean. Furthermore early-rifted blocks detached from the edge of the Arabian Shield formed isolated proximal platforms along the continental slope (later they were incorporated in the Hawasina Nappes). The continental margin slope deposits are clearly identiied (with slumps and intra-formational breccia) in the northwestern part of the Oman Mountains (Jabal Sumeini), where they form the basal part of the Maqam Formation dated as Roadian (Middle Permian). The distal isolated platform identiied as nappes in Baid and Jabal Qamar areas by Béchennec (1988), Béchennec et al. (1992), Pillevuit (1993) and Pillevuit et al. (1997) are mainly made of Middle–Late Permian open-shelf carbonates. The Jabal Qamar unit includes a fragment of the pre-Middle Permian Basement (Rann, Ayim and Asfar formations; Pillevuit, 1993) overlain in unconformity by the late Early to early Middle Permian shallow-marine carbonate Qamar Formation with its quartz-sandstone basal member. The Baid unit is truncated at the base and is made of about 100 m of the Middle– Late Permian (Capitanian–Wuchiapingian) shallow-marine carbonate (Baid Formation; Béchennec, 1988; Pillevuit, 1993; Pillevuit et al., 1997; Baud et al., 2001b). The distal paleogeographic position of these Permian tilted blocks in regard to the Arabian Platform is documented by: (1) the differences in terms of facies (open marine with ammonoids) with those restricted to the others parts of the Oman Mountains (Al Jabal al-Akhdar, Saih Hatat and Musandam); and (2) the presence of reworked boulders originating from these isolated platforms in the calcirudites of the proximal units of the basinal Hawasina Nappes.