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Figure R4 : Stratigraphic sketch of the Rustaq section 2 (modified from Pillevuit et al., 1997) with the ammonoid distribution.
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Citations
... Chen et al. Earth-Science Reviews xxx (xxxx) xxx-xxx Uncited references Baud et al., 2010Buser et al., 2007Chen and Lukeneder, 2017Orchard and Bucher, 1992Patterson and Walter, 1994Richoz et al., 2004Richoz et al., 2005Vennemann et al., 2002 ...
Three small-scale extinctions occurred in the Early Triassic with one of them recognized close to the Smithian-Spathian boundary. In the last two decades, the end-Permian mass extinction as well as the subsequent recovery have been intensively studied throughout the Tethys region, but correlations within the Lower Triassic are difficult due to conodonts endemism. Here we use paleontological and geochemical methods to document a high-resolution biostratigraphy of the Smithian-Spathian boundary interval from two sections of Oman. In combination with previously published data from both South-Central Europe and South China, a quantitative stratigraphic correlation has been achieved with 7 conodont UA Zones recognized using the unitary association method. Based on conodonts and carbonate carbon isotope data, the Smithian-Spathian boundary is identified in the interval from UAZ4 to UAZ5 close to the last occurrence of Nv. pingdingshanensis in Oman and South China, and within the range of P. inclinata, Ns. planus, Pl. regularis, and Pl. corniger in South-Central Europe. UAZ7 fauna displays a clear diachronism as it starts from South China, arrives a bit later in Oman and even later in western Tethys. Foliella gardenae and Icriospathodus zaksi are reported from Oman for the first time and thus expand the geographical distribution of these rarely reported species.
... The Permian-Triassic boundary interval is marked by laminated microbialitesstromatolites as characteristic disaster or anachronistic biota indicating the presence of worldwide stressful conditions around the PTB (Lehrman, 1999;Kershaw et al., 1999Kershaw et al., , 2002Baud et al., 2005;Richoz et al., 2005). Alternation of laminae represents exchanging of conditions that favor microbial growth (sphere clusters and threads) and accumulations of detrital calcitic component (microsparitic calcite, fine-grained bioclasts, peloids and microspheres). ...
... The microbial type limestone found in the PTB interval of the Masore I (Bende) section represents the first discovery of this distinct PTB related lithofacies in the Dinarid branch of the western Paleotethys (Fig. 5). Microbialitesstromatolites occurred at the very beginning of the Early Triassic in many sections of different regions of the Paleotethys as characteristic disaster or anachronistic microfacies pointing to stressful conditions around the PTB transition (e.g., Kershaw et al., 1999Kershaw et al., , 2002Lehrman, 1999;Baud et al., 2005;Richoz et al., 2005;Hips and Haas, 2006;Haas et al., 2007). In the previously studied Lukač section where the PTB has been identified (Kolar-Jurkovšek et al., 2011a), no microbial facies were found, but rather shallow subtidal and evaporite types of sedimentation occurred in the transitional interval. ...
... They provide a unique window to investigate the history of photosynthesis, evolution of the early atmosphere and microbe-environment interactions through geological time (Awramik 1992(Awramik , 2006Kah and Riding 2007;Kershaw et al. 2007Kershaw et al. , 2009Kershaw et al. , 2012Noffke and Awramik 2013). Early Triassic stromatolites have been reported from around the world (Schubert and Bottjer 1992;Sano and Nakashima 1997;Richoz et al. 2005;Hips and Haas 2006;Pruss et al. 2006;Farabegoli et al. 2007;Kershaw et al. 2011;Chen et al. , 2014Mata and Bottjer 2012) and are major components of post-extinction microbialites. Resurgence of microbial communities occurred throughout the entire Early Triassic recovery interval, during that time there were at least four major events of high microbialite abundance (Baud et al. 2007). ...
An Early Triassic stromatolitic deposit is documented in the Dienerian succession of the Lower Triassic Feixianguan Formation in the Xingyi area, Guizhou, southwest China. Five types of constructional microbial forms at various scales were observed. (1) Typical stratified columnar structures, up to 25 cm in height, with crinkled laminae. Dark-coloured laminae, 1 mm thick, are composed of upright filamentous tubes, average diameter 5 µm, showing a vertical growth fabric. (2) Prostrate filaments showing strong fluorescence, in sharp contrast to the micritic cement. (3) Coccoid-like spheroids and algal filaments are also common in stromatolitic laminae. These resemble present-day cyanobacteria, and thus may represent fossilized cyanobacteria. (4) Smaller bacilli resembling Pelodictyon are very common in the stromatolitic laminae. (5) Framboidal pyrite is also abundant and probably indicates biological involvement in stromatolite formation. Two major microbial functional groups, oxygenic phototrophs represented by lithified cyanobacteria and probable sulfate-reducing bacteria represented by framboidal pyrite, were present during stromatolite growth. Another possible microbial functional group, anoxygenic phototrophs represented by lithified remains resembling Pelodictyon clathratiforme, may be present in the Xingyi stromatolites, and were involved in stromatolite formation by capturing or adhering microcrystalline particles. All of these features demonstrate that the Early Triassic stromatolites are biogenic. The occurrence of the Xingyi stromatolites, corresponding to a second episode of microbial growth during the Early Triassic, reveals that post-extinction microbialites were widespread in the Dienerian. These Early Triassic stromatolites indicate that a microbial bloom took place in the aftermath of the Permian–Triassic mass extinction.
... Many attempts have been undertaken on documenting environmental and paleoecologic aspects of Lower Triassic microbialites (Schubert and Bottjer, 1992;Sano and Nakashima, 1997;Lehrmann, 1999;Ezaki et al., 2003Ezaki et al., , 2008Ezaki et al., , 2012Adachi et al., 2004;Richoz et al., 2005;Wang et al., 2005;Pruss et al., 2006;Hips and Haas, 2006;Baud et al., 2007;Farabegoli et al., 2007;Kershaw et al., 2007Kershaw et al., , 2011Kershaw et al., , 2012Woods and Baud, 2008;Mary and Woods, 2008;Bottjer, 2011, 2012;Yang et al., 2011;Chen et al., 2014;Wu et al., 2014). However, studies concerning geobiologic features and accretion process of those microbial deposits are largely lagging, although some attempts have been undertaken in the past decade (Ezaki et al., 2003(Ezaki et al., , 2008(Ezaki et al., , 2012Yang et al., 2011;Chen et al., 2014;Wu et al., 2014). ...
Widespread stromatolites and other microbialite deposits characterize Lower Triassic marine successions worldwide. This study documents a stromatolite deposit, 1.1. m thick, from the upper Spathian (Lower Triassic) of the Susong area, South China. The stromatolite comprises distinct laminated domes in the basal part and columns at the upper part. Dark laminae are loosely spaced and interlayered with thicker light colored laminae. Diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures, and yield copies of bacteria clump-like and coccoid-like spheroid aggregates. The former are characterized by cloudy, micrite nuclei rimmed by coarse-grained, euhedral sparry calcite crystals, while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes. The cloudy, micrite nuclei resemble bacteria clump-like structures observed in present-day travertine. Both the coccoid-like spheroids and bacteria clump-like structures are surrounded by coarse-grained euhedral calcite crystals, suggesting a similar accretion mechanism. Both spherical structures therefore could be crucial in the accretion of the Susong stromatolite. The laminated/microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes. Micro-analysis also unravels the common occurrence of authigenic micro-quartz crystals in association with Fe-bearing illite clay minerals in the stromatolite columns. Their coalescing nature with each other, together with the associated pyrite grains, strongly support the formation of micro-quartz crystals from microbial reduction of an Fe-bearing smectite precursor by sulfate reducing bacteria. A comparison of the Susong stromatolite with its counterparts from the upper Lower Triassic strata in Dajiang, South China reveals many similarities in stromatolite microstructures, suggesting that a harsh, euxinic-anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest Spathian in South China.
... These criteria for identifying the " upper SMB position " , when not overshadowed by faults, are recognised in all the wadis, and can be mapped along the entire northern side of Al Jabal al-Akhdar, and in Wadi Mu'aydin (Figure 1). This position was adopted in the geological maps of Al Jabal al-Akhdar (Rabu et al., 1986; Villey et al. 1986; Beurrier et al., 1986), and several papers, theses, and field guides (Coy, 1997Coy, , 2004 Atudorei, 1999; Richoz, 2001, 2005; Baud et al., 2010; Richoz et al., 2005 Richoz et al., , 2010 Richoz, 2006) (Figure 2 andTable 1). In Al Jabal al-Akhdar the " upper SMB position " has been dated by chemostratigraphy between the end of the Griesbachian to mid-Dienerian (Richoz, 2006), in the late Induan Age of the Early Triassic. ...
This note discusses the lithostratigraphic nomenclature used to characterise the Permian–Triassic transition at outcrop in the Oman Mountains, with emphasis on the position of the boundary between the Saiq and Mahil formations. Two inconsistent criteria for picking the Saiq/Mahil Boundary (SMB) prevail in the literature causing confusion regarding the correct position of the Permian/Triassic Boundary (PTB). The position of the PTB plays a central role in the correlation of these two formations from outcrop to the subsurface Khuff and overlying Sudair formations.
The Khuff Formation contains one of the world’s greatest reserves of non-associated gas, and
its outcrop equivalent in the Oman Mountains is increasingly being studied for the purposes of
regional correlations, reservoir characterisation and exploration. Therefore an agreement on the
position of the SMB is a pre-requisite for precise communication among geoscientists. In this note we review the historical source of the confusion and recommend applying stratigraphic rules to resolve the position of the Saiq/Mahil Boundary (SMB).
... The Middle Permian–Lower Triassic Khuff and correlative formations in the Arabian Plate consist mainly of carbonates and evaporites that attain a thickness of more than 1,000 m (Al-Jallal, 1995; Sharland et al., 2001). The formations overlie terrestrial clastics typified by the Gharif Formation of Oman, and their lower boundaries represent the start of the regional transgression of the " Fusulinid Sea " over many parts of the Arabian Plate (Montenat et al., 1976; Le Métour, 1987; Baud et al., 2001a, b; Osterloff et al., 2004; Richoz et al., 2005;, see references therein,Figure 1). The formations are overlain by the basal shales of the Lower Triassic Sudair Formation in Saudi Arabia (Manivit et al., 1983) and Oman (Osterloff et al., 2004; Forbes et al., 2010), and correlative rock units elsewhere in the Arabian Plate (Figure 2). ...
The Middle Permian (Guadalupian), Upper Permian (Lopingian) and Lower Triassic Khuff and correlative formations in the Arabian Plate consist of six “third-order” sequences, from oldest to youngest KS6 to KS1, and at least 45 “fourth-order” sequences. They are here dated using biostratigraphic constraints and correlated to two independent sequence-stratigraphic time scales: (1) global sequences calibrated in the Geological Time Scale GTS 2012; and (2) orbital-forcing glacio-eustatic sequences that track the 0.405 million year (Myr) orbital eccentricity signal in the M&H-2010 scale (Matthews and Al-Husseini, 2010). The chronostratigraphic calibration of the Khuff sequences provides a reference section and common nomenclature that can be used for regional and global correlations. It permits positioning the hydrocarbon reservoirs of the Khuff and equivalent formations in a sequence-stratigraphic framework that can be used in exploration and reservoir characterization.
The lower sequence boundary of the Khuff Formation (Khuff SB) is correlated to global Wordian SB Wor1 near the Roadian/Wordian Boundary at 268.8 ± 0.5 Ma, and correlative SB 19C at 268.9 Ma in the M&H-2010 scale. The upper sequence boundary of the Khuff Formation with the overlying Sudair Formation (Sudair SB) is correlated to Olenekian SB Ole1 near the Induan/Olenekian Boundary at 250.0 ± 0.5 Ma, and correlative SB 17 at 249.5 Ma in the M&H-2010 scale. These calibrations imply the Khuff was deposited in about 19.4 Myr, and consists of 48 “stratons”; i.e. transgressive-regressive (T-R) depositional subsequences with an average duration of 0.405 Myr corresponding to long-eccentricity orbital cycles 664 to 617. The 48 stratons are predicted to form four “dozons” (19C, 18A, 18B and 18C), each consisting of 12 stratons. Individual dozons lasted 4.86 Myr and are separated by regional sequence boundaries (SB 19C to SB 17A).
In Oman, Khuff Sequence KS6 on the Saiq Plateau is correlated to the subsurface Lower Khuff Member, and both are interpreted to consist of 12 subsequences that are correlated to stratons 664–653 forming Dozon 19C between 268.9–264.0 Ma. KS6 is correlated to the four global sequences Wordian Wor1 to Capitanian Cap1 dated between 268.8–264.0 Ma in GTS 2012. Khuff Sequence KS5 corresponds to the Middle Khuff Member up to the top of Middle Khuff Anhydrite in subsurface Oman. On the Saiq Plateau, KS5 potentially consists of 12 cycle sets (Koehrer et al., 2010) that are correlated to stratons 652–641 of Dozon 18A, between 264.0–259.2 Ma. It is correlated to global sequences Capitanian Cap2 and Cap3 dated between 264.0–259.8 Ma in GTS 2012. Khuff Sequence KS4 consists of 11 cycle sets on the Saiq Plateau and other localities in Al Jabal al-Akhdar in Oman (Koehrer et al., 2010, 2012). It is assumed that one cycle set remains unidentified in KS4, completing its correlation to stratons 640–629 of Dozon 18B between 259.2–254.3 Ma. KS4 correlates to the global sequences Wuchiapingian Wuc1 and Wuc2 dated between 259.8–254.2 in GTS 2012. Khuff sequences KS3, KS2 and KS1 combined consist of 10 cycle sets in Al Jabal al-Akhdar (Koehrer et al., 2010, 2012), and two are presumed unidentified so as to correlate to the 12 stratons 628–617 of Dozon 18C between 254.3–249.5 Ma. Sequence KS3 correlates to Changhsingian global sequences Cha1 and Cha2 dated between 254.2–252.5, and KS2 and KS1 to latest Permian–Early Triassic global sequences Cha 3 and Induan–Olenekian Ind1 dated between 252.5–249.9 Ma in GTS 2012. The Permian/Triassic Boundary (PTB), dated at 252.2 ± 0.5 Ma in GTS 2012, occurs in lowermost Khuff Sequence KS2, in cycle set KCS 2.3, and based on the orbital calibration of the Upper Permian (Lopingian) Series in South China, it occurs in Straton 623 between 252.3 and 251.9 Ma.
... 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(Baud et al., , b, 2005Richoz 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. 1998Angiolini et al. , 2003. ...
... Near Nahkl the volcanic series includes blocks of Middle Permian shallow-marine carbonate and is overlain by pelagic limestone (Weidlich, 2007). In the Rustaq area the volcanic succession is also capped by a condensed carbonate sequence (Hallstatt facies type) dated as Middle Permian (Wordian; Blendinger et al., 1992;Pillevuit et al., 1997;Baud et al. 2001b;Richoz et al., 2005). ...
... During the Dienerian, part of the margin was affected by a renewed extensional regime, tilting and drowning resulting in erosive deposition and accumulation of carbonate breccia (Unit C2 of the Saiq Formation) followed in the Al Jabal al-Akhdar by high-energy, partly oolitic dolomitized shallow-water deposits, Dienerian in age (Unit C3) and renewed breccias (Unit C4). The Saiq-Mahil transition (correlated with the Khuff-Sudair transition) is probably of late Induan age (chemostratigraphical correlations; Richoz, 2006 (Watts, 1985;Baud et al., 2001b;Richoz et al., 2005;Richoz, 2006). ...
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).
... A 1 m-thick stromatolite bed is described from slope deposits in the Maqam area . Baud et al. (2001), Richoz et al. (2005) and Baud & Bernecker (2010) reported and illustrated a 20-cm-thick laminated bed, interpreted as stromatolite, just above the main carbon isotope negative shift and within the parvus zone. However, the stromatolite fabrics are dolomitised and a microbial origin is not confirmed. ...
Permian-Triassic boundary microbialites (PTBMs) are thin (0.05-15 m) carbonates formed after the end-Permian mass extinction. They comprise Renalcis-group calcimicrobes, microbially mediated micrite, presumed inorganic micrite, calcite cement (some may be microbially influenced) and shelly faunas. PTBMs are abundant in low-latitude shallow-marine carbonate shelves in central Tethyan continents but are rare in higher latitudes, likely inhibited by clastic supply on Pangaea margins. PTBMs occupied broadly similar environments to Late Permian reefs in Tethys, but extended into deeper waters. Late Permian reefs are also rich in microbes (and cements), so post-extinction seawater carbonate saturation was likely similar to the Late Permian. However, PTBMs lack widespread abundant inorganic carbonate cement fans, so a previous interpretation that anoxic bicarbonate-rich water upwelled to rapidly increase carbonate saturation of shallow seawater, post-extinction, is problematic. Preliminary pyrite framboid evidence shows anoxia in PTBM facies, but interbedded shelly faunas indicate oxygenated water, perhaps there was short-term pulsing of normally saturated anoxic water from the oxygen-minimum zone to surface waters. In Tethys, PTBMs show geographic variations: (i) in south China, PTBMs are mostly thrombolites in open shelf settings, largely recrystallised, with remnant structure of Renalcis-group calcimicrobes; (ii) in south Turkey, in shallow waters, stromatolites and thrombolites, lacking calcimicrobes, are interbedded, likely depth-controlled; and (iii) in the Middle East, especially Iran, stromatolites and thrombolites (calcimicrobes uncommon) occur in different sites on open shelves, where controls are unclear. Thus, PTBMs were under more complex control than previously portrayed, with local facies control playing a significant role in their structure and composition.
... Carbonate ooids are widely distributed in the Lower Triassic of the Tethys Ocean region, including in southern Austria ( Krainer and Vachard, 2009), Germany (Weidlich, 2007), Hungary ( Hips and Haas, 2006), northern Italy ( Baud et al., 1997;Fraiser et al., 2005), Turkey ( Baud et al., 1989;Kershaw et al., 2010), Iran ( Gaetani et al., 2009), and Oman ( Richoz et al., 2005). In the eastern Tethys, the peri-equatorial South China Craton also developed extensive carbonate ooid deposits fol- lowing the end-Permian mass extinction (Fig. 1A). ...
... The base of slope deposits of the Arabian Platform (Maqam Formation, Sumeini Group) also recorded tectonic inquiescence during the deposition of Changhsingian cherty limestone with sponges, bryozoans and crinoids. The Permian–Triassic boundary interval is a silicified hardground, overlain by a sequence comprising yellow shale, Griesbachian–Dienerian thin bedded platy limestone and debris flows (basal Maqam C), a 7 m thick unit of Lower Smithian vermicular (intensely bioturbated) limestone and middle to upper Smithian platy limestone, debris flows and calciturbidites (Watts, 1987; Richoz et al., 2005). ...
Sedimentological, palaeontological, and geochemical data of a 152-m thick composite section of the Saiq Formation were used to describe the facies associations and the nature of carbonate precipitation during the Late Permian–Early Triassic at the eastern rim of the Arabian Platform (Sultanate of Oman, Saih Hatat, Wadi Aday). Changhsingian (Late Permian) platform carbonates, dominated by bryozoans, brachiopods and crinoids, are truncated by a mineralized discontinuity surface. The disappearance of Permian calcified metazoans, a negative δ13Ccarb excursion, and a sharp facies contrast collectively suggest that the Permian–Triassic boundary lies in this interval. Unfossiliferous siliciclastics with nodules of iron and manganese minerals on top of the unconformity were probably deposited during a phase when sea water was undersaturated with respect to calcium carbonate. After a gap, late Dienerian carbonate deposition started with abiotically precipitated lime mudstone and biotically induced microbialites having the lowest observed δ13Ccarb values (facies association A). Further up, 1–2 m of bioclastic wacke- and grainstones with a positive δ13Ccarb excursion indicate a short-lived interval of biotically controlled carbonate precipitation (facies association B). The overlying sequence of siliciclastics, laminated or bioturbated dolomitized mudstone, microbialites, dolomitic siltstone, and black calcite, which is characterized by a 2nd negative δ13Ccarb shift, marks the return to biotically induced carbonate precipitation (facies associations C–D). The recrystallized black calcite at the top of the sequence is capped by a thick palaeosol and overlain by late Early to Middle Triassic cycles consisting of biotically precipitated carbonate. The facies development of the rim of the Arabian Platform differs from that of the interior in having a pronounced discontinuity at the Permian–Triassic boundary and an Early Triassic bioclastic carbonate unit sandwiched between abiotically precipitated carbonates. The observed lateral changes in carbonate precipitation across the Arabian Platform could have been caused by changes in oceanic circulation, such as episodic upwelling of deep water.
