New Findings of Latest Early Olenekian (Early Triassic) Fossils in South Primorye, Russian Far East, and Their Stratigraphical Significance

Information on latest early Olenekian (latest Smithian) ammonoids is available apparently from only seven regions of the world, including South Primorye. Latest Smithian evidences on this topic are recorded from the West SMID (abbreviation from the Russian name of the quarry: Building Materials and Details), East SMID and Golyj Cape areas in South Primorye. This provides additional information on systematic composition of latest Smithian ammonoid, as well as conodont and brachiopod assemblages from the recently identified Shimanskyites shimanskyi Zone, located between lower Olenekian Anasibirites nevolini Zone and upper Olenekian Tirolites subcassianus Zone. There are many common ammonoid species in the Shimanskyites shimanskyi Zone and the underlying Anasibirites nevolini Zone, e.g., Prosphingitoides sp., Arctoceras septentrionale (Diener), Churkites syskoi Zakharov et Shigeta, Submeekoceras? subhhydaspis (Kiparisova), Prionites markevichi Zakharov et Smyshlyaeva, 'Anasibirites' simanenkoi Zakharov et Smyshlyaeva, Xenoceltites? subvariocostatus Zakharov et Smyshlyaeva, and Mianwaliites zimini Zakharov et Smyshlyaeva. The base of the Shimanskyites shimanskyi Zone, marked by a negative delta C-13(org) excursion in the Kamenushka-2 Section by our previous study, coincides with the FO (first occurrence) of ammonoids Shimanskyites shimanskyi Zakharov et Smyshlyaeva and Glyptophiceras cf. sinuatum (Waagen) and conodont Hindeodella budurovi Buryi. This zone is characterized additionally by some fossils common for the overlying upper Olenekian Tirolites subcassianus Zone: ammonoids of the genus Kamenushkaites, brachiopods Bittnerihyris margaritovi (Bittner) and Lepismatina sp. and conodont 'Neogondolella' (=?Borinella) jubata Sweet. The latest Smithian ammonoids recorded from the Shimanskyites shimanskyi Zone totally consist of 30 taxa belonging to 11 families (Sageceratidae, Ussuiriidae, Aspenitidae, Paranannitidae, Arctoceratidae, Proptychitidae, ?Galfetitidae, Prionitidae, ?Kashmiritidae, Xenoceltitidae and Palaeophyllitidae). The problems of global correlation of uppermost Smithian strata are also discussed.

Automated summary

Information on the latest early Olenekian (latest Smithian) ammonoids is primarily available from seven regions worldwide, including South Primorye. Evidence of the latest Smithian period is recorded in areas such as West SMID, East SMID, and Golyj Cape in South Primorye, providing additional data on systematic composition and assemblages within the Shimanskyites shimanskyi Zone.