Nitrogen and Carbon Isotope Data of Olenekian to Anisian Deposits from Kamenushka/South Primorye, Far-Eastern Russia and Their Palaeoenvironmental Significance

The Kamenushka Formation, exposed in the northern part of South Primorye (Kamenushka-1 and Kamenushka-2 sections), is one of the few localities in the world with richly fossiliferous Lower–Upper Olenekian sedimentary successions. Lower to Middle Triassic ammonoid-, brachiopod- and conodont-bearing silty-clayey deposits of the Kamenushka-1 and Kamenushka-2 sections have been isotope-geochemically investigated in detail. As a result, these sections, together with the previously investigated Abrek Section, exposed in the southern part of South Primorye, provide almost complete 15 N org - and 13 C org - records for the Lower Triassic of this region. Nine N-isotope intervals and the five negative C-isotope excursions, reflecting, apparently, unstable climatic and hydrological conditions, have been distinguished in the Lower Triassic of South Primorye. On the basis of the new C-isotope data the Mesohedenstroemia bosphorensis Zone (upper part), Shimanskyites shimanskyi and Neocolumbites insignis zones of South Primorye are correlated now with the Lower Smithian part of the Yinkeng Formation, the Upper Smithian part of the Helongshan Formation and the Middle Spathian part of the Nanlinghu Formation in South China, respectively, as has been observed in the Abrek, Kamenushka-2, West Pingdingshan and Majiashan sections.