BIOSTRATIGRAPHIC SCHEME OF THE CARNIAN AND LOWER NORIAN IN NE RUSSIA. PAPER 2. NEW ZONAL SCALES AND CORRELATION

Abstract

New detailed zonal scales for the Carnian and Lower Norian in northeast Russia are suggested. On the basis of ammonoids, the following have been distinguished in the Lower Carnian: Stolleyites tenuis zone, beds with Neosirenites aculeatus, the zones "Protrachyceras" omkutchanicum, Yanosirenites buralkitensis, Neoprotrachyceras seimkanense and Neosirenites armiger; in the Upper Carnian, the zones Yakutosirenites pentastichus, Sirenites yakutensis and Striatosirenites kedonensis; in the Lower Norian, the zones Striatosirenites kinasovi and Pinacoceras verchojanicum. The last zone comprises beds with Norosirenites nelgehensis and beds with N. obrucevi. Nautiloids aided division of the Carnian into the zones Proclydonautilus anianiensis, Cosmonautilus polaris (with the subzones Cosmonautilus polaris and Proclydonautilus goniatites) and Proclydonautilus pseudoseimkanensis. In the Lower Norian the zone Proclydonautilus seimkanensis has been distinguished, which is divided into the subzones P. spirolobus and P. seimkanensis. A description of biostratons is offered, and correlation of ammonoid and nautiloid scales are given. Correlation was made of the Carnian and Lower Norian in NE Russia, Svalbard, Arctic Canada, British Columbia, and Eastern Alps. The position the Carnian-Norian boundary in NE Russia in the base of the kinasovi zone is substantiated by the presence of ammonoids in the zone Striatosirenites kinasovi, which are also common in the zone Stikinoceras kerri in British Columbia.