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THE REGIONAL STRATIGRAPHIC CHART FOR THE ORDOVICIAN OF THE WESTERN PART ALTAI-SAYAN FOLDED AREA (NEW VERSION)

N. V. Sennikov 1, 2, O. T. Obut 1, 2, N. G. Izokh 1, T. P. Kipriyanova 1, E. V. Lykova 1, T. Yu. Tolmacheva 3, R. A. Khabibulina 1

1 Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia; 2 Novosibirsk National State Research University, Novosibirsk, Russia; 3 A. P. Karpinsky Russian Geological Research Institute, St. Petersburg, Russia

A new version of the Regional stratigraphic chart for the Ordovician of the western part of Altai-Sayan Folded Area and the explanatory note, compiled in accordance with the Russian Stratigraphic Code, introduce changes, additional and specified data in comparison with the previous (third edition) chart. The old version of the chart was approved by the Interdepartmental stratigraphic meeting held at Novosibirsk in 1979 and later validated by the USSR Interdepartmental Stratigraphic Committee as the official stratigraphic base for all types of the regional geologic activities. Since 1979 meeting, the stages of the Ordovician chart were changed completely. Instead of the traditional British stages (Tremadocian, Arenigian, Llanvirnian, Landeilian, Caradocian, Ashgillian) the following unites were adopted by the International Stratigraphic Chart and later by the Russian General Stratigraphic Charts – Tremadocian, Floian, Dapingian, Darriwillian, Sandbian, Katian, and Hirnantian. Volumes of the lower, middle and upper series were also changed. For the presented version of the Ordovician stratigraphic chart for the western part of the Altai-Sayan Folded Area, the new standard Ordovician stages and new volumes for series were used. All stages boundaries of the International and General Stratigraphic Charts are defined by the Global Stratotype Section and Points (GSSP) based on the first occurrences of the certain graptolite or conodont zones index-species. In accordance to this for the western part of the Altai-Sayan Folded Area by first appearance of same-name graptolite or conodont zones index-species (GSSP’s marker-species for the lower boundaries) in the certain sections, we were able to fix stratigraphic position of the lower boundaries for the following stages: Tremadocian, Floian, Darriwillian, Sandbian, Katian and Hirnantian. 

Keywords: Altai-Sayan Folded Area, Ordovician, Regional stratigraphic chart, explanatory note.