The lower boundary of the Toyonian stage (Cambrian) of the Siberian Platform

Publication year: 2011
Source: Russian Geology and Geophysics, Volume 52, Issue 7, July 2011, Pages 717-724

I.V., Korovnikov

The paper examines trilobite assemblages found in the Botomian–Toyonian (Lower Cambrian) boundary stratotype section in the middle reaches of the Lena River, Siberian Platform. It has been found that the trilobite assemblage from the Bergeroniellus ketemensis Zone (bottom of the Toyonian) is very much the same as that from the underlying Bergeroniaspis ornata Zone (terminal Botomian zone). It has been suggested to combine these zones into one with the index species Bergeroniaspis ornata. The greatest changes in the trilobite assemblages are observed at a higher stratigraphic level, at the bottom of the Lermontovia grandis Zone (second Toyonian zone). This suggests…