STABLE ISOTOPIC CALIBRATION OF THE EARLIEST SKELETAL FOSSIL ASSEMBLAGES IN EASTERN SIBERIA (PRECAMBRIAN-CAMBRIAN BOUNDARY)

Sections from the eastern margin of the Siberian Platform provide important reference sections for stable isotopic correlation of the newly defined Precambrian-Cambrian boundary level since they contain some of the earliest pre-Tommotian shelly fossil assemblages known, and are amenable to deltaC-13 stratigraphy. Stable isotopes are examined from the Dvortsy and Ulakhan-Sulugur sections (River Aldan), where sparse pre-Tommotian assemblages occur, and from the Uchur River region, where the putative Anabarites trisulcatus and Purella antiqua Zones of the Nemakit-Daldynian Stage are well-developed. Diagenetic resetting of delta-O-18 and deltaC-13 must be taken into account when comparing such sections. Simple corrections allow for stable isotopic correlation of basal Nemakit-Daldynian and Tommotian strata across eastern Siberia.