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 δ¹³C 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 δ¹⁸O and δ¹³C 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.