Arkarua

Abstract: New Ediacara-type macrofossils are described from the Irkineeva Uplift of East Siberia, Russia. Preliminary field studies within the Taseeva Group reveal probable examples of the Ediacaran taxa Arkarua adami and Beltanelliformis minutae; the organo-sedimentary structure 'Arumberia'; and 'elephant skin' microbial mat fabrics. These impressions are consistent with a latest Ediacaran age for the units of the upper Taseeva Group, suggesting that they are tens of millions of years younger than has previously been reported. Large discoidal specimens from the upper part of the Sukhoy Pit Group, likely to be Middle Riphean (Mesoproterozoic) in age, are tentatively assigned to the taxon Nimbia occlusa, and are suggested to be microbial in origin. These discs, and a contemporaneous acritarch assemblage of long-ranging sphaeromorphic taxa, cannot be precisely geochronologically constrained at present, but are highly likely to be pre-Ediacaran in age. The Irkineeva finds supplement a diverse suite of Russian Ediacaran (Vendian) fossil localities, and may be of considerable importance in correlating disparate Meso- and Neoproterozoic stratigraphic units across the Siberian Platform. This report emphasises the largely unexplored potential of the Irkineeva Uplift for palaeontological study, and provides tantalising evidence for the preservation of Late Ediacaran macro-organisms in this region.