NEW RE-OS AGES FROM THE NEOPROTEROZOIC HECLA HOEK SUCCESSION, SVALBARD, NORWAY

The Tonian-Ediacaran lower and middle Hecla Hoek succession of Svalbard, Norway represents one of the most complete and well preserved Neoproterozoic sedimentary successions worldwide. With diverse fossil assemblages, an extensive carbonate δ¹³C record, and sedimentary evidence for two distinct Cryogenian glaciations, this succession has the potential to yield profound insights into the Neoproterozoic Earth system; however, at present there are no radiometric age constraints for these strata. Current correlation schemes across northeastern Svalbard, as well as to Neoproterozoic successions globally, rely upon litho- and chemostratigraphic records.

Here we present the first direct radiometric age constraints from the Hecla Hoek succession. Two new Re-Os ages and initial Os values tightly constrain the age of Neoproterozoic glaciation in Svalbard and provide insight into pre- and post-glacial weathering regimes. An age from the Russøya Member (Elbobreen Formation) facilitates correlation of the negative carbon isotope excursion recorded therein with the pre-glacial Islay anomaly of the Callison Lake Formation (Windermere Supergroup) in Northwest Canada and the Didikama and Matheos formations (Tambien Group) in Ethiopia. Vase-shaped microfossils from this same member can now also be allied to global records with pre-Cryogenian biostratigraphic significance. These results solidify global chemo- and biostratigraphic correlations for the late Tonian Period and lay the groundwork for assessing the synchroneity of biogeochemical cycle perturbations during this interval. In addition, these new age constraints provide a unique opportunity to construct a temporally-calibrated geochemical, biological, and geological framework to assess the timing and triggers of early eukaryotic evolution and the most extreme climatic changes in Earth history.