THE FRASNIAN-FAMENNIAN MASS EXTINCTION: UNDER THE VOLCANO BUT WITHOUT THE BURP
The other section is a marginal marine upper Kellwasser equivalent drilled in a scientific borehole at Sosnogorsk, near Ukhta, Komi Republic, Russia. This revealed a remarkably well preserved 8 m thick interval of unconsolidated grey mudstone which contains a pristine record of both organic and carbonate stable isotope data integrated with pyrite framboid diameters, %S, TOC, calcite % and palynology. The TOC and calcite content reveals a pattern of orbital forcing and hence a time framework. High resolution isotope results from the key interval shows 2 negative excursions in δ13Corg and a single excursion in δ13CCaCO3. This data, integrated with quantitative palynological counts and silt content enables us to identify a peak in fresh water runoff. Interpretation of the %S, pyrite framboid sizes and δ13CAOM enables us to identify incursions of euxinic water with a component of remineralised carbon. Metabolized by green sulphur bacteria then produces an excursion that could otherwise be interpreted as methane release from clathrates.