50 Myr recovery from the largest negative δ13C excursion in the Ediacaran ocean

Sedimentary rocks deposited during the Ediacaran period (similar to 630-542 Ma) contain carbonates whose carbon isotopic ratios show a marked negative excursion consisting of a precipitous drop from +5 parts per thousand to -12 parts per thousand, followed by a sub-linear recovery to positive delta C-13 values. Isotopic ages (U/Pb) and thermal subsidence modelling are combined to constrain the excursion in time and indicate an onset at similar to 600 Ma, and duration of recovery of approximately 50 Myr. The excursion is widely recognized in Oman and has potential correlatives in Ediacaran strata elsewhere, and may thus represent a characteristic feature of the Ediacaran period. The amplitude of this carbon isotope excursion far exceeds those of other Neoproterozoic anomalies. The isotopic trend of negative excursion and long-term recovery spanned at least one short-lived glacial episode (at 580 Ma), but appears unrelated to glaciation, which indicates that negative anomalies in the Neoproterozoic marine carbon isotope record are not directly or uniquely linked to ice ages.