Ediacaran oxidation and biotic evolution - Reply

Calver and Grey point out the difficulties of relating the Australian acritarch record to the global record of environmental change. This results from the lack of documented stratigraphic sections that have overlapping chronologies of both acritarch evolution and global chemostratigraphic proxies, such as δ^(13)C_(carb), and we agree that coupled records are required to confirm our hypothesis. Until such records exist, any correlations between Australian acritarch-bearing strata and strata containing records of global secular variations in δ^(13)C_(carb), are necessarily tenuous. This uncertainty, however, does not affect the principal conclusion of our paper, which emphasizes the evidence for sequential chemical oxidation of the Ediacaran ocean. Our inferred correlation between chemical oxidation and biological evolution is supported by subsequent results on strata containing strong geochronologic tie-points and a robust biostratigraphic and chemostratigraphic record.