CONCLUSIONS

Whereas preliminary Ba2+ data suggest that the P/E boundary is characterized by elevated productivity, a CaCO3 hiatus would argue just the opposite: a decrease in productivity. At the same time, biogenic silica and C-org data reflect no change in productivity at Site 1221 at the P/E boundary. The three conflicting arguments might be resolved by accounting for a methane hydrate release as suggested by Dickens et al. (1995). Based upon biogenic silica and C-org data, productivity did not decline or increase at the P/E boundary. Oxidation of methane could have resulted in dissolution of CaCO3, while hydrate dissociation released dissolved Ba2+.

Site 1221 was not anoxic at the P/E boundary, as there was no increase in C-org. Although C-org can degrade in anoxic environments, the presence of high Mn2+ suggests that this was not the case.

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