Institute of Geological and Nuclear Sciences, New Zealand

Extreme global warming and massive input of (super 13) C-depleted carbon into the exogenic carbon cycle characterize the Paleocene-Eocene thermal maximum (PETM) circa 55.5 Ma. Previous work indicates that dissolved O (sub 2) concentrations dropped in some regions of the ocean during this event, but spatial, temporal, and causal relationships between warming, carbon input, and O (sub 2) deficiency remain elusive. We present lithologic, carbon isotopic, and trace fossil results from outcrops in New Zealand that clarify this issue. Sections exposed at Mead and Dee Streams in eastern Marlborough, South Island, contain expanded sedimentary intervals that were deposited before, during, and after the PETM on an upper continental slope. The PETM in these intervals is characterized by enhanced siliciclastic deposition, a hallmark negative carbon isotope excursion, and a loss of bioturbation. Importantly, however, the latter only occurs during the prominent drop in delta (super 13) C and not during its recovery. Our results suggest that South Pacific intermediate waters became hypoxic coincident to carbon injection at the start of the PETM. While higher sea surface temperatures throughout the PETM would have decreased the dissolved oxygen content of sinking surface waters, we argue here that oxygen depletion was driven by some combination of elevated temperature, water column stratification, and intermediate water methane oxidation.