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[BPT05-24] Earth system feedbacks statistically extracted from the Indian Ocean deep-sea sediments during the early Eocene hyperthermals
Keywords:deep-sea sediment, Indian Ocean, climate change, Eocene hyperthermals, Independent Component Analysis, multivariate analysis
Here we have constructed a comprehensive geochemical data set including major- and trace-element contents, δ13C, and CaCO3 contents of 250 bulk sediment samples taken from ODP Sites 752 and 738, located in the southeastern Indian Ocean and the Indian sector of the Southern Ocean, respectively. The analytical results show that the sediments of these cores record multiple carbon isotope excursions and reductions of carbonate contents, probably corresponding to the PETM and the early Eocene hyperthermals including the Eocene Thermal Maximum 2 (ETM2), H2 and I1/I2 events, and ETM3. We applied Independent Component Analysis to the high-dimensional compositional data matrix, and extracted four geochemical independent components that collectively account for 85.6% of the total sample variance. One of the components involving Ba content and δ13C indicates a signature of a negative feedback in Earth system that efficiently sequestered the excess carbon in recovery phases of the hyperthermals.