The Cretaceous/Tertiary Boundary: Deep-sea Benthic Foraminifera and the Cceanic Carbon Cycle

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This proposal seeks to investigate whether the generally accepted concept of collapse of primary productivity or the biotic pump at the Cretaceous/Tertiary extinction boundary can be supported. The hypothesis poses the question 'Why do deep-sea benthic foraminifera, which were one of the few groups of organisms that provides information on deep-sea ecosystems, not show significant extinction and only relatively minor transient changes given that these organisms rely on a flux of organic matter from the surface to survive'? The proposal hypothesizes that the carbon isotope record across the extinction may not be well understood and be much more complex than generally accepted. Furthermore, the record could have components of productivity collapse, addition of (at least in part) isotopically light carbon to the ocean-atmosphere system, and regional upwelling resulting in massive plankton blooms in a highly unstable environment, persisting for several hundred thousands of years. The PI proposes to investigate benthic foraminiferal assemblage composition, diversity and accumulation rates at high time resolution at various depths and in various oceans, and compare these data with carbon isotope gradients, as well as information on the floral composition of nanoplankton and planktonic foraminifera obtained on the same samples, in order to identify regional and global components of the global carbon cycle. The Broader Impacts include the dissemination of information for society to understand and evaluate possible effects of past major environmental disturbances on ocean ecosystems and the use of this information in teaching materials for middle and high school science teachers.