Testing geochemical proxy relationships under variable paleo-seawater chemical compositions

Columbia University, New York NY

Investigators

Abstract

The application of proxies to paleoceanographic reconstructions relies on calibrations that may be sensitive to changes in the ocean's chemistry (e.g., elemental abundances, isotopic composition). This project, led by a faculty member at Columbia University's Lamont Doherty Earth Observatory, will test the assumption that the sensitivity of paleo-proxies has remained constant as ocean chemistry has changed over time. Planktonic foraminifera, a common paleo-proxy archive, will be cultured in the laboratory under a range of seawater chemistries representing changing ocean conditions from the Eocene to the Cretaceous (~50 to 100 million years before present). The effects of these changing conditions will be assessed for several proxies, including stable oxygen and carbon isotopes and the B/Ca proxy for seawater carbonate chemistry. Complementary studies will examine the association and photosynthetic activity of symbiotic algae, which also affect chemical proxy composition in foraminifera shells. This research will advance our capacity to quantify past changes in ocean and climate, and thereby to understand potential for future changes. Funding supports a variety of education, outreach, and service activities. One graduate and one undergraduate student from the U.S. will be involved in the project, and two graduate students from Australia will also contribute. In addition, two high school students from the Young Women's Leadership School in East Harlem, New York City, will participate in the culturing program.