CAREER : A Research and Education Plan in Global Biogeochemical Cycles: Seawater Calcium Isotopes and Carbonate Deposition History

Paytan

Abstract

Funds are provided for a study of Ca concentrations and Ca isotopes in marine barite to study global biogeochemical cycles back to the last glacial maximum, and then use this data to better understand the Ca cycle and CaCO3 depositional history in the oceans and to ultimately relate them to tectonic and climate changes. This will be a two-part investigation. First, the calcium isotopic composition (delta 44Ca values) of barite in box core-tops will be compared with the known constant delta 44Ca of modern seawater to determine the fractionation between barite and seawater, and to evaluate the constancy of this fractionation in a range of modern environments. Then, a roughly 130 million year record of barite delta 44Ca will be produced, using existing deep-sea cores at a resolution of about 0.5 m.y., with higher-resolution sampling in a few key intervals. On the education side the PI will develop student-focused problem-based classes and a school-wide education outreach program at Stanford.

This field of study could provide valuable information regarding the sources and sinks of Ca, including carbonate production/burial and hydrothermal exchange reactions. Given linkages between the carbonate and carbon cycles, this work could also yield valuable perspectives on the long-term history of ocean pH and atmospheric CO2.