P2C2: Testing Speleothem-Based Radiocarbon Calibrations Through A Process-Based Cave Study and a New 35 Kyr Calibration Curve

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Funding is provided to improve the carbon-14 calibration curve that is used for dating paleoclimate samples. In general, geochemical modeling approaches will be used to study climatic controls on speleothem geochemistry while statistical analyses will be used to construct a new calibration curve. Specifically, the researcher will use speleothems from Heshang Cave, China to test the dead carbon fraction (DCF) effect on sample dating. The research goals include: (1) investigating the modern environmental controls on speleothem carbon-14 through expansion of the current environmental monitoring program to include carbon-14 and carbon-13 measurements of soil carbon, soil carbon dioxide, monthly modern calcite samples, monthly dripwater dissolved inorganic carbon samples, and cave air carbon dioxide for comparison with existing calibration data to constrain environmental controls on carbon cycling in the karst system and investigate links with other proxies; (2) investigating the location and structure of the radiocarbon bomb peak within the 2.5 meter annually-laminated HS4 stalagmite to determine soil-to-speleothem carbon transfer dynamics; (3) constructing a centennial-resolution Holocene carbon-14 record from HS4, tied to existing uranium-thorium (U-Th) dates, to investigate possible climatic controls on DCF over this time period; and (4) constructing a new, well-tested speleothem-based radiocarbon calibration curve from paired U-Th-carbon-14 dating of a 2.0 meter long stalagmite, HS7, which formed from 35,800 to 11,800 years ago. This research will support a new female investigator and students while strengthening international science collaborations.This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).