In order to most accurately identify the causes and mechanisms of climatic change, it is necessary for us to develop high-resolution paleoclimate records which tell us about past climate changes on seasonal, annual, and decadal timescales. Calcite speleothems are well suited for paleoclimate reconstruction because they are normally pure calcite, are well-preserved, can be precisely dated using Uranium-series methods, and contain multiple types of paleoclimate proxy data in their highly resolvable growth bands. In particular, measurements of del18O along speleothem growth axes are often used to reconstruct past rainfall del18O, which is related to temperature and/or rainfall amount. Additional information can be gained from other geochemical proxies, such as del13C and trace element composition, and from physical proxies, such as annual layer thickness and crystal morphology.
This project will involve seasonal resolution measurements of oxygen and carbon isotope composition in samples micromilled along the growth axis of a speleothem from China to investigate past seasonality of the Asian monsoon system. Analysis of modern rainfall del18O data from the Global Network for Isotopes in Precipitation in conjunction with instrumental climate data will be utilized to help interpret the speleothem record in terms of past rainfall and/or temperature. In addition, digital image analysis of speleothem growth bands will allow investigation of the timing of visible laminations and will be used to generate an age model, in combination with radiometric U-Th dates. The research experience will include the use of a computer controlled micromilling system, microscopes and digital image analysis software, microbalances, and a stable isotope mass spectrometer. (Project Time Allocations: Computer Lab = 25%, Sample Prep./Microscope Lab = 25%, Chemistry Lab = 50%)
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