Project:	Study of fossil shark teeth in deep-sea sediments as a paleo-redox archive
Discipline:	Geochemistry
Mentor:	Francois Tissot, Assistant Professor, (GPS), tissot@caltech.edu
AO Contact:	Haoyu Li, Haoyu.Li@caltech.edu
Background:	The uranium isotope composition (δ238U) of seawater is a powerful proxy for the extent of marine anoxia. For paleoredox reconstructions, carbonates are the most popular U isotope archive, but they have recently come under increased scrutiny as their δ238U values are subject to diagenetic alteration after deposition. Therefore, there is a need to investigate other archives that may record and preserve the original seawater δ238U signal. Recent work from our lab demonstrates that the performance of fossil shark teeth as a recorder of seawater U isotope composition can appear to roughly match that of carbonates. However, this preliminary conclusion is likely to be biased by the limited sample size of fossil shark teeth, which motivates to expand of the dataset. Previous studies suggest that fossil fish teeth from deep-sea sediments typically have better preservation for original signatures from the ambient aqueous environment, which has the potential to apply to the U isotopes.
Description:	The project involves assessing whether U isotopes in fossil shark teeth from deep-sea sediments can record primary seawater signatures. The student will work with a graduate student or postdoctoral fellow on sample preparation, U purification, and isotope analyses.
References:	Li, D., Peng, J., Chew, D., Liang, Y., Hollings, P., Fu, Y., Dong, Y., Sun, X., 2023. Dating rare earth element enrichment in deep-sea sediments using U-Pb geochronology of bioapatite. Geology 51(5), 428-433 Li H., Kipp M.A., Kim S.L., Kast, E.R., Eberle, J.J., Tissot F. L.H., 2023. U isotopes in shark teeth as a proxy for paleoredox conditions. Geochimica et Cosmochimica Acta (in press) Zhang, F., Lenton, T.M., del Rey, Á., Romaniello, S.J., Chen, X., Planavsky, N.J., Clarkson, M.O., Dahl, T.W., Lau, K. V., Wang, W., Li, Z., Zhao, M., Isson, T., Algeo, T.J., Anbar, A.D., 2020. Uranium isotopes in marine carbonates as a global ocean paleoredox proxy: A critical review. Geochim. Cosmochim. Acta 287, 27–49.
Student Requirements:	Work in a clean lab environment is rewarding but difficult and thus requires: - the capacity to work meticulously and pay great attention to details, - on the spot critical thinking, - fine motor skills to handle biological samples in ultra-clean hoods, - the capacity to learn from mistakes (one’s own and those of others) and adjust behaviors accordingly, - and the ability to focus for extended periods of time.
Programs:	This AO can be done under the following programs:   Program    Available To        Amgen Scholars    Non-Caltech students only          SURF    both Caltech and non-Caltech students  Click on a program name for program info and application requirements.