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DPhil: Trace Metals and Isotope in Carbonate: understanding past climate records
Supervised by: Prof. Gideon Henderson
Much of what we know about past climate is reconstructed by measurement of the chemistry of natural carbonate minerals. In the oceans, we rely on corals, foraminifera, and molluscs. In the terrestrial environment we rely on lake and cave carbonates. In all cases, interpretation of carbonate geochemistry as proxies for past climate change requires understanding of the controls on element or isotope incorporation into the carbonate. Such understanding is, however, frequently incomplete and, in the case of recently investigated isotopes systems, completely missing. The goal of this project is to improve our understanding of how and why speleothem carbonate chemistry responds to environmental variables.
To this end, I am growing synthetic carbonates in the laboratory with a tight control on the growth conditions (temperature, CaCO3 saturation index, CO2 levels, trace metal to Ca ratios, drip rate) and I replicate as faithfully as possible actual speleological growth conditions. In particular I use CO2 degassing as the growth mechanism rather than the combination of CaCl2 and NaHN03 and I grow the material in thin-solution-film conditions. We then analyse multiple facets of the growth-material that was grown in a series of specific growth conditions. Analyses include trace metals, stable isotopes, Scanning Electron Microscopy and Ca isotopes (with Linda Reynard, Oxford).
Utlimately, we are interested in applying this knowledge to palaeoclimate reconstruction and to understanding the physics and chemistry of the climate system in order to predict future changes, therefore fieldwork is also being carried out in Chile and Morocco. I am working on a young (Holocene) stalagmite sample from the Chilean island of Madre de Dios, collected by American collaborator Charlie Porter, and we are working in conjunction with Simon Blockley & Nick Barton (RLAHA) and with Bouzouggar Abdeljalil (Institut National des Sciences de l'Archeologie et du patrimoine, Rabat) in retrieving climate records from northern Morocco.
Information regarding forthcoming fieldwork in Chile