The Open University

Graduate Student, Earth and Environmental Sciences

Thesis Title: Organic matter preserved in cave sediments: a new environmental proxy

About

I graduated from the University of Southampton, with a Master of Geology degree in 2009, after completing a research project investigating the fossilisation rates of dinosaur bones and the transfer of REE’s under Clive Trueman.
A large part of this project focused on the preservation of organic macromolecules and the information preserved which could help inform us about the past. From this experience I chose a PhD project which would further develop my knowledge of organic geochemistry and learn about environmental applications.
In 2009 I began work at the Open University with Alison Blyth and Iain Gilmour, working on the use of clastic cave sediments as palaeoarchives, specifically plant lipid biomarkers.
Plants produce a range of organic compounds for the various processes they perform. Some of these compounds break down very quickly once they are out of the protected environment of the plant, however some are preserved in sedimentary environments for longer periods of time, often on geological time scales.
Alkanes, alcohols and alkanoic acids are a few of the compounds, which are preserved in records. Carbon is the dominant element in these compounds, however the number of carbon atoms can vary depending on where the alkane (for example) has come from. Plants generally produce alkanes with an odd number of carbon atoms and longer chain lengths (i.e. C21, C23, C25, C27, C29, C31, C33… etc.). Plants will usually produce a few dominant alkanes, these are called biological markers, because they tell us about the plant or the environment.
My research is currently focused on the use of organic compounds or lipids as plant biomarkers and stable isotopes in cave sediments, specifically South East Asia. The main aim of the project being to understand how the environment in Asia changed during the warming from the last glacial maximum.
Sea level is rising, and one of the areas that will be the worst affected will be the low-lying monsoonal regions, which are currently exposed to annual floods. Stable oxygen isotopes are thought to provide information about the amount of precipitation. Over the last 25,000 years the incoming solar radiation has increased, this has caused a change in the monsoon. 
Cave sediments have the potential to be a rich source of palaeoenvironmental data when multi-proxy analytical techniques are employed. During my PhD I utilized stable isotopes (δ13C, δ18O, C/N) and higher plant lipid biomarkers found in clastic cave sediments to determine the preservation of the environmental record from two archeological study sites in South East Asia.
The clastic cave sediments studied in this project were deposited by aeolian and anthropogenic mechanisms. Once deposited little post-depositional alteration occured, therefore providing an ideal environment for preservation of the palaeoenvironmental signal.
The cave sites I worked on for my PhD proved to be excellent climate archives. Land snail shells from the local forests were collected by hominids occupying the cave at the time and have been preserved in stratigraphic sequence within the cave deposits. The stable oxygen isotopes have been analysed and clearly show the monsoonal trends observed in other cave sites in China such as Hulu and Dongge (Yuan et al., (2004) Science, 304; Wang et al., (2001) Science, 294).
Understanding the impact of rising sea levels and surface temperatures will affect large climatic systems such as monsoons, is of high importance for the people living in these regions. My work aims to help us understand these complex climatic systems and the impact they have had on the environment.

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