Geochemistry of marine sediments

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The sediments accumulating on the sea-floor represent natural archives of oceanographic and climatic changes over a range of time-scales. Such changes need to be fully documented, and their causes identified, so that tests can be made of models of climate and environmental change, and predictions of future climate variations can be formulated. My research involves the construction of records of past oceanographic and atmospheric changes from the chemical and isotopic properties of cores of sediments recovered from the sea floor. Such properties can be used as indices of particular conditions in the ocean at the time the sediment was accumulating. For example, we are able to determine the sources of the sediment particles and the mode of transport of the particles on the sea floor, the productivity of the surface waters of the ocean overlying the core site, the temperature of the surface waters, bottom water oxygenation, the abundance of CO2 in the ocean and in the atmosphere, and the extent of phytoplankton nutrient utilization in the past. All of these pieces of information can be fitted together to arrive at a picture of the state of the ocean at previous times in Earth's history, and this can be used to find out how the ocean influences, and is influenced by, the atmosphere. This application requests support for studies of the palaeoceanography of the eastern equatorial Pacific, linkages between oceanic and atmospheric changes in the tropics and the polar regions, and the application of these approaches to discovering the possible modes of formation of ancient organic-rich sedimentary rocks.