Physical and chemical structure of freshwater ferromanganese nodules

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The research will focus on freshwater ferromanganese nodules which can be found in many lakes throughout Canada. These nodules occur on the sediment in the lake and grow slowly over hundreds to thousands of years by the continuous accumulation of iron- and manganese-oxide layers. Radiometric age dating indicates that some nodules may be as old as the lakes in which they grow - in some cases up to 10,000 years old. They appear to grow in a roughly concentric manner around a pebble nucleus, and, similar to growth rings in a tree trunk, they could contain a time series record of aquatic-chemical and climate conditions over much of the Holocene (the past 12,000 years). The objective of this research proposal is to develop methods to measure chemical and isotopic composition profiles in order to provide a historical record of aquatic-chemical and climate conditions.