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Geochemistry

During the Cambrian, variations in isotope ratios were more frequent and more pronounced than later in the Phanerozoic, with at least 10 carbon isotope (δ C) excursions (significant variations in global isotope ratios) recognised. These excursions record changes in the biogeochemistry of the oceans and atmosphere, which are due to processes such as the global rates of continental arc magmatism, rates of weathering and nutrients levels entering the marine environment, sea level changes, and biological factors including the impact of burrowing fauna on oxygen levels.