"Sedimentary phosphorite, fertilizer ore, and the evolving phosphorus cycle: an integrated approach"

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Phosphorite is a marine chemical sediment rich in phosphorus and a non-renewable fertilizer ore. Phosphorus is a bioessential element that forms skeletons and DNA, is essential for cellular energy transfer, and limits biologic productivity over geologic timescales. Since its precipitation is so closely tied to biology, phosphorite is not simply a recorder of geologic processes, but intimately involved in the evolution of life and ocean-atmosphere development. Research is focused on the Neoproterozoic-Paleozoic phosphogenic episode, Earth's second major period of phosphorite deposition. Four major episodes of phosphorite deposition are recognized that correspond to significant reorganizations of the Earth system. Studies are located in Cambrian and Ordovician strata of eastern and western Canada, and in Neoproterozoic, Silurian, and Devonian rocks of Brazil. These deposits are part of a system of P cycling prior to, during, and after the final stages of ocean-atmosphere oxygenation related to the emergence and diversification of animals. Precise causes remain unclear, but speculation about variations in the P cycle have been attributed to dramatic climate fluctuations, biologic evolution, supercontinent amalgamation and breakup, as well as changing ocean-atmosphere composition and circulation. Understanding the relationship between bioavailable P, ocean redox state, and the Ediacaran and Cambrian radiations is a primary focus. This will be done using an integrated approach combining sedimentology, sequence stratigraphy, and geochemistry to constrain the depositional and postdepositional context of phosphorites. Most recent studies are based on geochemical proxies, which are interpreted outside the sedimentologic, oceanographic, diagenetic, and metamorphic aspects of hosting sedimentary rocks. Significant to Canada is that this unique approach will enhance our nation's ability to acquire a stable and secure source of phosphorite by developing expertise on poorly understood deposits in New Brunswick, Quebec, and British Columbia.