Phosphogenesis in coastal upwelling systems - bacterially-induced phosphorite formation

Abstract

The burial of phosphorus and the formation of phosphorites (phosphogenesis) in marine sediments represent an important sink in the global phosphorus cycle. Phosphogenesis is not only an ancient phenomenon, it has been observed in recent suboxic to anoxic marine sediments of ocean upwelling regions, for example off the coast of Namibia, Chile, and Peru. Phosphorites and their distribution on the ocean floor have been frequently studied. So far, neither the phosphate source of massive phosphorite deposits nor the enrichment mechanisms resulting in supersaturation of pore water with respect to carbonate fluorapatite have been fully recognized. In particular, the importance and function of microorganisms in phosphogenesis has been widely not understood. In order to obtain insights into the involvement of microorganisms in recent and ancient phosphorite formation of upwelling areas, various biogeochemical and petrographic analyses were performed in this thesis on (1) Modern phosphogenic sediments from the coastal upwelling regions off Namibia, Peru, and Chile and on (2) Miocene to Pleistocene phosphorite crusts from the shelf off Peru (9Ã °40'S to 13Ã °30'S). In addition, dolomites of the Miocene Monterey Formation were analyzed.