East Australian Continental Margin phosphorites



The present-day formation of marine phosphorite nodules has been documented in only three areas, off Peru-Chile, Namibia, and eastern Australia. The Peru-Chilean and Namibian areas are both zones of coastal upwelling with associated high biological productivity, and the nodules form within rapidly accumulating anoxic, organic-rich (much greater than 1.0 wt%) diatomaceous oozes [Baturin et al., 1972; Burnett and Veeh, 1977]. The principal component of the nodules, carbonate fluorapatite, apparently precipitates because abundant PO43− is released from the bacterial degradation of organic matter. This model is supported by pore water profiles, which show PO43− release in the upper few centimeters of the sediments, followed by strong PO43− and F uptake at depth, the result of apatite precipitation.