Bacterial origin of East Australian continental margin phosphorites

Paleoenvironments and origin of the sedimentary phosphorites of the Napo Formation (Late Cretaceous, Oriente Basin, Ecuador)

“…However, studies of modern peloidal phosphorite deposits indicate that phosphogenic episodes may not be solely restricted to environments where prominent upwelling currents occur (O'Brian et al, 1981;Ruttenberg and Berner, 1993). Phosphates do not form in many present day upwelling environments but do form in certain non-upwelling environments such as shallow lagoons, estuaries, or deltas, where phosphate can be supplied by fluvial systems containing P and S-rich organic detritus (Riggs, 1979;Glenn and Arthur, 1990;Ruttenberg and Berner, 1993).…”

Miocene phosphorites from the Murray Ridge, northwestern Arabian Sea

“…This observation suggests that phosphatization occurred in several steps. These particles are also abundant in ancient and modern phosphorites and were interpreted as fossilized P-rich bacterial cells (O'Brien et al, 1981;Garrison and Kastner, 1990). Van Capellen and Berner (1991) synthesized similar apatite capsules and interpreted them as inorganic components originating from rapid precipitation of phosphate.…”

The influence of magnesium ions during the formation of stromatolitic phosphorites of Udaipur, Rajasthan, India

“…The presence of abundant magnesium ions in the stromatolites, therefore, requires further consideration since it can reasonably be assumed that they might have inhibited the process of phosphatization. Bacterial mediation in the transformation of organic compounds into inorganic phosphorus is now very well documented (O'Brien et al 1981;Riggs 1982;Soudry & Champetier 1983;Pr6v6t & Lucas 1986;Lucas et al 1990). However, the controversy still exists as whether the apatite is formed by direct precipitation or by replacement of calcium carbonate.…”

“…However, the controversy still exists as whether the apatite is formed by direct precipitation or by replacement of calcium carbonate. Many workers have concluded that most phosphorite deposits have formed due to accumulation of carbonate fluorapatite formed by the post mortem alteration of phosphorus-rich bacterial cells (O'Brien, et al 1981;Riggs 1982;Prtvtt & Lucas 1986;Lamboy 1990;Lewy 1990). On this basis it can be suggested that microorganisms were responsible for the phosphatized stromatolites of the Jhamarkotra and other deposits, and that mineralization took place preferentially in subtidal areas, in part because here stromatolites only originally contained low-Mg calcite, which was easily transformed into apatite.…”