Show simple item record

dc.contributor.authorRao, V.P.
dc.contributor.authorHegner, E.
dc.contributor.authorNaqvi, S.W.A.
dc.contributor.authorKessarkar, P.M.
dc.contributor.authorAhmad, S.M.
dc.contributor.authorRaju, D.S.
dc.date.accessioned2008-05-01T06:56:34Z
dc.date.available2008-05-01T06:56:34Z
dc.date.issued2008
dc.identifier.citationPalaeogeography, Palaeoclimatology, Palaeoecology, vol.260(3-4); 347-358p.
dc.identifier.urihttp://drs.nio.org/drs/handle/2264/1060
dc.description.abstractPhosphorites from the Murray Ridge, NW Arabian Sea comprise nodules, bioclasts, and bone fragments. The nodules are made up of a homogeneous, light-colored phosphate nucleus consisting of Rivulariacean filamentous cyanobacteria and a thin dark-grey colored phosphate cortex showing abundant microbial filaments and microborings. The bioclasts comprise of approx. 14-14.5 Ma old planktonic foraminifers, accepted as the time of deposition. Spherical to ovoid-shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts. Bone fragments exhibit apatite fillings. The nodules and bone fragments consist entirely of carbonate fluorapatite (CFA) with low Al, K, and Th concentrations suggesting absence of continental detritus. Shale-normalized REE patterns of the samples support a seawater-derived composition. The highly uniform initial Sigma sub(Nd) values of -4.8 to -5.1 are interpreted as the seawater value at the onset of phosphatization approx. 14 Ma ago. In contrast, sup(87) Sr / sup(86) Sr ratios show a large range of 0.709055 to 0.709124 corresponding to unusually young stratigraphic ages of approx. 1 to 3 Ma. The data are interpreted as evidence for post-depositional Sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater. It is concluded that the phosphorites formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of CFA during early diagenesis at the sediment–water interface on different substrates.
dc.language.isoen
dc.publisherElsevier
dc.rightsCopyright Elsevier [2008]. It is tried to respect the copyright. If it is brought to our notice that the rights are violated then the item would be withdrawn.
dc.subjectMurray Ridge
dc.subjectREE and trace elements
dc.subjectPhosphorites
dc.subjectMicrobial activity
dc.titleMiocene phosphorites from the Murray Ridge, northwestern Arabian Sea
dc.typeJournal Article


Files in this item

Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record