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Microbial dolomite crusts from the carbonate platform off western India

DRS at CSIR-National Institute of Oceanography

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Title Microbial dolomite crusts from the carbonate platform off western India
 
Creator Rao, V.P.
Kessarkar, P.M.
Krumbein, W.E.
Krajewski, K.P.
Schneider, R.J.
 
Subject dolomite
stromatolites
carbonates
pleistocene
concretions
microbiology
anoxic conditions
 
Description The occurrence of Late Pleistocene dolomite crusts that occur at 64 m depth on the carbonate platform off western India is documented. Dolomite is the most predominant mineral in the crusts. In thin section, the crust consists of dolomitized microlaminae interspersed with detrital particles. Under scanning electron microscopy, these laminae are made up of tubular filaments or cellular structures of probable cyanobacterial origin. Dolomite crystals encrust or overgrow the surfaces of the microbial filaments and/or cells; progressive mineralization obliterates their morphology. Well-preserved microbial mats, sulphide minerals (pyrrhotite and marcasite) and the stable isotope composition of dolomite in the crusts indicate hypersaline and anoxic conditions during dolomite formulation. The crusts are similar to dolomite stromatolites, and biogeochemical processes related to decaying microbial mats under anoxic conditions probably played an important role in dolomite precipitation. The dolomite is therefore primary and/or very early diagenetic in origin. The dolomite crusts are interpreted to be a composite of microbial dolomite overprinted by early burial organic dolomite. The results of this study suggest that a microbial model for dolomite formation may be relevant for the origin of ancient massive dolomites in marine successions characterized by cryptalgal laminites. The age of the crusts further suggests that the platform was situated at shallow subtidal depths during the Last Glacial Maximum
 
Date 2008-07-18T05:45:18Z
2008-07-18T05:45:18Z
2003
 
Type Journal Article
 
Identifier Sedimentology, Vol.50; 819-830p.
http://drs.nio.org/drs/handle/2264/1257
 
Language en
 
Rights Copyright [2003]. It is tried to respect the rights of the copyright holders to the best of the knowledge. If it is brought to our notice that the rights are violated then the item would be withdrawn.
 
Publisher International Association of Sedimentologists