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A simple method for the rapid determination of biogenic opal in pelagic marine sediments
Mortlock, R.A.; Froelich, P.N. (1989). A simple method for the rapid determination of biogenic opal in pelagic marine sediments. Deep Sea Res. (1977) 36(9): 1415-1426. hdl.handle.net/10.1016/0198-0149(89)90092-7
In: Deep-Sea Research (1953). Pergamon: Oxford; New York. ISSN 0146-6291, more
Peer reviewed article  

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Keywords
    Biogenic deposits; Chemical analysis; Chemical extraction; Fossils; Opal; Pelagic sedimentation; Sediment analysis; Silica; Marine

Authors  Top 
  • Mortlock, R.A.
  • Froelich, P.N.

Abstract
    Biogenic opal in marine sediments is determined with a single extraction of silica into 2 M Na2 CO3 solution at 85 degree C for 5 h. The method has been applied to sediments of varied opal contents (3-100% opal) and age (Recent to Pliocene). It is sufficiently simple, precise and rapid to be used routinely for high resolution spatial and temporal mapping of the biosiliceous component in deep-sea sediments. Evidence from timed dissolution experiments, germanium/silicon ratios, and comparisons with other methodologies demonstrates that systematic errors produced by leaching of silica from aluminosilicates or by incomplete dissolution of siliceous microfossils are small compared to the range of opal contents in biogenic sediments. When estimating mass accumulation rates, the authors report sedimentary biogenic opal both as %SiOPAL (silicon content) and as %OPAL (2.4 x %SiOPAL). This conversion accounts for the average water content of diatomaceous silica (about 10% water = SiO2 multiplied by 0.4 H2O).

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