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Organic Environment

  • Hervé Chamley

Abstract

The activity of benthic organisms living above or within sediments may have strong effects on physical properties like sorting, particle orientation (i.e., fabric) and aggregation (Rhoads and Boyer 1982). The influence of bioturbation on the fabric of argillaceous sediments, and the dependence of ichnofacies on different types of sedimentary substrates have been especially investigated for consolidated deposits. For instance, O’Brien (1987) considers the macrofabric (X-radio-graphy) and microfabric (scanning electronmicroscopy) of 50 samples of shales from five stratigraphic units: Jurassic of England, Permian of western Texas, Pennsylvanian of Iowa, Pennsylvanian of Illinois, Devonian of western New York state. The fabric of clay particles within the shales appears closely linked to the intensity of bioturbation:
  1. 1).

    Black shales formed under anaerobic conditions and devoid of bioturbation structures display fine lamination and a primary fabric characterized by parallel clay flakes.

     
  2. 2).

    Gray to dark-gray shales correspond to more oxic conditions and comprise either extensively or only partly bioturbated facies. The first facies shows a homogeneous aspect on X-radiographs with few recognizable burrows, as well as individually, randomly oriented particles similar to unbioturbated, flocculated clay; however, there are no the cardhouse structures typical of flocculated clays. The second facies includes both areas of randomly oriented particles and areas of parallel to subparallel particle orientation, which suggests a less important sediment mixing by benthic species.

     

Keywords

Black Shale Organic Environment Clay Mineral Assemblage Levantine Basin DSDP Site 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • Hervé Chamley
    • 1
    • 2
  1. 1.University of Lille IVilleneuve d’AscqFrance
  2. 2.University of Paris VIParis cedex 05France

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