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Upper Palaeocene and Lower Eocene interval in the Dieppe-Hampshire Basin: biostratigraphic analysis based on pyritized diatoms
Van Eetvelde, Y.; Dupuis, C. (2004). Upper Palaeocene and Lower Eocene interval in the Dieppe-Hampshire Basin: biostratigraphic analysis based on pyritized diatoms, in: Beaudoin, A.B. et al. The Palynology and Micropalaeontology of Boundaries. pp. 275-291. dx.doi.org/10.1144/GSL.SP.2004.230.01.14
In: Beaudoin, A.B.; Head, M.J. (2004). The Palynology and Micropalaeontology of Boundaries. Geological Society of London: London. ISBN 1-86239-160-2. 355 p pp., more

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  • Van Eetvelde, Y.
  • Dupuis, C.

Abstract
    Assemblages of brackish and marine pyritized diatoms have been examined from Thanetian and Ypresian sediments in the Dieppe-Hampshire Basin. Two sites were studied: the borehole of Saint-Josse and sections at Ailly, both located in northern France. Pyritized diatoms are preserved in the deposits by epigenesis or as internal moulds by the growth of pyrite crystals in internal cavities. In both sites studied, most groups of in situ microfossils (e.g. dinoflagellates, foraminifera, nannoplankton) were extremely rare or absent, in contrast to pyritized diatoms, which showed good recovery, thereby proving their utility across this interval. The Palaeocene-Eocene boundary referred to this study is the official boundary defined by the Carbon Isotope Excursion. This is recorded in both sites studied. Diatom assemblages change character through the stratigraphic sequence, with three major diatom assemblages being defined which provide a key reference marker for the Palaeocene-Eocene boundary sediments from the Dieppe-Hampshire Basin. The first assemblage, D1, is characterized by the abundance peak of Coscinodiscus morsianus var. moelleri and Coscinodiscus morsianus var. morsianus. This assemblage is recorded in Thanetian and Lower Sparnacian facies. The second assemblage, D2, is defined by the abundance peak of Fenestrella antiqua, the downhole occurrence of Coscinodiscus morsianus sp., and a great diversity of circular diatoms. The upper part of this zone is marked by the greatest occurrence of Fenestrella antiqua and the extinction of Coscinodiscus morsianus var. moelleri. This assemblage corresponds with the upper part of the Sparnacian facies. The last assemblage (D3), of Early Ypresian age, is characterized by the presence of Aulacodiscus, Trinacria, Craspedodiscus and the great diversity of triangular, oval and bipolar species; these are held to indicate a marked increase in marine influence. These diatom assemblages from the Dieppe-Hampshire Basin show similarities to those from the North Sea Basin. Correlations between these two basins are possible by the use of pyritized diatoms. Thanks to these correlations, it is now possible to locate the Carbon Isotope Excursion in the North Sea Basin.

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