Etude biostratigraphique des assemblages de diatomées pyritisées du Paléocène supérieur et de l'Eocène inférieur des Bassins danois,de Dieppe-Hampshire et belge: apports paléoenvironnementaux

Abstract

The stratigraphic distribution of the pyritized diatoms and their paleogeographic repartition are studied in Upper Paleocene and especially Lower Eocene from the Danish (Ølst Hinge), Dieppe-Hampshire (Saint-Josse and Ailly) and Belgian (Knokke) Basins. Different kinds of fossilisation are observed. In a first step of the diagenesis, a mould of the frustule is built thanks to the growth of authigenic minerals (pyrite and barite). The siliceous skeleton may also be completely replaced epigenetically by pyrite. These two types of fossilisation, that may coexist, keep diatoms identifiable. A reliable and reproducible methodology for the extraction of pyritized diatoms has been developed. The evolution of the diatom zones is underlined : four zones (D0 until D3) of association or abundance are recognized. This zonation is established for the southern and eastern basins of the North Sea Basin. It is interrelated with the biozonations of King (1983), Fenner (1985), Mudge & Copestake (1992a) and Mitlehner (1994, 1996) valid for the central part of the North Sea Basin. The zones D0-D3 allow correlations between the lithostratigraphic units of the various studied basins and the one of the North Sea. This enables among others to correlate the sediments of the sparnacien facies of the Dieppe-Hampshire with the formations of the North Sea. At last, the pyritized diatoms represent a new argument to locate the C.I.E. which base is the criterion for the identification of the Paleocene-Eocene boundary. The C.I.E. is located in the lower part of the D1 zone under the abundance peak of the Coscinodiscus morsianus var. moelleri species.

Date of Award	15 Jun 2005
Original language	French
Awarding Institution	University of Namur
Supervisor	Vincent Hallet (Supervisor), Christian Dupuis (Jury), Marie-Pierre Aubry (Jury), Jean-Pierre DESCY (President), Philippe Steemans (Jury) & Etienne Steurbaut (Jury)