The Oligocene of Belgium.
(Rupelian, Base Boom Clay)
The Belgian Oligocene is dominated by the early Oligocene, late Rupelian Boom Clay Formation (R2c), exposed in several quarries. Maurice Leriche (1910) made a great work about the sharks and rays of the Boom clay, figuring extraordinary specimens and some unique associated tooth sets. This large formation is deposited in relatively deep water and is divided in 69 layers. The Boom clay quarries are widespread, but the vertebrate remains are not. Some layers proved to be little better than others: layers 49, 41 and 35.

Numerous phosphatic nodules and some shark remains are present at the base of this Boom Clay. This exceptional early Rupelian phosphate bed (circa 32Ma) is covering the fine, glauconitic Ruisbroek Sands of the Zelzate Formation. The stratigraphic age of this formation is at the Eocene-Oligocene transition. Hard work is needed to access and sample this horizon; Carcharias acutissima (Agassiz, 1843) and Physogaleus latus (Storms, 1894) are by far the most commonly found shark species.

In 1991 and 1992, when widening the Albert canal in Gellik near Lanaken, also the sandy part of the Belgian Rupelian could be sampled. These sediments are dated early Rupelian in age and are belonging to the Bilzen Formation, Member of Kerniel (R1d). This (sandy) locality shares the same fauna diversity as the rest of the (mostly clayish) Belgian Rupelian.

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BAUT, J.P. & GENAULT, B., 1999. Les elasmobranches des Sables de Kerniel (Rupélien), à Gellik, Nord est de la Belgique. Memoirs of the Geological Survey of Belgium, 45.

LERICHE, M., 1910. Les Poissons Oligocènes de la Belgique. Mémoire du Musée Royal d'Histoire Naturelle de Belgique, 363 pp.

MOLLEN, F., 2007. A new species of Abdounia (Elasmobranchii, Carcharhinidae) from the base of the Boom Clay Formation (Oligocene) in northwest Belgium. Geologica Belgica, 10(1-2): 69-77.

STEURBAUT, E. & HERMAN, J., 1978. Biostratigraphie et poissons fossiles de la formation de l'argile de Boom (Oligocène moyen du bassin belge). Géobios 11/3.

VANDENBERGHE, N., HERMAN, J. & STEURBAUT, E., 2002. Detailed analysis of the Rupelian Ru-1 transgressive surface in the type area (Belgium). In Gürs, K. (ed.), Northern European Cenozoic Stratigraphy. Proceedings of the 8th Biannual Meeting of the RCNNS/ RCPNS, 67-81. Landesamt für Natur und Umwelt des Landes Schleswig-Holstein, Flintbek.

© P. De Schutter - 2006