Breda Formation

The Breda Formation (Dutch: Formatie van Breda; abbreviation: BR) is a geologic formation in the subsurface of the Netherlands. The formation consists of marine glauconiferous sands and clays that were deposited during the Miocene epoch. Although the formation is not very rich in fossils, sometimes bones of fishes, mammals (Leptophoca cf. proxima, Protophocaena minima),[1] shells and shark teeth (a.o of megalodon) are found.

Breda Formation
Stratigraphic range: Chattian-Pliocene
~28–3.6 Ma
TypeGeological formation
Unit ofUpper North Sea Group
Sub-unitsAalten Mb., Delden Mb., Eibergen Mb., Zenderen Mb.
UnderliesOosterhout Fm., Kiezeloolite Fm.
OverliesRupel Fm., Veldhoven Fm.
Thicknessup to more than 700 m (2,300 ft)
Lithology
PrimaryMarine sandstones and clays
OtherConglomerate
Location
RegionEurope
Country Netherlands
Type section
Named forBreda (North-Brabant)

Stratigraphy and lithology

The Breda Formation was deposited in the shallow sea that covered the Netherlands during the Miocene. It is mostly on top of the Oligocene clays of the Rupel Formation or late Oligocene sands and clays of the Veldhoven Formation. The Breda Formation can be a couple of meters to (in the Roerdal Graben) more than 700 metres (2,300 ft) thick. The top is formed by an erosional disconformity in the south and east of the Netherlands. In the west the contact with the Pliocene Oosterhout Formation is more gradual. In the Roerdal Graben the mostly Pliocene Kiezeloolite Formation is sometimes on top of the Breda Formation.

Locally the Breda Formation can be subdivided into members: the Aalten Member (silty calcareous clay, rich in shells), the Eibergen Member (clay alternating with thin sand layers, with a basal conglomerate in which shark teeth and whale bones were found), the Zenderen Member (green, glauconiferous fine sand) and the Delden Member (sandy, glauconite and goethite bearing clay and loam.

The Breda Formation corresponds largely with the Berchem Formation of northern Belgium.

References
  1. Liessel at Fossilworks.org

Bibliography
  • Doppert, J.W.C.; Ruegg, G.H.J.; Staalduinen, C.J. van; Zagwijn, W.H. & Zandstra, J.G.; 1975: Formaties van het Kwartair en Boven-Tertiair in Nederland, in: Zagwijn, W.H. & Staalduinen, C.J. van (eds.): Toelichting bij geologische overzichtskaarten van Nederland, Rijks Geologische Dienst, Haarlem, pp. 11–56. ((in Dutch))
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