Breda Formation

Breda Formation
Stratigraphic range: Chattian-Pliocene ~
Type	Geological formation
Unit of	Upper North Sea Group
Sub-units	Aalten Mb., Delden Mb., Eibergen Mb., Zenderen Mb.
Underlies	Oosterhout Fm., Kiezeloolite Fm.
Overlies	Rupel Fm., Veldhoven Fm.
Thickness	up to more than 700 m (2,300 ft)
Lithology
Primary	Marine sandstones and clays
Other	Conglomerate
Location
Region	Europe
Country	Netherlands
Type section
Named for	Breda (North Brabant)

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), shells and shark teeth (a.o of megalodon) are found.

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 (in the Roerdal Graben) to 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

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))

External links

• Westerhoff, W.E.; 2003: Formatie van Breda, TNO website (in Dutch)