Boom Member

Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1997; De Lang & Ebbing 2003).
Lithological description

Clay that becomes more silty towards base and top (Vis et al. 2016). Rich in pyrite, poor in glauconite and calcium carbonate tends to be concentrated in the septaria layers; their presence is speculative for most of the Dutch subsurface. The silt content does not only change towards the top and the bottom of the member. Detailed studies in the Boom Clay in Belgium initiated by Vandenberghe et al. (2014) have shown that silt and clay layers alternate at a decimetre to metre scale. Moreover, the organic-matter content is highly variable and distinct bituminous layers are present. Large intervals are practically devoid of calcareous microfossils. In areas relatively close to the basin margin, the clay can be subdivided into three parts. The lower part of the clay is silty and has a blue-grey colour. Higher in the succession a great number of bituminous bands is intercalated and the colour of the clay changes to dark green-grey, dark-brown or even black. The dark clays, which stand out on gamma-ray logs, are overlain by green-grey to green clays that are more marly and slightly more silty.

Depositional setting

Middle to outer neritic marine setting. The foraminiferal content suggests that anaerobic conditions intermittently prevailed at the sea bottom.

Definition of lower boundary

Conformably overlies the sandy Berg Member (previously known as Vessem Member) in most parts of the Netherlands. In places where the Berg Member is absent, the clays rest directly on the Asse or Engelsche Hoek members, which complicates definition of the boundary. However, on wire-line logs the Boom clays show somewhat higher gamma-ray response compared to the clays of the Lower North Sea Group.

Definition of upper boundary

Conformably overlain by the sandy deposits of the Steensel Member in the southeastern Netherlands. When the sandy member is missing, e.g. in part of the northeastern offshore, the transition with the overlying argillaceous Veldhoven Formation is unconformable. Where early Miocene erosion occurred, an unconformable contact exists with the overlying Breda Formation.

Thickness indication
Up to ~200 m.
Geographical distribution
Regional correlation
UK: Lark Formation; GER: Ratingen Member and Lintfort Member of the Rupel Formation; BEL: the Belgian Boom Formation covers only the part of the Dutch Boom Member that overlies the transgressive upper part of the Vessem Member (Marechal and Laga 1988).
early Oligocene (Rupelian and early Chattian, basinward also older: Priabonian).
Depth (thickness) AH:
1122 - 1213 m (91 m)
Depth (thickness) AH:
1317 - 1391 m (74 m)
Depth (thickness) AH:
715 - 779 m (64 m)
Origin of name
Named after the village of Boom in Belgium, near Antwerp along the River Rupel.
Previous name(s)
Boom Clay Member (NAM & RGD 1980). Van Adrichem Boogaert & Kouwe (1997) introduced the name "Rupel Clay Member" to avoid confusion with the original notion of the "Boom Clay" and to bring the nomenclature in line with that of the other dominant clay members in the Lower and Middle North Sea Group (e.g. Landen, Dongen formations and Wintelre Member). Renamed in 2019 because "Rupel" is already in use as a formation name and to better relate to the extensively studied Belgian equivalent which is named Boom Formation.
Reviewed by (date)
Dirk Munsterman (2018).
Vis, G.-J., Verweij, H., Koenen, M. 2016. The Rupel Clay Member in the Netherlands: towards a comprehensive understanding of its geometry and depositional environment. Netherlands Journal of Geosciences 95 (3), 221-251. [OPEN ACCESS].
De Lang, F.D., Ebbing, J.H.J. 2003. Beschrijving lithostratigrafische eenheid. Nederlands Instituut voor Toegepaste Geowetenschappen TNO. Utrecht.
NAM & RGD 1980. Stratigraphic nomenclature of The Netherlands. Verhandelingen van het Koninklijk Nederlands Geologisch Mijnbouwkundig Genootschap 32, 77 p.
Van Adrichem Boogaert, H.A. & Kouwe, W.F.P. 1997. Stratigraphic nomenclature of The Netherlands, revision and update by RGD and NOGEPA, Section I, Tertiary. Mededelingen Rijks Geologische Dienst, 50, 1-39.
Vandenberghe, N., De Craen, M., Wouters, L. 2014. The Boom Clay geology from sedimentation to present-day occurence: a review. Memoirs of the Geological Survey of Belgium 60. Royal Belgian Institute of Natural Sciences – Geological Survey of Belgium: 76 p.
Cite as
TNO-GDN ([YEAR]). Boom Member. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from