Werkendam Formation

ATWD

Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1994).

Sequence of grey, slightly marly, shaly claystones. Towards the middle of the succession a more calcareous, silty to sandy interval occurs, occasionally developed as silt- or sandstone beds. Pyrite, carbonaceous matter, macrofossils (ammonites, belemnites, gastropods, etc., frequently pyritised), iron oolites and up to dm-size ferruginous siderite nodules can be common.

Relatively shallow-water, open marine environment.

Placed at the top of the bituminous, shaly claystones of the underlying Posidonia Shale Formation.

Unconformably overlain by the Schieland Group or a younger unit. In more complete successions, the Werkendam Formation is conformably overlain by the sandy limestone/marl alternation of the Brabant Formation. Because of the Mid-Kimmerian unconformity in the Dutch Central Graben, the Lower Graben Formation of middle to late Callovian age unconformably overlies the Werkendam Formation.

Up to 750 m (K14-FA-106).

The unit is restricted to synclinal erosional remnants in the Roer Valley Graben, the West Netherlands Basin, the Central Netherlands Basin, the Broad Fourteens Basin, the Central Graben and some isolated occurrences in the Lower Saxony Basin and the eastern Central Netherlands Basin (Achterhoek).

UK: West Sole Group; GER: Dogger Group; BEL: -.

late Toarcian - early Bathonian.

Named after the municipality of Werkendam in ‘Het Land van Altena’ (northern part of the Dutch province of Noord-Brabant).

None.

Sander Houben (2017).

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. 1994. Stratigraphic nomenclature of The Netherlands; revision and update by RGD and NOGEPA, Section F, Lower and Middle Jurassic. Mededelingen Rijks Geologische Dienst, 50, 1-20.