Koewacht Formation

Code
NUKW
Status
Formal (Kiden 2010).
Lithological description

Generally fining upward. Greenish grey to light brown fine to medium sand, slightly silty with local shell grit. Subordinate light grey to light brown medium to very coarse sand with lags of fine gravel (mainly quartz and flint) and shell fragments. Local concentrations of shells reworked from older marine deposits. Sporadic thin silty clay beds, slightly sandy loam, peat and gyttja.

Depositional setting

Braided (early) to meandering (late; Bos et al. 2005, Kiden 2006) fluvial (Scheldt) (Flemish Valley, Tavernier 1946), including channel (sand and gravel), overbank (clay and loam), abandoned channel (clay and loam).

Definition of lower boundary

Commonly accentuated by a lag deposit. Generally sharp, erosive contact with greyish green to dark green, glauconitic and micaceous marine deposits with relatively firm clay (Maassluis, Oosterhout, Breda, Rupel, Tongeren and Dongen Formations) or with micaceous, silty and clayey fluvial-estuarine sand with clay laminae (Waalre Formation). Sharp and erosive but visually diffuse contact with marine sand (Eem Formation), marked by mutual reworking and intercalation.

Definition of upper boundary

Locally marked by a clay or loam layer. Typically, gradual and diffuse transition into finer, less calcareous, more organic aeolian and local river sand (Boxtel Formation), sporadically intercalated. Locally, sharp contact with or gradual transition into peat (Basisveen Bed, Nieuwkoop Formation), sharp contact with organic and finer floodplain and abandoned-channel clay and sand (Kreekrak Formation), or sharp and erosive contact with clayey tidal-channel sand (Walcheren and Wormer Members, Naaldwijk Formation).

Thickness indication
Up to about 20 m, averaging 10-15 m.
Geographical distribution
Seaward transition into partly intercalated marine sand (Eem Formation) or into coarser Rhine sand (Kreftenheye Formation).
Regional correlation
North Sea: not distinguished; UK: not present; GER: not present; BEL: Adegem, Oostwinkel and Eeklo formations.
Age
late Middle Pleistocene - Late Pleistocene (Saalian - Weichselian).
Holostratotype
Depth (thickness) AH:
6.70 - 17.95 m (11.25 m) below land surface
Parastratotype
Depth (thickness) AH:
7.73 - 14.84 m (7.11 m) below land surface
Origin of name
Named after the village of Koewacht, in the southwestern Netherlands.
Previous name(s)
Vlissingen Deposits, Schouwen Formation, Schouwen Deposits (Eem Formation) (Van Voorthuysen 1957; Van Rummelen 1965; Doppert et al. 1975; Schokker 2003).
Reviewed by (date)
Wim Dubelaar (2018), Sytze van Heteren (2019).
References
Bos, J.A.A., Huisman, D.J., Kiden, P., Hoek, W.Z., Van Geel, B. 2005. Early Holocene environmental change in the Kreekrak area (Zeeland, SW-Netherlands): a multi-proxy analysis. Palaeogeography, Palaoeclimatology, Palaeoecology 227, 259-289.
Doppert, J.W.Chr., Ruegg, G.H.J., Van Staalduinen, C.J., Zagwijn, W.H., Zandstra, J.G. 1975. Formaties van het Kwartair en Boven-Tertiair in Nederland. In: Zagwijn, W.H., Van Staalduinen, C.J. (eds.): Toelichting bij geologische overzichtskaarten van Nederland. Rijks Geologische Dienst, Haarlem, 11-56.
Kiden, P., 2006. De evolutie van de Beneden-Schelde in België en Zuidwest-Nederland na de laatste ijstijd. Belgeo 2006/3, 279-294.
Kiden, P. 2010. Beschrijving lithostratigrafische eenheid. Nederlands Instituut voor Toegepaste Geowetenschappen TNO. Utrecht.
Schokker, J. 2003. Patterns and processes in a Pleistocene fluvio-aeolian environment: Roer Valley Graben, south-eastern Netherlands. PhD Thesis. Nederlandse Geografische Studies, 314, Koninklijk Nederlands Aardrijkskundig Genootschap / Faculteit Ruimtelijke Wetenschappen Universiteit Utrecht, Utrecht, 142 p.
Tavernier, R. 1946. L'évolution du Bas Escaut au Pléistocène supérieur. Bulletin de la Societé Belge de Géologie, 65, 106-125.
Van Rummelen, F.F.F.E. 1965. Toelichtingen bij de geologische kaart van Nederland 1:50.000, Bladen Zeeuwsch-Vlaanderen West en Oost. Geologische Stichting, Afdeling Geologische Dienst, Haarlem, 79 p.
Van Voorthuysen, J.H. 1957. Algemeen geologisch overzicht tot een diepte van 40 meter. In: De Ridder, N.A. (ed.), Agrohydrologische profielen van Zeeland. Staatsdrukkerij, s-Gravenhage, 20-32.
Cite as
TNO-GDN ([YEAR]). Koewacht Formation. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from https://www.dinoloket.nl/en/stratigraphic-nomenclature/koewacht-formation.