Urk Formation

Formal (Zonneveld 1958). Amended (Doppert et al. 1975; Bosch et al. 2003).
Lithological description

Grey to yellowish brown, fine to very coarse sand, slightly to very gravelly, slightly micaceous, non-calcareous (in ice-pushed ridges) to calcareous, with plant remains (including wood), with augite and abundant pink minerals.. Subordinate clay layers, very sandy or silty and locally organic. Fine to very coarse gravel characterised by grey, brown, green and red sandstones and white quartz.

Depositional setting

Fluvial (Rhine, sediment source in the mountainous hinterland of central and southern Germany). Northward, transition into estuarine, tidal and shallow marine.

Definition of lower boundary

Locally, marked by an up to 3-m-thick clay bed (Zandstra 1971; Bosch 1990). Elsewhere, sharp and unconformable contact with greyer, finer, less glauconitic and less calcareous fluvial sand (Appelscha and Peize formations) or with finer, more micaceous, more organic and less multi-coloured fluvioglacial sand (Peelo Formation). Gradual transition into slightly finer, more clayey and more micaceous fluvial sand (Sterksel and Waalre formations) or into less multi-coloured periglacial sand (Drachten Formation).

Definition of upper boundary

Locally exposed at the surface. Elsewhere, sharp and unconformable contact with finer, more micaceous, more organic and less multi-coloured fluvioglacial sand (Peelo Formation). Gradual transition into finer periglacial sand (Drachten Formation). Diffuse transition into gravelly glaciofluvial sand (Schaarsbergen Member, Drente Formation), or into gravelly fluvial sand (Kreftenheye Formation), except where separated by a coarse channel lag.

Thickness indication
Up to about 60 m in thick fluvial channel fills (Bosch & Kok 1994). Elsewhere, up to about 30 m.
Geographical distribution
Southward, transition into interfingering Meuse deposits (Beegden Formation), with increasingly dominant Meuse-derived gravel. Offshore, transition into the marine Egmond Ground Formation.
Regional correlation
North Sea: marine Egmond Ground Formation and upper fluvial part of Yarmouth Roads Formation (defined and mapped in conjunction with the British Geological Survey; Long et al. 1988; Laban 1995); UK: not present; GER: Untere and Obere Mittelterrasse (Klostermann 1992; Zagwijn 1985); BEL: not present.
Middle Pleistocene (late Cromerian to middle Saalian).
B20E0048 (Urk)
Depth (thickness) AH:
28.26 - 71.9 m (43.64 m) below land surface
Is replaced by borehole B20B0024 (Enkhuizerzand) which better reflects the characteristics of this formation.
Depth (thickness) AH:
33.1- 61.0 m (27.9 m) below land surface
Replaces borehole B20E0048 (Urk) (Doppert et al. 1975).
Depth (thickness) AH:
37.00 - 51.95 m (14.95 m) below land surface
Origin of name
Named after the village of Urk in the northern-central Netherlands.
Previous name(s)
Vianen Formation. The 'Mengzone' deposits (cf. Doppert et al. 1975), previously part of the unit, are now assigned to the Appelscha Formation (Bosch et al. 2003).
Reviewed by (date)
Wim Dubelaar (2018), Sytze van Heteren (2019).
Bosch, J.H.A. 1990. Toelichtingen bij de Geologische kaart van Nederland 1:50.000. Blad Assen West (12W) en Blad Assen Oost (12O). Rijks Geologische Dienst, Haarlem.
Bosch, J.H.A., Busschers, F.S., Weerts, H.J.T. 2003. Beschrijving lithostratigrafische eenheid. Nederlands Instituut voor Toegepaste Geowetenschappen TNO. Utrecht.
Bosch, J.H.A., Kok, H. 1994. Toelichtingen bij de Geologische Kaart van Nederland 1:50.000. Blad Gorinchem (Gorkum) West (38W). Rijks Geologische Dienst, Haarlem.
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.
Klostermann, J. 1992. Das Quartär der Niederrheinischen Bucht. Geologisches Landesamt Nordrhein-Westfalen, Krefeld, 200 p.
Laban, C. 1995. The Pleistocene Glaciations in the Dutch Sector of the North Sea. A Synthesis of Sedimentary and Seismic Data. PhD thesis, University of Amsterdam, 194 p.
Long, D., Laban, C., Streif, H., Cameron, T.D.J., Schüttenhelm, R.T.E. 1988. The sedimentary record of climatic variation in the southern North Sea. Philosophical Transactions of the Royal Society London B, 318 (1191), 523-537.
Zagwijn, W.H. 1985. An outline of the Quaternary stratigraphy of the Netherlands. Geologie en Mijnbouw, 64, 17-24.
Zandstra, J.G. 1971. Geologisch onderzoek in de stuwwal van de oostelijke Veluwe bij Hattem en Wapenveld. Mededelingen Rijks Geologische Dienst, Nieuwe Serie 22, 215-259.
Zonneveld, J.I.S. 1958. Litho-stratigrafische eenheden in het Nederlandse Pleistoceen. Mededelingen van de Geologische Stichting, Nieuwe Serie 12, 31-64.
Cite as
TNO-GDN ([YEAR]). Urk Formation. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from http://www.dinoloket.nl/en/stratigraphic-nomenclature/urk-formation.