Wormer Member

NUNAWO

Formal (Weerts 2003).

Grey fine sand, silty or clayey, shelly, calcareous. Locally, medium sand. Intercalated silt and clay layers, bioturbated. Grey clay, silty or sandy, shelly, partly organic. Shell beds (lags).

Estuarine or back-barrier tidal basin behind an open coast segmented by many inlets with ebb- and flood-tidal deltas (Beets & Van der Spek 2000), including channel and channel-margin (coarsest shelly sand and clay), abandoned channel (clay), sand flat and mudflat (sand and consolidated mud), tidal marsh (organic consolidated mud), and lagoon (organic clay) (Van Straaten 1963; De Mulder & Bosch 1982; Westerhoff et al. 1987; Ebbing et al. 2003; Vos & Van Kesteren 2000; Donselaar & Geel 2007).

Commonly, sharp and erosive contact with peat (Basisveen Bed, Nieuwkoop Formation), locally gradual transition (in case of Velsen Bed). Elsewhere, sharp contact with various Pleistocene units.

Stratigraphically below peat (Hollandveen Member, Nieuwkoop Formation). Commonly, thick bluish grey clay layer at the top. Unconformable contact with oldest Hollandveen peat, tidal sand and clay (Walcheren Member; commonly jointly assigned to Naaldwijk Formation, undifferentiated), shoreface sand (Zandvoort Member, Naaldwijk Formation), fluvial sand and peaty clay (Echteld Formation), or marine sand (Southern Bight Formation) or mud (Urania Formation; Rijsdijk et al. 2005).

Up to about 40 m in tidal-channel fills.

Widely distributed in a broad coastal zone within the overall lateral extent of the Naaldwijk Formation, except in the Wadden Sea area (here, not distinguished from Walcheren Member).

North Sea: oldest part of the Elbow Formation, mapped in conjunction with the British and Belgian Geological Surveys Balson et al. 1991; Stoker et al. 2011); UK: British Coastal Deposits Group (McMillan et al. 2011); GER: Calais Unter-formation (Sindowski, 1968); BEL: Calais Member, Vlaanderen Formation (Paepe & Baeteman 1979).

Holocene (Greenlandian - Northgrippian).

Named after the village Wormer, located north of Amsterdam.

Calais Deposits (Doppert et al. 1975), Lower Member A (De Mulder & Bosch 1982).

Wim Dubelaar (2018), Sytze van Heteren (2019).

Balson, P.S., Laban, C., Schüttenhelm, R., Paepe, R., Baetman, C. 1991. Ostend Sheet 51° N-02° E, Sea bed sediments and Holocene geology. British Geological Survey, Rijks Geologische Dienst, Belgische Geologische Dienst, 1:250000.

Beets, D.J., Van der Spek, A.J.F. 2000. The Holocene evolution of the barrier and the back-barrier basins of Belgium and the Netherlands as a function of late Weichselian morphology, relative sea-level rise and sediment supply. Geologie en Mijnbouw / Netherlands Journal of Geosciences 79 (1), 3-16.

De Mulder, E.F.J., Bosch, J.H.A. 1982. Holocene stratigraphy, radiocarbon dating and paleogeography of centra land northern North Holland (The Netherlands). Mededelingen Rijks Geologische Dienst 36 (3), 111-160.

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.

Ebbing, J.H.J., Weerts, H.J.T., Westerhoff, W.E. 2003. Towards an integrated land–sea stratigraphy of the Netherlands. Quaternary Science Reviews, 22, 1579-1587.

Geel, C.R., Donselaar, M.E. 2007. Reservoir modelling of heterolithic tidal deposits: sensitivity analysis of an object-based stochastic model. Netherlands Journal of Geosciences - Geologie en Mijnbouw, 86 (4), 403-411.

McMillan, A.A., Hamblin, R.J.O., Merritt, J.W. 2011. A lithostratigraphical framework for onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain and the Isle of Man. British Geological Survey Research Report, RR/10/03. 343pp.

Paepe, R., Baeteman, C. 1979. The Belgian coastal plain during the Quaternary. In: Oele, E., Schüttenhelm, R.T.E., Wiggers, A.J. (eds), The Quaternary History of the North Sea, 143—146. Acta Univ. Ups. Symp. Univ. Ups. Annum Quingentesimum Celebrantis 2, Uppsala. ISBN 91-554-0495-2.

Rijsdijk, K.F., Passchier, S., Weerts, H.J.T., Laban, C., Van Leeuwen, R.J.W., Ebbing, J.H. 2005. Revised Upper Cenozoic stratigraphy of the Dutch sector of the North Sea Basin: towards an integrated lithostratigraphic, seismostratigraphic and allostratigraphic approach. Netherlands Journal of Geosciences 84, 129-146.

Stoker, M.S., Balson, P.S., Long, D., Tappin, D.R., 2011. An overview of the lithostratigraphical framework for the Quaternary deposits on the United Kingdom continental shelf. British Geological Survey Research Report, RR/11/03. 48pp.

Sindowski, K.H., 1968. Gliederungsmöglichkeiten im sandig ausgebildeten Küsten-Holozän Ostfrieslands. Eiszeitalter und Gegenwart 19, 209-218.

Van Straaten, L.M.J.U. 1963. Aspects of the Holocene sedimentation in the Netherlands. Verhandelingen van het Koninklijk Nederlands Geologisch Mijnbouwkundig Genootschap. Geologische Serie, 21 (1), 149-172.

Vos, P.C., Van Kesteren, W.P. 2000. The long-term evolution of intertidal mudflats in the Northern Netherlands during the Holocene; natural and anthropogenic processes. Continental Shelf Research 20, 1687-1710.

Weerts, H.J.T. 2003. Beschrijving lithostratigrafische eenheid. Nederlands Instituut voor Toegepaste Geowetenschappen TNO. Utrecht.

Westerhoff, W.E., De Mulder, E.F.J., De Gans, W. 1987. Toelichtingen bij de Geologische kaart van Nederland 1: 50.000 Blad Alkmaar West (19W) en Blad Alkmaar Oost (19O). Rijks Geologische Dienst, Haarlem.