Geology and Genesis

Pleistocene
The Pleistocene is a time period characterised by large climatic fluctuations, with alternations of glacials, interglacials, stadials and interstadials. The last but one glacial period (Saalien, 200,000-130,000 years BP) is important for the genesis of the island of Texel. In this glacial period the Scandinavian glaciers reached the Netherlands. Beneath the glaciers thick layers of boulder clay are deposited. When the ice retreated several ice pushed ridges became obvious in the landscape. One of these ridges lies in the line Coevorden – Steenwijk – Gaasterland – Wieringen – Texel.

In the last glacial (Weicheselien, 120,000-10,000 years BP) the Scandinavian ice did not reach the Netherlands. In this period a periglacial climate prevailed in the Netherlands and coversands were deposited by the strong winds.

Holocene
The Holocene is the time period since about 10,000 years BP. The Holocene can be regarded as an interglacial period. At the beginning of the Holocene the sea level was about 120 m lower than today. Because the ice caps started melting the sea level started to rise again.

Between 10,000 and 7,000 years BP the sea level rose at a high speed with a minimum of 80 cm per century to several metres per century. This caused the coastline to move landwards. The ice pushed ridge (on the place of the current islands of Texel and Vlieland) divides a brackish or salt lagoon in the western Netherlands from the precursor of the Wadden Sea. This ‘Wadden Sea’ consists of estuaries with lagoons and mudflats.

In the period between 7,000 and 5,000 years BP the same trend as before is taking place (landward movement of the ‘Wadden area’) but at a much smaller speed. The sea level rise is approximately 40 to 80 cm per century. The Pleistocene High (the ice pushed ridge at the current location of Texel) is being eroded. The Wadden area is getting more and more like the current Wadden Sea. Along the coast of North- and South Holland beach ridges are forming and dune formation is taking place, which results in a relatively stabile coastline with estuaries and tidal inlets. Behind this coastline a zone of tidal marshes and mudflats was present and in the hinterland peat was being formed.

Between 5,000 and 3,000 years BP the sea level rise was much less, between 20 and 40 cm per century. The amount of sediment transported by the rivers to the sea is higher than the sea level rise and the coast progresses seawards. In the north however, erosion is still taking place of the Pleistocene High and the ‘Wadden coast’.

After 3,700 years BP, the sea inundates the tidal marsh area and the Wadden Sea emerges. The area around Texel inundates at approximately 3000 years BP.

Since the Middle Ages man plays a big role in the formation of the coast by building dikes, polders, peat reclamation and damming up the estuaries and tidal inlets.

The Dunes of Texel
Between 5000 BP and 2500 BP a coastal barrier formed along the coast of western Netherlands, in a period with a relatively low sea level rise. A vast and broad series of sandbanks lying parallel to the coast originated, only broken by beach plains and river mouths. The sandbanks were partly covered with small dunes (Old Dunes).

Between 1000 AD and 1600 AD a new period of dune formation took place, the formation of the Younger Dunes. Part of the older coastal barrier was eroded and a more steep coastal profile had developed. The formation of the Younger Dunes started with a mobile sand phase in which mobile dune complexes formed. These dunes are located on top of the coastal barrier and Old Dunes. When more vegetation started to grow, parabolic dune forms originated. About 1600 the formation of the Young Dunes was completed.
On the island of Texel mankind has played an important role in the dune formation. The Dunes of Texel can be divided into several units and the formation, characteristics and the influence of man are described in Large variety in the dune landscape of Texel.
 

References:

• Louters T. & Gerritsen F. (1994) Het mysterie van de Wadden; Hoe een getijdesysteem inspeelt op de zeespiegelstijging; Rapport RIKZ-94.040. (33R1DHM94)
• Berendsen H.J.A. (1996) De Vorming van het land, inleiding in de geologie en de geomorfologie; Fysische geografie van Nederland; Van Gorcum & Comp, Assen.