Sedimentary Sequences of the Sub-Recent North Sea Coast of the Western Netherlands Near Alkmaar
bookPart
On the basis of sedimentary structures, the upper 4–5 m of a sub-recent beach plain sequence, exposed in pits around the town of Alkmaar in the western part of Holland, could be subdivided into three units. The upper unit (usually less than 1 m thick) consists largely of aeolian structures and is supratidal. The middle unit (c. 2·25 m thick) is characterized by sets of coast-directed, low-angle cross-bedding, alternating with wave-rippled strata. Assuming that the tidal range during deposition of the sequence was not much different from the present range off Alkmaar, it is concluded that this unit is largely intertidal. The lower unit consists mainly of coast-directed sets of high-angle cross-bedding. Both the low- and high-angle cross-bedded sets are interpreted as lee deposits of ridges, with the wave-rippled sand representing the runnel floors. The foresets of the ridges, in particular those of the inferred intertidal zone, show regular, lateral variations in the type of lamination, which is interpreted as due to the daily shift in wave base because of the tides. The beach plain sequence is compared to one underlying a dune ridge and to recent beaches at the Dutch coast. It is concluded that beach plain sequences are characteristic of periods of rapid progradation, whereas dune ridges represent more stagnant phases in the beach development.
Topics
Dune ridge sequenceInferred intertidal zone, showing regular, lateral variationsProgradation - most rapid when waves are dissipatedReplacement of thin sandy mudflat facies in upper part of intertidal zoneThe 'Older Dune' landscape- low dune ridges separated by depressionsSedimentologyTidesDune ridge sequenceIntertidal zonesLateral variationsProgradationThe 'Older Dune' landscape- low dune ridges separated by depressionsBeaches
TNO Identifier
954071
ISBN
9781444303
Publisher
Wiley Blackwell
Source title
Holocene Marine Sedimentation in the North Sea Basin
Editor(s)
Nio, S.D.
Shüttenhelm, R.T.E.
Weering, T.C.E. van
Shüttenhelm, R.T.E.
Weering, T.C.E. van
Place of publication
Oxford
Pages
133-145
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