Geological Significance of North Sea Sand Transport Rates

Abstract

THE history of many marine sandstones is difficult to determine because the origins of Quaternary sands of offshore shallow seas, to which they may be equivalent, are not yet known. To lessen this gap in our knowledge, a quantitative observational and theoretical study is being made of sand transport and deposition in the southern bight of the North Sea near Holland, for which a qualitative interpretation is already available¹. There is probably as much information about currents, sediment grade and sorting, and wave heights and spectra, for this area as for any other sea in the world. In general terms, the southern part has near-surface tidal currents which reach peak speeds of about two knots and the floor of medium sand grade is wrought into large sand waves approximately transverse to the flow. In the northern part, the tidal currents are weaker, and the floor of very well sorted fine sand is flat or probably ripple marked. In between, there is a narrow zone of small sand waves with crest separation of about 10 m (Fig. 1). The inferred net travel of sand is from south to north, with erosion at the southern end and deposition all along the northern reaches of this transport path. The depth of water is only about 80–120 feet; both tidal currents, and wind-produced currents and waves, can be important.