Sediment Response to Waves and Currents, North Yorkshire Shelf, North Sea
- S.-D. Nio,
- R. T. E. Shüttenhelm and
- Tj. C. E. Van Weering
Published Online: 29 JUN 2009
Copyright © 1981 The International Association of Sedimentologists
Holocene Marine Sedimentation in the North Sea Basin
How to Cite
Jago, C. F. (1981) Sediment Response to Waves and Currents, North Yorkshire Shelf, North Sea, in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch22
- Published Online: 29 JUN 2009
- Published Print: 23 DEC 1981
Print ISBN: 9780632008582
Online ISBN: 9781444303759
- response of shelf sediments;
- measuring concentrations and in situ grain size distributions of sediments;
- following dispersal of sea-bed and sea-surface drifters;
- examining surficial sediment distribution from shoreline;
- tidal variations of current velocity and total flocculated suspended sediment
The response of shelf sediments off North Yorkshire to the contemporary hydraulic regime has been examined by: (1) measuring the concentrations and in situ grain size distributions of sediments put into suspension by tidal currents, (2) following the dispersal of sea-bed and sea-surface drifters, and (3) examining the surficial sediment distribution from the shoreline out to 50 m depth.
Both tidal currents and waves can entrain sand-size grains, and the sediment distribution reflects the present-day hydraulic regime. Sediments, mostly silt-size, are suspended near the bottom by tidal currents, both concentration and mean grain size fluctuate during the tidal cycle, reaching maxima at peak currents on spring tides. Grains suspended by tidal currents reach neither the surface nor mid-depths except in winter, when waves reinforce tidal currents, stir the bottom and attack an eroding shoreline.
Sea-bed drifters identify a residual bottom drift that is shoreward. Sea-surface drifters indicate that surface water moves in response to winds, with a seawards component of drift when winds are offshore. Since surface concentrations of suspended sediment are high during the winter months, seawards movement of suspended sediment will occur if winds are offshore. But during the summer months suspended sediment, confined near the bottom, will not move seawards against the residual bottom drift. Drifters can move northwards along the coast under certain conditions, but their long-term movement is to the south. Sediments suspended by tidal currents, although redeposited at slack water, will have a net southerly drift.
The surficial bottom sediments are aligned in well-defined zones.
(1) A nearshore sediment-free wave cut platform that extends from the foreshore to 20–40 m.
(2) Well sorted sands characterized by a seaward-fining textural gradient that is established by shoaling waves; these extend to 30 m but occur only in certain areas.
(3) Well sorted sands characterized by a seaward coarsening textural gradient that is established by tidal currents (which increase in deeper water) and/or residual currents (shorewards on the bottom); these extend to 44 m.
(4) Sandy gravels and sandy muds at depths greater than 44 m. Muds encroach on the shoreface during the summer months. Although deepwater patches of mud may locally interrupt it, the textural trend is one of increasing mean grain size seawards. This trend may be a valid analogue for shelf sediments deposited in ancient tidal seas.