Palaeotidal modelling of continental shelves: marine implications of a land-bridge in the Strait of Dover during the Holocene and Middle Pleistocene

Abstract

Abstract Numerical models of the tide on the NW European continental shelf are useful in predicting basic tidal dynamics (amplitude, current, bed stress, mixing) from bathymetry, coastline configuration and a known ocean tide at the shelf edge. Using the M 2 constituent of the ocean tide, a numerical model has been used to investigate the tidal regime of the English Channel/southern North Sea at successive stages during the Holocene transgression, and also during the maximal sea-levels of Middle Pleistocene temperate stages, by incorporating palaeogeographical interpretations of geological data from these time-slices. Prior to the breaching of the Strait of Dover in the early Holocene, the Southern Bight of the North Sea was a quiet, shallow embayment of low M 2 tidal amplitude (<0.5 m); following breaching it attained the present state of vigorous tidal action with mean amplitudes of around 2 m. Changes in sediment transport paths and shelf-sea fronts are also indicated. Models of the Middle Pleistocene interglacial English Channel incorporate modified palaeobathymetries to compensate for tectonic uplift in the central Channel area over the past 400 000 years. These models indicate increased seasonal stratification in the Channel compared with the present mixed condition. This is in agreement with independent evidence from coccolith assemblages contained within sediments of the same age from the central Channel area.