|
Subdepartment of Quaternary Research, Botany School, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
Godwin Institute of Quaternary Research, Department of Geography, Downing Place, Cambridge CB2 3EN, UK
The Strait of Dover (Pas-de-Calais) is a narrow sea passage that links the North Sea and the English Channel between Britain and France. Much evidence suggests that the Dover Strait did not exist throughout most of the Pleistocene. Instead, a Chalk barrier was present, formed by the Weald-Artois anticline. Advance of the continental ice-sheet across the North Sea in the Middle Pleistocene Elsterian/Anglian Stage apparently dammed the southern part of the basin and water discharging into it was prevented from reaching the Atlantic to the north. The resulting lake apparently drained by spilling over the barrier and initiated the gap. This scenario is supported by sediments at Wissant, France. This theory contrasts with one, proposed by French geologists, that favours a structural origin.
Overflow from the lake has been interpreted as having been catastrophic. This was invoked to explain the origin of the complex anastomosing system of valleys or channels that occurs on the floor of the Channel cut into bedrock, predominantly of Mesozoic age. These valleys are interlinked to form a drowned drainage system and can also be linked to present rivers that enter the Channel on both the British and French sides. However, it is highly probable that the drowned valley system is multigenetic, resulting from repeated fluvial and marine erosion and deposition rather than representing a single, short-lived event. The valley system probably originated in the late Early to early Middle Pleistocene as a consequence of uplift of the Weald-Artois region.
Once the Dover Strait was formed, the rivers Thames and Scheldt were deflected through the gap and into the Channel River system during periods of low relative sea-level. Subsequently these rivers were probably joined by the Maas and Rhine, diverted by glaciation in the Drenthe Sub-stage (Saalian/Wolstonian Stage). The narrows seem to have been progressively enlarged by marine tidal scour and coastal erosion during high sea-level events.
This article has been cited by other articles:
 |
|
 |
|
  D. K. C. Jones On the uplift and denudation of the Weald Geological Society, London, Special Publications, 1999; 162: 25 - 43. [Abstract] [PDF]
|
|
