Why the submerged sealed beaches, last remnants of the low stands of the Upper Pleistocene regression, are better expressed in the Western than in the Eastern English Channel?

Abstract

It is known that the Pleistocene conglomerate found under the English Channel results from the cementation of old beaches under a loess cover when the seawater was at lower levels. This conglomerate represents the only remnants of the Upper Pleistocene low stands of the sea. In the Western English Channel the various remnants of the beaches are clearly separated and always follow the bathymetry on their western side, which suggests a discontinuous cementation. On the contrary, in the Eastern English Channel, it seems that the cementation has been continuous, even during the high stands of the sea. Since an underwater cementation cannot be envisaged during these cold periods of time, a study of the now submerged river valleys and of the onshore neighbouring loess has been developed. They suggest that the observed discrepancy is not related: 1/ to a local erosion of the conglomerate by the rivers during lower stands of the sea; 2/ to the thickness of the initial loess cover; 3/ to their carbonate concentration. This discrepancy is more likely the result of a local overlap of some of the consolidated beaches during the little transgressions which interrupted the general regression.
Highlights
• The conglomerate of the English Channel corresponds with old cemented beaches.
• The beaches were cemented under Weichselian loess during low stands of the sea.
• The distribution of the old beaches is different in the Western and Eastern English Channel.
• This discrepancy is not the result of different cementation processes or of erosion.
• It results from a different orientation of the beaches with respect to the general EW loess deposits coating the submerged basement cliffs.