Late-Weichselian conditions in south eastern Britain: organic deposits at Colney Heath, Herts

Abstract

Peat erratics in gravel at Colney Heath, near St Albans, have been shown to have a radio-carbon age of 13560 years ± 210. Detailed pollen analyses, identifications of macroscopic plant remains and identifications of Bryophyta are now presented and linked with reports upon Coleopteran remains already published. These results are shown to be closely similar to those of other river terrace deposits of the region including the Lea Valley Arctic Plant Bed, the Barnwell Station Plant Bed, and stages of the Nazeing (Lea Valley) deposits. Radiocarbon dates place all these within the late Weichselian and it appears that all were formed and preserved by temporary and local changes in the valleys, rather than as a result of general climatic shift. They may be taken to reflect the general late-Weichselian fauna and flora that persisted south of the ice-sheets in Britain during the later part of the last glaciation, and they are the antecedent stage to the now well-known late-Glacial Period. The late-Weichselian vegetation of this region was apparently without woodland, although dwarf shrubs including arctic birch and dwarf willows were abundant, there was a considerable variety of dry-land plants, including many heliophytes and plants of open ground, and aquatic and marsh plants were present in abundance and variety. The plant lists include many of strongly northern or arctic alpine range, but there are already present a few species with decidedly southern range, as well as many widely ranging species. A few species of both oceanic and continental range are also present. The plant evidence accords with that from the animal remains.