Le confluent Erdre-Loire, étude pollenanalytique du remplissage sédimentaire atlantique (Nantes-France).

Abstract

Pollen and radiocarbon analysis of a coring made in the alluvium of a fluvial palaeovalley enables the development of the landscape over the course of the Breton Atlantic to be described. It also provides new informations on sea levels. The standstill, or even regression of the sea between 7630 BP and 7300 BP is particularly well documented, with the establishment of alder carr. The subsequent drowning of the alder carr in about 7300 BP, at - 9 m NGF***, corresponds to the renewed onset of the marine transgression. A new marine standstill phase is evident at about 6300 BP, with the establishment of alder carr once again. At that period the level of the highest seas was between - 4 and - 5 m NGF. The natural accumulation of sediments at this site ceases at approximately - 2 m NGF, at about 6000 BP; the reason for the absence of any sediments from the period 6000 BP to the present day has yet to be explained.