Were there locally two ancylus stages in the Baltic?

Abstract

Radiocarbon dates from shells in Ancylus fluviatilis bearing deposits on the islands of Öland and Gotland in the Baltic are reported. The deposits are situated at a much lower altiltude than the Ancylus limit for the two islands and have been dated at the pre-Boreal pollen zone (IV, Jessen). Ancylus layers in Finland have been dated at approximately the same ages. In 1927 the Early Ancylus Substage (A I) was defined by Thomasson for the pre-Boreal. It is suggested that the numerous deposits on the Island of Gotland with 'too low' Ancylus faunas should be studied for further evidence of pre-Boreal age, and to elucidate the question of whether these finds belong to the classical Ancylus stage or to an earlier stage separated from the classical by the Yoldia stage.