Weichselian interstadials at Riipiharju, northern Sweden - interpretation of vegetation and climate from fossil and modern pollen records

The most complete records of Weichselian ice-free conditions in northern Sweden have been retrieved from kettleholes in the Riipiharju esker. In an earlier study, the Riipiharju I core was described as containing two Weichselian interstadials and Riipiharju was chosen as type site for the second Weichselian interstadial in northern Sweden. Here, we present a palynological investigation of two new sediment cores (Riipiharju II and III) retrieved from Riipiharju. Together, the new cores comprise a late cold part of the first Weichselian interstadial recorded in northeastern Sweden (Tarendo I, earlier correlated with Perapohjola in Finland) as well as a long sequence of the second Weichselian interstadial (Tarendo II, earlier named Tarendo). The results indicate that the climate during deposition of the Tarendo II sequence was more variable than earlier suggested. According to the present interpretation it was relatively warm in the early part of Tarendo II; thereafter a long cold phase persisted, and finally the climate was warmer again in the late part of Tarendo II. The warm phases are characterized by Betula-dominant pollen assemblages, while the cold phase is characterized by high percentages of Artemisia and Gramineae pollen. Since there is still no firm chronology established of the interstadials in northeastern Sweden, two possible correlations are discussed; either Tarendo I and II are correlated with Brorup (MIS 5c) and Odderade (MIS 5a), or, perhaps more likely, they are correlated with Odderade and early Middle Weichselian (MIS 3) time.