Late Pleistocene and Holocene paleolimnology and climate history in Southern Sweden reconstructed from chironomid, diatom and pollen records

Abstract

The late-pleistocene and holocene sediments of two mesotrophic lakes, Stora Kroksjon and Lilla Toeklsjon in Blekinge, Southern Sweden, were analysed for chironomid, diatom and pollen remains. From both lakes, ca. 3.5m sediment were retrieved; the correlation of single cores was achieved using 14C dating and matching of the loss-on-ignition curve. The Stora Kroksjon sequence incorporated ca. 14,000 years, the Lilla Torkelsjon sequence ca. 10,000 years. Using the chironomid stratigraphy and a calibration data set, mean July air temperatures were reconstructed for both sites. At Stora Kroksjon, chironomid data indicate significantly lowered temperatures during the Younger Dryas and rising trophic status in the late Holocene. Temperature trends agreed well with other central- and northeuropean reconstructions. For the Younger Dyras, around 10,200 and 8200 cal BP, significantly cool temperatures were reconstructed. In shallow Lilla Torkelsjon, chironomid and diatom data point towards significantly lowered water levels bewteen 4500 and 2700 cal BP. In this part of the sequence, the diatom flora was near-exclusively benthic and profundal cironomids were rare. Reconstructed temperatures were uncommonly high due to reduced water depth. There were indications of mild pH fluctuations during the Holocene at Lilla Torkelsjon.