Holocene vegetation and paleoclimatic and paleomagnetic history from Lake Johnston, Tasmania

Lake Johnston cirque contains some of the best subalpine rainforest in Tasmania. Pollen from the sediments shows Lagarostrobos franklinii, which presently reaches 1040 m, may be a glacial relict. Nothofagus cunninghamii-Nothofagus gunnii subalpine rainforest developed between 9000 and 6000 C-14 yr B.P., with a maximum at 8700 C-14 yr B.P. After 6000 C-14 yr B.P. Nothofagus gunnii became more important, and from 3600 14C yr B.P. sclerophyll and heath components increased. Partial burning of the catchment occurred periodically. Early Holocene climate was warmer and wetter than late Holocene climate. The vegetation and climate changes are similar to those recorded from western South Island New Zealand and Chile. Radiocarbon dates give a sedimentation rate of 0.43 mm/yr. Cores are correlated by magnetic susceptibility. Magnetic ages are assigned by matching with the C-14-dated secular variation master curve for southeastern Australia. Magnetic ages are consistent with the C-14 chronology when the former are adjusted by 350 years. (C) 2001 University of Washington.