LAKE BOKSEHANDSKENS EARLIEST POSTGLACIAL SEDIMENTS AND THEIR PALEOENVIRONMENTAL IMPLICATIONS, JAMESON LAND, EAST GREENLAND

Lake Boksehandsken, the largest lake on Jameson Land, central East Gre enland, is situated 54 m a.s.l. and holds a long (6.3 m) and complex s tratigraphy. It was analysed with respect to lithology, carbon content , C-14, micro- and macrofossils. The diamict material in the bottom is overlain by a fining-upwards sequence, possibly deposited close to a receding ice margin in a glaciomarine environment. These deposits are interpreted to have been formed at the time of the marine limit (c. 70 m) in the area. In spite of a large series of C-14 datings, very few of the obtained dates were considered reliable. This is because the se diments contain coal fragments and old redeposited plant remains. Base d on a set of arguments and correlations to the surrounding glacial st ratigraphy it is implied that the marine limit and deglaciation cannot be much older than 10 000 BP. The lithology of the lake sediments, in combination with occurrence of marine macrofossils, shows that deglac iation was succeeded by a (glacio)marine depositional environment. The lake was isolated from the sea at c. 9000 BP, followed by a short tra nsgression and a final isolation at c. 8400 BP. This sequence of event s is demonstrated by both litho- and biostratigraphy and possible caus es are discussed. A later oscillation some time between 8000 and 7500 BP, evidenced by litho-, carbon-, pollen- and Pediastrum stratigraphy, is interpreted as a regional climatic cooling possibly correlatable t o a distinct partial derivative(18)O minima in the Greenland ice cores .