Ice margin features in the Julianehåb District, South Greenland

Abstract

The present report deals with the extension of the ice margin deposits in the Julianehåb district, South Greenland. An attempt is made to establish a Holocene chronology for the ice margin deposits within the region on the basis of their association with raised marine shorelines, combined with a determination of fluctuations of the glaciation limits of the individual stages in Holocene times. As the Narssarssuaq region in the north-eastern part of the district contains numerous extensive ice deposits, this region is treated in more detail than the other localities within the district. On the basis outlined above, it is attempted to establish a relative chronology for the ice margin deposits in the Narssarssuaq region. The remaining deposits within the district are then tentatively incorporated in the chronological scheme for the Narssarssuaq region. After the deglaciation of the district during the last phases of the Wisconsin, four periods of stagnation or readvance of the glacier lobes and the ice caps (four "stages") seem to have given rise to the formation of ice deposits. The earliest of these stages is the Niaqornakasik stage (older Dryas??), succeeded by the Tunugdliarfik stage (probably younger Dryas), the Narssarssuaq stage (probably Roman time), and the maximum extension of the ice in historie times (ca. 1750-1900 A.D.). The variation in the volume of the ice coverings (the inland ice and the Julianehåb ice cap) during the period from the Tunugdliarfik stage to the present day is studied. The superficial conditions of the ice covering above an altitude of ca. 1,700 m do not seem to have altered much since the Tunugdliarfik stage. Finally, deposits from former ice-dammed lakes in the Narssarssuaq region are treated. All the deposits from such lakes found here seem to show that all the lakes at the glacier front had a maximum height of the water level of 120-150 m. This is in accordance with J.W. Glen's theory of subglacial outbursts of ice-dammed lakes.