RECONSTRUCTING HOLOCENE GLACIER VARIATIONS FROM GLACIAL LAKE SEDIMENTS: STUDIES FROM NORDVESTLANDET AND JOSTEDALSBREEN-JOTUNHEIMEN, SOUTHERN NORWAY

Glacial and non-glacial (control) lakes are used to reconstruct a continuous record of Holocene glacier variations from C-14-dated glacio-lacustrine sediments in four distal glacial lakes from southern Norway. Silt/clay bands (commonly 5-10 cm thick), characterized by low organic content, high X-ray density, high mineral magnetic susceptibility and high natural remanent magnetisation (NRM) intensity, are attributed to enhanced minerogenic sedimentation following glacierization of the catchment. These glacigenic bands are different from thinner (0-2 cm) minerogenic laminations found in both glacial and non-glacial lakes with steep slopes in the catchment. Glaciers disappeared from at least three of the catchments shortly after 9000 BP and remained absent throughout the 'Climatic Optimum' of the early- to mid-Holocene. Relatively large glaciers and higher-altitude glaciers formed earlier, existed longer and/or exhibited more Neoglacial expansion episodes. Glaciers existed in the lake catchments at least during the following intervals: Midtivatnet, 3400-3000, 2200-2100, and after 1000 BP; Gjuvvatnet, 6400-5900, 3000-2600, 2500-2300, 1600-1400, and for two intervals after 750 BP; Flatbrevatnet II, continuously since 4900 BP; Storevatnet. one interval after 1000 BP. All glaciers attained their Neoglacial maxima during the last major Neoglacial expansion episode (the 'Little Ice Age'). This pattern implies a response to a fluctuating but generally deteriorating climate during the mid- to late-Holocene.