Holocene palaeosols and aeolian activities in the Umimmalissuaq valley, West Greenland

Abstract

Aeolian sand sheets and active dunefields preserve an ancient Holocene land surface represented by palaeosols that occur around the present ice margin in the Kangerlussuaq area, West Greenland. To determine the relation between Holocene aeolian activities and periods of soil formation, both substantially dependent on the deglaciation history, palaeosols, aeolian sand sheets and dunefields were analysed using field data, grain size analyses, optically stimulated luminescence dating and AMS 14C data in an area of about 15 km2 of the Umimmalissuaq valley. Palaeosols are developed close to the ice margin (<2 km) in fine-grained aeolian sediment (silt loam) and covered by sandy aeolian layers. Silt contents of palaeosols (partly >60 wt%) are comparable with aeolian sand sheets currently formed at greater distances (4–5 km) from the present ice margin. We propose a transport distance for fine aeolian sediments, in which the palaeosols are formed, of at least 4 km from inboard of the present ice margin. Soil formation of the palaeosols started around 2700 cal. yr b2k. Ages from the youngest parts of the palaeosols suggest a stable period of around 2400 years, allowing for pedogenesis. This period was characterised by low but constant aeolian activity. Since aeolian activity intensified after around 300 cal. yr b2k and is still resulting in active dunefields with coarse and medium sand accumulation, the ice margin must have reached its present position at that time.