HOLOCENE AEOLIAN SEDIMENTATION AND EPISODIC MASS-WASTING EVENTS RECORDED IN LACUSTRINE SEDIMENTS ON LANGøYA IN VESTERåLEN, NORTHERN NORWAY

In this study, the frequency of mass-wasting events and past storminess has been reconstructed throughout the Holocene (11500 cal. yr BP to present) from lacustrine sediments in lake Trehynnvatnet (33 m a.s.l.), which is located in a glacially carved valley at Nykvåg on the outmost coast of western Langøya, Vesterålen, northern Norway. Sediment cores (~2-5 m long) have been examined by use of high-resolution magnetic susceptibility and XRF-scanning as well as grain size and loss-onignition analysis. In total 35 episodic event layers have been identified throughout the Holocene. The majority of these events are characterized as discrete coarse-grained sediment layers followed by normal grading, and are related to past mass-wasting activity within the catchment. Periods with high mass-wasting activity are dated to 11000-10500, 5500- 4500, 4000-3500, 3000-2500, 2000-1000 and 500-0 cal. yr BP. The continuous input of sand grains (>250 μm) has been systematically investigated throughout the sediment cores. The sand grains are related to catchment samples from the sandy beach deposits in Sandvikbukta c. 750 m away in SW direction, and are suggested to indicate (niveo-) aeolian influx to the lake. The content of sand grains varies greatly throughout the record, although there is a clear increase in influx of sand during the last 2800 years. Periods with high aeolian influx are proposed to indicate increased storminess, which occurred between 1600-1550 (AD 350- 400), 1400-1300 (AD 450-550), 750-550 (AD 1200-1400) and 250-20 cal. yr BP (AD 1700-1930), which to some degree coincides with periods of increased storminess and winter precipitation recorded in other studies around the North Eastern Atlantic region.