99 Geomorphology (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

MIDDLE TO LATE WEICHSELIAN GLACIER FLUCTUATIONS AND ROCK-GLACIER ACTIVITY RELATED TO THE SEA-LEVEL HISTORY OF NORTHERN ANDøYA, ARCTIC NORWAY

Paper number: 99-3
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Northwards transport of Atlantic water by the Norwegian Current warms the Norwegian Arctic coast 5-10°C above the annual mean for latitude 69°N. A reduction in heat transport would cause a shift from anomalously warm and maritime open-ocean climate to a cold and continental regime with seasonal sea-ice cover. Its proximity to the shelf break and diversity of geomorphological features has made the island Andøya (69°N, 15°E) a key area for reconstructing ice-age history and palaeoclimatic investigations for more than a century. Palaeoclimatic archives from this region facilitate testing of key hypotheses on the role of ocean, sea-ice, atmospheric processes, and feedbacks in driving Arctic climate variability during the shift from glacial to peak interglacial climates. In order to resolve the Late Weichselian glacial, periglacial and sea level history of northern Andøya we have combined the use of optically stimulated luminescence dating and cosmogenic nuclide surface exposure dating.

Optically stimulated luminescence dating has been performed on glaciofluvial and glaciolacustrine deposits (supra- and sub-till positions), as well as beach deposits underneath relict rock glaciers.

Surface exposure dating has been performed on rock samples from a variety of landforms and surfaces. The most comprehensive glacial erosion phase occurred prior to 40 ka with glacial erosion up to at least 100 m asl on both the western and eastern side of the northern part of the island. Surface exposure ages from boulders on marginal moraines indicate isolation from the continental ice sheet since c. 35 ka on the northwest side, and that low-elevation cirque glacier activity persisted until c. 12-13 ka. Beach ridges on the western side of the island developed at c. 20 m asl suggest a limited ice extent and seasonally open water conditions around 19 ka. Talus-derived rock glaciers on the western side of the island overrun the c. 19 ka shoreline and became inactive c. 14.3 ka, constraining the timing of suitable conditions for rock glacier formation close to the present sea level to between 19 and 15 ka.