OVRE AERASVATN - PALYNOSTRATIGRAPHY OF A 22,000 TO 10,000 BP LACUSTRINE RECORD ON ANDOYA, NORTHERN NORWAY

Radiocarbon datings of a 4.10 m long lacustrine sequence from Lake Ovre AErasvatn reveal continuous sediment accumulation during most of the Late Weichselian, starting before 21,800 +/- 410 BP. The pollen record for the period 21,800 to 12,800 BP is uniform and is strongly dominated by Poaceae. Pollen influx variations suggest a succession of climatic ameliorations and deteriorations. Low to Middle Arctic, interstadial conditions prevailed from 21,000 to 19,650 (19,000) BP. A pronounced climatic deterioration followed, culminating at c. 18,850-18,500 BP, synchronous with a glacial advance over the nearby Endletvatn and Nedre AErasvatn basins. At c. 18,300 BP, a climatic amelioration triggered important changes in the lacustrine environment. Organogenic gyttja (2.56 m) accumulated from 18,300 to 15,000 BP, indicating a eutrophic lacustrine environment. Sparsity of minerogenic material suggests an arid climate with low surface runoff. Further ameliorations occurred from c. 17,400 to 16,800 BP and 16,000 to 15,000 BP. From c. 15,000 BP onwards, a climatic deterioration is indicated. The 12,800 to 10,500 BP record is fragmentary. At c. 10,500 BP, an improving climate induced establishment of Betula nana -Empetrum heaths, rapidly succeeded by mesic Betula pubescens-Filipendula woodlands.