HIGH RESOLUTION STUDIES OF LAKE SEDIMENTS FROM THE LOFOTEN ISLANDS, NW NORWAY

We hypothesise that the Lofoten islands are sensitive to changes in ocean currents (fluctuations of the North Atlantic Drift) and to circulation shifts associated with different modes of the North Atlantic circulation. At present, the outer islands are bathed in waters that reach +11°C in summer (+5-6°C in winter) in spite of their high latitude location within the Arctic Circle. Changes in the strength and or position of this warm water tongue will drastically affect the Lofoten environment. The islands have many deep, fresh water lakes and peat bogs with Holocene records; lake sediment cores and peat sections were recovered to provide a detailed record of late Holocene environmental changes in the region. To provide the best possible chronological control, a major effort has been made to develop a tephrostratigraphy for the region. As no tephra work had been done in this area before, several peat profiles were selected to develop a local tephra stratigraphy before applying this to more complex lake sediments. Two peat profiles have been analysed and show one of the best historical tephra sequences outside of Iceland itself. A good range of historical tephras has been identified, including among others, tephras from AD 1875 (Askja), AD 1510 (Hekla), AD1362 (Oraefajokull), AD 1158 (Hekla) and AD 1104 (Hekla) eruptions and also the big eruption of Hekla in 2310 BC. The AD 1158 and 2310 BC tephras have already been used to provide chronological control in our pilot cores from lacustrine and brackish water sediments. These layers can be used to correlate from core to core and lake basin to lake basin. Furthermore, we will also be able correlate with other work along the Atlantic seaboard of Europe at key dates such as the 2310 BC (Hekla 4). Using these chronostratigraphic markers, sediments from low elevations lakes in the Lofoten Islands have been analysed at high resolution, providing a detailed & chronologically well-controlled record of late Holocene environmental changes in the region.