HOLOCENE FLUCTUATIONS OF THE VESTFIRDIR ICECAP, NW ICELAND

The geomorphic and terrestrial record of northern and eastern Vestfirdir, NW Iceland, documents Holocene fluctuations of the Vestfirdir Icecap and sea level history. Chronology of glacial advances is determined by radiocarbon dates, tephrochronology, 36Cl exposure ages, lichenometry, morphostratigraphic relationships and historical accounts. Preboreal, Neoglacial, and Little Ice Age glacial expansion are documented in the valleys of Kaldalón, Reykjarfjordur, and Leirufjordur, which contain modern outlet glaciers. 36Cl exposure ages on boulders from the crest of an end moraine in Kaldalón have an average of 10.6± 0.9 cal ka B.P. (n=3), and the Saksunarvatn tephra is present in at least three terrestrial locations. This suggests that an extensive advance (or still-stand during retreat) occurred during the Preboreal (similar to what has been shown for the main Iceland ice sheet). There is a gap in the record from the Preboreal until ~5000 yr B.P., when peat formed beyond the outlet glaciers. Evidence for Neoglacial activity includes a well vegetated moraine in Kaldalón and possible cirque reoccupation throughout Vestfirdir. The minimum age for this Neoglacial advance is ~ 2500 yr B.P. based on radiocarbon dates on peat above the moraine in Kaldalón, although marine and lake cores suggest Neoglacial cooling earlier than this. This discrepancy is probably due to the lag time for moraine stabilization and subsequent peat growth.

The marine limit on northern and eastern Vestfirdir varies from 14 m asl to 48 m asl, and based on morphostratigraphic relationships, the higher marine limits (30 m asl to 48 m asl) are interpreted to be older than the Preboreal. Below the marine limit in Ísafjardardjúp (30 m asl) and Jokulfirdir (14m asl) there is a second, extensive shoreline at an average elevation of 5 m asl, but varies between 4-7 m asl. A reservoir corrected radiocarbon date of 3212 ± 40 yr B.P. on a bivalve at Lónseyri demonstrate a potential chronologic link with the Nucella layers in south and southwest Iceland. A third shoreline is present along the Leirufjordur and part of the Jokulfirdir coastline at 30-50 cm asl. It has a reservoir corrected radiocarbon age of 131 ± 46 yr B.P., which approximately corresponds to the Little Ice Age maximum.