Lateglacial to Holocene relative sea-level changes in the Bjarkarlundur area near Reykholar, North West Iceland

Abstract

This paper presents results from seven isolation basins to investigate the relative sea-level history from the Lateglacial and the mid to late Holocene from the Bjarkarlundur area near Reykhólar on the Reykjanes peninsula in North West Iceland. Results presented help to constrain the timing and rate of relative sea-level (RSL) change since deglaciation and also the timing of deglaciation itself in the Bjarkarlundur area. The marine limit is estimated to be approximately 80 m above sea level based on an isolation basin with sill altitude at 79.1 m. The maximum age of this marine limit and, hence, local deglaciation is estimated at 12.2 14C ka BP. Relative sea level then fell rapidly during the late Bölling–early Alleröd at a rate of approximately −35 mm 14C a−1 to below 50 m by 11.4 14C ka BP. After this the rate of RSL fall decreased significantly during the late Alleröd and Younger Dryas Chronozones (averaging −6 mm 14C a−1 between 11.4 and 9.7 14C ka BP). Based on isolation basins with sill altitudes of 51.1 and 41.1 m, our data constrain any possible fluctuation in RSL produced by regrowth of ice during the Younger Dryas to below 10 m. After 9.7 14C ka BP the rate of RSL fall increased significantly to approximately −23 mm 14C a−1 to at least 9.0 14C ka BP. If eustatic sea-level rise is taken into account and the calibrated timescale is used, actual crustal uplift rates are estimated at +56 and +46 mm cal. a−1 during Lateglacial and early Holocene times, respectively. During the mid to late Holocene RSL then rose to at least 1 m above present-day levels, gradually falling to the present-day level from 3.1 14C ka BP. These results demonstrate the potential of isolation basin data for investigating the timing and rate of RSL change in Iceland. This can add important well-constrained information on RSL when combined with data from raised beaches. Copyright © 2009 John Wiley & Sons, Ltd.