A high‐resolution sea‐level proxy dated using quartz OSL from the Holocene Skagen Odde spit system, Denmark

Abstract

The contact between wave‐influenced foreshore and aeolian‐influenced backshore sediments (BA boundary) in raised spit deposits (Skagen Odde) is here used as a proxy for palaeo‐sea level over the past 7600 years. The elevation of the BA boundary was measured at 57 sample sites along the northwestern coast of the spit, and the age of these sites determined by optically stimulated luminescence (OSL) dating of quartz grains. The elevation of the BA boundary with age gives past variation in relative sea level; relative sea level rose between c. 7600 and c. 6250 years ago, when it reached a peak value around 12.5 m above present mean sea level (apmsl), followed by a slow sea‐level fall until c. 4600 years ago before it dropped rapidly to reach 2 m apmsl c. 2000 years ago. From the new data it is tentatively deduced that the land uplift rate declined from about 3 mm a−1 6000 years ago to about 1.5 mm a−1 2000 years ago (low estimate), or alternatively from 5 mm a−1 5000 years ago to 1.5 mm a−1 2000 years ago (extreme estimate). These data indicate that the long‐term average rate of vertical land movement during the past 5000 years was around 1.8 mm a−1 (low estimate) or around 2.5 mm a−1 (extreme estimate). These values seem reasonable compared with a modern value of about 1.6 to 1.7 mm a−1. The lack of an independent data set illustrating the isostatic uplift history with time, however, precludes the construction of a well‐constrained eustatic sea‐level curve.