Middle and Late Holocene relative sea level changes and coastal development at Rugård, Denmark

Abstract

Denmark has been subject to complex interactions of isostatic uplift and eustatic sea level changes since the last deglaciation. Prominent coastal beach ridges as well as lagoonal and lake deposits from this period have been investigated at a number of sites in the region to constrain the relative sea level (RSL) changes. However, despite the common occurrence of former coastal lagoons and lakes in proximity to raised beach ridges, they have rarely been studied in combination. In this study, we use a multiproxy approach including geospatial data, lake sediment coring, ground penetrating radar and optically stimulated luminescence dating to investigate the Holocene coastal evolution and RSL history at Rugård in Mols Bjerge National Park, on the east coast of the Jutland Peninsula. Our results show that the coastal area at Rugård was transgressed between c. 7.6 and 7.0 cal. ka BP and that RSL was ~4.5 m higher than present between c. 6.6 and 5.9 ka ago, when the highest section of the beach ridge plain was deposited. The elevation and timing of this relative highstand are in good agreement with previous estimates of the Littorina transgression and contribute to our combined knowledge about RSL history and coastal evolution in the southern Kattegat. Subsequently, isostatic adjustment has caused uplift and erosion of the beach ridge plain, but renewed progradation and deposition of a lower beach plain have taken place since c. 1740 CE. Our results demonstrate the value of using a multiproxy approach to study RSL changes and coastal evolution.