Morphology and sedimentary architecture of a beach-ridge system ( Anholt, the Kattegat sea): a record of punctuated coastal progradation and sea-level change over the past ∼1000 years.

Flakket on the island of Anholt in Denmark is a cuspate foreland facing the microtidal Kattegat sea. It is composed of a number of beach ridges typically covered by dune sand and separated by swales and wetlands. OSL dating indicates that the evolution of Flakket began c. AD 1000. Foreland growth was punctuated by a major episode of coastal reorganization leading to coastal retreat c. AD 1800. Coastal retreat led to the formation of an erosion surface that separates older and higher-lying beach-ridge and swale deposits from younger and lower-lying deposits. The palaeo-sea level is deduced from the architecture of the deposits, and interpretation of ground-penetrating radar data and geomophological observations indicates that relative sea level was about 1.90±0.25 m above present sea level c. AD 1000, but about 0.00±0.25 m relative to present sea level c. AD 1830 and c. AD 1870. Anholt is situated at the margin of the uplifted Fennoscandian area; assuming uplift to be about 1.2 mm a⁻¹ it follows that absolute sea level was about +0.70±0.25 m at AD 1000, but around −0.22±0.25 m at AD 1830 and around −0.17±0.25 m at AD 1870. Within the uncertainties of the age control, the sea-level indicators mapped by ground-penetrating radar reflections and the variability of estimates of uplift found in the literature, the result obtained for AD 1000 is consistent with findings from the Stockholm area in Sweden and with a recently published global sea-level curve. [ABSTRACT FROM AUTHOR]