A 7000-year record of coastal evolution, Vejers, SW Jutland, Denmark

Abstract

The Holocene coastal lowland at Vejers in western Jutland has formed during the last 7000 years. The lowland is composed of a large, NNE-SSW trending spit system associated with minor and only locally developed strandplain or beach ridge systems. The main spit and back-barrier system is bounded to the north and east (inland) by old moraine landscapes (Varde Bakkeø). Most of the coastal system and also large parts of the adjacent moraine landscape is covered by aeolian sand. In this study one of the minor strandplain systems is investigated. This system is developed at the south-western margin of the old moraine landscape at Grovsø, a lake near Vejers. The Holocene sedimentary evolution of this latter system is evaluated on the basis of data from two closely situated cores and Ground-Penetrating Radar (GPR) mapping. Both cores consist of a lowermost unit with marine sediment, a middle unit with lake-aeolian sand and an uppermost unit with aeolian sandplain deposits. Peat layers and peat-rich paleosols are common. These peat-rich horizons are dated by the Accelerator Mass Spectrometry (AMS) radiocarbon technique, while the intervening sand layers are dated by Optically Stimulated Luminescence (OSL). Combined evidence from the sedimentological and chronological studies of the cores and the GPR survey, indicate that the area was first transgressed at about 5100 BC. During the subsequent period (5100–2700 BC) relative sea level rose about 5 meters, the strandplain prograded, and small coastal dunes formed. During this progradational event a large strandplain lake formed behind the frontal dune ridge and this lake was filled primarily by aeolian sand. Aeolian sand drift may have been most intense around 3000 BC. This first period of large-scale aeolian activity ended some time before 2300 BC with formation of a peat-rich paleosol. Aeolian activity, however, was soon re-established and resulted in the formation of a large sandplain with small dunes. Aeolian sand movement and accumulation, however, was punctuated by periods of landscape stabilisation and peat-rich paleosol formation. Changes from landscape stabilisation to dune field activity took place at about 2300 BC, 1450 BC, 800 BC, and 650 BC. Aeolian accumulation at the study site terminated at about AD 0, but other evidence indicates renewed aeolian activity in the dune field after AD 300 and between AD 1100 and 1900. The chronology of some of these aeolian activity phases are synchronous with cooling events in the North Atlantic region suggesting that climatic change strongly influenced dune field dynamics.