The Holocene formation of inland sand dunes in the North of Schleswig-Holstein (Northern Germany) and its palaeoenvironmental significance

Abstract

Geomorphological investigations were carried out in the Süderlügum inland dune field and at two existing dune outcrops near Enge-Sande (North Frisia). The focus was on the age of the dunes, possible anthropogenic or climatically induced reactivation phases and their triggers against the backdrop of a palaeoenvironmental reconstruction. To this end, corings and outcrops were created, which were described and classified in terms of soil geography. The sands were dated using six radiocarbon dates and three OSL ages. In addition, some samples were examined for their phytolith content, biomarkers (n-alkanes), the grain size composition of the dune sands in comparison to other dune fields on the Jutland Peninsula, and, furthermore, the degree of roundness of the sand grains. The study found that at all sites investigated, only horizontally deposited drift sand covers and, at most, low dunes with a maximum height of 2 m can be identified for the Late Glacial. Later, Holocene podzols developed. The current dune relief, which reaches up to 8.5 m high, only emerged after the Roman Empire, but probably not until the early Middle Ages. The surfaces buried by the dunes date back to the pre-Roman Iron Age, and an early influence of the Late Neolithic Single Grave Culture (SGC) is presumed, which is attributed to pastoral farming on loose soils. Analysis of biomarkers indicates the influence of Erica and Juniperus in recent soils, while prehistoric surfaces suggest grass vegetation but no forest. The results are confirmed by the pollen profile from an adjacent peat bog. Under the dunes, there were even indications of moisture-loving vegetation. The analysis of phytolith content also revealed high levels for one of the old surfaces, indicating semi-open grass and bush vegetation. Artificial deforestation followed by grazing should therefore be regarded as the main trigger for the proven formation of new dunes.