Sedimentology, stratigraphy and landscape evolution of a Holocene coastal dune system, Lodbjerg, NW Jutland, Denmark

The stratigraphy and landscape evolution of the Lodbjerg coastal dune system record the interplay of environmental and cultural changes since the Late Neolithic. The modern dunefield forms part of a 40 km long belt of dunes and aeolian sand-plains that stretches along the west coast of Thy, NW jutland. The dunefield, which is now stabilized, forms the upper part of a 15-30 m thick aeolian succession. The aeolian deposits drape a glacial landscape or Middle Holocene lake sediments. The aeolian deposits were studied in coastal cliff exposures and their large-scale stratigraphy was examined by ground-penetrating radar mapping. The contact between the aeolian and underlying sediments is a well-developed peaty palaeosol, the top of which yields dates between 2300 BC and 600 BC. Four main aeolian units are distinguished, but there is some lateral stratigraphic variation in relation to underlying topography. The three lower aeolian units are separated by peaty palaeosols and primarily developed as 1-4 m thick sand-plain deposits; these are interpreted as trailing edge deposits of parabolic dunes that moved inland episodically. Local occurrence of large-scale cross-stratification may record the head section of a migrating parabolic dune. The upper unit is dominated by large-scale cross-stratification of various types and records cliff-top dune deposition. The nature of the aeolian succession indicates that the aeolian landscape was characterized by alternating phases of activity and stabilization. Most sand transported inland was apparently preserved. Combined evidence from luminescence dating of aeolian sand and radiocarbon dating of palaeosols indicates that phases of aeolian sand movement were initiated at about 2200 BC, 700 BC and AD 1100. Episodes of inland sand movement were apparently initiated during marked climate shifts towards cooler, wetter and more stormy conditions; these episodes are thought to record increased coastal erosion and strong-wind reworking of beach and foredune sediments. The intensity, duration and areal importance of these sand-drift events increased with time, probably reflecting the increasing anthropogenic pressure on the landscape. The formation of the cliff-top dunes after AD 1800 records the modern retreat of the coastal cliffs.