GEUS Geology of Denmark

The map of Quaternary deposits in Denmark is based on a systematic geological mapping, where the Quaternary sediments are tested with a hand auger in a depth of one meter for about each 100 m. Furthermore well data from the water well data base are used for support of the interpretation in the less than 15 % of the land area, which remains to be covered. Ten units are differentiated in the geological map of Quaternary sediments, which are grouped in glacial deposits, extra-marginal late glacial deposits, post glacial marine deposits, freshwater deposits, and aeolian sand.The glacial deposits constitute sandy and gravelly till including sandy or leached lodgement till as well as ice-contact deposits (5), clayey till, mainly deposited as lodgement till (6), glaciofluvial sand and gravel deposited on pro-glacial outwash plain (7), glaciolacustrine clay, silt and fine-sand either deposited in proglacial lake depressions or in ice-dammed basins (8).The extra-marginal deposits were formed in the foreland to an ice margin and were thus never superposed by till deposits. The outwash sand deposits are sand and gravel deposited in a sandur setting less than 20.000 years old (9). The extra marginal glaciomarine marine deposits comprise the Vendsyssel Formation dated to 17-15.000 years before present, which was subsequently glacio-isostatically elevated about 20 m above present sea level in northern Denmark (10).The post glacial deposits comprises beach ridges (4) and marine shore near deposits (3) isostatically elevated since the Stone Age time. The post glacial freshwater deposits (2) include peat, gyttja, clay, silt and sand deposited in lake basins or in the consequent drainage system of the present geomorphology.The most recent deposits are the aeolian dune sands (1). These deposits are either inn-land dune sands dated to be as old as 7.000 years before present or the coastal dunes, which mainly started to migrate inland from about 2-300 years ago.