Denmark / by Elwyn Davies [and others].

  • Great Britain. Naval Intelligence Division.
Date:
1944
Catalogue details

Licence: Public Domain Mark

Credit: Denmark / by Elwyn Davies [and others]. Source: Wellcome Collection.

    26/726 (page 6)
    First and Second Glacial Periods Three glacial periods can be recognized in Denmark, as in north Europe generally, in contrast with the four periods generally described for the Alps. The earliest, or Gunz, glaciation of the Alps cannot be distinguished in northern Europe where the first glacial period corre- sponds to the second or Mindel glaciation of the Alps; the second and third glacial periods of northern Europe correspond to the Riss and Wiirm glaciations of the Alps respectively. The first glacial period, during which the whole of Denmark was covered by ice, may be dismissed briefly, since its effects were largely obliterated by the deposits of the second glacial period which also invested the whole country. The morainic clay which was laid down during the first | glacial period has been identified, beneath later deposits, in some localities as a dark grey, hard and sandy clay, with small stones and fine gravel forming a much larger proportion of the deposit than the true clay. Large stones are relatively few, but the foreign boulders in it indicate that the ice came first from west Sweden and east Norway, and later from the Baltic. The first and second glacial periods were separated by an inter- glacial period which corresponds to the Mindel-Riss inter-glacial period of the Alps. During this period of warmer climate and water drainage, parts, if not all, of the country lay beneath the sea, and marine clays were deposited. Such are the Yoldia clays and the Tellina clays which in the west, as around Esbjerg, are sometimes covered by marsh and alluvium only or by fluvio-glacial deposits of the second glaciation; in the east the Tellina clays are covered by glacial drift. During the second glacial period, the ice sheets advanced once more from Scandinavia and the Baltic and extended across the whole country. They spread a covering of morainic clay and sand over the deposits of the first glacial and the first inter-glacial periods. Improve- ment in climate brought a second inter-glacial period during which the sea invaded western Slesvig and communicated through narrow straits with a large inland sea which seems to have occupied approxi- mately the basin of the modern Baltic Sea from east Slesvig to East Prussia. On the floor of this inter-glacial sea, marine deposits of gravel, sand, mud, clay and sand in succession (the Eem deposits and the Skerumhede series) were laid down. On the land from which the ice had temporarily retreated, fresh-water deposits of clay, mud, peat and sand were laid down in lake basins and depressions, while inter- glacial streams eroded valleys in the glacial deposits.