Marine foreland. Erosional valleys.
Hellerød Kær is a low-lying marshy area largely enclosed by uplands with marked valleys. It is located at Tambohuse on the east coast of Thyholm (Figure 32-1). The area is a marine foreland and the valleys are probably erosional valleys from the late glacial period.
The low-lying area is surrounded on three sides by glacial hills that reach 10-20 m above the marsh. They are cut by marked erosional periglacial valleys and gullies. Similar valleys occur elsewhere in the geopark such as at site 22 (Trælborgdalen) and site 20 (Klosterheden). The valleys were formed by the action of melt- and rainwater soon after the ice in this area melted, and before the steep valley sides became stabilized by vegetation.
As at, for example, site 29 (Veserne-Engbjerg-Plet) the landscape was affected by the marked changes in sea level that took place at the end of the Weichselian glaciation. During the Atlantic period (9.000-6.000 years ago), sea level in this area was about 2 m higher than at present and the Littorina Sea inundated the low-lying areas. Hellerød Kær was a shallow fjord/bay in the Littorina Sea, probably with extensive mussel banks and many sea snails. It is likely that many wading birds inhabited the area. This resulted in the deposition of lime- and organic-rich mud (lime gyttja) in the fjord/bay.
The relative elevation of the land since the Atlantic period has raised the area above present sea level. The area is, however, still low-lying and bogs and marshy areas (fenland) have been a feature of the area in historical times. No serious attempts have been made to drain the fen, although a few ditches have been dug and the fen´s natural hydrology with, for example, many small springs, remains intact. Because of the occurrence of lime gyttja the groundwater is extremely hard and the fen is a habitat for a wide range of plants that have adapted to the environment, including orchids. Hellerød Kær is a splendid example of the very uncommon type of habitat called an alkaline fen (Figure 32-2).
Hellerød Kær has been listed as a Natura 2000 site. Most of the area consists of protected bogs and common land. Hellerød Kær lies within the National Geological Interest and National Coastal Landscape area Kås-Bredning-Skibsted Fjord.
There is a path to a bird-watching tower on the edge of the area that provides a good view of the fen and the fjord. The occurrence of alkaline fen in the area requires maintenance so that willows and reeds do not become established. Local volunteers have carried out nature maintenance in the area for the past ten years, including clearing willows. A local grazing society ensures that the area is grazed by cattle. Through a EU LIFE project, Struer municipality has been granted finance for scientific investigations, communication and maintenance of the area.