Bovbjerg Profile
International Geosite
The Bovbjerg profile is a unique coastal cliff in Geopark Vestjylland. On the 6 km long coastline, a geological cross-section through the main line of the Weichselian Ice Age can be seen.
About Bovbjerg Profile
The Bovbjerg profile is a coastal cliff that stretches along 6 km of the west coast of Jutland from Ferring in the north to Fjaltring in the south. The main section of the profile is located on the 3 km long stretch from Ferring to Trans Kirke. The Bovbjerg profile is a unique coastal cliff that contains a profile section through the main residence line of the Weichselian ice age. The profile includes the entire glacial landscape series from the inner depression to the marginal moraine, meltwater plain and hill island. The locality thus contains an illustrative section down through the main residence line and the glacial landscape series that characterizes the landscape throughout the Geopark West Jutland. The layers in the cliff and the internal structure of the landscape are clearly visible. Layers from the Elster, Saale and Weichselian ice ages have been encountered in the cliff. In addition, there are significant examples of glacial tectonics.
The main residence line
The cliff at Bovbjerg is the only place in Denmark and perhaps the world to have a geological profile through the Main Retention Line of the Weichselian Ice Age. The Main Retention Line marks the boundary of the ice during the Main Thrust of the Weichselian Ice Age (23,000-21,000 years ago) and is a landscape element that can be traced in large parts of Jutland. The Main Retention Line thus runs through the entire Geopark Westjylland from Bovbjerg in the west to Karup Å in the east, and it can be found at many of the geopark's other locations. Elements of the glacial landscape series around it can also be found at many of the locations, and the Main Retention Line and the glacial landscape series are the geopark's main theme. The Bovbjerg profile is unique in that it contains a profile section through the Main Retention Line and the glacial landscape series around it. The location is thus the geopark's central location in terms of ice age geology.
Landscape
From Ferring Sø the terrain rises steadily to Bovbjerg Lighthouse, which is located at a height of just over 40 metres. Ferring Sø is an inner depression and Bovbjerg Lighthouse is located on top of a marginal moraine. The steady rise with the top of the marginal moraine is interrupted by a series of smaller east-west oriented ridges, which are matched by flake structures that can be observed in the coastal cliff. The southern side of the marginal moraine extends approx. 1 km south of the lighthouse, where it is replaced by the meltwater plain. The transition from the marginal moraine to the meltwater plain marks the Main Residence Line. The precise location of the line in the landscape is not clear when you are on top of the cliff, but can be observed where there is a change in the soil from clay to more sandy. South of Dybå there is a low hill island, Fjaltring Bakkeø, whose deposits can be observed in the coastal cliff at Fjaltring.
The profile
The coastal cliff at Bovbjerg represents a continuous profile, which shows the internal structure of the landscape and the composition of the soil layers. The northern part of the profile, from Ferring to a little north of Bovbjerg Lighthouse, is not so exposed and consists mainly of moraine clay. The central part of the marginal moraine, approx. 200-300 m north and south of the lighthouse, is characterized by significant deformations, where meltwater sediments and moraine deposits are folded and pushed up into flakes. The flakes strike east-west and tilt towards the north, corresponding to an ice thrust from the north. The flakes were pushed up in front of the ice during its advance to the Main Retention Line. After the push up, the flakes were overrun by the ice, which deposited a layer of moraine clay over the pushed up marginal moraine.
A little way south of the lighthouse the layers lie horizontally again, and most of the deposits are visible. Approximately 1 km south of the lighthouse the Main Retention Line is clearly observed, where the uppermost moraine clay layer tapers out and disappears. South of the Main Retention Line the cliff is dominated by sandy and gravelly meltwater deposits, but at Fjaltring there is a low cliff with, among other things, clay meltwater deposits.
An interesting landscape element along the cliff are the striking erosion gorges, originally formed by large landslides, but where flowing water (seeping groundwater or drainage water) has eroded deep into the sediments. This has created a landscape that is unique in the geopark and rare in the lowlands of Northwest Europe.
The layers in the cliff
The layers in the cliff consist of moraine and meltwater deposits. The cliff at Fjaltring contains the oldest deposit in the profile. It consists of meltwater clays, which are attributed to the Elster Ice Age. Similar deposits are found at several other locations in the Geopark.
In the profile between Trans and Ferring there are three different moraines: the lower, the middle and the upper moraine. The lower moraine consists of moraine clays from the Saale glaciation. It occurs here and there in the lower part of the profile and in the displaced flakes.
The rest of the strata series was deposited during the Weichselian glaciation. The lower moraine is overlain by upward-increasing meltwater sediments, which were probably deposited during the period when the Kattegat Ice Stream approached the area approximately 31,000-29,000 years ago. Characteristic of this strata sequence is the occurrence of layers of re-embedded Miocene lignite.
The middle moraine consists of moraine clays deposited by the Kattegat Ice Stream (approx. 29,000-27,000 years ago). The layer can be followed almost unbroken in the central part of the profile. The unit is overlain by coarse-grained deposits with many stones (of northern origin, e.g. from the Oslo area). This deposit forms the meltwater plain south of the Main Retention Line.
The upper moraine consists of moraine clay and can be followed from the beach at Ferring to the main retention line. It was deposited during the Main Thrust of the Weichselian Ice Age (23,000-21,000 years ago). The moraine is split into several units, which reflects that the ice has for a period advanced/melted away in the area around the Main Retention Line.