Vardekampen (Øyer)
The bedrock in large parts of Innlandet County consists of slates, sandstones and other sedimentary rocks that were deposited between 750 and 541 million years ago (Nystuen, 2013). These rocks were formed in a rift basin, the Hedmark basin. This basin or "bay" as it really was, was formed when the continental plate Baltika, with Norway, broke away from the supercontinent Rodinia. With time this bay was filled in with sediments, that later formed the rocks we today refer to as the Hedmark Group. Today, the Hedmark Group is located in Innlandet County, mainly in the old Hedmark County. However, the western part of the Hedmark Group extends well into the old Oppland County and that is where we find Vardekampen in Gudbrandsdalen.
Although these rocks are located in Innlandet today, it does not mean that it was there that they were formed. When the continent of Baltica left Rodinia it was in the southern hemisphere, far from the northern location of Norway today. Also in relation to the basement of the Baltika Plate, the Hedmark Group is in the wrong place, since the Hedmark Basin was originally located outside the coast of Møre, more than 100 km to the north-west. This is because, on its way north, Baltica collided with Greenland 500 – 405 million years ago. This collision, which was an early step in the formation of a new super continent, Pangea, formed a large mountain range in Baltica, the Caledonian mountain range. One result of this collision was that the Hedmark Group was pushed well over 100 km onto land and ended up where it is today. In some places, such as at Vardekampen, the layers broke up and twisted such that we can see all the formations in the Hedmark Group.
As a collective term for the area covered by the Hedmark Group, the older term Sparagmite Region is sometimes used. Sparagmite refers to a gray feldspathic sandstone (arkose) with poorly rounded, coarse grains, i.e. an immature sandstone.
Englund (1972) mapped the rocks at Vardekampen and the area around Tretten and Øyer. From oldest to youngest, he found these formations: Brøttum Formation (layers of black shale/slate and gray turbidite sandstone up to 750 million years old), Biskopåsen Formation (A (river deltaic) conglomerate), Biri Formation (shales and limestones), Ring Formation (sandstone), Moelv Tillite (Tillite from Varanger glaciation (Marinoan glaciation) "630-590 million years ago" (Nystuen, 2013), an ice age that may have covered the entire earth "The Snowball Earth"), the Ekre Formation (shale), the Vangsåsen Formation (sandstone). The map above is based on Englund (1972). The contour lines represents 20 m, with the thicker lines being 100 m.
References
Vardekampen
Vardekampen as seen form the south-east. In the Early Iron Age some defensive fortifications was constructed on Vardekampen. This hill was a strategic important location as it overlooked the main road up and down the Gudbrandsdalen valley. The road passed beneath the cliff seen in the picture and through a narrow side valley to right of the picture, a natural choke point. The Gudbrandsdalslågen river flows much deeper down in the main valley to the left.
Geologic profile
A rough sketch of the geological profile of Vardekampen from north to south. The profile covers the distance on the map above and shares the same legend. The profile is based on Englund (1972) and Sidlecka, Nystuen, Englund & Hossack (1987), but is only a sketch as neither source gives accurate dips for each layer.