Geological fun facts following the Arctic Race of Norway 2022
Please join us for a geology tour following the World Tour race Arctic Race of Norway 2022.
The geological framework for the Arctic Race of Norway 2022 is set by the collision between the two old continents, Baltica (present day Northern Europe and Russia) and Laurentia (present day North America and Greenland), approximately 500-400 million years ago. At this stage of the history Baltica had already started to subduct below Laurentia and detached slices of both the basement and the oceanic crusts between the two continents were thrusted upon the old and already worn-down continent of Baltica.
We hope you enjoy the geology tour as well as the bike race.
You can read more about the Arctic Race of Norway on their homepage.
Stage 1, 11 Aug. Mo i Rana- Elsfjord-Mo i Rana
Seljeli ophiolite complexes at Elsfjord. Photo: Agnes Raaness, NGU.
The first stage of the Arctic Race of Norway is set well situated within the Uppermost bedrock nappes that were thrusted upon the Baltic continent. These bedrock units are in general very rich in mineral resources, and both present and previous mining activities are important for the town of Mo i Rana. Iron ore is still mined east of the town, talc and calcite marble was mined in the west, and the mountain just south of the town are rich in sink deposits.
Just as the riders hit north and head back to Mo in the Drevja valley, there are soapstone deposits. And by the Elsfjord summit, white dolomite is being quarried at Seljeli.
Both the iron ore deposits, and the marble deposits are sedimentary deposits, while the soapstone deposits are related to ultramafic rocks once part of ophiolite complexes and a part of the oceanic crust of the former Iapetus Ocean.
Stage 2, 12 Aug. Mosjøen-Brønnøysund
De syv søstre synes på kysten på Helgeland. Photo: Morten Smelror, NGU.
The 2nd stage takes place within the Uppermost Allochthon, these are the bedrock sheets that has been transported the longest distance and might once have been a part of the Laurentian side of the ocean. In this area, the main bedrock types are mica schists and mica gneisses as well as large granitic batholiths.
The large granitic and granodioritic batholites were formed app. 450-430 million years ago when basaltic magma rose from the mantle, intruded the continental crust above including melting the country rocks and mixing with these melts. This is a process common above subduction zones even today.
One of these batholiths is known as the Bindal Batholith and the route of this stage goes along two of the sides of the batholith. The larger and dramatic mountain range to the west of the route is set within this granite.
Lomsdal-Visten National Park cover a large part of the Bindal Batholith. Photo: Fredrik Høgaas, NGU.
Stage 3, 13 Aug. Namsos-Levanger
Migmatittic gneiss from the Western Gneiss Region. Photo: Agnes Raaness, NGU.
A special feature of the Caledonides of southern Norway is the exposure of a large area of basement rocks, known as the Western Gneiss Region, and it is bounded by the Caledonian nappes in the east.
The most important rock types in the Western Gneiss Region are, not surprisingly, various kinds of granitic gneisses and migmatites, often with layers or lenses of micaceous gneisses and amphibolites.
The third stage take is a transverse from these basement rocks to the Upper and Middle Allochthons on the east. Once the riders have entered the Caledonian Nappes, the border between the Upper and Middle Allochtons will be crossed several times. Speaking of crossing borders, this stage is also a transverse of the much younger Møre – Trøndelag fault zone, which defines the major topographic features in central Norway such as the Trondheim fjord, and some major valleys parallel to it.
Stage 4, 14 Aug. Trondheim
This picture is of Trondhjemitt from Støren. Foto Agnes Raaness, NGU.
The final stage of Arctic Race of Norway 2022 is, geologically speaking, a tour of the Upper Nappes in the Trondheim area. These are fragments of deformed ophiolites; greenstone (metabasalt), gabbro and dyke complexes, andesite and trondhjemite as well as marine deposits of sandstones, limestones, dark schists and turbidites.
As a fun observation, at least twice on this stage, the cyclists will move upwards through the ophiolite sequence, from the gabbro, trough sheeted dikes and pillow lavas to the sediments deposited above.
There are some tell-tales signs within these types of rock when it comes to the geological history of the area. The ophiolites are fragments of oceanic crusts, and with their geochemical fingerprint of immature island arcs, they are the first sign that the prehistoric Iapetus Ocean had begun to close.
Both the ophiolites and the later more mature island arcs with its explosive volcanism are intruded by various types of light-coloured granites. The oldest of these intrusions are a type of granitoid rock that is named after the city of Trondheim hosting the final stage: The trondhjemite.
We hope you have enjoyed our geological tour as well as the bicycle ride.