The Western Gneiss Region ( no, Gneisregionen) is a large

geological unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

chiefly made of

gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

rock that formed through

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...

during the

Caledonian orogeny The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occ ...

. It makes up a tectono-stratigraphic terrane of the

Scandinavian Caledonides The Scandinavian Caledonides are the vestiges of an ancient, today deeply eroded orogenic belt formed during the Silurian–Devonian continental collision of Baltica and Laurentia, which is referred to as the Scandian phase of the Caledonian oroge ...

and is also part of the

Baltic shield The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean and ...

. The region extends across western Norway from Bergen to Trondheim as a Caledonian window, outliers of the Western Gneiss Region crop out as far north as the Lofoten archipelago. The rocks of the Western Gneiss Region are made up of variously deformed

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...

, and cover rocks of

autochthonous Autochthon, autochthons or autochthonous may refer to: Fiction * Autochthon (Atlantis), a character in Plato's myth of Atlantis * Autochthons, characters in the novel ''The Divine Invasion'' by Philip K. Dick * Autochthon, a Primordial in the ' ...

and para-autochthonous origin with evidence of medium to high

grade Grade most commonly refers to: * Grade (education), a measurement of a student's performance * Grade, the number of the year a student has reached in a given educational stage * Grade (slope), the steepness of a slope Grade or grading may also ref ...

metamorphism including

ultra-high-pressure metamorphism Ultra-high-pressure metamorphism refers to metamorphic processes at pressures high enough to stabilize coesite, the high-pressure polymorph of SiO2. It is important because the processes that form and exhume ultra-high-pressure (UHP) metamorphic r ...

. Rocks of the Western Gneiss Region formed 1700 to 1600 million years ago in the Late Paleoproterozoic. What was to become the Western Gneiss Region was intruded by

migmatites Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock tha ...

and

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

s during the

Sveconorwegian orogeny The Sveconorwegian orogeny was an orogenic system active 1140 to 960 million years ago and currently exposed as the Sveconorwegian orogenic belt in southwestern Sweden and southern Norway. In Norway the orogenic belt is exposed southeast of the f ...

References

External links

Virtual "fieldtrip" of the Western Gneiss Region
Leeds University {{Geology of Fennoscandia Geology of Norway Terranes