Geology of Norway
Encyclopedia
The geology of Norway encompasses the history of earth that can be interpreted by rock types found in Norway
, and the associated sedimentological history of soils and rock types.
The Norwegian mountains were formed around 400 million years ago during the Caledonian orogeny
.
age in Norway are confined to a few 10 km-scale areas within younger metamorphic belt
s exposed on islands off the west coast of northern Norway and as smaller fragments locally in the Western Gneiss Region in south-central Norway.
Despite intense reworking during the Caledonian orogeny
in some areas, three major belts can be recognised in the Proterozoic
rocks of Norway, the Neoproterozoic
and Mesoproterozoic
Gothian and Sveconorwegian, the Palaeoproterozoic Svecokarelian and the intervening Transscandinavian igneous belt of late Palaeoproterozoic age.
The later part of the Neoproterozoic records the break-up of the Rodinia
supercontinent
and the formation of the Iapetus Ocean
. Passive margin sequences are preserved within the lowermost allochthon
and parautochthon of the Caledonian thrust
sheets. In southern Norway the sequence is known as Sparagmite. The depositional environment
changes from fluvial
in the parautochthon to deepwater marine in the lowermost allochthon consistent with a paleogeography of an originally westward deepening basin
.
The uppermost part of the Neoproterozoic sequence throughout Norway includes a tillite, a record of the Varanger ice age
which occurred between roughly 630-590 Ma, the final part of the Cryogenian
Period. This was followed by fluvial and shallow water marine deposits of the Ediacaran
before a major marine transgression
at the start of the Cambrian
.
with the accretion
of terrane
s and ophiolite obduction
during the Late Ordovician and continent-continent collision at the end of the Silurian
.
the following sequence is recognised from the base upwards:
This vertically stacked sequence thus represents the passive margin
s of Baltica and Laurentia and intervening island arcs and back-arc basin
s telescoped together and emplaced on top of the Baltic Shield
, involving hundreds of kilometres of shortening.
, Kvamshesten, Håsteinen and Hornelen
basins along the west coast between Sognefjord
and Nordfjord
, on the islands of Smøla
, Hitra
and the western end of the Fosen
Peninsula in Trøndelag and at Røragen near Røros
close to the Swedish border. Further Devonian deposits are found on Svalbard.
During the Devonian
Period the thickened welt of crust formed by the Caledonian orogeny began to collapse. Some thrust surfaces show evidence of reactivation as low-angle extensional faults, but the main structures formed at this time were large-scale extensional detachments
. Movement on these detachments led to deposition of thick sequences of continental clastic sediments in their hanging walls and was in part responsible for the exhumation of late Caledonian ultra high-pressure metamorphic rock
s, including eclogite
s, in their footwalls. The displacements on these structures range from nearly orthogonal to the Caledonian chain in the south to being strongly oblique in mid-Norway.
age strata preserved onshore are found on Svalbard
. Rocks of this age have also been proved by drilling beneath the Barents Sea
, but nowhere else on the Norwegian continental shelf.
was a period of W-E directed rift
ing with associated igneous activity, during which the Oslo graben
formed.
rocks preserved onshore are found on Svalbard but strata of this age are also widely known from the results of exploration drilling along the entire continental shelf.
age are exposed onshore at one locality on Andøya
and have been discovered nearshore and beneath one fjord (Beitstadsfjord) northeast of Trondheim. As with the Triassic, Jurassic strata have a wide distribution along the whole continental shelf. They were dominantly deposited in a deltaic
to shallow marine environment.
The Late Jurassic was the main rifting phase in the Central Graben, Viking Graben, More Basin, Vøring Basin and on the Barents shelf. This was also the period of deposition of the main source rock
that has generated most of the petroleum
discovered in the offshore areas.
post-rift sequence. These are dominated by mudstone
s although the Upper Cretaceous sequence from the Viking Graben and south is dominated by chalk
.
In the outer parts of the Vøring margin rifting restarted in the late Cretaceous, continuing through to the early Palaeocene. This event is interpreted to be a precursor to the break-up of the North Atlantic.
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, and the associated sedimentological history of soils and rock types.
The Norwegian mountains were formed around 400 million years ago during the Caledonian orogeny
Caledonian orogeny
The Caledonian orogeny is 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 occurred from the Ordovician to Early Devonian, roughly...
.
Precambrian
Rocks of ArcheanArchean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
age in Norway are confined to a few 10 km-scale areas within younger metamorphic belt
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s exposed on islands off the west coast of northern Norway and as smaller fragments locally in the Western Gneiss Region in south-central Norway.
Despite intense reworking during the Caledonian orogeny
Caledonian orogeny
The Caledonian orogeny is 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 occurred from the Ordovician to Early Devonian, roughly...
in some areas, three major belts can be recognised in the Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
rocks of Norway, the Neoproterozoic
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
and Mesoproterozoic
Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...
Gothian and Sveconorwegian, the Palaeoproterozoic Svecokarelian and the intervening Transscandinavian igneous belt of late Palaeoproterozoic age.
The later part of the Neoproterozoic records the break-up of the Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
and the formation of the Iapetus Ocean
Iapetus Ocean
The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...
. Passive margin sequences are preserved within the lowermost allochthon
Allochthon
thumb|right|250px|Schematic overview of a thrust system. The hanging wall block is called a [[nappe]]. If an [[erosion]]al hole is created in the nappe that is called a [[window |window]]...
and parautochthon of the Caledonian thrust
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
sheets. In southern Norway the sequence is known as Sparagmite. The depositional environment
Sedimentary depositional environment
In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock...
changes from fluvial
Fluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
in the parautochthon to deepwater marine in the lowermost allochthon consistent with a paleogeography of an originally westward deepening basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
.
The uppermost part of the Neoproterozoic sequence throughout Norway includes a tillite, a record of the Varanger ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
which occurred between roughly 630-590 Ma, the final part of the Cryogenian
Cryogenian
The Cryogenian is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran...
Period. This was followed by fluvial and shallow water marine deposits of the Ediacaran
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
before a major marine transgression
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water...
at the start of the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
.
Early Palaeozoic
The early Palaeozoic history of Norway is recorded in sequences preserved either as autochthon or at various levels within the allochthon. They relate to the further widening of Iapetus during the Cambrian, the start of closure during the Early OrdovicianOrdovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
with the accretion
Accretion (geology)
Accretion is a process by which material is added to a tectonic plate or a landmass. This material may be sediment, volcanic arcs, seamounts or other igneous features.-Description:...
of terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
s and ophiolite obduction
Obduction
Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks at a convergent plate boundary. It can occur during an orogeny, or mountain-building episode....
during the Late Ordovician and continent-continent collision at the end of the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
.
Caledonian orogeny
Within the entire exposed 1800 kilometre length of this orogenic beltOrogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
the following sequence is recognised from the base upwards:
- Autochthon
- undisturbed foreland of the Baltic plateBalticaBaltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...
- Parautochthon
- thrustThrust faultA thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
sheets that have moved only a short distance (up to tens of km) from their original position- Lower allochthonAllochthonthumb|right|250px|Schematic overview of a thrust system. The hanging wall block is called a [[nappe]]. If an [[erosion]]al hole is created in the nappe that is called a [[window |window]]...
- Lower allochthon
- far travelled thrust sheets derived from the Baltic plate passive marginPassive marginA passive margin is the transition between oceanic and continental crust which is not an active plate margin. It is constructed by sedimentation above an ancient rift, now marked by transitional crust. Continental rifting creates new ocean basins. Eventually the continental rift forms a mid-oceanic...
, mainly sediments associated with the break-up of RodiniaRodiniaIn geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
- Middle allochthon
- also derived from the margin of the Baltic plate, ProterozoicProterozoicThe Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
basement and its psammiticPsammitePsammite is a general term for sandstone. It is equivalent to the Latin-derived term arenite. Also, it is commonly used in various publications to describe a metamorphosed sedimentary rock with a dominantly sandstone protolith. In Europe, this term was formerly used for a fine-grained, fissile,...
cover- Upper allochthon
- thrust sheets including island arcIsland arcAn island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates....
and ophiolitic sequences- Uppermost allochthon
- thrust sheets containing sediments with fossil assemblages indicating an origin on the margin of the Laurentian plateLaurentiaLaurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
This vertically stacked sequence thus represents the passive margin
Passive margin
A passive margin is the transition between oceanic and continental crust which is not an active plate margin. It is constructed by sedimentation above an ancient rift, now marked by transitional crust. Continental rifting creates new ocean basins. Eventually the continental rift forms a mid-oceanic...
s of Baltica and Laurentia and intervening island arcs and back-arc basin
Back-arc basin
Back-arc basins are geologic features, submarine basins associated with island arcs and subduction zones.They are found at some convergent plate boundaries, presently concentrated in the Western Pacific ocean. Most of them result from tensional forces caused by oceanic trench rollback and the...
s telescoped together and emplaced on top of the Baltic Shield
Baltic Shield
The Baltic Shield is located in Fennoscandia , northwest Russia and under the Baltic Sea. The Baltic Shield is defined as the exposed Precambrian northwest segment of the East European Craton...
, involving hundreds of kilometres of shortening.
Devonian
Devonian age continental sediments are exposed in three main areas in and around mainland Norway; the SolundSolund
Solund is a municipality in the county of Sogn og Fjordane, Norway. It is located in the traditional district of Sogn. Solund is the westernmost island municipality in Norway, and the only municipality in Sogn og Fjordane county that is made up only of islands...
, Kvamshesten, Håsteinen and Hornelen
Hornelen
Hornelen is a mountain in the municipality of Bremanger, in Sogn og Fjordane county, Norway. At , it is the highest sea cliff in Europe, and has for a long time been used as a landmark for naval navigation. The horizontal distance from the summit to the sea shore is approximately...
basins along the west coast between Sognefjord
Sognefjord
The Sognefjord is the largest fjord in Norway, and the second longest in the world. Located in Sogn og Fjordane county, it stretches inland to the small village of Skjolden...
and Nordfjord
Nordfjord
Nordfjord is a fjord and a traditional district in the northern part of Sogn og Fjordane county in Western Norway. The district comprises the municipalities of Selje, Vågsøy, Bremanger, Eid, Gloppen, Hornindal, and Stryn. Nordfjord covers an area of and is home to a population of approximately...
, on the islands of Smøla
Smøla
Smøla is a municipality in Møre og Romsdal county, Norway. It is part of the Nordmøre region. The administrative centre of the municipality is the village of Hopen, other villages include Dyrnes, Råket, and Veiholmen.-General information:...
, Hitra
Hitra
Hitra is a municipality and an island in Sør-Trøndelag county, Norway. The municipality covers the island of Hitra and several smaller islands, and is part of the Fosen region...
and the western end of the Fosen
Fosen
Fosen is a traditional district in Trøndelag, consisting of the municipalities Osen, Roan, Åfjord, Bjugn, Ørland, Rissa, Agdenes, Snillfjord, Hemne, Hitra and Frøya. The district is dominated by forested valleys, lakes, coastal cliffs but also shallow areas, and in the interior mountains reaching...
Peninsula in Trøndelag and at Røragen near Røros
Røros
is a town and municipality in Sør-Trøndelag county, Norway. It is part of the Gauldalen region. The administrative centre of the municipality is the town of Røros. Other villages include Brekken, Glåmos, Feragen, Galåa, and Hitterdalen....
close to the Swedish border. Further Devonian deposits are found on Svalbard.
During the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Period the thickened welt of crust formed by the Caledonian orogeny began to collapse. Some thrust surfaces show evidence of reactivation as low-angle extensional faults, but the main structures formed at this time were large-scale extensional detachments
Detachment fault
Detachment faulting is associated with large-scale extensional tectonics. Detachment faults often have very large displacements and juxtapose unmetamorphosed hanging walls against medium to high-grade metamorphic footwalls that are called metamorphic core complexes...
. Movement on these detachments led to deposition of thick sequences of continental clastic sediments in their hanging walls and was in part responsible for the exhumation of late Caledonian ultra high-pressure metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s, including eclogite
Eclogite
Eclogite is a mafic metamorphic rock. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth...
s, in their footwalls. The displacements on these structures range from nearly orthogonal to the Caledonian chain in the south to being strongly oblique in mid-Norway.
Carboniferous
The only CarboniferousCarboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
age strata preserved onshore are found on Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...
. Rocks of this age have also been proved by drilling beneath the Barents Sea
Barents Sea
The Barents Sea is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents...
, but nowhere else on the Norwegian continental shelf.
Permian
In southern Norway the PermianPermian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
was a period of W-E directed rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing with associated igneous activity, during which the Oslo graben
Oslo Graben
The Oslo Graben or Oslo Rift is a graben formed during a geologic rifting event in Permian time, the last phase of the Variscan orogeny. The main graben forming period began in the late Carboniferous, which culminated with rift formation and volcanism, with associated rhomb porphyry lava flows...
formed.
Triassic
The only TriassicTriassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
rocks preserved onshore are found on Svalbard but strata of this age are also widely known from the results of exploration drilling along the entire continental shelf.
Jurassic
Rocks of JurassicJurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
age are exposed onshore at one locality on Andøya
Andøya
Andøya is the northernmost island in the archipelago of Vesterålen. Andøya is located in the Andøy municipality in Nordland county, Norway.The island has an area of 489 km², making it the tenth largest island in Norway. The island is connected to the neighboring island of Hinnøya using the...
and have been discovered nearshore and beneath one fjord (Beitstadsfjord) northeast of Trondheim. As with the Triassic, Jurassic strata have a wide distribution along the whole continental shelf. They were dominantly deposited in a deltaic
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
to shallow marine environment.
The Late Jurassic was the main rifting phase in the Central Graben, Viking Graben, More Basin, Vøring Basin and on the Barents shelf. This was also the period of deposition of the main source rock
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
that has generated most of the petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
discovered in the offshore areas.
Cretaceous
The Late Jurassic basins offshore were infilled and onlapped by the CretaceousCretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
post-rift sequence. These are dominated by mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s although the Upper Cretaceous sequence from the Viking Graben and south is dominated by chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
.
In the outer parts of the Vøring margin rifting restarted in the late Cretaceous, continuing through to the early Palaeocene. This event is interpreted to be a precursor to the break-up of the North Atlantic.