The Satakunta dyke swarms are a series of

dyke swarm A dike swarm (American spelling) or dyke swarm (British spelling) is a large geological structure consisting of a major group of parallel, linear, or radially oriented magmatic dikes intruded within continental crust or central volcanoes ...

s, a group of magmatic intrusions, of

Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), ...

age in the

Bothnian Sea The Bothnian Sea ( sv, Bottenhavet; fi, Selkämeri) links the Bothnian Bay (also called the Bay of Bothnia) with the Baltic proper. Kvarken is situated between the two. Together, the Bothnian Sea and Bay make up a larger geographical entity, t ...

and western and central

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

. They are made up of Subjotnian

diabase Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-graine ...

dikes Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes, ...

, associated with rapakivi

magmatism Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...

. They were most likely formed on the

Columbia supercontinent Columbia may refer to: * Columbia (personification), the historical female national personification of the United States, and a poetic name for America Places North America Natural features * Columbia Plateau, a geologic and geographic region in ...

Föglö dyke swarm

Häme dyke swarm

The Häme dyke swarm formed due to the upwelling of mantle, possibly related to the

Gothian orogeny The Gothian orogeny ( sv, Gotiska orogenesen) or Kongsberg orogeny was an orogeny in western Fennoscandia that occurred between 1750 and 1500 million years ago. It precedes the younger Sveconorwegian orogeny that has overprinted much of it. The Go ...

. The swarms were triggered by

extensional In any of several fields of study that treat the use of signs — for example, in linguistics, logic, mathematics, semantics, semiotics, and philosophy of language — an extensional context (or transparent context) is a syntactic environment in w ...

plate tectonics and convection of hot

upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appro ...

. Tholeiitic magmas, formed under the

continental lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years o ...

, were probably encouraged by elevated mantle temperature underneath the

. The time of formation was approximately 1640 million years ago.

Satakunta-Ulvö dyke swarm

The dyke swarm has been considered to be a result of a

failed rift An aulacogen is a failed arm of a triple junction. Aulacogens are a part of plate tectonics where oceanic and continental crust is continuously being created, destroyed, and rearranged on the Earth’s surface. Specifically, aulacogens are a rift ...

in the Bothnian Sea that developed as part of an extensional tectonic setting within the

supercontinent In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...

of Columbia. At various location dykes of the swarm cut across Jotnian sediments indicating a Postjotnian age for the dyke swarm. Viewed in a map the dyke swarm has the form of a 90-degrees fan radiating open to the east from a point in the Bothnian Sea.

References

{{Geology of Fennoscandia Dike swarms Mesoproterozoic magmatism Geology of Finland Geology of Sweden

Föglö dyke swarm

Häme dyke swarm

Satakunta-Ulvö dyke swarm

See also

References