The Jan Mayen Microcontinent is a fragment of

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

within the oceanic part of the western Eurasian Plate lying northeast of

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. At the onset of separation between the

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

and Eurasian plates 55 million years ago, it formed part of the eastern margin of the Greenland Plate. Propagation of a new spreading center from the Reykjanes Ridge separated this microcontinent from the Greenland Plate. For a short period it formed a microplate, until the Aegir Ridge became inactive, after which it formed part of the Eurasian Plate. The island of

Jan Mayen Jan Mayen () is a Norway, Norwegian volcanic island in the Arctic Ocean with no permanent population. It is long (southwest-northeast) and in area, partly covered by glaciers (an area of around the Beerenberg volcano). It has two parts: la ...

is a much younger feature, formed of

volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...

, built up at the northernmost tip of the microcontinent.

Extent

The microcontinent extends about 500 km southwards from the Jan Mayen

fracture zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on eit ...

. It is up to 160 km wide. The Jan Mayen Ridge separates the

Norwegian Sea The Norwegian Sea (; ; ) is a marginal sea, grouped with either the Atlantic Ocean or the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separate ...

(the Norway Basin) from the Greenland Sea.C.Michael Hogan. 2011. Norwegian Sea. Eds. P.Saundry & C.J.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment (U.S.) Washington DC

Identification

The microcontinent was identified originally on the basis of being a bathymetric high, a positive free-air gravity anomaly and due to the lack of magnetic anomalies, all indicating that it consisted of continental crust. This interpretation has been confirmed using wide-angle seismic reflection and

refraction In physics, refraction is the redirection of a wave as it passes from one transmission medium, medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commo ...

data, coupled with standard normal incidence seismic reflection data.

Make-up

The microcontinent consists of the prominent bathymetric high, the Jan Mayen Ridge and several subsidiary ridges and intervening basins towards the south and west. Investigations using seismic reflection and refraction data have identified two passive margin sequences on the two sides of the microcontinent. Faults mapped on seismic reflection data are roughly N-S trending in the northern part becoming SW-NE trending to the south. The crustal thickness reaches a maximum of 16 km on the eastern side of the main ridge.

History

At the time of the initial break-up along the North Atlantic margin ( Aegir Ridge in this area), the Jan Mayen Microcontinent formed part of the

passive margin A passive margin is the transition between Lithosphere#Oceanic lithosphere, oceanic and Lithosphere#Continental lithosphere, continental lithosphere that is not an active plate continental margin, margin. A passive margin forms by sedimentatio ...

developed along the East Greenland margin. Towards the end of the Eocene period, at about the time marked by chron 17 ( Middle to

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

) a new spreading centre began to propagate northeastwards from the Reykjanes Ridge, forming the Kolbeinsey Ridge. During the period when both the Kolbeinsey and Aegir ridges were active, the microcontinent underwent a 30°–50° anti-clockwise rotation. This was caused by the northeastward propagation of the Kolbeinsey Ridge, with simultaneous reduction in the rate of spreading at the southwestern end of the Aegir Ridge. An alternative but challenged model involves no rotation but the development of several short-lived fracture zones cutting through the microcontinent. With both ridges active the microcontinent was also temporarily a microplate. The Kolbeinsey Ridge reached the Jan Mayen Fracture Zone and therefore linked up to the Mohns Ridge, at about chron 6 (

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

). At this time activity on the Aegir Ridge died away and the microcontinent became part of the Eurasian Plate. The northern end of the microcontinent was affected by renewed displacement on the Jan Mayen Fracture Zone. The volcanic island of Jan Mayen only formed in the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

, possibly related to a hotspot, known as the Jan Mayen hotspot, at the triple junction at the end of the Mohns Ridge.

Economic resources

The area around the microcontinent has recently become open for licensing for

hydrocarbon exploration Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for hydrocarbon deposits, particularly petroleum and natural gas, in the Earth's crust using petroleum geology. Exploration methods ...

. Licenses in the southern part, known as the northern Dreki area, have been offered by the National Energy Authority for the Icelandic government and the northern area is being assessed for future petroleum activity by the Norwegian Petroleum Directorate.

References

{{coord, 69.6, -8.2, display=title Geography of Jan Mayen Geography of Norway Geology of the Atlantic Ocean Continental fragments