Nena, an acronym for

Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe Northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54°N, or may be based on other geographical factors ...

–

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

, was the Early

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided i ...

amalgamation of

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, ...

and

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

into a single "cratonic landmass", a name first proposed in 1990. Since then several similar Proterozoic

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

s have been proposed, including Nuna and Arctica, that include other Archaean

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...

s, such as

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...

and

East Antarctica East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almos ...

. In the original concept Nena formed in the Penokean, Makkovikan, Ketilidian, and Svecofennian

orogenies Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

. However, because Nena excludes several known Archaean cratons, including those in India and Australia, it is strictly speaking not a supercontinent. Although Nena and Nuna share many similarities, Nena accounted for a larger landmass than Nuna. This extended landmass included the Angara, Antarctica,

, and Siberia bodies. Nena, or Nuna, can, nevertheless be thought of as the core of

Columbia 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 i ...

, another supercontinent concept with several proposed configurations. The first concept of the Nena supercontinent originated with the southern regions of proto-Laurentia and the western regions proto-Baltica merging throughout the Proterozoic eon. This concept would eventually be developed to the modern day conceptualization of the Nena supercontinent which includes additions of the Angara, Antarctica, and Siberia landmasses. Throughout the amalgamation of the microcontinents which would form proto-Nena, several significant geologic processes occurred including orogenesis and continental magmatic accretion. The by-products of these processes can be found numerous regions such as southwest Ontario, northwest British Isles, and Greenland. These by-products include the Marquette Range supergroup and the Moran Lake and lower Aillik groups northwest of the Makkovik orogen. These geologic findings provided a basis for the concept of the Nena supercontinent. Nena as a continent has been associated with the Sudbury Basin Impact.

References

;

External links

Referred to as Nuna
Former supercontinents Proterozoic {{Geology-stub