Noreán Formation
Early Jurassic geological formation in northern Colombia / From Wikipedia, the free encyclopedia
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The Noreán Formation (Spanish: Formación Noreán, J1-2n,[2][3] J1n)[4] is a geological formation of the Eastern Ranges of the Colombian Andes, the Serranía de San Lucas and as basement underlying the southernmost Lower and northern Middle Magdalena Valleys. The formation consists of volcanic and pyroclastic lavas that range from andesites to rhyolites. Vitric, lithic and crystal tuffs and andesitic dikes and hypabyssal bodies are also present in the formation.
Noreán Formation | |
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Stratigraphic range: Sinemurian-Toarcian 194.6–174.8 Ma | |
Type | Geological formation |
Sub-units | See text |
Underlies | Tablazo & La Luna Formations |
Overlies | Bocas, Morrocoyal & Sudán Formations Norosí Batholith, San Lucas & Bucaramanga Gneiss |
Thickness | 2,062 m (6,765 ft) |
Lithology | |
Primary | Andesitic-rhyolitic lavas & pyroclastics |
Other | Ignimbrites, thin sandstones |
Location | |
Coordinates | 8°00′00″N 74°00′00″W |
Region | Bolívar, Cesar & Santander |
Country | Colombia |
Extent | Serranía de San Lucas & Eastern Ranges, Andes VIM & VMM (subsurface) |
Type section | |
Named for | Caserío Noreán |
Named by | Clavijo |
Location | Aguachica |
Year defined | 1995 |
Coordinates | 8°22′54″N 73°36′38″W |
Region | Cesar |
Country | Colombia |
Paleogeography of Northern South America 200 Ma, by Ron Blakey |
The more than 2,000 metres (6,600 ft) thick formation was deposited in a continental arc magmatic setting in an Early Jurassic graben that presently forms the basement of the Middle Magdalena Valley (VMM). A positive anomaly of Pb suggests a subduction-related genesis dominated by explosive volcanism.