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Famatinian orogeny
The Famatinian orogeny ((スペイン語:Orogenia de Famatina)) is an orogeny that predates the rise of Andes and that took place in what is now western South America during the Paleozoic, leading to the formation of the Famatinian orogen also known as the Famatinian belt. The Famatinian orogeny lasted from the Late Cambrian to at least the Late Devonian and possibly the Early Carboniferous, with orogenic activity peaking about 490 to 460 million years ago. The orogeny involved metamorphism and deformation in the crust and the eruption and intrusion of igneous rock along a Famatinian magmatic arc that formed a chain of volcanos. The igneous rocks of the Famatinian magmatic arc are of calc-alkaline character and include gabbros, tonalites and granodiorites. The youngest igneous rocks of the arc are granites.〔
==Outcrops and sediments==
The Famatinian orogen's main outcrops lie in Sierras Pampeanas in northwestern Argentina.〔〔 Only the western part of Sierras Pampeanas bears evidence of the Famatinian orogeny; the eastern parts appear to have been largely unaffected.〔 In northern Chile the Belén Metamorphic Complex is believed to be part of the orogen as it was subject to metamorphism in the early Paleozoic. To the south in La Pampa Province, outcrops associated with the orogeny are scarce as most of that region has become blanketed by much more recent Quaternary sediments.〔
Towards what is now the east of the Famatinian magmatic arc a Precambrian sedimentary basin developed into a back-arc basin during the Ordovician. This basin went from Peru, through Bolivia to northwestern Argentina. The basin collected sediments from the Famatinian orogen and arc and while it did not contain oceanic crust it was a marine basin.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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