The Chon Aike formation is a large geological structure forming part of the Deseado Massif (Spanish: Macizo del Deseado) in north-central Santa Cruz Province, Patagonia, Argentina. It covers an area of approximately 100,000 km2 and consists of rhyolitic volcanic rocks, particularly ignimbrites and lavas, with smaller amounts of agglomerates and tuffs.
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Chon Aike formation Wikipedia(Text) CC BY-SA