Resumo

COIRA, Beatriz et al. Niveles piroclásticos como herramientas de correlación en los depósitos cenozoicos del grupo Payogastilla, Valles Calchaquí, Tonco y Amblayo, en el noroeste de Argentina. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.2, pp.147-160. ISSN 0004-4822.

The tuffs in the Cenozoic sedimentary sequences of the Payogastilla Group in the Calchaquí, Tonco and Amblayo valleys, Salta, Argentina, can be divided into three distinct textural, mineralogical and geochemical groups that correspond to: (from older to younger) the Angastaco, the Palo Pintado and the San Felipe Formations. Chemical analyses of these tuffs show that they are calc-alkaline magmas with medium-K compositions in the Angastaco and Palo Pintado Formations and with high-K compositions in the San Felipe Formation. Rhyodacite-dacite and traquiandesite composition characterize the Payogastilla Group tuffs. Rare andesitic tuffs also occur in the Angastaco Formation. The chemistry of these tuffs is like that of arc magmas with similar light REE (La/Sm=4,0-6,2) and distinct heavy REE patterns (Sm/Yb=1,6-2,4 in the Angastaco Fm. 3,9-4,1 in the Palo Pintado Formation and 4,0-5,6 in the San Felipe Formation). Using the chemistry, mineralogy and published ages of the tuffs, as a guide, possible eruptive centers are the 15-13 Ma Agua Escondida center (Angastaco Formation), the 10-7 Ma Calama-Olacapato-El Torro group centers (Palo Pintado Formation) and the 6-3 Ma Cerro Galán, Toconquis and Cueva Negra ignimbrite centers (San Felipe Formation).

Palavras-chave : Tuffs; Chronostratigraphic markers; Cenozoic deposits; Foreland basin.

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