Los depósitos piroclásticos de la Zona Volcánica Central sur de los Andes (25-28ºS)

GUZMÁN, SILVINA; MONTERO, CAROLINA; GROSSE, PABLO

Aportes sedimentológicos a la geología del noroeste argentino. Relatorio XIII Reunión Argentina de Sedimentología

SCS Publisher

Lugar: Salta; Año: 2012; p. 95 - 109

The present contribution is a review describing the spatial?temporal distribution and characteristics of the pyroclastic deposits of the southern Central Volcanic Zone (25-28ºS) of the Central Andes. We have compiled a database of the pyroclastic units of the region, defining their geographic locations and areas, and discriminating their ages, compositions, pumice and crystal contents, welding degrees and, when possible, their associated volcanic centres. The deposits cover an area of at least 7,750 km2 and are distributed mainly along NNE-SSW and NW-SE belts. The production and spatial distribution of the deposits has varied with time: major 14.5 Ma they concentrated west of 69ºW; 14.5-11.5 Ma they migrated east of 67ºW; minor 11.5 Ma they became more dispersed. Between ca. 67 and 67.5ºW no pyroclastic rocks are observed in any time interval. The intervals of 26-18 Ma, 14.5-11.5 Ma and minor-equal 5.3 Ma correspond to peaks of ignimbrite production. The larger deposits are mostly related with collapse calderas. Dacitic compositions dominate during the Miocene, whereas rhyodacitic and rhyolitic compositions are more abundant since the Pliocene.