The large eruption 4.2 ka BP in Cerro Blanco, Central Volcanic Zone, Andes: Insights to the Holocene eruptive deposits in the southern Puna and adjacent regions

FERNANDEZ-TURIEL, JOSE LUIS; SAAVEDRA, J.; LOBOS,A.; GALLARDO, J.; RODRIGUEZ-GONZALEZ, ALEJANDRO; REJAS,M.; CARRIZO, J.I.; PEREZTORRADO, FRANCISCO; CARRACEDO, J.C. ; OSTERRIETH, M; RATTO, NORMA

ESTUDIOS GEOLOGICOS

CONSEJO SUPERIOR INVESTIGACIONES CIENTAFICAS

Lugar: Madrid; Año: 2019 vol. 75

0367-0449

The eruption of the Cerro Blanco Volcanic Complex, in the southern Puna, NW Argentina dated at 4410?4150 a cal BP, was investigated to produce new information on stratigraphy, geomorphology, physical volcanology, radiocarbon dating, petrography, and geochemistry. Identification of pre?, syn?, and post?caldera products allowed us to estimate the distribution of the Plinian fallout during the paroxysmal syn?caldera phase of the eruption. The new results provide evidence for a major rhyolitic explosive eruption that spread volcanic deposits over an area of ~500,000 km2, accumulating >100 km3 of tephra (bulk volume). This last value exceeds the lower threshold of Volcanic Explosive Index (VEI) of 7. Ash-fall deposits mantled the region at distances >400 km from source and thick pyroclastic-flow deposits filled neighbouring valleys up to 35 km away. This eruption is the largest documented during the past five millennia in the Central Volcanic Zone of the Andes, and is probably one of the largest Holocene explosive eruptions in the world. We have also identified two additional rhyolitic eruptions in the region from two other eruptive sources: one during the Early?Holocene and another in the Late?Holocene. The identification and characterisation of these significant volcanic events provide new constraints into regional Holocene geological and archaeological records, and offer extensive regional chronostratigraphic markers over a wide geographical area of South America.