La caldera Vilama y el Complejo Caldérico Eduardo Avaroa, Puna argentina – Altiplano boliviano

SOLER, M.M., CAFFE, P.J., COIRA, B. Y ONOE, A.T.

La Plata

Congreso; XVI Congreso Geológico Argentino; 2005

Asociación Geológica Argentina - Universidad Nacional de La Plata

The Vilama caldera is one of the largest calderas associated to the ‘ignimbrite flare-up’ recorded in the Puna – Altiplano during Upper Miocene – Pliocene. The structural rim was traced using domes and stratovolcanoes which are supposed to have channelled through it, representing poscollapse volcanism. It is an elongated NW-SE structure of 35 x 15 km with central coordinates 22°24’S - 66°57’W. Only the Vilama ignimbrite (8.4-8.5 Ma) was associated to caldera formation, involving a volume of 2100 km3. This unit is characterized by two facies: intracaldera deposits, formed by a thick sequence (>400 m) of ignimbrites with different welding and phase vapour alteration, and extracaldera deposits, comprising two cooling units that show a very different welding grade. Location and shape of Coruto and Cerro Guacha calderas suggest that these centers have nested with the Vilama caldera, conforming the Eduardo Avaroa Caldera Complex. The latter, 70 x 40 km across, is the largest recognized feature of this kind in the central Andes. Caldera axes rotation within the complex need more sudies to be explained.