BAEZ Walter Ariel
The polycyclic scoria cones of the Antofagasta de la Sierra basin, Southern Puna Plateau, Argentina
BAEZ WALTER; CARRASCO NUÑEZ GERARDO; GIORDANO GUIDO; VIRAMONTE JOSE G.; CHIODI AGOSTINA
GEOLOGICAL SOCIETY OF LONDON SPECIAL PUBLICATION
GEOLOGICAL SOCIETY OF LONDON
Despite the existence of several works focused on the geodynamic implications of the recent Southern Puna mafic magmatism, volcanologic and stratigraphic studies are still little developed. This paper presents a detailed map of two well-preserved Quaternary scoria cones, showing their complex stratigraphy. Complementary morphometric, morphostructural, petrographic and geochemical data were used to reconstruct the evolution of both volcanoes. The occurrence of more than one eruption at each volcano was inferred by recognition of temporal hiatuses using a morpho-stratigraphic criteria. The polycyclic nature of both scoria cones could be related to a combination of a high input magma in response to lithospheric delamination, a favourable regional stress field and interaction of rising magma with pre-existing faults. The youngest eruptions in both volcanoes were complex with shifts of the eruptive style from violent strombolian to hawaiian/strombolian phases and probably lasted a few years. The explosive activity was accompanied by the emission of lava flows from lateral vents. During the waning stages of the eruptions phreatomagmatic activity was triggered. The occurrence of more than one eruption in a single scoria cone and the changes in the eruptive style during long lasting eruptions are important topics for volcanic hazard assessment in the Southern Puna.