INVESTIGADORES
CAFFE pablo Jorge
congresos y reuniones científicas
Título:
Neogene monogenetic volcanoes from the northern Puna of Argentina, Central Andean plateau.
Autor/es:
CAFFE, P.J., MARO, G., PRESTA, J.F., FLORES, P.I., PERALTA, Y.
Lugar:
Auckland
Reunión:
Congreso; Fourth International Maar Conference: a multidisciplinary congress on monogenetic volcanism; 2012
Institución organizadora:
IAVCEI - IAS
Resumen:
Mafic (basaltic andesite to andesite) volcanic rocks are rare in the Neogene volcanic record of the northern Puna (Fig. 1), an area dominated by voluminous silicic (dacite to rhyolite) ignimbrites and lavas sourced from large calderas or composite volcanoes (Coira et al., 1993) erupted during the Miocene to Pleistocene. Scoria cones exhibit typical facies of Strombolian edifices elsewhere (e.g., Vespermann and Schmincke, 2000). Recognized facies include: rare massive and cross bedded beds, interpreted as hydrovolcanic deposits formed during explosive encountering of magma and ground-water; b) unwelded spindle-shaped bomb and scoria deposits that dip away from the vent, typical of the external wall facies of the cone; c) minor beds of better sorted and finer material (ash or fine lapilli) interstratified with the coarser facies; d) interstratified beds of weakly welded scoria and moderately to strongly welded spatter in many rafts, and especially in layers that dip towards the interior of the edifice, interpreted as the internal wall and crater facies of the cone (e.g., El Toro, Cerro Morado, Jama); d) vertical to inclined lava dykes, as well as lava filling breaks in the cone, interpreted as the representant of the complex plumbing system that cut different parts of the cones. From cone facies and morphology, as well as compositional correlation between deposits of several cones and lava flows, it is possible to infer that pyroclastic and effusive eruptions were probably concurrent, as is confirmed by abundant rafts of welded (internal) to unwelded (external) cone deposits on the top of lava flows. Eruptions had a typical Strombolian style, with brief periods of fountaining and/or development of short-lived eruptive columns that alternated with the predominantly pulsatory Strombolian dynamics.