El Pozo Volcanic Complex: Evolution of a group of maars, central Mendoza province, Argentina

Abstract

Abstract The El Pozo Volcanic Complex, in the south-central Mendoza province, is formed by three maars, the first to be described in the Payenia Volcanic Province and one of the few examples in Argentina. The maars of El Pozo Volcanic Complex (1, 2 and 3) show large craters (0.97\u202fkm, 1.2\u202fkm and 0.96\u202fkm, respectively) and their depth is between 10 and 57\u202fm below the pre-eruptive surface. Their deposits are described from the only outcrops that have been found, called El Pajarito and El Visitante. It was interpreted that the first maar to be formed would have been No. 2, from which only the deposits corresponding to El Pajarito (3.6\u202fm) and the lower section of El Visitante (28\u202fm) are preserved. We suggest that its shape is the result of lateral vent migration and coalescence of successive vents. Then, after a short break represented by the angular unconformity in the El Visitante section, the active vent would have shifted more to the W and the maar No.3 is thought to have been formed. The activity of this maar is represented in El Visitante upper section, with features resulting from the presence of water in the time of deposition. Maar No. 1 was probably active simultaneously with maar no. 3, with which coalesces but the lack of outcrops does not guarantee this affirmation. Towards the end of the eruptive cycle, depletion of water produced a change in activity from phreatomagmatic to Strombolian and effusive. This gave rise to the nested pyroclastic scoria cone, El Pozo cone, which lies in the maars 1 and 3 craters floors. El Pozo cone is related to lava flows with a tumulus and the deposit of a lapilli-bearing tephra plume.