Reverse steptoes in Llancanelo Volcanic field, Mendoza-Argentina: geological and geophysical evidences

PREZZI, CLAUDIA BEATRIZ; RISSO, CORINA; MARÍA JULIA ORGEIRA; NULLO, FRRANCISCO; MARGONARI, LILIANA; NÉMETH, KAROLY

Montevideo

Congreso; Latinmag Tercera Reunión Bienal de la Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo; 2013

In this paper we analyze what happens in a sector of the Llancanelo Volcanic Field where there are ?circular patterns?/steptoes with the ages in reverse, i.e. the surrounding lava flow is older than the inland pyroclastic cone. The geophysical-geological studies carried out, support the proposed model for the formation of the ?circular patterns? that sorround some newly scoria cones located along lineaments in the Llancanelo Volcanic Field, Mendoza, Argentina. Such ?circular patterns? would have been formed by secondary fracturation of previous solidified basaltic lava flows associated to reverse dipolar magnetic anomalies, due to a new ascent and degassing of magma. The younger scoria cones (i.e., Las Bombas), associated to normal dipolar magnetic anomalies and negative complete Bouguer anomalies, would have been formed by such new magma ascent, in the depressions generated by the fracturation of the older basaltic lava flows. The younger scoria cones were eroded, reaching the heights and slopes observed today. This morphological modification underwent by the scoria cones allowed the formation of small sedimentary basins around them viewed as ?circular patterns?.