Inverse Steptoes in Las Bombas Volcano, as evidence of explosive volcanism in a solidified lava flow field. Southern Mendoza-Argentine

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

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 63 p. 360 - 374

0895-9811

In this paper we analyze what happens in a sector of the LVF where there are "circular patterns?/steptoes with the ages in reverse, i.e. when the around 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 formations of small sedimentary basins around them viewed as ?circular pattern?.