Comment on 'Geochronology (Ar-Ar, K-Ar and He-exposure ages) of Cenozoic magmatic rocks from northern Chile of the central Andes' of Wörner et al. (2000)

Abstract

presented new and important geochronologic data on the Cenozoic magmatic rocks of northern Chile, and proposed magmatic and tectonic interpretations for them. Here we comment on one of their interpretations about the Miocene tectonic evolution of the Precordillera of Arica (Pampa Oxaya, ca. 18º30'S), a region referred by them as 'Oxaya Block'. According to their geochronological data and geomorphological observations, the area, which mainly consists of Lower Miocene ignimbrites of the Oxaya Formation, is interpreted as a large gravitationally collapsed rotational block. They interpret the collapse to have been produced by gravitational instability due to steepening of the western Andean slope during uplift of the Altiplano in an overall compressive regime.