Estudio geomorfológico de la avalancha de rocas Piedras Blancas, prov. de Mendoza, Argentina

MOREIRAS S.M.

Córdoba, . Acta I: 23-31.

Congreso; Congreso de Geomorfología y Cuaternario; 2006

Facultad de Cs Exactas, Físicas y Naturales. Univ. Nacional de Córdoba

The extraordinary Piedras Blancas rock avalanche, with a volume ~8.9 x 108 m3 and H/D relation equal to 0.2, dammed the Cerro Minero gully generating a paleo-lake of ~0.7 km2 area. This lake sequence and relict deposits of the rock avalanche are overlain by alluvial fans where three ash layers are interbedded. According to field observations and geochemistry analysis, these ash layers should be those analysed in previous studies determining an age of 350±80 Ky for the middle ash level by Ar39/Ar40 method (Moreiras, 2006). Therefore a Pliocene- Middle Pleistocene age is established for this huge event. Furthermore, sediments of the paleo-lake sequence are intensively deformed may be due to a paleo-earthquake extending the paleo-seismicity of this region and suggesting the Quaternary activity of regional faults. This lake sequence and relict deposits of the rock avalanche are overlain by alluvial fans where three ash layers are interbedded. According to field observations and geochemistry analysis, these ash layers should be those analysed in previous studies determining an age of 350±80 Ky for the middle ash level by Ar39/Ar40 method (Moreiras, 2006). Therefore a Pliocene- Middle Pleistocene age is established for this huge event. Furthermore, sediments of the paleo-lake sequence are intensively deformed may be due to a paleo-earthquake extending the paleo-seismicity of this region and suggesting the Quaternary activity of regional faults.