Dinamismos eruptivos de los periodos de actividad pertenecientes al Pleistoceno Tardío del volcán Chimborazo, en base a las características de los piroclastos de caída del corte de Totorillas

Abstract

The present study focuses on the deposits of pyroclastic falls generated by CH-III during the eruptive stages of the Late Pleistocene. For its development, 10 samples taken from the Totorillas outcrop were analyzed, under physical and chemical parameters. By interpreting the results, three eruptive styles are proposed: (1) Vulcanian, corresponds to eruptions with high lytic content and fine material, appears generally as a precursor of (2) Subplinian eruptions; this second defined style has greater compositional variability with respect to the rest, from basaltic andesitic to dacite, with average porosity of juvenile pyroclastics between 65 and 85%, (3) Pliniano, is characterized by powerful deposits with high lytic content and fine material. The granulometric, densimetric, study of components and porosity carried out in the samples indicates that the particles retain characteristics associated with the eruptive dynamism under which they were formed. The efficiency of the fragmentation, transport and deposition of the pyroclasts is reflected in the granulometric distributions (mostly unimodal), the composition of the magma, its fluidity, the content of volatiles, is determined by density and porosity tests, the analysis of components allows to differentiate the type of material present in the eruptions and determine the characteristics of the canal-crater system. The combination of these analyzes helps estimate the eruptive style of each layer.