Abstract

SANTAMARIA, Santiago et al. Record of eruptions occurred in the northern Andes during the Holocene: New results obtained from the Potrerillos peatbog, Chiles-Cerro Negro Volcanic Complex. Rev Politéc. (Quito) [online]. 2017, vol.39, n.2, pp.7-16. ISSN 2477-8990.

Several eruptive periods have occurred in the Northern Andes during the Holocene. In order to look for these eruptive periods, a manual drilling was carried out on the southeast flank of the Cerro Negro volcano, in the Potrerillos area, Ecuador - Colombia border. In the drill core, 12 layers of medium to extremely fine grain volcanic ashes were identified. Nine radiocarbon ages were obtained from organic sediments found immediately below the major layers, showing an age range from ~ 140 to 6900 years BP. The component analysis of each ash layer revealed the predominance of pumice and free crystals (plagioclase, amphibole, ± biotite, ± pyroxene, ± quartz). Two groups of ash were identified: (1) a group of acid ashes, probably erupted from the Azufral volcano (Colombia), corresponding to an explosive activity that took placed between ~ 3830-6650 years BP; and (2) a group of intermediate to acid ashes probably related to the Ecuadorian volcanic front (Western Cordillera). In this last group, we identified a layer possibly related to the 10th century Guagua Pichincha’s eruption. Accordingly, none of the layers found seems to be directly related to the Chiles - Cerro Negro Volcanic Complex, suggesting an absence of explosive activity within the last ~ 6900 years BP.

Keywords : Chiles-Cerro Negro volcanic complex; Holocene ashes; peatbog.

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