“Identification and Characterization of Paleoalluvial Events in the Ranrahírca Hydrographic Unit, Cordillera Blanca, Perú”
- 1INAIGEM, Instituto Nacional de Investigación en Glaciares y Ecosistemas de Montaña, Lima, Perú; (harrinson.jara@gmail.com)
- 2CNRS, IRD, IFSTTAR, ISTerre, Université Grenoble Alpes, Université Savoie Mont Blanc, 38000, Grenoble, France
- 3Programa de Maestria en Geologia, Mencion en Geotecnia, Universidad Nacional Mayor de San Marcos, Lima, Perú
Abstracts
The Cordillera Blanca, located in Peru, is a mountain range with peaks exceeding 6000 meters, preserving tropical glaciers on its surface. Currently, due to global climate change resulting from both natural and anthropogenic causes, glaciers are rapidly losing surface area and volume. Over a period of 58 years, between 1962 and 2020, the Cordillera Blanca (CB) has lost 301.4 km2 of glacier surface, equivalent to 41.50% of the total area. This has led to an increased occurrence of ice and rock avalanches, triggering violent overflow events of glacial lakes and alluvial processes. In this context, the Hydrographic Unit (HU) Ranrahírca has recorded the occurrence of two extreme avalanche events originating from the North Peak of Nevado Huascarán, corresponding to the 1962 event in Ranrahírca and the 1970 event in Yungay.
The objective is to identify, differentiate, categorize, and correlate unconsolidated deposits with different historical alluvial events (Paleoalluvions) of significant magnitude that occurred on the north peak of Nevado Huascarán, Cordillera Blanca. This involves a detailed grain size analysis of soils, with emphasis on lithology, dimensions, shape, and degree of weathering of the clasts in their composition, as well as their fine material content, aiding in temporally situating the origin event. The primary study area is the Yungay district, located at the lower part of Nevado Huascarán, where Quaternary material from various paleoalluvions has accumulated in a fan-shaped pattern in the lower part of the Ranrahírca HU. This area extends for several kilometers, currently encompassing the urban areas of Yungay and Ranrahírca.
To achieve this, fieldwork was conducted in August 2023 in the Yungay and Ranrahírca areas. Seven (07) chronostratigraphic columns were surveyed, and thirteen (13) soil samples were collected from different cut sections of slopes. These efforts have allowed the differentiation of various paleoalluvionic events and, in some cases, evidence the transition between them.
Keywords: Cordillera Blanca, rock-ice paleoavalanche, grain size analysis, chronostratigraphic column.
How to cite: Jara Infantes, W. H., Cosi, M. C., Torres, J. C., Lehmann, B., Zerathe, S., Villafane, H., Melgarejo, E., Caballero, A., Cachay, S., and Mamani, L.: “Identification and Characterization of Paleoalluvial Events in the Ranrahírca Hydrographic Unit, Cordillera Blanca, Perú”, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20856, https://doi.org/10.5194/egusphere-egu24-20856, 2024.
