Caracterización geológica de la quebrada chalán (Chimborazo) a escala 1:25000.

Abstract

The geological characterisation in the Chalan Gorge and its surroundings encompassed both petrographic, cartographic, and paleontological studies, which allowed us to describe their morpho stratigraphy, relative depositional ages and paleoenvironments. This region is conformed, from the base to the top, of a metamorphic basement from the Cretaceous age belonging to the Guamote Formation and a granodiorite intrusion, which elevated Cerro de Licto to the northwest during the Eocene age (Pungalá Granite), covered by fluvial and volcano-sedimentary Pliocene sequences from the Yaruquíes and Sicalpa Formations. On the other hand, during the Pleistocene, the uplift of the Cordillera Real caused intense volcanism. The consequent activity generated many volcanic materials. These materials were reworked by either wind or water and periclinally deposited on the Inter-Andean valley up to the Chunchi zone in Chimborazo Province. This volcano-sedimentary product, known as Cangahua, is typically recognised for having a characteristic khaki colour and containing evidence of Pleistocene fossil fauna. Three distinct Cangahua units were identified and differentiated during this research by their morpho-stratigraphic disposition, sedimentology, stratigraphic structure, lithology and colour. Based on a database obtained from the Department of Biology of the Ecuadorian National Polytechnic School and other older publications, the presence of megafauna was recognised in the Cangahua formation within the area of research. However, some information was missing from the database (i.e. the spatial and stratigraphic locations where the samples were extracted). As a result of the research, sixteen fossils of macro and micro mammals from the Upper Pleistocene were recorded. Additionally, twelve points were recognised where several Cangahua stone balls were found. The research resulted in the interpretation of two fossiliferous levels that must have developed in different ages and environments.