Alluvial soils as paleoenvironmental indicator in fluvial environments: a case study from Colombia

The study site La Chorquina ravine is located in the northern part of the Colombian in the western Andes region, where three alluvial fans with different altitudinal levels have been identi fi ed, being one of them the object of this study. These sedimentary deposits have been associated with the “El Guásimo” landslide, a downstream deposit that was considered responsible for the damming of the Cauca River. Paleoenvironmental reconstructions carried out during the last years question the existence of paleolakes, and support the hypothesis of a typical alluvial plain dynamic in fl u-enced by the Cauca River tributaries. In this research, two pro fi les were subjected to a complete pedostratigraphic fi eld characterization (structure, horizons differentiation, colour, porosity, and stoniness); Selected soil samples were submitted to physicochemical and mineralogical analyses, of which 11 micromorphological analysis were performed, and carbonates, gypsum, iron and manganese oxides, cutans, nodules, concretions and other pedological features were identi fi ed. The research proved the predominance of alluvial soils under an alluvial sedimentary environment with a predominance of features associated to the dynamic alluvial system characterized by little mineral alteration and similar mineralogical composition. The presence of carbonates and gypsum evidences seasonality changes in the climatic conditions. By means of the study of alluvial soils it is possible to identify paleoclimatic seasonality through edaphological records, which makes these soils a powerful tool for the study of Quaternary processes and paleoclimatic seasonality in tropical fl uvial environments.