ABSTRACT

This paper presents stratigraphy, mineralogy, multi-element geochemistry, organic and inorganic carbon contents in the sediments along a 255 cm long depth profile from Lake Tecocomulco in the north-eastern part of the Basin of Mexico. Mineralogical abundance, elemental ratios, chemical index of alteration (CIA), abundance of CO₃ and C_org divide the depth profile into geochemical zones and provide insight to the volcanic eruptions and phases of different paleohydrological events during the last 31,000 ¹⁴C yr BP. The dacite to rhyolite air fall tephra pre-date the LGM (ca. 31,000 ¹⁴C yr BP) and might be from a Plinian eruption event at the Tláloc volcano located at 60 km in the south-west of the lake. The lake sediments are characterized by higher CIA values and metal contents between ca. 30,000-29,000 ¹⁴C yr BP. Between ca. 28,000-25,700 ¹⁴C yr BP, sediments have lower CIA values and contain easily weatherable amphiboles. Abundant calcite and low CIA suggest arid conditions during ca. 25,700 and ca. 16,300 ¹⁴C yr BP, respectively. Between ca. 16,300 and 3,300 ¹⁴C yr BP, the sediments show lower CIA and sediments of the last ca. 3,300 ¹⁴C yr BP show highest CIA, C_org and higher metal contents. Given the regional nature of this record, we interpret the geochemical history at Lake Tecocomulco in terms of variable precipitation, inflow and aeolian activity.