Late Pleistocene-Holocene geochemical history inferred from Lake Tecocomulco sediments, Basin of Mexico, Mexico

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 Corg 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 Tlaloc 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, Corg 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. Copyright © 2009 by The Geochemical Society of Japan.