Geochemical variability since the Late Pleistocene in Lake Mascardi sediments, northern Patagonia, Argentina

Abstract

A sediment core from Lake Mascardi, which includes Late Pleistocene–Recent material and cachment basin sediments, was analyzed for major and trace elements. By comparing the chemical features of detrital materials with those of country rocks, we identified the basalts outcropping in the drainage as source rocks. The global chemical composition of sediments reveals a close association with parental rocks that includes the most mobile elements. The rapid removal of weathered material (also known as a weathering limited denudation regime) was recognized as the main process that controls the sediment chemistry in the Manso River and Lake Mascardi drainage basin. To assess the degree of chemical weathering during the Holocene, we modeled the Eu fractionation that derives the losses of soluble or weathered material in Lake Mascardi sediments. The variability of geochemical parameters indicates a relatively constant source and denudation regime throughout the period. Pronounced cold conditions, such as those registered during the Younger Dryas (11.5–10.2 kyr bp), resulted in Eu/Eu ∗ values close to those for basalts and minimum losses (less than 5%) as soluble or weathered detritus. Holocene climatic warming brought about increased weathering and erosion, which still continues.