Abstract

We present a multidisciplinary study based on short cores from four lakes along a transect spanning coastal sites (Bucalemito and Colejuda) to Central Valley (Batuco) and Cordillera de la Costa (Name) in Chile. We use sedimentological and high resolution geochemical analyses performed with an AVAATECH X-Ray Fluorescence Core Scanner and a chronology based on AMS 14C dates and 210Pb dating to investigate recent environmental and paleohydrological changes. Silicate – related elements (Al, Si, K, Fe, Ti, Zr, Rb) are used as proxies for sediment delivery whereas Ca and Sr are indicative of carbonate productivity, commonly associated with increased water chemical concentration. Mn, S and Fe re�lect changes in redox conditions. Cu/Zr and Cu/Rb ratios are used as proxies for excess atmospheric Cu deposition. Excess copper deposition in the uppermost sediments occurred in the four of the studied sites, particularly in coastal lakes, since the beginning of the 20th century, when the �irst industrial smelters were commissioned. Laguna Colejuda records the transition from a more humid period, possibly the Little Ice Age, to more arid conditions during the 20th century. Laguna Grande de Bucalemito re�lects important environmental variability over the last 50 years, with deeper depositional conditions during the 1980s and 1990s decades. The Ciénaga del Name sequence shows higher detrital input at the base, a transition to lower sediment delivery and likely lower �luvial connectivity, and a return towards higher clastic deposition in recent times along with greater �luvial input. At the Batuco wetlands, sedimentological and geochemical evidence also point to recent increases in lake level. These preliminary results show a high sedimentary variability that seems to re�lect a rapid dynamics in the lake ecosystems in response to both human and climate –induced changes during the last decades and centuries.