The Salar de Atacama in northern Chile hosts a massive, geologically young salt deposit which contains one of the world's most economically important lithium-rich brines. This brine is currently the source of the majority of the world's lithium supply. The evolution of the salt and brine deposits is controlled by the tectonics of the Salar de Atacama basin and the extreme arid climate of the Atacama Desert. Climate records for these types of environments give important clues to understanding modern and future climate change patterns of the Earth. The Salar de Atacama is one of the most important hyper-arid environments on the planet and therefore is the focus of many climate proxy investigations. An unprecedented opportunity to extend the climate record back to 4 million years exists through sediment cores that have recently been recovered by the lithium mining industry from the south and transitional margin of the Salar de Atacama basin. This project will focus on characterizing the depositional environments and climate proxies preserved in these cores and on placing these records in a robust chronological framework. As such, radioisotopic dating of the deposits is important in determining environmental change at the margin of Salar de Atacama over the last 4 million years. This study will provide a framework relevant to future research questions related to the origin of the lithium-rich brine, life in extreme environments, and climatic change in hyper-arid environments.
Abstract (technical)
The goal of this work is to develop a paleoenvironmental record derived from recently recovered strata in drill cores from the southern margin of the Salar de Atacama, Chile. The focus of this work will be to develop a robust chronological framework within which to interpret the complex and high- resolution stratigraphic record of environmental dynamics. Strong gradients in tectonic processes, topography, and climate of this region give rise to one of largest active salt depo-centers in the world. This area is of considerable scientific interest because it is one of the most extreme environments on the planet. The new drill cores span a modern environmental gradient including alluvial environments, groundwater discharge marshes, sulfate-rich playas, saline lagoons, and a halite nucleus with shallow subsurface brine. Some of the cores contain strata that may be as old as 3.5?4.0 Ma. Many of these cores exhibit obvious and astounding shifts in paleoenvironment. Therefore, this study will provide the most detailed and comprehensive record of climate and environment from the Salar de Atacama. The geologic materials from the cores are sensitive to environmental conditions and therefore need to be sampled and analyzed within an appropriate timeframe. The cores will be described, and key intervals of ignimbrite and ash, carbonates, halite, mud and other sediments will be sub-sampled for the geochronologic work and for elemental and isotopic proxy investigations. Dating techniques will include a combination of 40Ar/39Ar, 14C and U-Th depending on the sediment and volcanic deposit types. Stable isotopes of carbon and oxygen in carbonate will be measured to constrain changes in climatic conditions. Lithium concentrations in salts will be measured to further understand the dynamic water balance in the system through time. Hydrogeological characteristics of the materials will aid in understanding the pathways of fluids in the subsurface, and inform climatic interpretation of shifting environments in this hydrologically complex system.
