A Plio-Pleistocene record of environment and climate from the Salar de Atacama basin based on recently recovered sediment cores

智利北部的阿塔卡马盐湖（Salar de Atacama）拥有一个巨大的、地质年代较短的盐矿，其中含有世界上最具经济价值的富锂盐矿之一。这种卤水是目前世界上大部分锂供应的来源。盐和卤水矿床的演化受阿塔卡马盆地的构造和阿塔卡马沙漠的极端干旱气候的控制。这些类型环境的气候记录为理解地球现代和未来的气候变化模式提供了重要线索。阿塔卡马盐沼是地球上最重要的超干旱环境之一，因此是许多气候代理调查的重点。最近锂矿业从阿塔卡马盐沼盆地的南部和过渡边缘恢复了沉积物岩心，这是一个前所未有的机会，可以将气候记录延长到400万年前。该项目将重点描述这些岩心中保存的沉积环境和气候代用物的特征，并将这些记录置于一个可靠的年代框架中。因此，沉积物的放射性同位素定年对于确定过去400万年来阿塔卡马盐湖边缘的环境变化非常重要。该研究将为未来研究富锂盐水的起源、极端环境下的生命、超干旱环境下的气候变化等问题提供一个框架。摘要（技术）这项工作的目标是建立一个来自智利阿塔卡马盐湖南缘最近恢复的岩心地层的古环境记录。这项工作的重点将是发展一个强大的时间框架，在其中解释环境动力学的复杂和高分辨率的地层记录。该地区的构造过程、地形和气候的强烈梯度形成了世界上最大的活跃盐沉积中心之一。这个地区具有相当大的科学价值，因为它是地球上最极端的环境之一。新的钻孔岩心跨越了现代环境梯度，包括冲积环境、地下水排放沼泽、富含硫酸盐的playas、咸水泻湖和具有浅层地下盐水的岩盐核。有些岩心包含的地层可能有3.5 ~ 4.0 Ma。许多这些岩心显示出明显而惊人的古环境变化。因此，这项研究将提供阿塔卡马盐沼最详细和全面的气候和环境记录。岩心的地质物质对环境条件很敏感，因此需要在适当的时间内取样和分析。将对岩心进行描述，并对烟灰岩、碳酸盐、岩盐、泥浆和其他沉积物的关键间隔进行亚采样，以进行地质年代学工作以及元素和同位素代用研究。根据沉积物和火山沉积物类型，测年技术将包括40Ar/39Ar、14C和U-Th的组合。将测量碳酸盐中碳和氧的稳定同位素，以限制气候条件的变化。将测量盐中的锂浓度，以进一步了解系统中随时间变化的动态水平衡。材料的水文地质特征将有助于理解地下流体的路径，并为这个水文复杂系统中变化环境的气候解释提供信息。

Abstract (nontechnical)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.