Collaborative Research: Deconvolving the southern South American Pleistocene-Holocene dust production pathways

从南美大陆吹到海洋中的尘埃一直是海洋生物营养物质的重要来源，也是影响地质时期大气二氧化碳水平的复杂自然系统的一部分。我们目前对该系统过去如何运作的了解有限，这主要是因为我们对大陆上何时、何地或如何产生尘埃的信息知之甚少。该项目将追踪南美洲南部地质记录中存档的风吹尘埃的单个颗粒，以确定最近的过去在哪里产生了尘埃，它是如何穿越大陆然后被吹到大气中的，以及这些过程如何随着时间和不同气候而变化。这些信息将有助于将陆地、大气和海洋科学联系起来，完善未来的气候模型，并促进美国和南美科学家之间的合作。 本项目将利用粉砂至砂粒级沉积物的单颗粒碎屑矿物地质年代学，确定南美洲中部和南部黄土沉积物的沉积物来源和搬运路径。大观察（即，将通过沉积物的产生途径，采用大氮铀铅碎屑锆石年代学来追踪沉积物，以确定随时间推移尘埃源的位置和相对贡献。样品将从安第斯山脉、现代和近代河流沉积物以及前陆盆地的黄土和黄土质单元中采集。这些数据将有助于解决从以前的地球化学和地质方法得出的南美洲粉尘产生的相互冲突的模型，并用于重建整个地区粉尘产生的时空变化。这项调查的结果将揭示在南半球这一领域运作的假设的灰尘气候反馈系统。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Dust blown from the South American continent into the oceans has been an important source of nutrients for marine organisms and is part of a complex natural system that influences atmospheric CO2 levels over geologic time. Our current understanding of how this system has operated in the past is limited, largely because we have little information on when, where or how dust has been generated on the continent. This project will trace individual grains of wind-blown dust archived in the geologic record of southern South America in order to determine where dust has been produced in the recent past, how it was transported across the continent and then blown into the atmosphere, and how these processes have changed through time and under different climates. The information will help link terrestrial, atmospheric and ocean sciences, refine future climate models, and foster collaborations between U.S. and South American scientists. This project will determine sediment sources and transport pathways of central and southern South American loess deposits using single-grain detrital mineral geochronology on silt- to sand-sized sediment. Large observation (i.e., Large-n) U-Pb detrital zircon geochronology will be applied to trace sediments through their production pathways in order to determine the location and relative contribution of dust sources over time. Samples will be collected from the Andes mountains, modern and recent river deposits, and from loess and loessoid units in the foreland basin. These data will help resolve conflicting models of South American dust production derived from previous geochemical and geological approaches, and be used to reconstruct spatio-temporal variations in dust production across the region. Results from this investigation will shed light on hypothesized dust-climate feedback systems operating in this sector of the southern Hemisphere.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.