Collaborative Research: Elucidating the Nature, Causes and Climate Importance of the Mid-Cenozoic Loess in the Western USA

黄土沉积物由细粒度的风吹沉积物组成，包含有关大陆干旱化过程的关键信息，这些信息是了解生物进化和气候变化的关键。该项目综合了怀俄明州、内布拉斯加州和蒙大拿州3700万至3000万年前黄土沉积的野外数据、实验室分析和古气候模拟，以了解这些黄土沉积的性质、成因和古气候重要性。这项研究将支持为期两天的GEOCAMP，为来自德克萨斯州东部的历史上代表性不足的高中生提供支持，从而促进STEM的多样性。此外，该项目将促进高分辨率群落地球系统模型的进一步发展，用于更好地了解古代气候变化。本项目将对美国怀俄明州、内布拉斯加州和蒙大拿州的古黄土沉积物进行野外沉积学观测和实验室分析，包括对大块沉积物和石英粒度、石英表面形态、碎屑和高精度锆石U-Pb年代学进行研究。这些替代数据将约束黄土的范围、时间、模式和特征；确定沉积物的来源和沉积物的循环机制。这些数据将与一个大气-陆地耦合模式相结合，模拟地形变化、全球气候变冷、冰川作用和海岸线退化引起的区域气候和植被变化，以了解黄土的成因和气候意义。除了获得对黄土沉积的基本认识外，该项目还将揭示1)始新世-渐新世过渡时期（~ 3400万年前）气候变化对生物进化的影响；2)美国西部不同地表隆起模型的有效性；3)矿物粉尘排放增加对过渡时期全球变冷的潜在正气候反馈。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Loess deposits consist of fine-grained, windblown sediments and contain critical information about continental aridification processes that are key to understanding biotic evolution and climate change. This project integrates field data collected from loess deposited ~37-30 million years ago in Wyoming, Nebraska and Montana, laboratory analyses, and paleoclimate simulations to understand the nature, causes, and paleoclimatic importance of these loess deposits. The research will advance STEM diversity by supporting a two-day GEOCAMP for historically underrepresented high-school students from east Texas. In addition, this project will promote further development of the high-resolution Community Earth System Model to be used to better understand ancient climate changes. This project will include field sedimentological observation and lab analyses of bulk sediment and quartz grain-size, quartz surface morphology, detrital and high-precision zircon U-Pb geochronology to study the ancient loess deposits in Wyoming, Nebraska and Montana, USA. These proxy data will constrain the extent, timing, pattern and characteristics of the loess; and determine sediment provenance and sediment recycling mechanisms. These proxy data will be integrated with a coupled atmosphere-land model to simulate changes of regional climate and vegetation induced by topography changes, global climate cooling, glaciation and shoreline regression to understand the cause and climate significance of the loess. In additional to gaining fundamental understanding of the loess deposits, the project will shed light on 1) the influence of climate change on biotic evolution at the Eocene-Oligocene transition (~34 million years ago); 2) the validity of different models of surface uplift in the western USA; and 3) the potential positive climate feedback of enhanced mineral dust emissions on global cooling at the transition.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.