Collaborative Research: Developing a multi-proxy approach for reconstructing deep-time silicate weathering

在地球的整个历史中，大气中的二氧化碳含量一直受到地表不同类型岩石反应的影响。二氧化碳侵蚀岩石，如玄武岩，将元素释放到河流中，最终这些元素与海水联合收割机结合形成新的岩石。 大气中二氧化碳含量的变化导致了数千万年或数亿年的气候变化。有充分的证据表明，7亿年前，地球经历了地球历史上最长和最极端的冰川作用，冰一直延伸到赤道。不幸的是，我们不知道是什么导致了这次冰川作用，也不知道冰川作用之前的气候是什么样的。该项目将通过使用新的先进分析方法检查海洋中沉积的古代岩石中的特定元素来调查冰川作用的起因。 通过观察冰川作用前在古代海洋中形成的岩石的化学成分，地球科学家可以追踪海洋化学的变化，然后推断导致这次冰川作用的古代大气条件。这些调查将有助于培养未来的地球科学家，并为研究人员提供机会，从一个新的角度向各种受众传播地球历史和气候科学。这些研究的结果将为地球科学家提供独特的见解，了解地球和海洋在一个令人难以置信的迷人时期的化学演化。新元古代（1000-539 Ma）见证了Rodinia超大陆的组装和分裂，地球化学循环的巨大波动，生物学的第一次和创新以及被称为雪球地球事件的极端冰川。我们对这些雪球地球事件和复杂生命进化之间相互作用的理解最近的进展集中在冰川和进化事件的时间和持续时间上。尽管取得了这些进展，但在理解雪球冰川的驱动因素方面取得的进展很少。挪威斯瓦尔巴特群岛的地质是一个厚厚的原始，低级沉积岩的继承，这些图表的领先地位和这些全球冰川的后果，并代表了一个独特的设置，以测试各种假设有关的原因冰川及其对生物/地球化学循环的影响。该奖项支持两名早期职业助理教授，一名博士后助理和一名硕士生对这些沉积单元进行详细的地球化学，沉积学和地质年代学研究。特别是，这项研究将耦合到一个强大的地层和地质年代学框架，以阐明负责雪球地球事件的机制，并跟踪海水的化学演变之前和之后立即冰川众多的放射性和稳定同位素系统。此外，该项目还将为两名初级学者提供在北极工作的机会，了解并体验在这些地区工作的后勤和环境独特性。虽然该项目是针对新元古代的，但这种将广泛的同位素系统结合在一起的新方法将大大有利于所有时间尺度上的地球科学研究。除了将从这次调查中产生的科学研究产品外，PI还将与耶鲁皮博迪自然历史博物馆和耶鲁大学的大学预科“科学之路”项目合作，该项目在纽黑文公立学校系统内运作，有直接的机会体验大学并了解更多关于上层STEM教育的信息。达特茅斯和耶鲁大学的多名本科生也将参与样品处理、湿实验室化学和质谱分析，作为高级论文项目的一部分。该奖项反映了NSF的法定使命，并被认为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来支持。

Throughout Earth's history the amount of CO2 in the atmosphere has been influenced by reactions with different types of rocks at the surface. The CO2 erodes rocks such as basalt which releases elements into rivers and eventually these elements combine with seawater to form new rocks. The variations in atmospheric CO2 content contribute to variations in the climate over tens or hundreds of millions of years. There is good evidence that 700 million years ago the Earth experienced the longest and most extreme glaciation in our planet's history and ice reached all the way to the equator. Unfortunately, we do not know what caused this glaciation or what the climate was like before the glaciers. This project will investigate the lead-up to the glaciation by examining specific elements in ancient rocks deposited in oceans using new advanced analytical methods. By looking at the chemical composition of rocks that formed in the ancient oceans prior to the glaciation, Earth scientists can trace the changing ocean chemistry and then infer the ancient atmospheric conditions leading up to this glaciation. These investigations will help to train future Earth scientists and provide researchers with opportunities to communicate Earth history and climate science from a novel angle to a variety of audiences. The results from these studies will provide Earth scientists unique insights into the chemical evolution of our planet and oceans during an incredibly fascinating time period.The Neoproterozoic Era (1000-539 Ma) witnessed the assembly and fragmentation of the Rodinia supercontinent, huge swings in geochemical cycles, biological firsts and innovations as well as extreme glaciations known as Snowball Earth events. Recent advances in our understanding of the interplay between these Snowball Earth events and the evolution of complex life have focused on the timing and duration of the glaciations and of the evolutionary events. Despite these advances very little progress has been made in understanding the drivers of the Snowball glaciations. The geology of Svalbard, Norway is host to a thick succession of pristine, low-grade sedimentary rocks that chart the lead-up and aftermath of these global glaciations and represents a unique setting to test a variety of hypotheses related to the causation of the glaciations and their impact on bio/geochemical cycles. This award supports two early-career Assistant Professors, a post-doctoral associate and a Masters student to conduct a detailed geochemical, sedimentological and geochronologic study of these sedimentary units. In particular, this research will couple numerous radiogenic and stable isotope systems tied to a robust stratigraphic and geochronologic framework to elucidate the mechanisms responsible for the Snowball Earth events and trace the chemical evolution of seawater prior to and immediately after the glaciations. Additionally, the project will provide two junior scholars the opportunity to work in the Arctic, gaining exposure to and experience of the logistical and environmental uniqueness of working in these regions. Although the project is specific to the Neoproterozoic, The new approach that couples a wide range of isotope systems will greatly benefit research in the Earth sciences across all timescales. In addition to the scientific research products that will result from this investigation, the PIs will collaborate with the Yale Peabody Museum of Natural History and Yale's pre-college "Pathways to Science" a program that operates within the New Haven public school system with direct opportunities to experience college and learn more about upper-level STEM education. Multiple undergraduate students at Dartmouth and Yale University will also be involved in sample processing, wet-lab chemistry and mass spectrometry as part of senior thesis projects.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.