High precision U-Pb dating of seminal earth events

具有影响力的地球事件的高精度 U-Pb 测年

• 批准号: RGPIN-2019-07078
• 负责人: Davies, Joshua
• 金额: $ 2.19万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=765311
• 关键词: precision; Pb; dating; seminal; earth

The overarching goal of my research program is to investigate the feedbacks between Earth's sedimentary record and its climate by determining what drives climatic variability and how it results in changes in the sedimentary record. Climatic variability is directly implicated in mass extinctions recorded in the sedimentary record, and also controls the deposition of sediments through changes in the Earth's orbital parameters (Milankovitch cycles). Unfortunately, the drivers of climate variations, for example large igneous provinces, which are thought to cause the climate change that drives mass extinctions, are typically found in other parts of the world than the sediments containing the mass extinction event. Therefore proving causation between the events is problematic. Also, regular alternations in sediments may have a hierarchical structure and dominant periodicities of cyclicity as expected from orbital forcing, however without an independent check on the deposition rate the proof of climate driven forcing is not possible. My long term objective is to tackle these problems using a combination of high precision U-Pb geochronology and isotope stratigraphy to determine tempo of changes in the stratigraphic record. This proposal focus on two main themes to address this objective: 1. Determining the relationship between the Wrangellia flood basalts (WFB) and the Carnian Pluvial Event (CPE), where climatic perturbations caused rapid extinction rates, and set the stage for the expansion of the dinosaurs. By dating the CPE in the stratigraphic sections in Italy, and dating the WFB on Vancouver Island at high precision, we will determine if there is a causal relationship between the two events. We will augment the study using isotope proxies (Os and Mo) in our newly temporally calibrated sedimentary sections to precisely determine the effects of the WFB in the sedimentary record. Our results will have implications for the cause of mass extinctions and we anticipate that this integrated stratigraphic and geochronologic approach will become the baseline for future studies. 2. Determine whether the cyclic deposition banded iron formation (BIF) sediments in Australia was forced by the climate. The cyclic nature of these sediments and the apparent consistency of the cyclicity over large areas suggests a climatic control, but current depositional rate estimates based on imprecise and inaccurate U-Pb zircon ages are not suitable to confirm this. We will apply state of the art U-Pb dating techniques to accurately reconstruct depositional rates to determine whether the cyclicty in BIF is orbitally forced. We will combine our age models with isotopic tracers (Mo isotopes) to help elucidate the origin of BIF and potentially determine if climate played a role in the oxygenation of the Earth's atmosphere. This innovative study has potentially ground breaking implications for not only BIF formation, but also the parameters of the solar system.

我的研究计划的首要目标是通过确定是什么驱动气候变化以及它如何导致沉积记录的变化来调查地球沉积记录和气候之间的反馈。气候变化直接牵涉到沉积记录中记录的大规模物种灭绝，还通过地球轨道参数(米兰科维奇周期)的变化控制沉积物的沉积。不幸的是，气候变化的驱动因素，例如大型火成岩省份，被认为是导致导致大规模物种灭绝的气候变化的原因，通常在世界其他地区找到，而不是在包含大规模物种灭绝事件的沉积物中找到。因此，证明事件之间的因果关系是有问题的。此外，沉积物中的规则变化可能具有层级结构和轨道强迫所预期的主要周期性，然而，如果没有对沉积速率的独立检查，气候驱动强迫的证据是不可能的。我的长期目标是利用高精度的U-Pb年代学和同位素地层学相结合的方法来解决这些问题，以确定地层记录的变化速度。这项建议侧重于两个主题来解决这一目标：1.确定Wrangellia洪水玄武岩(WFB)和卡尼安暴雨事件(CPE)之间的关系，其中气候扰动导致恐龙迅速灭绝，并为恐龙的扩张奠定基础。通过测定意大利地层剖面中的CPE和温哥华岛上的WFB的高精度年龄，我们将确定这两个事件之间是否存在因果关系。我们将在我们新的时间校准的沉积剖面中使用同位素替代物(Os和Mo)来加强研究，以精确地确定WFB在沉积记录中的影响。我们的结果将对大规模灭绝的原因产生影响，我们预计这种综合的地层学和地质年代学方法将成为未来研究的基线。2.确定澳大利亚旋回沉积带状铁建造(BIF)沉积物是否是气候强迫的。这些沉积物的旋回性和大面积旋回性的明显一致性表明，这是一种气候控制，但目前基于不精确和不准确的锆石U-Pb年龄的沉积速率估计不适合证实这一点。我们将应用最先进的U-Pb测年技术来准确重建沉积速率，以确定BIF中的旋回是否是轨道强迫的。我们将结合我们的年龄模型和同位素示踪(钼同位素)来帮助阐明BIF的来源，并潜在地确定气候是否在地球大气层的氧化中发挥了作用。这项创新的研究不仅对BIF的形成，而且对太阳系的参数都具有潜在的开创性意义。