Snowball Earth in Space and Time

时空中的雪球地球

• 批准号: 2247238
• 负责人: Francis Macdonald
• 金额: $ 26.32万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247238&HistoricalAwards=false
• 关键词: Snowball; Earth; Space; Time

At least twice during the Cryogenian Period (720-635 million years ago), ice covered the Earth for millions of years in Snowball Earth events. These are the most extreme episodes of climate change in the geological record, but the duration of glaciation and the rate of ice movement remain poorly constrained. The research team will use sediment core of glacial deposits in Antarctica, coupled with drone-based mapping and precise isotopic dating on Snowball Earth deposits in Namibia, to construct a rate-dependent stratigraphic model. They will also develop a research exchange between University of Namibia and UCSB to train students in the field in Namibia and in the lab in California. This training will occur during the course of geological field mapping and sample analysis that is essential context for their research goals of constraining the tempo and nature Snowball Earth, and will prepare students for careers in Geosciences, including critical minerals. The largest uncertainty in the timeline of Cryogenian glaciations is the onset age of the Marinoan glaciation, which is not only important for constraining the rate and nature of glacial processes, but also mechanisms for initiation and deglaciation. Previous studies have suggested that water-lain sediments deposited during Snowball Earth are incompatible with a weak hydrologic cycle. A proposed reconciliation is that during late stages of Snowball Earth with high CO2, ice-sheets could respond to orbital forcing leading to a more active hydrological cycle. However, because these studies have not been able to constrain rate, it is unclear if the apparent cyclicity in these stratigraphic sections is due to Quaternary-like orbital forcing or autogenic processes internal to the ice sheet that have little to do with external forcings. The researcher's preliminary U-Pb zircon geochronology and drone-based mapping data document multiple datable volcanic horizons that can be used to constrain the rate of grounding-line oscillation, and provide the first temporally quantitative facies model for Snowball Earth glacial deposits.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.

在冰原期（7.2 - 6.35亿年前）至少有两次，在雪球地球事件中，冰覆盖了地球数百万年。这是地质记录中最极端的气候变化事件，但冰川作用的持续时间和冰川移动的速度仍然缺乏限制。该研究小组将利用南极洲冰川沉积物的沉积物岩心，加上基于无人机的测绘和对纳米比亚雪球地球沉积物的精确同位素定年，构建一个与速率相关的地层模型。他们还将在纳米比亚大学和加州大学圣巴巴拉分校之间开展研究交流，培训纳米比亚实地和加州实验室的学生。这种训练将在地质实地测绘和样本分析过程中进行，这是他们限制雪球地球的速度和性质的研究目标的基本背景，并将为学生在地球科学，包括关键矿物方面的职业生涯做好准备。在冰期时间轴上最大的不确定性是马里诺冰期的开始年龄，这不仅对限制冰川过程的速率和性质很重要，而且对冰川开始和消冰的机制也很重要。先前的研究表明，在雪球地球期间沉积的水沉积物与弱水文循环不相容。一种建议的和解是，在二氧化碳含量高的雪球地球后期，冰盖可能对轨道强迫做出反应，导致更活跃的水文循环。然而，由于这些研究无法限制速率，因此尚不清楚这些地层剖面中明显的旋回性是由于第四纪类似的轨道强迫还是由于冰盖内部的自生过程，而这些过程与外部强迫几乎没有关系。研究人员初步的U-Pb锆石年代学和基于无人机的测绘数据记录了多个可用于限制地线振荡速率的火山层位，并为雪球地球冰川沉积物提供了第一个时间定量相模型。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。