Snowball Earth in Space and Time

在低温世时期(7.2亿-6.35亿年前)至少有两次，在雪球地球事件中，冰覆盖了地球数百万年。这些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没有得到很好的限制。研究小组将使用南极洲冰川沉积物的沉积核心，再加上基于无人机的测绘和纳米比亚Snowball Earth沉积物的精确同位素测年，以构建依赖速率的地层学模型。他们还将在纳米比亚大学和UCSB之间开展研究交流，以培训纳米比亚和加州实验室的学生。这项培训将在地质现场测绘和样品分析过程中进行，这是他们限制速度和自然雪球地球的研究目标的基本背景，并将为学生在包括关键矿物在内的地球科学领域的职业生涯做好准备。低温冰川时间线中最大的不确定性是马里诺冰川的开始年龄，这不仅对于限制冰川过程的速度和性质，而且对于冰川开始和消融的机制也是重要的。以前的研究表明，雪球地球期间沉积的水沉淀物与弱的水文循环不相容。一个建议的调和是，在高二氧化碳的Snowball Earth的后期阶段，冰盖可能会对轨道强迫做出反应，导致更活跃的水文循环。然而，由于这些研究未能限制速率，尚不清楚这些地层剖面中的明显旋回性是由于类似第四纪的轨道强迫还是冰盖内部与外部强迫几乎没有关系的自生过程所致。研究人员的初步U-Pb锆石年代学和基于无人机的测绘数据记录了可用于限制接地线振荡速率的多个可测年火山层，并提供了第一个Snowball Earth冰川沉积的时间定量相模型。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.