COLLABORATIVE RESEARCH: Calibrating the Cryogenian in the Yukon

1148499，哈佛大学；Mark Schmitz.1148058，博伊西州立大学摘要：雪球地球假说引起了新元古代地质学的广泛兴趣；然而，该假说仍然存在争议，主要是因为对全球冰川形成的时间、持续时间和启动机制的不确定性。通过先前和初步的研究，我们已经证明，育空地区的斯特尔斯蒂安冰川沉积物的年龄与位于热带劳伦蒂亚东部边缘的富兰克林大火成岩省(LIP)的年龄没有什么区别，富兰克林大火成岩省处于化学风化的理想位置。这很耐人寻味，因为玄武岩比一般的大陆地壳更容易风化，而且有人提出，雪球地球事件是由风化能力的增加和随之而来的二氧化碳消耗的增加引发的。然而，富兰克林冰缘上的年龄范围和误差条仍然太大，无法确定火山活动是长期的还是短暂的，以及冰川作用是发生在火山活动主脉冲期间、之前还是之后。通过拟议的研究，PI打算通过高分辨率的岩浆锆石U-PbID-TIMS定年和支撑冰川沉积物的碎屑锆石的LA-ICPMS定年来限制育空地区Sturtian冰川和Franklin LIP的时间和持续时间。

COLLABORATIVE RESEARCH: Calibrating the Cryogenian in the YukonFrancis MacDonald.1148499, Harvard University; Mark Schmitz.1148058, Boise State UniversityABSTRACTThe Snowball Earth hypothesis has galvanized broad interest in Neoproterozoic geology; however, the hypothesis remains controversial largely due to uncertainty about the timing, duration, and initiation mechanism of global glaciation. With previous and preliminary studies, we have demonstrated that the age of Sturtian glacial deposits in the Yukon is indistinguishable from the age of the Franklin large igneous province (LIP), which was emplaced on the eastern margin of Laurentia, in the tropics, in an ideal position for being chemically weathered. This is intriguing, because basalt is more weatherable than average continental crust, and it has been proposed that Snowball Earth events were initiated by an increase in weatherbility and a concomitant increase in CO2 consumption. However, the age range and error bars on the Franklin LIP are still too large to determine if the volcanism was long- or short-lived, and if the glaciation occurred during, before or after the main pulse of volcanism. With the proposed research PIs intend to constrain the timing and duration of the Sturtian glaciation and the Franklin LIP in the Yukon with high resolution U-Pb ID-TIMS dating of magmatic zircons and LA-ICPMS dating of detrital zircons that bracket the glacial deposits.