Fluctuating tidewater glaciers, chemical weathering and survival of reef-dwelling organisms: the Marinoan snowball, South Australia

波动的潮水冰川、化学风化和珊瑚礁生物的生存：南澳大利亚的马里诺雪球

• 批准号: 0842946
• 负责人: Adam Maloof
• 金额: $ 20.3万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0842946&HistoricalAwards=false
• 关键词: Fluctuating; tidewater; glaciers; chemical; weathering

Fluctuating Tidewater Glaciers, Chemical Weathering and Survival ofReef-Dwelling Organisms: the Marinoan Snowball, South AustraliaAdam MaloofPrinceton UniversityThe snowball Earth hypothesis posits that the oceans were sealed in ice for millions of years, at least once or twice, between 720 and 635 million years ago. However, three observations have caused some to question this backbone of the snowball Earth hypothesis: (1) There is geological evidence for dynamic wet-based glaciers, in the form of thick glacially derived sediments and deep glacial erosion. How was sufficient snow delivered to ice sheets to keep them flowing when the oceans were covered in ice? (2) There is geological and geochemical evidence for thermal episodicity during a single snowball interval in the form of interbedded glacial and non-glacial sediments. How would ice advance and retreat and how would variable temperature/humidity conditions develop on a deeply frozen Earth with ice-covered oceans? (3) Photosynthesizing eukaryotes appear to survive the glaciation, unscathed. How did photosynthesizers survive millions of years of freezing conditions in isolated refugia without having a major influence on the course of evolutionary biology? The Marinoan (ended 635 Ma) glacial succession of South Australia (SA) contains the most reliable paleomagnetic evidence for equatorial sedimentation of any Neoproterozoic glacial deposit worldwide. Additionally, the Flinders and Gammons ranges of SA boast superb outcrop for hundreds of kilometers along and across paleo-shoreline strike, allowing for detailed reconstruction of sedimentary environments and lateral chemical and isotopic gradients, all in the context of 3-dimensional stratigraphy and basin analysis. With the possible exception of northern Namibia, nowhere else in the world provides such an opportunity to study the sedimentary and geochemical record of Neoproterozoic glaciation. The proposed study will document the Marinoan low-latitude glaciation in South Australia through a multidisciplinary study of the pre-, syn- and post-glacial deposits exposed in the Flinders and Gammon Ranges. Our work will evaluate the intensity of the hydrological cycle, the thermal regime of equatorial glaciers, and the evidence that multicellular life predated and survived a snowball Earth episode.

涨潮冰川、化学风化和珊瑚礁生物的生存：南澳大利亚的马里诺雪球”普林斯顿大学的亚当·马鲁夫“雪球地球”假说认为，在7.2亿到6.35亿年前，海洋被冰封了数百万年，至少有一两次。然而，三个观测结果使一些人对雪球地球假说的这一支柱提出了质疑：(1)有地质证据表明存在动态湿基冰川，其形式是厚厚的冰川衍生沉积物和深层冰川侵蚀。当海洋被冰覆盖时，如何将足够的雪输送到冰盖上以保持它们的流动？(2)有地质和地球化学证据表明，在一个单一的雪球区间内，以冰与非冰沉积物互层的形式存在热幕式。在冰封的地球和被冰雪覆盖的海洋上，冰会如何前进和后退？变化的温度/湿度条件会如何发展？(3)光合作用的真核生物似乎毫发无损地在冰期生存了下来。光合作用生物是如何在孤立的避难所度过数百万年的寒冷环境而不对进化生物学进程产生重大影响的？南澳大利亚（SA）的Marinoan（结束于635 Ma）冰川演替包含了全世界新元古代冰川赤道沉积最可靠的古地磁证据。此外，SA的Flinders和Gammons山脉拥有沿古海岸线走向数百公里的绝佳露头，可以在三维地层学和盆地分析的背景下详细重建沉积环境和横向化学和同位素梯度。可能除了纳米比亚北部，世界上没有其他地方能提供这样的机会来研究新元古代冰川的沉积和地球化学记录。拟议的研究将通过对弗林德斯山脉和Gammon山脉暴露的前、同步和后冰川沉积物的多学科研究来记录南澳大利亚的马里诺低纬度冰川作用。我们的工作将评估水文循环的强度，赤道冰川的热状态，以及多细胞生命早于雪球地球事件并存活下来的证据。