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

波动的潮汐冰川，化学风化和珊瑚礁生物的生存：南澳大利亚州的马里诺雪球普林斯顿大学的亚当·马卢雪球地球假说认为，海洋在7.2亿至6.35亿年前被封在冰中数百万年，至少有一次或两次。 然而，三个观测结果引起了一些人对雪球地球假说的质疑：（1）有地质证据表明动态湿基冰川存在，其形式是厚厚的冰川沉积物和深冰川侵蚀。 当海洋被冰覆盖时，是如何将足够的雪输送到冰盖上以保持它们的流动的？(2)有地质和地球化学的证据表明，在一个单一的雪球间隔的冰和非冰的沉积物层间的形式的热幕。冰是如何前进和后退的，在一个有着冰覆盖的海洋的深冻地球上，温度/湿度条件的变化又是如何发展的？(3)具有光合作用的真核生物似乎毫发无损地在冰川作用中幸存了下来。 光合作用生物是如何在与世隔绝的避难所中，在数百万年的冰冻环境中生存下来，而不对进化生物学的进程产生重大影响的？南澳（SA）的Marinoan（结束于635 Ma）冰川演替包含了全球新元古代冰川存款赤道沉积的最可靠的古地磁证据。 此外，南澳弗林德斯和加蒙斯山脉拥有沿沿着和横跨古海岸线走向数百公里的极好露头，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方之外，世界上没有其他地方提供这样的机会来研究新元古代冰川作用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山脉暴露的冰前、同期和冰后沉积物进行多学科研究，记录南澳的马里诺期低纬度冰川作用。我们的工作将评估水文循环的强度，赤道冰川的热状况，以及多细胞生命先于雪球地球事件并幸存下来的证据。

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.