Carbon Isotopic Tests of Neoproterozoic Snowball Earth Phenomena

雪球地球假说提出，在大约6亿至7.5亿年前冰川特别普遍的时期，表层海洋完全被冰覆盖，导致海洋生物大规模灭绝。这类事件的发生对地球气候系统以及复杂的多细胞生物的进化具有重要影响，这些生物在这些严重冰河时代的最后证据出现后立即出现在化石记录中。雪球地球假说所呼吁的对海洋生态系统的破坏应记录在冰川事件期间沉积的碳酸盐岩的碳同位素值中。纳米比亚、澳大利亚和北美的科迪勒拉地区也出现了适当的继承，以检验这一预测，并提供对雪球海洋中的生活的洞察。初步结果表明，与雪球事件之前相比，生命并没有太大的不同，因此挑战了海冰面积大到足以扰乱海洋生态系统的观点。这项研究中收集的数据还将被用来检验为这些冰河时代提出的其他假设，包括最近的一种说法，即冰川后甲烷笼状化合物的大规模不稳定是这一记录的许多特殊特征的原因。

The snowball Earth hypothesis proposes that during times of especially widespread glaciation some 600 to 750 million years ago, the surface ocean became completely covered with ice, resulting in the mass extinction of marine life. The occurrence of such events has important implications for the Earth's climate system as well as for the evolution of complex multicellular organisms, which appear in the fossil record immediately after the last evidence of these severe ice ages. The disruption of marine ecosystems called for in the snowball Earth hypothesis should be recorded in the carbon isotopic values of carbonate rocks deposited during the glacial event. Appropriate successions are present in Namibia, Australia and the North American Cordillera, to test this prediction, and provide insight into life in a snowball ocean. Initial results suggest life was not terribly different than before the snowball event, thus challenging the notion that sea ice was extensive enough to disrupt marine ecosystems. The data collected in this study will also be used to test other hypotheses proposed for these ice ages including the recent suggestion that post glacial massive destabilization of methane clathrates was responsible for many of the peculiar features of this record.