The Dalradian 'snowball Earth' section - use of stable isotopes to correlate glacial events and Neoproterozoic stratigraphy of Scotland and Ireland

“雪球地球”理论一直是媒体广泛关注的主题，特别是其主要支持者保罗霍夫曼教授的生动辩护。这一时期的地球历史从7.5亿至5.4亿年前可能包含多达5个极端事件的气候波动。在最冷的时候，地球仪可能完全被冰覆盖。直到最近几年，对这个时代的岩石的研究主要集中在世界上寒冷或炎热的沙漠地区，这些地区有非常好的露头和未变形的沉积物堆，但一些最完整的，但暴露不佳的这个时代的岩石部分在更容易到达的地区，如苏格兰和爱尔兰。沉积物的年代测定极其困难，这些岩石序列的年代依赖于罕见的火山岩。现在，基于石灰岩中碳的同位素，这些冰川时期的全球框架已经形成，但没有其他的年代学证据，这只能说这些岩石与冰川事件有关，而不是哪一个。在这一时期，硫的同位素受到地球海洋和大气中氧含量迅速增加的限制，这导致许多物种的快速进化和脊椎动物的发展。这种硫信号在最大的“雪球地球”事件后迅速变化，最近的研究表明，这种独特的信号可能是全球公认的。在苏格兰和爱尔兰，在一系列岩石中发现了3个冰期，这些岩石的底部大约有8亿年的历史，6亿年大约是从底部向上的75%，在顶部附近含有5.4亿至5.2亿年的脊椎动物化石。在这2.6亿年的时间里，将冰川期与特定的全球事件联系起来已经被证明是困难的。结合新的硫同位素数据的矿物黄铁矿从石灰石和黑色页岩，碳同位素数据和有机碳含量将使这些冰川事件在苏格兰和爱尔兰的相关性，并把全球范围内。这些新数据将对苏格兰和爱尔兰的这些岩石进行更好的年龄限制，并提高全球对这一时期地球历史的理解。人类对地球的影响可能已经破坏了气候系统的稳定，因此我们必须了解过去极端气候变化的原因和影响。

The 'snowball Earth' theory has been the subject of widespread media attention, particularly its lively defence by key proponent, Prof. Paul Hoffman. This period of earth history from 750 to 540 million years ago contained perhaps as many as 5 extreme events of climatic fluctuation. During the coldest of these the globe may have been entirely covered in ice. Until recent years research into the rocks of this age had focussed mainly on cold or hot desert areas of the world with very good outcrop and undeformed piles of sediments, but some of the most complete, but poorly exposed rock sections of this age are in more accessible areas such as Scotland and Ireland. Sediments are extremely difficult to date and ages of these rock sequences rely on the rare occurences of volcanic rocks. There is now the makings of a global framework of these glacial periods based on the isotopes of carbon in limestones, but without other dating evidence this can only say that the rocks are related to a glacial event, not which one. The isotopes of sulphur are constrained during this period by the rapid increase in the oxygen content of earth's oceans and atmosphere which resulted in the rapid evolution of many species and the development of vertebrate animals. This sulphur signal changed rapidly after the largest 'snowball Earth' event and recent studies suggest that this distinct signal might be globally recognisable. In Scotland and Ireland 3 glacial periods have been recognised in a seqence of rocks aged approximately 800 million years old at the base, 600 million about 75% of the way up from the base and containing 540-520 million year old vertebrate fossils close to the top. Linking the glacial periods to a particular global event in this 260 million year period has proved difficult. Combining new sulphur isotope data for the mineral pyrite from limestone and black shale rocks, with carbon isotope data and organic carbon content will allow these glacial events in Scotland and Ireland to be correlated and put into global context. This new data will place better age constraints on these rocks in Scotland and Ireland and improve the global understanding of this period of Earth history. Man's influence on the planet might have destabilised the climate system, so it is important that we understand the causes and effects of extreme climate variation in the past.