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

“滚雪球地球”理论一直是媒体广泛关注的主题，尤其是其主要支持者保罗·霍夫曼教授对其进行了生动的辩护。从7.5亿年到5.4亿年前的这段地球历史，可能包含了多达5次气候波动的极端事件。在最冷的时候，地球可能完全被冰覆盖。直到最近几年，对这个时代岩石的研究主要集中在世界上寒冷或炎热的沙漠地区，那里有非常好的露头和未变形的沉积物堆，但这个时代一些最完整但暴露较少的岩石段位于更容易接近的地区，如苏格兰和爱尔兰。沉积物的年代测定极其困难，这些岩层的年龄依赖于罕见的火山岩。现在已经根据石灰岩中碳的同位素建立了这些冰期的全球框架，但没有其他测年证据，这只能说这些岩石与冰川事件有关，而不是哪一次。在此期间，由于地球海洋和大气中的氧含量迅速增加，导致许多物种的快速进化和脊椎动物的发育，硫的同位素受到限制。这一硫磺信号在最大的“雪球地球”事件后迅速改变，最近的研究表明，这一独特的信号可能在全球范围内都能识别。在苏格兰和爱尔兰，在基座一系列岩石中发现了三个冰期，这些岩石的年龄约为8亿年，其中6亿年约为基座向上的75%，靠近山顶的地方含有5.4亿-5.2亿年的脊椎动物化石。事实证明，将冰川时期与这2.6亿年期间的特定全球事件联系起来是困难的。将来自石灰岩和黑色页岩的矿物黄铁矿的新硫同位素数据与碳同位素数据和有机碳含量结合起来，将使苏格兰和爱尔兰的这些冰川事件能够相互关联，并放在全球范围内。这一新数据将对苏格兰和爱尔兰的这些岩石施加更好的年龄限制，并提高全球对这段地球历史的理解。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.