An Integrated Sedimentological and Multi-proxy Geochemical Investigation of the Neoproterozoic Climatic Paradox

在新元古代，在所有主要克拉通的热带纬度地区，冰川玛瑙辉绿岩夹在明显温暖的碳酸盐岩中的独特地质悖论仍然是一个未解的谜团。全球冰前负碳漂移始于冰晶岩下10至20米处，在冰后盖层碳酸盐序列中，碳同位素剖面在数十米内为负，然后恢复到新元古代背景水平。已经提出了几种模型来解释这种明显的气候极端之间的快速波动，称为新元古代气候悖论(NCP)，以及与之相关的海水化学中的同位素变化。“软”和“硬”雪球地球模型引起了大多数科学兴趣，并提出至少发生了两次全球冰川。还有其他几个模型，并不是所有的模型都会引起气候的剧烈变化。我们建议在露头和岩心中进行沉积学和多指标的综合地球化学研究，以研究NCP。这项研究将使用多学科方法，涉及更大的专家小组的协作。研究将集中在纳米比亚、南澳大利亚和乌拉尔三个地区的临界间隔，包括在(冰前)和(冰后)硬英质岩之下和(冰后)之上的序列、硬玉英岩单元本身以及旧的斯特里昂和年轻的马里诺二叠世之间的间冰期岩石。

The unique geological paradox of glaciomarine diamictites intercalated within apparently warm-water carbonates at tropical latitudes on all major cratons during the Neoproterozoic remains an unsolved puzzle. A global preglacial negative carbon excursion begins 10 to 20 of metres below the tillites, and the carbon isotope profile is negative for several tens of metres in the postglacial cap carbonate succession before returning to Neoproterozoic background levels. Several models have been proposed to explain these apparent rapid swings between climatic extremes, termed the Neoproterozoic climatic paradox (NCP), and the associated isotopic changes in seawater chemistry. The "soft" and "hard" Snowball Earth models have generated most scientific interest and propose at least two global glaciations occurred. Several other models exist, not all of which invoke dramatic climatic changes. We propose an integrated sedimentological and multi-proxy geochemical study in outcrop and core to investigate the NCP. The study will use a multidisciplinary approach involving collaboration of a larger group of specialists. Research will focus on the critical intervals in three areas, Namibia, Southern Australia and the Urals and include the succession below (preglacial) and above (postglacial) the diamictites, the diamictite units themselves, and the interglacial rocks between the older Sturtian and younger Marinoan diamictites.