Collaborative Research: Biogeochemistry of Neoproterozoic Snowball Earth and Its Aftermath in South China

新元古代地质记录包含极端气候变化的证据，这可能深刻地影响了生物进化的过程，特别是在斯特林、马里诺和加斯基尔冰川的所谓雪球地球事件周围。在新元古代，被解释为来自多细胞动物的遗体化石和分子生物标志物已被报道，尽管目前在斯特尔特冰川和马里诺冰川之间的某个时候，基底动物的辐射受到很好的限制。本研究旨在通过分子生物标志物分析、有机和无机稳定同位素记录(包括13C、2H和34S)和古氧化还原无机地球化学指标对南华盆地中国南部四个剖面的新元古代海洋生物地球化学进行详细的时间记录。这将使我们能够研究低纬新元古代冰川作用对初级生产力、碳循环和氧化还原结构的影响，这些结构适用于浅陆架-深盆地古环境样带。鉴于科学家对中国南部陡山沱组的动物化石和其他化石的兴趣，目前还没有关于中国南部新元古代的详细分子生物标志物记录，这似乎令人惊讶。这无疑是由于一些区段的热成熟度较高，以及在石油衍生污染物的重要背景之上识别低浓度的真正新元古代生物标志物信号的固有问题。一项范围研究表明，南华盆地4个剖面地层的热成熟度对于保存可检测的生物标志物油气信号不成问题。本文提出的生物标志物类脂工作的原创性和主要优势在于获得了干酪根结合的生物标志物记录，使我们能够获得南华盆地大部分保存下来的生物标志物记录，基本上不受污染的影响。PI的研究已经证明了连续流动催化加氢热解(HHY)技术在裂解干酪根和释放共价结合的生物标记物成分方面的有效性，基本上证实了所有生物标记物脂质数据的真实性。我们将解决有关中国南部新元古代生物地球化学史的一些基本问题：-我们能否使用我们的无机和生物标志物替代品在斯特里昂和马里农冰川之后立即检测到海洋氧化还原结构的重大变化，如果是的话，是否有强有力的证据表明来源生物输入的波动？-我们能否从氧化还原剖面和生物群的角度区分浅水和深水环境对冰川后果的显著不同反应？-我们能否检测到南华盆地基础动物(海绵)的特定类固醇标志物，如果是的话，这些标志何时首次出现在斯特里昂和马里诺冰川之上？更广泛的影响。这项研究将通过改变营养循环、溶解氧供应和在低纬度海洋环境中创造环境生态位，显著提高我们对斯特里安冰川和马里诺冰川强烈气候冲击对海洋微生物群落影响程度的理解。在提供教育机会方面，Love和Lyons将在每个项目年参加UCR导师暑期研究实习计划，根据该计划，来自历史上在科学(特别是地球科学)中代表性较低的种族的本科生将在两个实验室获得实践经验。最后，我们的项目将从与中国科学院地质与地球物理研究所朱学雷教授及其研究小组的合作中受益匪浅，他们在研究中国南部新元古代冰川地层方面拥有丰富的经验。朱和他的同事将在项目过程中访问加州理工大学和加州大学伯克利分校的南加州生物地球化学社区，讨论发现并促进长期合作联系。

The Neoproterozoic geological record contains evidence for extreme climatic change which may have profoundly influenced the course of biological evolution, particularly around the so-called Snowball Earth episodes of the Sturtian, Marinoan and Gaskiers glaciations. During the Neoproterozoic, body fossils and molecular biomarkers interpreted as being derived from multicellular animals have been reported although the radiation of basal animals is presently poorly constrained at sometime between the Sturtian and Marinoan glaciations. In this study, we aim to produce detailed temporal records of Neoproterozoic marine biogeochemistry from molecular biomarker analyses, organic and inorganic stable isotope records (including 13C, 2H and 34S) and from inorganic geochemical proxies of paleoredox for four sections in the Nanhua Basin in South China. This will allow us to investigate the effects of low-latitude Neoproterozoic glaciation on primary production, carbon cycling and redox structure applied to a shallow shelf-to-deep basinal paleoenvironmental transect. Given the scientific interest in fossilized animal fauna and other fossils from the Doushantuo Formation in South China, it may seem surprising that no detailed molecular biomarker records currently exist for the Neoproterozic in South China. This is undoubtedly due to the high thermal maturity of some sections and due to the inherent problems of discerning low concentrations of genuine Neoproterozic biomarker signals above a significant background of petroleum-derived contaminants. A scoping study has revealed that the thermal maturity of strata in our four sections in Nanhua Basin is not problematic for preserving detectable biomarker hydrocarbon signals. The originality and principal strength of the biomarker lipid work proposed here lies in obtaining kerogen-bound biomarker records which allow us to access a high proportion of the preserved biomarker record in Nanhua Basin essentially free from contamination effects. The PI's research has demonstrated the efficacy of a continuous flow catalytic hydropyrolysis (HyPy) technique for fragmenting kerogen and releasing covalently-bound biomarker constituents to essentially ground-truth all the biomarker lipid data obtained. We will address some fundamental questions regarding the biogeochemical history of the Neoproterozoic in South China: -Can we detect significant changes in marine redox structure in the immediate aftermath of the Sturtian and Marinon glaciations using our inorganic and biomarker proxies and, if so, is there strong evidence for concomitant fluctuations in source organism input? -Can we discern significantly different responses of shallow- versus deep-water settings to the aftermath of the glaciations in terms of their redox profiles and biota? -Can we detect specific steroid markers for basal animals (sponges) in the Nanhua Basin and, if so, when do these first appear relative to the Sturtian and Marinoan glaciations? Broader Impacts. The research will significantly improve our understanding of the extent to which the intense climatic shock of the Sturtian and Marinoan glaciations impacted on marine microbial communities by modifying nutrient cycling, dissolved oxygen availability and creating environmental niches in low latitude marine environments. In terms of providing educational opportunities, Love and Lyons will participate during each of the project years in the UCR Mentoring Summer Research Internship Program, whereby undergraduate students from ethnic groups historically underrepresented in the sciences (particularly the earth sciences) will receive hands-on experience in the two labs. Finally, our project will benefit greatly from collaboration with Professor Xuelei Chu (Institute of Geology and Geophysics, Chinese Academy of Sciences) and his research group, who have considerable experience of studying Neoproterozoic glacial strata in South China. Chu and colleagues will visit the Southern California biogeochemical community at Caltech and UCR during the course of the project to discuss findings and to promote long-term collaborative links.