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

新元古代的地质记录包含极端气候变化的证据，这种变化可能深刻地影响了生物进化的过程，特别是在所谓的Sturtian、Marinoan和Gaskiers冰川的雪球地球事件前后。在新元古代，身体化石和分子生物标志物被解释为来自多细胞动物已被报道，虽然目前的基础动物的辐射在斯特阶和马里诺冰期之间的某个时候限制得很差。本文通过分子生物标志物分析、有机和无机稳定同位素（13C、2H和34S）记录以及古氧化还原无机地球化学指标，对南华盆地新元古代海洋生物地球化学进行了详细的时间记录。这将使我们能够调查低纬度新元古代冰川对初级生产力，碳循环和氧化还原结构的影响，适用于一个浅陆架到深盆古环境样带。鉴于科学界对中国南方陡山沱组的化石动物群和其他化石的兴趣，似乎令人惊讶的是，中国南方新元古代目前没有详细的分子生物标志物记录。这无疑是由于某些部分的高热成熟度以及由于在石油衍生污染物的显著背景之上辨别低浓度的真正新元生物标志物信号的固有问题。范围研究表明，南华盆地四个剖面的地层热成熟度对于保存可检测的生物标志物烃类信号是没有问题的。生物标志物脂质工作的原创性和主要优势在于获得干酪根结合的生物标志物记录，这使我们能够访问南华盆地保存的生物标志物记录的高比例基本上没有污染的影响。PI的研究已经证明了连续流催化加氢热解（HyPy）技术用于破碎油母岩并释放共价结合的生物标志物成分的有效性，以基本上真实地获得所有生物标志物脂质数据。我们将解决一些基本的问题，在华南新元古代的地球化学史：-我们可以检测到海洋氧化还原结构的显着变化，在紧接其后的Sturtian和Marinon冰川使用我们的无机和生物标志物代理，如果是这样的话，有强有力的证据，伴随波动源生物输入？- 我们能否辨别浅水环境与深水环境对冰川作用后的氧化还原概况和生物群的显著不同反应？- 我们能否在南华盆地的基底动物（海绵）中检测到特定的类固醇标记物？如果是的话，这些标记物相对于斯特阶和马里诺阶冰川是什么时候首次出现的？更广泛的影响。这项研究将大大提高我们对斯特阶和马里诺冰川的强烈气候冲击通过改变营养循环，溶解氧可用性和在低纬度海洋环境中创造环境生态位而影响海洋微生物群落的程度的理解。在提供教育机会方面，爱和里昂将参加在UCR指导暑期研究实习计划，其中来自历史上在科学（特别是地球科学）中代表性不足的种族群体的本科生在两个实验室将获得实践经验的项目年。最后，我们的项目将受益于与朱学雷教授（中国科学院地质与地球物理研究所）及其研究小组的合作，他们对研究华南新元古代冰川地层有着丰富的经验。在项目进行期间，朱棣文及其同事将访问加州理工学院和加州大学河滨分校的南加州地球化学社区，讨论研究结果并促进长期合作关系。

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.