Development and evolutionary patterns in Cambrian eukaryotic primary producers and their relationship to perturbations in the carbon cycle

真核浮游植物提供了环境变化的重要记录，确实是全球变化的驱动力。稳定同位素研究最近使人们认识到晚寒武世早期的一次重大全球变化事件(SPICE事件)。有趣的是，香料事件与原生生物(古生代真核浮游植物的优势类群)的主要多样性广泛相关。这个博士项目的目的是提供第一个详细的研究中晚寒武世浮游植物记录的劳伦斯跨越SPICE事件。它将检验SPICE事件与中上寒武世浮游植物进化更替之间存在因果联系的假设，浮游植物产量的增加是产生碳同位素漂移的关键因素。该项目将基于与古大陆劳伦西亚接壤的海洋中-上寒武统序列的孢粉学和同位素样品的新收集。样本将从美国大盆地东部的斯特普托层序中采集，香料事件最初就是在那里发现的。样品还将从中上寒武统康纳索加群和诺克斯群的露头和钻孔(例如喜悦-2岩心)物质中采集，来自劳伦西亚东缘(沿美国东部阿巴拉契亚带露头)，那里也有SPICE事件的报道。众所周知，这些地层产生了保存完好、热成熟度较低的各种钠长石组合。将使用各种观测技术(包括激光扫描共聚焦显微镜等新技术)分析并系统地描述这些原始生物。一个关于事件发生、生物多样性和差异的数据库将与SPICE事件进行比较，以检验这一假设。此前，这两个地区的几个单独部门都报道了SPICE事件。将获得同位素数据，以确定新采样区段中的SPICE信号，以获得地球化学背景信息，并能够在世界范围内与SPICE信号的所有其他出现情况进行关联。田野工作将为学生提供地质和古生物研究技能方面的培训，补充将从对疑难生物的详细研究中获得的密集研究专业。谢菲尔德大学和CASE合作伙伴(自然历史博物馆)都将为孢粉学研究提供最先进的设施，广泛的互补专业知识，并融入积极研究有机围墙浮游植物的进化及其与全球环境变化的联系的研究小组。这主要是一项学术研究，有助于更深入地了解全球气候变化和长期地质时间尺度上生物圈-地圈相互作用的发展。然而，学生还将接受生物地层孢粉学方面的培训，因此有望在学术界或行业找到工作(例如，作为一名探索孢粉学家)。研究结果将发表在同行评议的科学文献上，并在国际会议上公布。通过与自然历史博物馆教育部门，特别是达尔文中心现场节目的合作，向公众提供了更多介绍的机会。

Eukaryotic phytoplankton provide an important record of environmental change and are indeed a driving force in global change. Stable isotopes studies have recently lead to recognition of a major global change event in the early Late Cambrian (SPICE event). Intriguingly the SPICE event is broadly correlative with a major diversification in acritarchs (the dominant group of Palaeozoic eukaryotic phytoplankton). This PhD project is designed to provide the first detailed examination of the Middle to Late Cambrian phytoplankton record of Laurentia across the SPICE event. It will test the hypotheses that the SPICE event and the Middle-Upper Cambrian phytoplankton evolutionary turnover are causally linked, with enhanced phytoplankton production a key factor in producing the carbon isotope excursion. The project will be based on new collections of palynological and isotope samples from Middle-Upper Cambrian sequences for the oceans bordering the palaeocontinent Laurentia. Samples will be collected from the Steptoean sequence of the eastern Great Basin, USA, where the SPICE event was originally identified. Samples will also be collected from outcrop and borehole (e.g. JOY-2 core) material from the Middle-Upper Cambrian Conasauga Group and Knox Group from the eastern margin of Laurentia (cropping out along the Appalachian Belt of eastern USA), where the SPICE event has also been reported. These strata are known to yield diverse assemblages of acritarchs that are well preserved and of low thermal maturity. The acritarchs will be analysed using a variety of observational techniques (including novel techniques such as confocal laser-scanning microscopy) and systematically described. A database of occurrences, biodiversity and disparity will be compared with the SPICE event to test the hypothesis. The SPICE event has previously been reported from a few individual sections in both areas. Isotopic data will be obtained to determine the SPICE signal in the newly sampled sections, to achieve geochemical background information and to enable worldwide correlations with all other occurrences of the SPICE signal. The fieldwork will provide the student with training in geological and palaeontological research skills, complementing the intensive research specialisation, which will be gained from the detailed study of the acritarchs. Both the University of Sheffield and the CASE partner (Natural History Museum) will provide access to state of the art facilities for palynological study, a wide body of complementary expertise and integration into active research groups investigating the evolution of organic-walled phytoplankton and its links to global environmental change. This is primarily an academic study leading to a deeper understanding of global climate change and development of biosphere-geosphere interactions on long geological timescales. However, the student will also be trained in biostratigraphical palynology, and can thus expect to find employment in either academia or industry (e.g. as an exploration palynologist). Results will be published in the peer-reviewed scientific literature and presented at international conferences. Opportunity for additional presentations to the general public is provided through collaboration with the Natural History Museum's Education Department and particularly the Darwin Centre Live programme.