When Life Got Big - Ediacaran evolution in a period of profound global change

当生命变大时——全球深刻变革时期的埃迪卡拉演化

• 批准号: RGPIN-2020-06741
• 负责人: Narbonne, Guy
• 金额: $ 2.62万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=740593
• 关键词: When; Life; Got; Big; Ediacaran

The Neoproterozoic was a time of massive changes in the Earth System that included breakup of supercontinent Rodinia, several 'snowball Earth' ice ages of global extent, marked fluctuations in the isotopic composition of seawater, and increased but fluctuating levels of oxygen in the oceans and atmosphere. Against this backdrop of Neoproterozoic global change we see an equally profound change in the evolution of life, the late Ediacaran (571 million years ago) appearance of abundant specimens and multiple taxa of large and architecturally complex life-forms after three billion years of mostly microbial evolution. The Ediacara biota is a global assemblage of soft-bodied marine creatures, now preserved as fossil impressions under event beds of sandstone or volcanic ash, that underlie the abundant shelly fossils and complex burrows of the Cambrian. Ediacaran life was a mixture of biotic groups that did not survive the end of the Ediacaran Period (e.g. rangeomorphs), alongside stem-group animals that diversified during the Cambrian explosion and were the ancestors of all animal life in our modern world. The oldest Ediacara-type fossil impressions known anywhere are rangeomorph fossils up to 2 meters long that occur in the upper part of the Drook Formation within the newly inscribed Mistaken Point UNESCO World Heritage Site; broadly coeval Avalonian assemblages also occur in central England and NW Canada. Over the next five years, I will assess the inter-relationship between Ediacaran global change and biotic evolution through studies of the oldest Ediacara-type fossils in Avalonian Newfoundland, NW Canada, and Australia and a synthesis extending through the entire period worldwide. Our field studies are stratigraphic, sedimentological, and paleontological and will also utilize international collaborators in isotope and redox geochemistry. In Newfoundland we will analyse a superbly exposed succession of Mall Bay-Drook strata, previously known only at a reconnaissance level, that predate most of the fossiliferous succession at Mistaken Point and thus can provide information on environmental conditions that immediately preceded the appearance of biological complexity in Avalonian Newfoundland. Work in NW Canada will focus on fossils in the deep-water Nadaleen Formation to enhance the data set and interpretation of this recent extension of the Avalonian assemblage into Laurentia. All known occurrences of the Avalon assemblage are from deep-water settings. Our study of the Wonoka Formation, which contains sparse specimens of the oldest Ediacara-type fossils in Australia that may be coeval with the youngest fossils at Mistaken Point, will document the fossils and environmental conditions of these shallower-water carbonate environments. Collectively, these studies will elucidate the early development of large size and biological complexity in the context of Ediacaran global change and will provide training for 2 PhD, 3 MSc and 5 BSc HQP.

新元古代是地球系统发生巨大变化的时期，包括罗迪尼亚超大陆的分裂、全球范围内的几次“雪球地球”冰河时代、海水同位素组成的显着波动以及海洋和大气中氧含量的增加但波动。在新元古代全球变化的背景下，我们看到生命进化也发生了同样深刻的变化，在经历了三十亿年的微生物进化之后，埃迪卡拉晚期（5.71亿年前）出现了丰富的标本和大型且结构复杂的生命形式的多个分类群。埃迪卡拉生物群是全球软体海洋生物的组合，现在以化石形式保存在砂岩或火山灰事件层下，位于寒武纪丰富的贝壳化石和复杂的洞穴之下。埃迪卡拉生物是在埃迪卡拉纪末期未能幸存的生物群（例如兰形动物）的混合物，以及在寒武纪大爆发期间多样化的干群动物，它们是我们现代世界所有动物生命的祖先。已知的最古老的埃迪卡拉型化石印记是长达 2 米的兰格化石，出现在新列入联合国教科文组织世界遗产名录的 Mistaken Point 内 Drook 地层的上部；大致同时代的阿瓦隆人群落也出现在英格兰中部和加拿大西北部。在接下来的五年中，我将通过对阿瓦隆纽芬兰、加拿大西北部和澳大利亚最古老的埃迪卡拉化石的研究以及对全世界整个时期的综合研究，评估埃迪卡拉纪全球变化与生物进化之间的相互关系。我们的实地研究涉及地层学、沉积学和古生物学，还将利用同位素和氧化还原地球化学领域的国际合作者。在纽芬兰，我们将分析裸露的 Mall Bay-Drook 地层序列，这些地层以前仅在勘察水平上已知，其早于 Mistaken Point 的大部分化石序列，因此可以提供有关在阿瓦隆尼亚纽芬兰出现生物复杂性之前的环境条件的信息。加拿大西北部的工作将重点关注深水纳达林地层中的化石，以增强数据集和对最近阿瓦隆组合延伸到劳伦西亚的数据集和解释。所有已知的阿瓦隆组合都来自深水环境。我们对沃诺卡组的研究将记录这些浅水碳酸盐环境的化石和环境条件，其中包含澳大利亚最古老的埃迪卡拉型化石的稀疏样本，这些化石可能与错误点最年轻的化石同时期。总的来说，这些研究将阐明埃迪卡拉纪全球变化背景下大尺寸和生物复杂性的早期发展，并将为 2 名博士、3 名硕士和 5 名理学学士 HQP 提供培训。