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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715289
• 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 BayDrook 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解体，全球范围内的几个“雪球地球”冰期，海水同位素组成的显著波动，以及海洋和大气中氧气水平的增加但波动。在新元古代全球变化的背景下，我们看到了生命进化的同样深刻的变化，在30亿年的主要是微生物进化之后，埃迪卡拉纪晚期(5.71亿年前)出现了丰富的标本和多个大型和建筑复杂的生命形式的分类群。埃迪卡拉生物群是软体海洋生物的全球组合，现在作为化石印记保存在砂岩或火山灰事件层下，这些岩石或火山灰是寒武纪丰富的壳化石和复杂洞穴的基础。埃迪卡拉生物是在埃迪卡拉纪末期没有幸存下来的生物群(例如，浪形动物)和在寒武纪大爆发期间多样化的干群动物的混合体，是我们现代世界所有动物的祖先。已知的最古老的埃迪卡拉类型化石印记是长达2米的范围形态化石，出现在新列入联合国教科文组织世界遗产错点的德鲁克组的上部；在英格兰中部和加拿大西北部也发现了广泛同时代的阿瓦隆组合。在接下来的五年里，我将通过对加拿大西北部阿瓦洛尼亚纽芬兰和澳大利亚最古老的埃迪卡拉类型化石的研究，以及一项贯穿全球整个时期的综合研究，来评估埃迪卡拉纪全球变化和生物进化之间的相互关系。我们的实地研究包括地层学、沉积学和古生物学，还将利用同位素和氧化还原地球化学方面的国际合作者。在纽芬兰，我们将分析之前仅在侦察水平上已知的Mall BayDrook地层的高度暴露的序列，这些地层早于Erren Point的大多数化石序列，因此可以提供有关环境条件的信息，这些环境条件紧接在阿瓦隆纽芬兰出现生物复杂性之前。加拿大西北部的工作将侧重于深水纳达林地层中的化石，以加强数据集和对阿瓦隆组合最近延伸到劳伦西亚的解释。所有已知的阿瓦隆组合产状都来自深水环境。我们对Wonoka组的研究将记录这些浅水碳酸盐环境的化石和环境条件。Wonoka组包含澳大利亚最古老的Ediacara类型化石的稀疏样本，可能与Erren Point最年轻的化石同龄。总而言之，这些研究将阐明在埃迪卡拉纪全球变化的背景下大型生物复杂性的早期发展，并将为2名博士、3名理学硕士和5名理科硕士提供培训。