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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=754992
• 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，包括超大陆罗迪尼亚的分裂，全球范围内的几个“雪球地球”冰河时代，海水同位素组成的显著波动，海洋和大气中氧气含量的增加但波动。在新元古代全球变化的背景下，我们看到了生命进化中同样深刻的变化，埃迪卡拉纪晚期（5.71亿年前）经过30亿年以微生物为主的进化，出现了丰富的标本和多个大型、结构复杂的生命形式分类群。埃迪卡拉生物群是全球软体海洋生物的集合，现在作为化石印记保存在砂岩或火山灰的事件床下，在丰富的贝壳化石和寒武纪复杂的洞穴之下。埃迪卡拉纪的生物是埃迪卡拉纪末期灭绝的生物群（如rangeomorphs）和在寒武纪大爆发期间多样化的茎群动物的混合体，它们是我们现代世界所有动物生命的祖先。世界上已知的最古老的埃迪卡拉类型化石印痕是长达2米的范围形化石，它们出现在新列入联合国教科文组织世界遗产名录的错点（Mistaken Point）内的乌鸦组（Drook）上部；大致同时期的阿瓦洛尼亚组合也出现在英格兰中部和加拿大西北部。在接下来的五年里，我将通过对纽芬兰阿瓦洛尼亚、加拿大西北部和澳大利亚最古老的埃迪卡拉类化石的研究，以及在整个世界范围内延伸的综合研究，评估埃迪卡拉纪全球变化与生物进化之间的相互关系。我们的实地研究是地层学、沉积学和古生物学，也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，我们将分析一个非常暴露的Mall Bay-Drook地层演替，以前只在侦察水平上知道，它早于错误点的大多数化石演替，因此可以提供关于阿瓦洛尼亚纽芬兰生物复杂性出现之前的环境条件的信息。在加拿大西北部的工作将集中在深水Nadaleen组的化石上，以加强数据集和对最近将Avalonian组合扩展到Laurentia的解释。所有已知的阿瓦隆组合都来自深水环境。我们对Wonoka组的研究将记录这些浅水碳酸盐岩环境的化石和环境条件，该组包含澳大利亚最古老的埃迪卡拉型化石的稀疏标本，可能与在错误点发现的最年轻的化石同时代。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HQP学士提供培训。