Taphonomic and paleoecological investigation of carbonate-hosted Ediacara-type fossils in the Shibantan Member of Yangtze Gorges area

在寒武纪大爆发前夕：石板滩碳酸盐岩中埃迪卡拉类生物的化石保存与生态学我们所熟悉的动物在大约5.41 - 5.2亿年前的寒武纪早期发生了大爆发。然而，它们在寒武纪之前的进化祖先却鲜为人知。研究埃迪卡拉纪（653-541 Ma）的化石记录是阐明寒武纪大爆发前动物进化史的一个重要方法。本项目旨在对中国埃迪卡拉纪石坂滩段进行研究，以扩大我们对埃迪卡拉纪动物和相关生物的生物学、生态学和保护的认识。之所以选择石板滩段，是因为它拥有丰富的动物痕迹（即早期动物留下的足迹和洞穴），以及一套宏观的埃迪卡拉类化石，这些化石被不同地、有争议地解释为动物、真菌、地衣甚至细菌菌落。此外，与大多数在砂岩中发现的埃迪卡拉类化石不同，石板滩化石保存在石灰岩中，从而为研究这些神秘生物的全方位环境分布提供了机会。本项目将采用现场与实验室相结合的方法，系统挖掘、描述和分析十板滩化石，获取和整合一套跨学科的数据，对十板滩化石的生物学、生态学和保存进行分析，并对其与动物、地衣和细菌的亲缘关系进行各种假设检验。最终，这项提议的研究将为埃迪卡拉-寒武纪边界的进化史提供新的线索。该提案为研究生提供了资助机会，并为弗吉尼亚州K-12教育和STEM项目做出了贡献。该项目由美国国家科学基金会地球同步轨道前沿基金、地表地球过程分部和国际科学与工程办公室共同资助。diacara型化石为研究寒武纪大爆发前夕宏观和形态复杂的真核生物的演化提供了重要的见解。在过去的十年里，埃迪卡拉型化石的研究取得了重大进展，新发现和新技术使我们对埃迪卡拉型关键化石的形态、地学、生态学和进化动力学的认识更加清晰。但是，仍然存在很大的差距和争议。特别是，埃迪卡拉型化石大多保存在砂岩和粉砂岩中，而很少在黑色页岩和灰岩中发现，它们在砂岩/粉砂岩相中的优先出现是一种潜在的地学倾向还是一种环境偏好尚不确定。为了更全面地了解埃迪卡拉型化石的古生态和地学多样性，本项目拟采用野外观测技术、光镜、电镜和稳定同位素质谱相结合的方法，对中国长江三峡地区十板滩段沥青灰岩中的埃迪卡拉型化石进行系统的挖掘、描述和分析。目的是获取和整合一整套古生物学、沉积学、岩石学和地球化学数据，以了解这些化石的埋藏学和古生态学，验证关于埃迪卡拉型化石系统发育亲缘性和古生态学的各种假设，并为埃迪卡拉-寒武纪过渡时期埃迪卡拉型化石消失的模式和可能的原因提供见解。该提案为通过弗吉尼亚理工大学现有的一个专注于代表性不足群体的项目招募一名研究生提供资金，为通过弗吉尼亚理工大学地球科学博物馆部署的K-12资源工具包开发新材料，并为地区STEM教育做出贡献。该项目由美国国家科学基金会地球同步轨道前沿基金、地表地球过程分部和国际科学与工程办公室共同资助。

Revised Title: On the eve of the Cambrian explosion: Fossil preservation and ecology of Ediacara-type organisms hosted in carbonate rocks of the Shibantan MemberNon-technical AbstractAnimals we are familiar with evolved explosively during the early Cambrian Period, about 541-520 million years ago (Ma). However, their evolutionary ancestry before the Cambrian Period is poorly known. One important way to illuminate the evolutionary history of animals before the Cambrian explosion is to examine the fossil record of the Ediacaran Period (653-541 Ma). This project is designed to investigate the Ediacaran Shibantan Member of China in order to expand our knowledge about the biology, ecology, and preservation of Ediacaran animals and related organisms. The Shibantan Member is chosen because it hosts abundant animal traces (i.e., tracks and burrows made by early animals) and a suite of macroscopic Ediacara-type fossils that have been variously and controversially interpreted as animals, fungi, lichens, or even bacterial colonies. Additionally, unlike most Ediacara-type fossils that are found in sandstones, the Shibantan fossils are preserved in limestones and thus offer an opportunity to investigate the full range of environmental distribution of these enigmatic organisms. In this project, researchers will systematically excavate, describe, and analyze the Shibantan fossils using a combination of field and laboratory techniques, to obtain and integrate a suite of interdisciplinary data, to analyze the biology, ecology, and preservation of the Shibantan fossils, and to test various hypotheses about their affinities with animals, lichens, and bacteria. Ultimately, the proposed study will shed new light on the evolutionary history across the Ediacaran-Cambrian boundary. The proposal provides funding opportunity for a graduate student and contributes to the Virginia K-12 education and STEM programs. The project is jointly funded by NSF's GEO Frontier Fund, Section of Surface Earth Processes, and International Science and Engineering Office.Technical AbstractEdiacara-type fossils provide important insights into the evolution of macroscopic and morphologically complex eukaryotes on the eve of the Cambrian explosion. The past decade has seen significant progress in the study of Ediacara-type fossils, with new discoveries and new techniques sharpening our views about the morphology, taphonomy, ecology, and evolutionary dynamics of key Ediacara-type fossils. However, significant gaps and controversies still exist. In particular, Ediacara-type fossils are mostly preserved in sandstones and siltstones but rarely in black shales and limestones, and it is uncertain whether their preferential occurrences in sandstone/siltstone facies represent a potential taphonomic bias or an environmental preference. To achieve a more complete understanding of the paleoecological and taphonomic diversity of Ediacara-type fossils, the PI proposes to systematically excavate, describe, and analyze Ediacara-type fossils hosted in bituminous limestone of the Shibantan Member in the Yangtze Gorges area in China, using a combination of field observation techniques, light microscopy, electron microscopy, and stable isotope mass spectroscopy. The objective is to obtain and integrate a suite of paleontological, sedimentological, petrographic, and geochemical data, in order to understand the taphonomy and paleoecology of these fossils, to test various hypotheses about the phylogenetic affinities and paleoecology of Ediacara-type fossils, and to offer insights into the pattern and possible causes of the disappearance of Ediacara-type fossils at the Ediacaran-Cambrian transition. The proposal provides funding for a graduate student to be recruited through one of Virginia Tech's existing programs focusing on under-represented groups, develops new material for K-12 resource kits to be deployed through Virginia Tech Museum of Geosciences, and contributes to regional STEM education. The project is jointly funded by NSF's GEO Frontier Fund, Section of Surface Earth Processes, and International Science and Engineering Office.