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

修订标题：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和生态非技术摘要我们熟悉的动物在寒武纪早期，大约5.41 - 5.2亿年前（Ma）爆发性进化。然而，它们在寒武纪之前的进化祖先却知之甚少。阐明寒武纪大爆发前动物进化史的一个重要方法是检查埃迪卡拉纪（653-541 Ma）的化石记录。该项目旨在调查中国埃迪卡拉纪石板滩段，以扩大我们对埃迪卡拉纪动物和相关生物的生物学，生态学和保护的知识。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），以及一套肉眼可见的埃迪卡拉类化石，这些化石被不同且有争议地解释为动物、真菌、地衣，甚至是细菌群落。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，因此提供了一个研究这些神秘生物的全方位环境分布的机会。在该项目中，研究人员将系统地挖掘，描述和分析石板滩化石，使用现场和实验室技术相结合，获得和整合一套跨学科的数据，分析石板滩化石的生物学，生态学和保存，并测试各种关于其与动物，地衣和细菌的亲缘关系的假设。最终，这项研究将为埃迪卡拉-寒武纪边界的进化历史提供新的线索。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NSF的GEO前沿基金、表层地球过程科和国际科学与工程办公室共同资助。技术摘要埃迪卡拉类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，埃迪卡拉类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类关键化石的形态学，埋藏学，生态学和进化动力学的看法更加清晰。然而，仍然存在重大差距和争议。特别是，埃迪卡拉型化石大多保存在砂岩和粉砂岩，但很少在黑色页岩和石灰岩，它是不确定的优先出现在砂岩/粉砂岩相代表一个潜在的埋藏的偏见或环境的偏好。为了更全面地了解埃迪卡拉类化石的古生态和埋藏学多样性，PI建议系统地挖掘，描述和分析中国长江三峡地区石板滩段沥青灰岩中的埃迪卡拉类化石，采用野外观察技术，光学显微镜，电子显微镜和稳定同位素质谱相结合。目的是获得和整合一套古生物学，沉积学，岩相学和地球化学数据，以了解这些化石的埋藏学和古生态学，测试各种假说的系统发育的亲和力和古生态学的埃迪卡拉型化石，并提供洞察埃迪卡拉型化石消失的模式和可能的原因在埃迪卡拉-寒武纪过渡。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资源包开发新材料，并为区域STEM教育做出贡献。该项目由NSF的GEO前沿基金，地表地球过程部门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.