Spatial and temporal trends in Ediacaran-Cambrian ichnofaunas

埃迪卡拉-寒武纪界线代表了生命历史上的一个主要分界线。埃迪卡拉纪生物群以软体生物为主，现在认为它们大部分与现代多细胞动物群无关。埃迪卡拉纪生物在全球冰川作用后繁荣起来，这一全球冰川作用目前被称为雪球地球事件。另一方面，寒武纪见证了几乎所有现代动物群的快速发展，包括骨骼动物群的兴起，这是一个被称为寒武纪大爆发的重大进化创新。埃迪卡拉-寒武纪过渡期的大部分演化研究都是基于对身体化石的分析。然而，遗迹学记录（由动物留下的足迹、痕迹和洞穴组成）提供了一条独立的证据线来校准寒武纪大爆发。 最近的许多研究都强调埃迪卡拉生态系统的反现实主义特征，表明与现代环境不同，这些生态系统由与抗性微生物垫直接相关的底栖生物群落主导。在埃迪卡拉生态系统中，微生物结合使沉积物稳定是一个主要因素。在早寒武世，由于垂直生物扰动作用的开始，matgrounds变得罕见，并在被称为“农艺革命”的事件中被mixgrounds取代。综合沉积学和遗迹学分析提供了这些古老生态系统的生态一瞥，特别是有关了解终端元古宙寒武纪过渡的底栖生物群落。本项目的目的是分析埃迪卡拉-寒武纪遗迹动物群的时空格局。计划开展的活动包括：（1）在几个埃迪卡拉-寒武纪演替中的野外工作，（2）修订痕迹化石收集，（3）建立埃迪卡拉-寒武纪遗迹动物群数据库，（4）研究与胁迫环境中微生物基质相关的现代生物结构。实地考察将在阿根廷西北部、南非、西班牙、中国、加拿大落基山脉和肯尼亚进行。

The Ediacaran-Cambrian boundary represents a major divide in the history of life. Ediacaran biotas were dominated by soft-bodied organisms that are now considered for the most part to be unrelated with modern multicelular faunas. Ediacaran organisms flourished after a global glaciation that is presently known as the Snowball Earth episode. On the other hand, the Cambrian witnessed the rapid development of almost all modern groups of animals, including the rise of skeletal faunas, a major evolutionary innovation known as the Cambrian explosion. The majority of evolutionary studies on the Ediacaran-Cambrian transition have been based on the analysis of body fossils. However, the ichnologic record (that consisting of tracks, trails and burrows produced by animals) provides an independent line of evidence to calibrate the Cambrian explosion. Many recent studies have stressed the anactualistic character of the Ediacaran ecosystems by showing that, unlike modern environments, these ecosystems were dominated by benthic communities that developed in direct association with resistant microbial mats. Sediment stabilization by microbial binding was a major factor in Ediacaran ecosystems. During the Early Cambrian, matgrounds became rare due to the onset of vertical bioturbation and were replaced by mixgrounds in an event referred to as the "agronomic revolution". Integrated sedimentological and ichnological analysis provides a glimpse into the ecology of these ancient ecosystems and is particularly relevant to understanding the benthic communities of the terminal Proterozoic-Cambrian transition. The aim of this project is to analyze the spatial and temporal patterns of Ediacaran-Cambrian ichnofaunas. Planned activities include: (1) fieldwork in several Ediacaran-Cambrian successions, (2) revision of trace fossil collections, (3) construction of a database of Ediacaran-Cambrian ichnofaunas, and (4) study of modern biogenic structures associated with microbial matgrounds in stressed environments. Fieldwork will be done in northwest Argentina, South Africa, Spain, China, the Canadian Rockies and Kenya.