Trace Fossils, Ichnofabrics and Problematic Sedimentary Structures at the Proterozoic-Cambrian Transition: Implications for the Early Evolution of Animals and their Habitats

元古宙-寒武纪过渡期的遗迹化石、遗迹组构和有问题的沉积构造：对动物及其后代早期进化的启示。对这一事件的理解至关重要的是软体动物的洞穴，足迹和足迹的记录，并保存在化石记录中;这些被称为痕迹化石。 此外，动物混合或搅动沉积物，产生一种称为遗迹组构的斑驳结构。 遗迹学记录的重要性体现在前寒武纪-寒武纪界线是根据遗迹化石确定的（Narbonne等人，1987年）。这项研究项目将是第一个详细的系统的现场分析的变化的相关性的遗迹组构，离散的痕迹化石和垫相关的沉积结构跨越前寒武纪-寒武纪边界。 对于拟议的项目，PI选择了位于纽芬兰、纳米比亚、南澳和美国西部的四个部分。这些剖面提供了完整的浅水硅质岩相。对元古代末期遗迹化石的研究可以应用于两侧对称动物的外观问题。 此外，生物扰动（沉积物混合）在终端元古宙-寒武纪边界间隔的上升深刻和不可逆转地改变了底栖生境。一个后果是减少微生物结合的硅质沉积物，这似乎已经发生在完全海洋环境。这些微生物垫可能是负责不寻常的风格保存的软体埃迪卡拉类动物群。不寻常的沉积结构也可能是由于这些席的形成和保存。迄今为止，还没有对遗迹组构和离散遗迹化石的变化进行详细的研究，以限制“埋藏窗”消失的概念

Trace Fossils, Ichnofabrics, and Problematic Sedimentary Structures at theProterozoic-Cambrian Transition: Implications for the Early Evolution ofAnimals and Their HabitatsMary DroserEAR-0074021The Cambrian radiation was the most significant event in the history of complex animals. Critical to this understanding this event is the record of the burrows, tracks and trails made by soft-bodied animals and preserved in the fossil record; these are known as trace fossils. Additionally, animals mix or churn the sediment and produce a mottled fabric known as ichnofabric. The importance of the ichnological record is exemplified by the fact that the Precambrian-Cambrian boundary is defined on the basis of trace fossils (Narbonne et al., 1987). This research project will be the first detailed systematic field analysis of the correlation of changes in ichnofabrics, discrete trace fossils and mat-related sedimentary structures across the Precambrian-Cambrian boundary. For the proposed project PI has selected four sections located in Newfoundland, Namibia, South Australia and western United States. These sections provide a complete range ofshallow-water siliciclastic facies. Examination of terminal Proterozoic trace fossils has applications to questions of the appearance of bilaterian animals. In addition, the rise in bioturbation (sediment mixing) at the terminal Proterozoic-Cambrian boundary interval profoundly and irreversibly changed the benthic habitat. One consequence was the reduction in microbial binding of siliciclastic sediments, which seem to have occurred in fully marine settings. These microbial mats may have been responsible for the unusual style of preservation of the soft-bodied Ediacara-type faunas. It is also likely that unusual sedimentary structures owe their formation and preservation to these mats. To date there has been no detailed examination of the changes in ichnofabric and discrete trace fossils to constrain the notion of the disappearance of a 'taphonomic window'