Taphonomy and Paleoecology of Ediacaran Assemblages (Flinders Ranges, South Australia): Do we Have a Census?

元古界末期埃迪卡拉纪生物群一直是现代古生物学中争议较大的问题之一。它的时间位置在所谓的寒武纪大爆发之前，表明它应该提供关于动物早期进化的关键信息。埃迪卡拉纪生物群的研究传统上集中在个体分类群的描述和解释上，最近则集中在地层分布和古地理上。埃迪卡拉生物群研究的一个主要缺陷是缺乏对群落结构和雌雄同体其他方面的研究。没有先验的理由为什么不应该用与显生目动物群落相同的方法来检查晚期元古代化石组合。特别是作为保存埃迪卡拉纪化石的模型(Gehling 1999)，他们预测它们可能会产生普查群落。这项拟议的研究项目将是首次对高度多样性的埃迪卡拉纪组合(包括所有遗体和遗迹化石、有问题的构造和无机表面)进行详细的现场分析，方法是对南澳大利亚可挖掘大型顺层层面(超过数百平方米)的地点进行研究。野外工作方案包括挖掘和重新组装已在地层序列中仔细记录的地层。将详细研究这些层面，并记录所有遗迹化石和沉积构造，并根据保存的性质和性质对其进行分类。然后用标准的统计方法分析化石的分布。初步研究表明，在直接的地层序列中，化石和层间层理的性质存在着意想不到的高度差异。该项目的一个重要目的是解释这些观察结果；这些差异在多大程度上代表了保存偏见或复杂的群落？该项目的一个重要部分是详细记录遗迹化石以及大量存在问题的无机和有机起源的结构。在此之前，没有详细研究过晚元古代遗迹化石相对于遗体化石的分布情况以及遗迹所在地层的性质。晚元古代遗迹化石的记录是有问题的，因为许多错误的识别与有问题的结构。在专注于离散身体化石的研究中，这些有问题的结构在很大程度上被忽视了，但它们持有关于这些群落性质的重要信息。只有通过对大型层理平面的研究，才能了解这些物体的性质，我们才能最终了解埃迪卡拉纪组合上的敲击叠加，从而解开埃迪卡拉纪的生态。为这项研究挖掘的平面图将被重新组装，以允许开发一个供学生和其他感兴趣的各方参观的地点(正如之前与土地所有者安排的那样)。这个项目非常适合本科生参与，资金预算用于2名本科生到澳大利亚旅行和实地工作。澳大利亚当地居民也将参与挖掘和相关活动。通过这种方式，这笔存款和其他类似存款的意义可以被传达出来。该项目将开发和保护一个世界级的化石遗址，其全部潜力仍未开发。

The terminal Proterozoic Ediacaran biota remains one of the great controversies inmodern paleontology. Its temporal position, preceding the so-called Cambrian explosion,suggests that it should provide key information on the early evolution of animals. Studies of theEdiacaran biota have traditionally focussed on the description and interpretation of individualtaxa and more recently on the stratigraphic distribution and paleogeography. A majorshortcoming in the study of the Ediacaran biota is the paucity of studies of the communitystructure and other aspects of synecology. There is no a priori reason why late Proterozoicassemblages should not be examined by the same means as Phanerozoic communities.Particularly as models for the preservation of Ediacaran fossils (Gehling 1999) predict that theypotentially should yield census communities. The proposed research project will be the firstdetailed systematic field analysis of a high-diversity Ediacaran assemblage (including all bodyand trace fossils, problematic structures and inorganic surfacesls) by the study of selectedlocalities in South Australia in which large sequential bedding planes (over hundreds of squaremeters) can be excavated.The fieldwork protocol involves excavation and re-assembly of beds that have beencarefully logged in stratigraphic succession. These bedding-planes will be examined in detail andall body and trace fossils and sedimentary structures recorded and categorized with respect toproperties and nature of preservation. The distribution of fossils is then analysed by standardstatistical methods. Preliminary examination suggests that there is an unexpected high differencein fossils and the nature of bedding planes between beds in immediate stratigraphic succession.An important aim of the project is to explain these observations; to what extent do thesedifferences represent preservational biases or complex communities?An important part of this project is to document in detail trace fossils as well as thenumerous problematic structures of both inorganic and organic origin. Previously there has beenno detailed examination of the distribution of late Proterozoic trace fossils with respect to bodyfossils and the nature of the beds on which the traces occur. The record of late Proterozoic tracefossils is problematic because of numerous misidentifications with problematic structures. Theseproblematic structures have largely been ignored in studies focussed on discrete body fossils, butthey hold important information on the nature of these communities. It is only by examination oflarge bedding plane surfaces that the nature of these objects can be understood and we canultimately understand the taphonomic overprint on Ediacaran assemblages and thus, unravelEdiacaran ecology.Broader ImpactEdiacaran assemblages are the oldest diverse macroscopic fossil assemblages on Earth.As such, they are of considerable interest to a wide range of geologists and biologists. Beddingplanes that will be excavated for this study will be reassembled in a manner that allows for thedevelopment of a site for students and other interested parties to visit (as previously arrangedwith the landowner).This project is ideally suited for undergraduate participation and monies are budgeted for2 undergraduates to travel to Australia and work in the field. Local Australians will also beinvolved with the excavation and related activities. In this way, the significance of this depositand others like it can be conveyed. This project will develop and protect a world class fossillocality the full potential of which has remained untapped.