Plugging the preservational pipeline: an integrated approach to tracking taphonomic histories of Cambrian skeletal fossil assemblages

并不是所有的生物都有同样的可能性被保存在化石记录中。环境中有各种限制因素(生物和/或物理因素)，可以过滤掉更易分解的脆弱形式。通常，只有动物的坚硬骨骼(即骨骼、牙齿和贝壳)被保存下来，然而这是否意味着骨骼记录本身是可靠的？为了避免偏颇我们对地球生命历史的看法，这个项目将探索“保存管道”中泄漏的骨骼记录。这个项目的目标可能是被称为寒武纪(5.41亿-4.88亿年前)的最重要的地质时期，在此期间，我们所知的动物生命进化和多样化。该项目包括一个多学科的研究小组，他们将从南澳大利亚州的伊卡拉-弗林德斯山脉采集寒武纪年代的岩石和小壳化石样本，以解决以下问题：骨骼化石记录的缺失比例？保护这些甲壳动物需要哪些环境条件？这些化石数据集在保存特定动物种群或细分地质时代方面的可靠性如何？为了解决这些问题，研究小组将结合现场和实验室的沉积学、地球化学和化石数据，以及先进的成像技术(Micro-CT和3D可视化软件)来重建过去的环境，并评估保存偏见对这些化石群落的影响。这种综合的方法有可能从根本上改变古生物学家分析和跟踪化石记录中的偏差的方式。此外，该项目将包括为大学本科生和研究生提供与地质学、古生物学和3D虚拟化领域相关的实用、技术和软技能培训。教育产出将包括以虚拟实地考察形式的在线托管媒体、前往南澳大利亚州伊卡拉-弗林德斯山脉的全球重要地质遗址和小径的旅行以及相关的课程材料。虚拟实地考察将在Google Trekker的帮助下进行，Google Trekker是一个安装了360度摄像头的背包，让人们可以进入这片偏远而非凡的古代景观。寒武纪小壳化石(SSF)组合继续塑造着我们对早期后生动物进化的理解，涉及到系统发育关系、生物创新(即生物矿化)和显生界生态系统的兴起。然而，要理解这一骨骼记录的生物学保真度，需要从整体上看待通过时间和空间控制石化的过程。南澳大利亚州寒武纪序列拥有世界上最丰富的SSF组合之一，跨越各种沉积梯度，为研究保存模式与古环境变化之间的联系提供了独特的环境。该项目将采用一种深度整合的方法，将沉积学、地球化学学和化石数据集与三维体积分析和古生态分析相结合，以便更好地了解可能扭曲我们对这一早期化石记录的看法的偏差来源。随着对控制选定保存模式的变量的全面了解，我们可以更好地为以前和未来对骨骼记录的解释提供信息，不仅是整个寒武纪，而且是整个化石记录。因此，这项研究提供的补充数据旨在：1)比较不同保存模式所代表的骨骼成分，量化常规化石提取程序所施加的选择性偏差以及生物因素(形态、成分和亲和力)；2)分析不同沉积体系中古沉积物的物理和地球化学特征，以重建古环境、氧化还原条件、营养通量和替代矿物的来源；3)量化和对比动物群组成、保存模式和古环境，以评估SSFS在区域和全球同期岩石序列测年中的可靠性和应用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Not all organisms have the same likelihood of being preserved in the fossil record. There are a variety of limiting factors (biological and/or physical) operating in the environment which can filter out more vulnerable forms prone to decomposition. Typically, only the hard skeletons of animals are preserved (i.e. bones, teeth, and shells), however does this mean that the skeletal record itself is reliable? To avoid biasing our view of the history of life on our planet this project will probe the skeletal record for leaks in the 'preservational pipeline'. This project targets perhaps the most important period of geological time known as the Cambrian Period (541-488 million years ago), during which animal life as we know it evolved and diversified. This project includes a multidisciplinary group of researchers who will sample Cambrian-aged rocks and small shelly fossils from the Ikara-Flinders Ranges of South Australia to address the following questions: What proportion of the skeletal fossil record is missing? What environmental conditions were required for the preservation of these shelly animals? And how reliable are these fossil datasets in preserving particular animal groups or for subdividing geological time? To address these questions the team will use a combination of field and lab-based sedimentological, geochemical, and fossil data, as well as advanced imaging techniques (micro-CT and 3D visualization software), to reconstruct past environments and assess the impact of preservation bias on these fossilized communities. This integrated approach has the potential to fundamentally change how paleontologists analyze and track bias in the fossil record. In addition, the project will include training for university undergraduate and graduate students with practical, technical, and soft skills relevant to fields of geology, paleontology, and 3D virtualization. Educational outputs will include online hosted media in the form of virtual fieldtrips to globally significant geological sites and trails in the Ikara-Flinders Ranges of South Australia, and their associated curricular materials. The virtual fieldtrips will be made with the assistance of a Google Trekker -a backpack mounted with a 360 degree camera- to make accessible this remote and extraordinary ancient landscape. Cambrian small shelly fossil (SSF) assemblages continue to shape our understanding of early metazoan evolution with respect to phylogenetic relationships, biotic innovations (i.e. biomineralization), and the rise of Phanerozoic-style ecosystems. However, to comprehend the biological fidelity of this skeletal record requires a holistic view of the processes controlling fossilization through time and space. The Cambrian successions of South Australia -host to one of the richest SSF assemblages in the world and spanning various depositional gradients- provide a unique setting in which to investigate the link between preservational mode and paleoenvironmental variations. This project will employ a deeply integrated approach combining sedimentological, geochemical, and fossil datasets in tandem with three-dimensional volume analysis and paleoecological analyses, in order to better understand sources of bias that might skew our perceptions of this early fossil record. With a comprehensive understanding of the variables controlling select preservational modes, we can better inform previous and future interpretations of the skeletal record, not just across the Cambrian, but the entire fossil record. As such, the complimentary data afforded by this research aims to 1) compare skeletal constituents represented by different preservational modes and quantify selective bias exerted by common fossil extraction procedures as well as biological factors (morphology, composition, and affinity); 2) analyze the physical and geochemical characteristics of ancient sediments from different depositional systems to reconstruct paleoenvironment, redox conditions, nutrient flux, and sources of replacive minerals; and 3) quantify and contrast faunal composition, preservational modes, and paleoenvironment to assess the reliability and application of SSFs for regional and global dating of contemporaneous rock successions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.