Burgess Shale-type deposits and the ichnology of fine-grained systems

伯吉斯页岩型（BS）矿床有助于重建中生代开始时生命的多样性和复杂性。缺氧的优势，作为内在相关的BS存款，导致了有害的想法，痕迹化石不存在或太罕见，是有用的古生态重建或揭示宏观演化趋势。然而，在世界各地的大多数BS矿床中都记录了遗迹化石，它们的研究开始揭示有关寒武纪生态和控制BS化石lagerstätten形成的古环境参数的关键信息。 BS矿床的一个共同特征是氧胁迫;这种基本的生态控制反映在遗迹化石的大小范围、在沉积物中的渗透和分类组成上。然而，与这些矿床的独特埋藏有关的其他控制似乎也发挥了重要作用，值得进一步探索。此外，越来越多的认识到，许多细粒地层传统上被称为"非生物扰动"，实际上包含洞穴正在改变我们的沉积动力学和生态学的细粒沉积系统的理解。 其目标是：（1）记录与BS沉积物相关的遗迹动物群，并评估其潜力，以提高我们对寒武纪和早奥陶世生态的理解;（2）探索遗迹信息如何提供对环境参数和埋藏叠印的见解;（3）在宏观演化尺度上解决BS痕迹化石组合的意义;（4）在细粒沉积体系的背景下框架BS遗迹动物群。计划开展的活动包括：（1）在BS各地点的野外工作;（2）修订收集;（3）岩心描述和解释;（4）建立BS矿床和相关细粒矿床中遗迹动物群的全球数据库。 研究结果将有助于：（1）在演化古生态学背景下构建BS型遗迹动物群;（2）整合所选BS矿床的遗迹化石、体化石、埋藏学和沉积学数据;（3）比较全球不同BS型遗迹动物群，以更好地理解环境和演化控制;（4）通过地质时代对细粒系统中的遗迹动物群进行校正，以适应早古生代泥质基底的实际条件。该项目将通过在完全基于身体化石记录分析的重建中增加遗迹学维度来扩大我们对生态系统结构和功能的理解。最后，最终的目标是在全球和宏观进化的尺度上从BS lagerstätten中框定遗迹动物群，以解决寒武纪大爆发的相互冲突的观点，即一个可解释性的人工制品或现代生命的大爆炸（即现代门）。

Burgess Shale-type (BS) deposits have been instrumental to reconstruct the diversity and complexity of life at the beginning of the Phanerozoic. The preponderancy of anoxia, as intrinsically related to BS deposits, has resulted in the detrimental idea that trace fossils were inexistent or too rare to be useful in paleoecologic reconstructions or to reveal macroevolutionary trends. However, trace fossils have been recorded in most BS deposits worldwide, and their study is starting to reveal crucial information about Cambrian ecology and paleoenvironmental parameters governing formation of BS fossil lagerstätten. A common feature of BS deposits is oxygen stress; this fundamental ecologic control is reflected in size range of trace fossils, penetration in the sediment, and taxonomic composition. However, other controls related to the unique taphonomy of these deposits seem to also have played a significant role and warrant further exploration. In addition, the growing realization that many fine-grained strata traditionally referred to as “unbioturbated” do in fact contain burrows is changing our understanding on the sedimentary dynamics and ecology of fine-grained depositional systems. The objectives are to: (1) document ichnofaunas associated with BS deposits, and evaluate their potential to improve our understanding of Cambrian and Early Ordovician ecology; (2) explore how ichnologic information provides insights into environmental parameters and taphonomic overprints; (3) address the significance of BS trace-fossil assemblages at a macroevolutionary scale; and (4) frame BS ichnofaunas within the context of fine-grained depositional systems. The activities planned include: (1) fieldwork in various BS localities; (2) revision of collections; (3) core description and interpretation; and (4) construction of a global database of ichnofaunas in BS deposits and related fine-grained deposits. The results of this investigation will allow: (1) framing BS ichnofaunas within an evolutionary paleoecology context; (2) integration of trace fossil, body fossil, taphonomic and sedimentologic data for the selected BS deposits; (3) comparison of different BS-type ichnofaunas worldwide to best understand environmental and evolutionary controls; and (4) calibration of ichnofaunas from fine-grained systems through geologic time to accommodate the anactualistic conditions of early Paleozoic muddy substrates. This project will expand our understanding of ecosystem structure and functioning by adding an ichnologic dimension to reconstructions based exclusively on the analysis of the body-fossil record. Finally, the ultimate goal is to frame ichnofaunas from BS lagerstätten at a global and macroevolutionary scale in order to address conflicting views of the Cambrian explosion, namely an artifact of preservability or the big bang of modern life (i.e. modern phyla).