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

Burgess页岩型(BS)沉积有助于重建显生界开始时生命的多样性和复杂性。与BS矿床有内在联系的缺氧的优势，导致了一种有害的观点，即遗迹化石不存在或太稀有，不能用于古生态重建或揭示宏观演化趋势。然而，世界上大多数BS化石中都记录了痕迹化石，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气胁迫；这种基本的生态控制反映在痕迹化石的大小范围、沉积物中的穿透性和分类组成上。然而，与这些矿床独特的埋藏学有关的其他控制似乎也发挥了重要作用，值得进一步勘探。此外，越来越多的人认识到，许多传统上被称为“非生物扰动”的细粒地层实际上包含洞穴，这正在改变我们对细粒沉积体系的沉积动力学和生态的理解。其目的是：(1)记录与BS沉积有关的遗迹动物群，并评估它们改善我们对寒武纪和早奥陶世生态的理解的潜力；(2)探索信息如何提供对环境参数和埋藏学叠加的见解；(3)在宏观演化尺度上解决BS遗迹化石组合的重要性；以及(4)在细粒沉积体系的背景下，将BS遗迹化石组合框架。计划开展的活动包括：(1)在BS各地方进行实地考察；(2)修订收藏品；(3)核心描述和解释；(4)建立BS矿藏和相关细粒矿藏生物动物群全球数据库。这项调查的结果将有助于：(1)在演化的古生态背景下建立BS遗迹动物群；(2)整合所选BS矿床的遗迹化石、遗体化石、埋藏学和沉积学数据；(3)世界各地不同BS类型遗迹动物的比较，以最好地了解环境和演化控制；以及(4)通过地质时代校准细粒系统的遗迹动物群，以适应早古生代泥质底质的不平衡条件。这个项目将扩大我们对生态系统结构和功能的理解，在完全基于身体化石记录的分析基础上为重建增加一个生物维度。最后，最终目标是在全球和宏观进化的尺度上框定BS Lagerstätten的遗迹动物群，以解决对寒武纪大爆发的相互矛盾的观点，即可保存的人工制品或现代生活的大爆炸(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).