Collaborative Research: Toward a global timeline of biological and ocean geochemical change during the early Cambrian

该项目的首要目标是重建早期动物生命和海洋化学进化的速率和模式。为此，主要研究人员将汇编50年来已发表的地层数据，包括最近来自中国、蒙古、西伯利亚和南澳大利亚的地质年代学、化学地层学和生物地层学数据，以及北美和摩洛哥的新实地项目，以建立一个完整的、可获取的、全球相关的、辐射测量限制的早寒武纪化石出现和地球化学变化的时间表。有了新的时间表，他们将使用耦合的海水来测试动物进化模式与环境变化之间的联系，反之亦然。孔隙流体地球系统模型。下寒武统的全球对比一直难以实现。许多早期动物类群（包括三叶虫）的局部性以及化石首次出现基准（FADs）不可避免的历时性阻碍了生物地层对比。同样地，仅仅基于定性的？摆动匹配?碳（ä13C）或锶（87Sr/86Sr）同位素等化学地层记录通常是模糊的，并且可能因不整合和碳酸盐岩成岩作用而扭曲。此外，如果没有来自互层凝灰岩和火山碎屑岩的U-Pb锆石，即使地层在相对时间上有很好的相关性，也无法限制重要的生物和地球化学变化的速度和持续时间。主要研究人员将建立一个综合的动物化石产状、岩性和化学地层学、层间火山碎屑U-Pb锆石年代学数据库。来自全球的不同多样性和完整性的多代理记录将使用CONOP（约束优化）序列化软件进行关联。由此产生的复合地层学将把每个地方的记录放在相对和绝对时间上，而不是基于一个变量，如FADs或ä13C，而是基于所有可用的地层观测。

The overarching goal of this project is to reconstruct rates and patterns in the evolutionof early animal life and ocean chemistry. To this end, the principal investigators will compile 50 years of publishedstratigraphic data, including recent geochronological, chemostratigraphic and biostratigraphic data from China, Mongolia, Siberia and South Australia, together with new field projects in North America and Morocco, to develop an integrated and accessible, globally correlated and radiometrically constrained timeline of early Cambrian fossil appearances and geochemical change. With the new timeline, they will test hypotheses that link patterns in animal evolution to environmental change, and vice versa, using a coupled seawater ? pore fluid Earth-system model.Global correlation of the lower Cambrian has been difficult to achieve. Biostratigraphic correlation has been hampered by the provinciality of many early animal groups, including trilobites, and the inevitable diachroneity of fossil first appearance datums (FADs). Likewise, deriving correlations based only on qualitative ?wiggle matching? of chemostratigrapic records such as carbon (ä13C) or strontium (87Sr/86Sr) isotopes usually is ambiguous, and can be distorted by disconformities and carbonate diagenesis. Furthermore, without U-Pb zircon ages from interbedded tuffs and volcaniclastic rocks, even stratigraphy that is well correlated in relative time will not constrain the rate and duration of important biological and geochemical changes. The principal investigators will construct a comprehensive database of animal fossil occurrences, litho- and chemostratigraphy, and U-Pb zircon geochronology of interbedded volcaniclastics. Multiproxy records of variable diversity and completeness from around the globe will be correlated using the CONOP (constrained optimization) seriation software. The resulting composite stratigraphy will place each local record in relative and absolute time, based not on one variable, like FADs or ä13C, but rather on all available stratigraphic observations.