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的进化速率和模式。为此，主要研究人员将汇编50年来收集的地层数据，包括来自中国、蒙古、西伯利亚和南澳的最新地质年代学、化学地层学和生物地层学数据，以及在北美和摩洛哥开展的新的实地项目，以制定一个综合的、可获取的、全球相关的、受辐射限制的早寒武世化石外观和地球化学变化时间轴。有了新的时间轴，他们将使用耦合海水来测试将动物进化模式与环境变化联系起来的假设，反之亦然？下寒武统的全球对比一直难以实现。生物地层对比一直受到许多早期动物群体（包括三叶虫）的地方性和化石首次出现基准（FAD）不可避免的历时性的阻碍。同样，仅基于定性推导相关性？摆动匹配化学地层记录的碳（~（13）C）或锶（~（87）Sr/~（86）Sr）同位素通常是不明确的，并且可能被不整合面和碳酸盐成岩作用所扭曲。此外，如果没有来自互层凝灰岩和火山碎屑岩的锆石U-Pb年龄，即使在相对时间上相关性很好的地层学也不会限制重要的生物和地球化学变化的速率和持续时间。主要研究人员将建立一个综合数据库，包括动物化石产状、岩石和化学地层学以及互层火山碎屑岩的U-Pb锆石年代学。来自地球仪的可变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局部记录置于相对和绝对时间中，不是基于一个变量，如FAD或Δ 13 C，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.