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演化的速率和模式。为此，首席调查员将汇编50年来公布的地层学数据，包括中国、蒙古、西伯利亚和南澳大利亚州最近的地质年代学、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、可访问、全球相关和辐射受限的早寒武世化石外观和地球化学变化时间表。有了新的时间表，他们将使用耦合的海水来测试将动物进化模式与环境变化联系起来的假说，反之亦然？孔隙流体地球系统模型：下寒武统全球对比一直难以实现。许多早期动物群体的地域性，包括三叶虫，以及化石首次出现数据(FADS)不可避免的历时性，阻碍了生物地层对比。同样，仅仅基于定性的、摆动的匹配来推导相关性？化学地层记录，如碳(ä13C)或锶(87Sr/86Sr)，通常是模棱两可的，可能会受到不整合和碳酸盐成岩作用的影响。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，即使在相对时间上有很好相关性的地层也不会限制重要生物和地球化学变化的速度和持续时间。首席调查人员将建立一个全面的数据库，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锆石U-Pb年代学。来自全球的多样性和完整性可变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记录放在相对和绝对时间，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.