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

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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.