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Shanan Peters Colloquium Abstract (Mar 1, 2017)

Earth's Long-Term Biogeochemical Evolution: a View From the Upper Crust

Earth's surface chemistry is controlled, at the most fundamental level, by mass exchanges occurring between the surface environment and the lithosphere. Although this has been recognized for more than 100 years, it has generally been assumed that erosion and recycling are the dominant process signals in the surviving rock record, and that erosion and destruction is roughly in balance with rates of sedimentation. Here, I use Macrostrat, a database designed to quantitatively describe the geographic and chronostratigraphic distribution, thickness, and composition of rocks in Earth's upper crust, to provide new constraints on the surviving sedimentary rock record across Earth history. The signature of erosion and destruction of rocks is present in subsets of the data, but it is not characteristic of the sedimentary rock record as a whole. Instead, the time series of sedimentary rock quantity bears many similarities to geochemical and biological proxy records that indicate major changes in the composition of Earth's atmosphere and diversity of life. Possible causal mechanisms for the empirical similarities between proxy records and the sedimentary rock record are explored.