Joint EESS/GES Winter Seminar Series, Erik Sperling, Harvard University
Joint EESS/GES Winter Seminar Series, Erik Sperling, Harvard University, "Signal and noise in the record of Neoproterozoic oxygenation", Abstract: Few associations in historical geobiology are more iconic or enduring than that between animals and oxygen. Specifically, a hypothesized oxygenation event near the Precambrian-Phanerozoic transition is generally considered a main driver in the evolution of large, ecologically diverse animals. And indeed, there is obvious volatility in marine geochemical proxy records during this time. Published evidence for oxygenation, however, spans ~200 million years of Earth history, calling into question the nature of oxygenation and the direct links to early animal evolution. Here the evidence for oxygenation is examined using a geochemical database of redox proxy data (utilizing both published data and de novo measurements), with a view towards distinguishing global signal from local heterogeneity. Statistical analyses of the current dataset support only a small rise in oxygen levels in the Ediacaran and Cambrian, if any. This suggests that if changing pO2 facilitated animal diversification it did so by a limited rise past critical ecological thresholds, such as seen in the modern Oxygen Minimum Zone benthos. Oxygen increase to modern levels thus becomes a Paleozoic problem, and one in need of better sampling if a database approach is to be employed.