Biogeochemical markers hosted in sedimentary rocks are the primary archives that document how the Earth’s air, water, and life have evolved throughout geologic time. However, sediments are unreliable bookkeepers. The strata omit information at random and without warning because external factors—like rainfall on mountain hillslopes and earthquakes on continental margins—induce scale-dependent internal feedbacks that shred and buffer environmental signals. In this talk, I focus on the forensic record of intensified flooding, one of the most likely and dangerous effects of future climate warming. Using a set of physical sedimentary experiments, I demonstrate how river dynamics scale non-monotonically with intensified flooding. Drawing from outcrop observations, I build on this insight to explore how fluvial responses to flooding can fractionate grain sizes in sedimentary basins, propagating sedimentary signals downstream. I then show that when flood intensity varies through time, co-evolving sedimentary dynamics distort how time is sampled in the strata. This process introduces a predictable structure to paleoclimate records recovered from sedimentary rocks. Taking this feedback into account requires revising common assumptions, like steady sediment accumulation between dated horizons. Finally, I synthesize these findings to outline a framework for sharpening interpretations of environmental signals from sedimentary strata, and I identify the key barriers that stand in the way of precisely reconstructing Earth history.
(Host: Prof. Adam Maloof & Bolton Howes)
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