SEPM Research Conference Propagation of Environmental Signals within Source-to-Sink Stratigraphy June 5-9th, 2017 — Tremp & Ainsa, Spanish Pyrenees The impact of variable sedimentation on reconstructing climate signals in deltaic and shelf deposits: Models and examples from the Paleocene-Eocene Thermal Maximum Sheila M. Trampush1 and Elizabeth A. Hajek1 1The Pennsylvania State University, University Park, Pennsylvania, U.S.A. The stratigraphic record provides a vital opportunity to investigate how different landscapes and seascapes respond to small and large climatic events. This is especially important in coastal and shallow marine environments, which are likely to be highly sensitive to both the rate and magnitude of the climate change. However, the signature of the landscape response to climate change may be masked or removed by the highly variable sedimentation that is characteristic of coastal and shallow marine environments. A common solution is to independently identify climatic events using geochemical proxies, such as carbon and oxygen isotopes. This approach does not account for the potentially significant variability in deposition and erosion time series that result from events like storms, floods, or autogenic processes like channel avulsion or delta lobe switching. In order to explore how geochemical proxy records could be overprinted by landscape dynamics, we use a 3D sedimentation model to build synthetic stratigraphy deposited in a fluvial-dominated marine shelf. The synthetic stratigraphy has a proxy value assigned to each sediment package according to age, which can then be used to create artificial 1D proxy records at random locations through the deposit. We assess the degree to which the magnitude, duration, and shape of the proxy curve can be reconstructed from the synthetic 1D sections. We find that the inherent sedimentation variability created by autogenic deltaic processes easily overprints the proxy climate signal, regardless of the distance from the sediment source or the magnitude and duration of the climatic event. We then compare our model results to observations of the carbon isotope excursions of the Paleocene Eocene Thermal Maximum (PETM) preserved within shallow marine deposits in the Mid-Atlantic coastal plain. From cores drilled in Maryland, Virginia, and New Jersey across a range of depths, we conclude that although the sedimentary processes change dramatically from the proximal to distal cores, all cores show evidence of variable sedimentation altering the apparent duration and shape of the PETM carbon isotope excursion. Our results suggest that we may be able to use existing geochemical proxy records within well studied, global climatic events such as the PETM, to constrain how sedimentation may have responded to the climatic event in different environments.
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