Signals of Relative Sea Level perturbations: Defining the divide between autogenic signal shredding vs. preservation in the stratigraphic record
Recent theoretical work suggests that autogenic processes in sediment transport systems have the capacity to shred signals of environmental and tectonic perturbations prior to transfer to the stratigraphic record. We view this theory as a major conceptual and quantitative breakthrough in long time scale Earth-surface processes and stratigraphy, but the general theory still needs to be adapted to deal with specific types of signals. Many argue that the tug of Relative Sea Level (RSL) change represents the most important boundary condition forcing affecting continental margin transport systems. However, we still lack quantitative theory to explain what properties RSL cycles must have to be stored in stratigraphy, thus limiting the usefulness of stratigraphy for defining paleo-environments. Results from our previously conducted laboratory experiments suggest that RSL cycles with amplitudes less than a channel depth and of periodicities less than the amount of time necessary to deposit, on average, one channel depth of stratigraphy over a delta-top are susceptible to signal shredding. Our hypothesis is supported using existing data sets and new numerical and physical experiments in which the surface process response and preserved record of RSL cycles of varying magnitudes and periodicities is constrained. Quantitative theory and predictions produced from this work is benchmarked against stratigraphy from the Late Miocene to Quaternary stratigraphy of the Mississippi Delta. During this time interval a significant change in the magnitude and periodicity of RSL cycles occurred. RSL cycles in the Late Miocene for the Mississippi Delta are predicted to be shredded, while more recent cycles are predicted to be preserved.