Preservation and Shredding of Relative Sea-level Signals in Stratigraphy

Abstract:

Recently studies present quantitative theory, tested with experiments, that signals of allogenic forcings can be shredded by autogenic processes in transport systems. However, we currently lack theory for predicting the properties external forcing must have to be stored in the stratigraphic record. One of the most important boundary conditions influencing dynamics of sediment transport systems and their resulting stratigraphy is Relative Sea-Level (RSL). In this study, we use physical experiments to explore the capacity of autogenic processes to shred perturbations of RSL prior to transfer to the stratigraphic record. We are currently testing the hypothesis that RSL cycles with amplitudes greater than one channel depth (H_c) and/or periodicities longer than the time necessary to deposit, on average, one channel depth of thickness over an entire basin (T_c) will be preserved in stratigraphy. RSL cycles with magnitudes less than H_c and periods less than T_c, though, should be prone to signal shredding prior to transfer to the immobile stratigraphic record. We are conducting a series of physical experiments subject to cycles of RSL with amplitudes and periodicities on either side of our hypothesized shredding thresholds. Initial time series analysis of deposition rates from an experiment with RSL cycles characterized by amplitudes and periods a factor of 2 greater than H_c and T_c, respectively, show signal preservation. Specifically, auto-correlation analysis reveals periodicity in deposition rates equal to the imposed periodicity of RSL cycles. This study improves our ability to predict and interpret allogenic signals in the stratigraphic record and separate these signals from the products of autogenic processes.