Autogenic Deposits as A Potential Recorder of High-Frequency Signals: The Role of Autogenic Processes Revisited

Studies (e.g., Jerolmack and Paola, 2010) have suggested that autogenic processes act as a filter for high-frequency environmental signals, and the underlying assumption is that autogenic processes can cause fluctuations in sediment and water discharge that modify or shred the signal. This assumption, however, fails to recognize that autogenic processes and their final products are dynamic and that they can respond to allogenic forcings. We compile a database containing published field studies, physical experiments, and numerical modeling works, and analyze the data under different boundary conditions. Our analyses suggest different conclusions. Autogenic processes are intrinsic to the sedimentary system, and they possess distinct patterns under steady boundary conditions. Upon changing boundary conditions, the autogenic patterns are also likely to change (depending on the magnitude of the change in the boundary conditions). Therefore, the pattern change provides us with the opportunity to restore the high-frequency signals that may not pass through the transfer zone. Here we present the theoretical basis for using autogenic deposits to infer high-frequency signals as well as modern and ancient field examples, physical experiments, and modeling works to illustrate the autogenic response to allogenic forcings. The field studies show the potential of using autogenic deposits to restore short-term climatic variability. The experiments demonstrate that autogenic processes in rivers are closely linked to sediment and water discharge. The modeling examples reveal the counteracting effects of some autogenic processes to form a self-organized pattern under a set of specific boundary conditions. We also highlight the limitations and challenges that need more research efforts to restore high-frequency signals. Some critical issues include the magnitude of the signals, the effect of the interference between different signals, and the incompleteness of the autogenic deposits.