The strength of the sediment-derived autogenic signal relative to overlapping environmental cycles greatly improves our ability to differentiate between allogenic (i.e., regional or environmental) and autogenic (i.e., local or sediment derived) controls on deposition. This can be shown experimentally using an avalanching pile of brown rice. Rice pile avalanches triggered by a constant input of rice exhibit chaotic, nonlinear behavior (Frette et al., 1996), and thus can serve as a proxy for storage/release processes observed in sediment transport systems. The autogenic signal is produced by measuring the weight output of release events over time. A power spectrum of the time series data is generated by means of a Fourier transform, from which the frequency of the largest avalanche event produced by the system can be found. The robustness of the signal can then be tested against the signals of different environmental cycles by cycling the input at frequencies above and below the upper extent of the autogenic signal. Preliminary results show that if the frequency of the environmental cycle is lesser than that of the upper extent of the autogenic signal, then the signal of the cycle is recorded on the power spectrum, as expected. However, if the frequency of the environmental cycle is greater than that of the upper extent of the autogenic signal, i.e., the environmental cycle overlaps the autogenic signal, the environmental signal is obliterated by the system and the power spectrum of the system remains unchanged.
All too often, the sedimentary rock record is immediately interpreted in terms of allogenic controls on deposition. High- to low-period allogenic cycles are evoked in the creation of depositional narratives, and oftentimes rightfully so: for instance, are millennia-scale climate cycles or seasonal precipitation cycles preserved? On the other hand, autogenic controls on deposition have been evoked in these narratives so far as to acknowledge localized parameters that work within and modify region-scale controls: local topographic features or scour surfaces, for example (e.g., Yang et al., 1998; Pietras et al., 2006). But as of yet, no real consideration has been given to the signature of the sediment transport system itself. This insight into the strength of the sediment-derived signal will ultimately improve the accuracy of our interpretation of the sedimentary rock record, as we can put a hard lower limit on the extent to which we cite allogenic controls in depositional narratives.