Signal transformation in erosional landscapes: insights for reconstructing tectonic history from sediment flux records

Abstract:

Changes in tectonics can affect erosion rates across a mountain belt, leading to non-steady sediment flux delivery to fluvial transport systems. The sediment flux signal produced from time-varying tectonics may eventually be recorded in a depositional basin. However, before the sediment flux from an erosional watershed is fed to the downstream transport system and preserved in sedimentary deposits, tectonic signals can be distorted or even destroyed as they are transformed into a sediment-flux signal that is exported out of a watershed . In this study, we use the Channel-Hillslope Integrated Landscape Development (CHILD) model to explore how the sediment flux delivered from a mountain watershed responds to non-steady rock uplift. We observe that (1) a non-linear relationship between the erosion response and tectonic perturbation can lead to a sediment-flux signal that is out of phase with the change in uplift rate; (2) in some cases in which the uplift perturbation is short, the sediment flux signal may contain no record of the change; (3) uplift rates interpreted from sediment flux at the outlet of a transient erosional landscape are likely to be underestimated. All these observations highlight the difficulty in accurately reconstructing tectonic history from sediment flux records. Results from this study will help to constrain what tectonic signals may be evident in the sediment flux delivered from an erosional system and therefore have the potential to be recorded in stratigraphy, ultimately improving our ability to interpret stratigraphy.