Together with colleagues from the COLORS project, we developped and calibrated a new landscape evolution numerical model that simulates a sedimentary system from the eroding catchements (sources) to the continental and marine sedimentary basins (sinks).

The code is based on the following equations:

Surface processes and stratigraphic records can also be studied via laboratory experiments. This approach requires time but contrary to numerical simulations, the physics of sediment transport is not imposed. This is a valuable aspect because the transport of sediments within rivers, in particular when several grain sizes are involved is an active field of research. In lab experiments, it is thus possible to use several grain sizes and to analyse how they are transported and deposited.

We use this approach to look at the baydeltas that can be observed within incised valleys. These deltas are often interpreted as the result of sediment flux variations or sea-level change fluctuations within a transgressive trend. We develop a simple geometrical model that suggests these deltas can be purely autogenic. Applied to a lab experiment, we do observe the progradation of a coarse-grained sheet during constant sea-level rise, without any external perturbation. The geometry of the valley is sufficient to induce a transient progradation, as you can see in this video (click on the figure to access the video):

We use this model to the Trinity and Brazos river systems (Texas) to decipher whether or not the observed deltas could be autogenic. Spoiler: the answer is yes !