Lithology and Landscape Evolution

The complexities of the response of bedrock rivers to encountering contacts can impart significant variations in erosion rates and deviation from erosional steady state. This leads to complicated histories of landscape evolution and changes in erosion rate, for example as preserved in stratigraphic records, even when rates of rock uplift are static. Details of this are explored in Forte et al., 2016.

Contacts within river profiles generate their own sets of knickpoints, some which remain fixed to the contact as it moves through the profile but also knickpoints that propagate through the profile away from the contact. Similarly, knickpoints generated from base level fall can change their vertical velocities upon encountering contacts and contact associated knickpoints. This presents issues for using the elevation of knickpoints to extrapolate details for changes in rock uplift rates. Details of this are explored in Wolpert & Forte, 2021.

Actively deforming locations are often characterized by contrasts in rock strength and complicated rock velocity patterns. However, prior work considering the influence of landscape transience related to erosion through strata with different erodibilities focused on only vertical rock motion. The introduction of horizontal components of motion to rocks and contacts, as would be expected in many environments, potentially introduces additional complications. Results of landscape evolution models indicate that landscape transience is increased when considering tectonically driven horizontal contact motion as explored in Mitchell & Forte, 2023.

In addition to the expectation of significant landscape transience, another outcome of erosion through different rock packages is the potential for these changes to influence sediment provenance records downstream of erosional landscapes. A variety of statistically complicated methods are employed to interpret provenance records, like detrital zircon U-Pb ages, but the nuances of surface process influences are rarely robustly considered. In an ongoing project, we are exploring the extent to which landscape evolution influenced by lithologic variation impact the fidelity of sediment provenance records through joint modeling of landscapes and provenance. Preliminary results of these efforts will be presented at GSA in 2023.