Preprints
https://doi.org/10.5194/egusphere-2024-351
https://doi.org/10.5194/egusphere-2024-351
21 Feb 2024
 | 21 Feb 2024

Autogenic vs Subsidence Controls on Grain Size Fining through Multi-Channel Landscape Evolution Modelling

Amanda Lily Wild, Jean Braun, Alexander C. Whittaker, and Sebastien Castelltort

Abstract. Within the stratigraphic record, changes in grain size are often interpreted as a signature of external forcing events. However, it is not yet well constrained how autogenic processes (such as channel mobility) influence grain size signatures within the fluvial system. Here, we combine a landscape evolution model based on the Stream Power Law but modified for sedimentation (Yuan et al., 2019) with an extension of the self-similar grain size model Fedele and Paola (2007) to multiple dimensions (i.e., along dynamically evolving river channels) to study the relative importance of autogenic processes in con- trolling grain size fining. We first show how our new model can reproduce the results obtained by classical analytical solutions assuming that fining is controlled by subsidence only, in a single or amalgamated channel. We then show that deviations from past (subsidence and single channel only) predictions arise when varying two main parameters: first the ratio between the incoming sediment flux and integrated subsidence rate (F ), which increases with the degree of bypass of the system; and second, the ratio of the discharge leaving the mountain to the discharge generated within the subsiding basin (β), which controls the shape of the topography of the basin. We demonstrate that there exists two regimes, one corresponding to low values of F or high values of β, where the grain size fining is controlled by subsidence, and one corresponding to high F and low β values, where grain size fining is controlled by autogenic processes under steep topographic slopes that propagate sedimentary waves through the basin. Coupling the LEM to a flexural model predicts that grain size fining evolves from subsidence to autogeniccontrol in basins characterized by a progressive increase of F (under-filled to over-filled foreland), as seen in the case example of the Alberta Foreland Basin. Our results indicate that grain size fining during low filling conditions (e.g. early stage as the basin is forming) can indicate the dominantly tectonic controlled parameter of the flux relative to underlying subsidence ratio (F ); whereas, any fining under high bypass conditions (e.g. late stage once the basin is overfilled) can indicate the climate controlled upstream vs downstream ratio (β).

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Amanda Lily Wild, Jean Braun, Alexander C. Whittaker, and Sebastien Castelltort

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-351', Anonymous Referee #1, 18 Apr 2024
    • AC1: 'Reply on RC1', Amanda Wild, 23 Apr 2024
  • RC2: 'Comment on egusphere-2024-351', Eric Barefoot, 25 Apr 2024
    • AC2: 'Reply on RC2', Amanda Wild, 30 Apr 2024
Amanda Lily Wild, Jean Braun, Alexander C. Whittaker, and Sebastien Castelltort
Amanda Lily Wild, Jean Braun, Alexander C. Whittaker, and Sebastien Castelltort

Viewed

Total article views: 583 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
428 128 27 583 28 14 15
  • HTML: 428
  • PDF: 128
  • XML: 27
  • Total: 583
  • Supplement: 28
  • BibTeX: 14
  • EndNote: 15
Views and downloads (calculated since 21 Feb 2024)
Cumulative views and downloads (calculated since 21 Feb 2024)

Viewed (geographical distribution)

Total article views: 621 (including HTML, PDF, and XML) Thereof 621 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 05 Dec 2024
Download
Short summary
Sediments deposited within river channels form the stratigraphic record, which has been used to interpret tectonic events, basin subsidence, and changes in precipitation long after ancient mountain chains have eroded away. Our work combines methods for estimating gravel fining with a landscape evolution model in order to analyze the grain size preserved within the stratigraphic record with greater complexity (e.g. considering topography and channel dynamics) than past approaches.