Holocene fluvial depositional regimes of the Huab River, Skeleton Coast, Namibia

Walsh, E.; Caracciolo, Luca; Ravidà, Domenico C.G.; Burrough, Sallie L.; Thomas, David S.G.

doi:10.1002/esp.5349

Cited by 4 publications

(1 citation statement)

References 120 publications

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“…In other areas such as the western Coastal Cordillera of northern Chile (Walk et al, 2020) or along the Skeleton Coast of Namibia (Walsh et al, 2022), sedimentary fans forms with little or no subsidence of the underlying basement and must therefore be characterised by high F -values. These high by-pass systems are in the autogenic fining regimes and their stratigraphy is likely to record variations in β or fan extent related to variations in precipitation/climate (right portion of figure 16A).…”

Section: Natural Examplesmentioning

confidence: 99%

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

Wild,

Braun,

Whittaker

et al. 2024

Preprint

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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).

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Section: Natural Examplesmentioning

confidence: 99%