Abstract

Plane beds develop under flows in fluvial and marine environments; they are recorded as parallel lamination in sandstone beds, such as those found in turbidites. However, whereas turbidites typically exhibit parallel lamination, they rarely feature dune-scale cross lamination. Although the reason for the scarcity of dune-scale cross-lamination in turbidites is still debated, the formation of dunes may be dampened by suspended load. Here, we perform, for the first time, linear stability analysis to show that flows with suspended load facilitate the formation of plane beds. For a fine-grained bed, suspended load can promote the formation of plane beds and dampen the formation of dunes. These results of theoretical analysis were verified with observational data of plane beds under open-channel flows. Our theoretical analysis found that suspended load promotes the formation of plane beds, which suggest that the development of dunes under turbidity currents is suppressed by the presence of suspended load.

Highlights

  • The interactions between fluids and erodible surfaces generate small-scale topographic features called bedforms both on terrestrial surfaces and on extra-terrestrial surfaces (Bourke et al, 2010; Gao et al, 2015; Hage et al, 2018; Cisneros et al, 2020)

  • Our theoretical analysis found that suspended load promotes the formation of plane beds, which suggest that the development of dunes under turbidity currents is suppressed by the presence of suspended load

  • Comparing the results where D = 0.12 mm and the observational data, in the case without suspension, all the plane bed data are within unstable region; most values plot in the region where kd > 1 (Fig. 2a)

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Summary

Introduction

The interactions between fluids and erodible surfaces generate small-scale topographic features called bedforms both on terrestrial surfaces (e.g., riverbeds, deserts, and deep-sea floors) and on extra-terrestrial surfaces (Bourke et al, 2010; Gao et al, 2015; Hage et al, 2018; Cisneros et al, 2020). Such bedforms are preserved in sedimentary rocks as sedimentary structures such as cross- and parallel lamination (Harms, 1979). The reason for the paucity of dune-scale cross-lamination in turbidites is still debated (Lowe, 1988; Arnott, 2012; Schindler et al, 2015; Tilston et al, 2015), it could be attributed to the presence of suspended load. The influences of suspended load on the suppression of dune development and the formation of plane beds must be considered

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