Migrating bedforms (ripples, dunes) in rivers are preserved as cross-stratified sedimentary structures—fluvial cross strata— that are abundant in the rock record on Earth and Mars. Our understanding of bedform preservation is largely based on steady-state flow conditions, which rarely occur in rivers. In natural rivers, multiple scales of bedforms evolve simultaneously (e.g., dunes, bars) leading to spatially-varying flow conditions; however, our understanding of the influence of co-evolution of multiple bedform scales on preservation of cross strata is limited. To address this, we simulated multi-scale bedform evolution in an experimental channel and characterized the controls on cross-strata preservation under deposition-dominated conditions.

The data herein accompanies the manuscript “Controls on Preservation of Fluvial Cross-strata in the Deposition-dominated Regime ” by Debsmita Das, Vamsi Ganti, and Arjan Reesink. In this manuscript, we conducted a physical flume experiment of superimposed bedform evolution on a large host bedform, analogous to a bar, under constant flow discharge rates. We collected high resolution bathymetric data of bedform evolution for 300 hours, attached herein, and used it to quantify superimposed bedform geometry as well as set thickness statistics from constructed stratigraphy. Additionally, we quantified aggradation rates over the host bedform. We show that superimposed bedform dimensions and celerity decline along the host-bedform lee slope due to spatial gradients in sediment transport. This leads to localized bed aggradation, creating a deposition-dominated regime with high sedimentation rates. We find that the preservation ratio of cross sets is primarily controlled by the local bedform climb angle and that the coefficient of variation of set thickness is consistently low in a deposition-dominated regime. Our results demonstrate that fluvial morphodynamic hierarchy is a fundamental determinant of sedimentary strata.