Controls on Preservation of Fluvial Cross Strata in the Deposition-dominated Regime

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.