Observation of Density Segregation inside Migrating Dunes

TL;DR

This study experimentally demonstrates that in migrating dunes, denser particles tend to accumulate near the top center, revealing a new aspect of sediment segregation that could impact geological dating methods.

Contribution

The paper presents novel experimental evidence of density-based segregation in dunes, contrasting with traditional size-based segregation models.

Findings

Heavier particles accumulate near the dune's top center.

Density segregation occurs independently of particle size.

Results enhance understanding of natural sedimentary structures.

Abstract

Spatiotemporal patterns in nature, such as ripples or dunes, formed by a fluid streaming over a sandy surface show complex behavior despite their simple forms. Below the surface, the granular structure of the sand particles is subject to self-organization processes, exhibiting such phenomena as reverse grading when larger particles are found on top of smaller ones. Here we report results of an experimental investigation with downscaled model dunes revealing that, if the particles differ not in size but in density, the heavier particles, surprisingly, accumulate in the central core close to the top of the dune. This finding contributes to the understanding of sedimentary structures found in nature and might be helpful to improve existing dating methods for desert dunes.