Why are star dunes rarely recognised in the rock record?

Abstract

Star dunes are the tallest dunes on Earth and are amongst the largest and most spectacular dynamic landforms. Although they are widespread in modern sandy deserts star dunes are rarely recognised in the rock record probably due to a lack of suitable models. This stratigraphic study of a star dune in the Sahara Desert shows that the dune has developed recently and grown rapidly to create a 100 m high dune within the past thousand years. At the base of the dune there is a period of around eight thousand years that appears to lack sand accumulation, probably due to stabilization of the dunes during the African humid period (AHP). The star dune accumulation post-dates the end of the AHP. We present a new model for the structure of a star dune based on a geophysical and geochronological investigation. Individual structural features in star dunes are similar to those from linear or barchanoid dunes, likely leading to misidentification in the rock record, but the suite of features we describe will permit identification of star dunes in future studies of the rock record.