Dune Sediments

This chapter discusses the sedimentary characteristics of loess deposits. Dune sediments hold very considerable amounts of information about dune processes. The chapter provides an overview of the characteristics of dune sediments. The mineralogical composition of dune sands is primarily controlled by their source, and the sources of dune sands are many and varied. Particle size distributions of aeolian dune sands are generally finer, better sorted and less positively (coarse) skewed than fluvial, glacial or marine sediments. Changes in wind strength and wind direction result in changes in dune morphology which may be represented by layers of sediment enclosed by erosion surfaces, termed bounding surfaces. Eolianites are wind-driven subaerial accumulations of carbonate-dominated and carbonate-cemented sand. Most eolianites are associated with large scale landward dipping cross-strata, grainflow and pinstripe lamination, slump scar features, footprints, and pedogenic alteration. Preservation of cross-strata in the rock record permits reconstruction of dune morphodynamics.