sandsheets

Sandsheets are extensive, relatively thin layers of sand that blanket landscapes in arid, semiarid, and coastal regions. They are distinct from dune fields in that they lack the large-scale, three-dimensional dune morphologies and move as broad, flat or gently undulating sheets rather than as rising dunes. Sandsheets can underlie or interdigitate with dunes and may cover plains, river valleys, and shorelines where sand supply is abundant and vegetation is sparse.

Formation and distribution

Sandsheets form primarily through wind-driven (aeolian) sediment transport, often sourced from distant sand deposits. When wind conditions are favorable and moisture is low, sand grains are deposited to create uniform sheets across low-relief surfaces. They can also accumulate by reworking previously deposited sands from floodplains, beaches, or dune fields. In deserts and coastal regions, sandsheets may extend over large areas and persist for long periods, sometimes becoming partially cemented or lithified with time.

Characteristics

Sandsheets typically consist of fine to medium sand and may exhibit planar bedding or gentle ripple lamination on the surface. Their thickness ranges from a few centimeters to several meters, usually thinner than extensive dune fields. The surface can show subtle undulations, ripple marks, or mud cracks if moisture periodically alters the sediment. Relative lack of internal dune features and a broad, uniform extent help distinguish sandsheets from individual dunes.

Geological significance

In sedimentology, sandsheets help reconstruct past wind regimes, sediment supply, and climatic conditions. They can host aquifers in certain settings and influence groundwater flow. Mapping sandsheets aids in distinguishing aeolian deposits from dune bodies in geological surveys and paleoenvironmental studies.

See also: dune field, aeolian processes, sedimentary rock formations.