sandsedimentation

Sandsedimentation refers to the accumulation of sand-size mineral particles from a transport medium, typically water or air, creating sand-sized sedimentary deposits. Sand grains are conventionally defined as about 0.0625 to 2 millimeters in diameter, smaller than gravel and larger than silt and clay. The process occurs wherever a suspension or bedload of sand is carried by a current and loses enough energy to settle and accumulate as layers.

Deposition begins when transport velocity drops below the particle's settling velocity, or when turbulence is damped, or when particle concentration promotes hindered settling or flocculation. In water, settling behavior depends on grain shape, density, and flow regime, and is often more complex than idealized models suggest.

Sandsedimentary deposits form in a range of environments, including river channels and floodplains where sands build cross-bedded layers; deltas and prodelta plains; beaches and shorefaces with well-sorted sands; and deserts where wind-blown sands accumulate in dune fields with characteristic stratification. Subaqueous dunes and ripple marks are common features, yielding cross-bedding and planar bedding in the stratigraphy.

The study of sandsedimentation informs interpretation of past environments, contributes to assessments of porosity and permeability in aquifers and hydrocarbon reservoirs, and aids in predicting sediment transport in modern systems. Methods include grain-size analysis, stratigraphic description, and numerical models of depositional processes.