sedimentasjonstakt

Sedimentationstakt, or sedimentation rate, is the speed at which solid particles settle from a suspension or accumulate as sediment in a basin. It is commonly expressed as a distance traveled per unit time (for example millimeters per year in geological records) or as an accumulated thickness per unit area per time (such as millimeters or centimeters per thousand years) depending on context.

In geology and sedimentology, the rate controls how quickly a sedimentary sequence grows and is influenced by sediment supply, transport energy, accommodation space (subsidence and sea level), and post-depositional processes such as compaction and diagenesis. Determining the sedimentation rate helps reconstruct past climates, tectonics and basin history. Methods include direct dating of dated layers (varves, tephra layers), radiometric ages, and biostratigraphy; thickness measurements of well-dated stratigraphic sections; and occasionally using continuous records like varved lake sediments.

In engineering and water treatment, sedimentation rate refers to the settling velocity of particles in a clarifier or settling tank. It depends on particle size, density, shape, fluid viscosity and turbulence; for dilute suspensions, settling velocity can be estimated by Stokes’ law. At higher concentrations, hindered settling reduces effective rates. Engineering practice uses jar tests and settling tests to design basins and predict performance.

Interpretation of sedimentation rate must consider post-depositional effects such as compaction, cementation, and erosion, which can alter the apparent rate. While useful for broad reconstructions, exact rates are often uncertain and context-dependent.