Relict Sediment

Relict sediment is seabed sediment that was deposited under past environmental conditions and is out of equilibrium with the present regime, surviving because modern processes do not rework it. The type example is the sand on many outer continental shelves: it was laid down near the shoreline during Quaternary sea-level lowstands and now sits below the reach of present waves and currents, stranded as the sea rose. Recognizing relict from modern sediment matters for interpreting shelf dynamics, because the surface texture does not reflect today’s currents. Palimpsest sediment is the intermediate case, relict material partly overprinted by present-day processes.