1. n. [Geology]

A layer of sediment or sedimentary rock, or stratum. A bed is the smallest stratigraphic unit, generally a centimeter or more in thickness. To be labeled a bed, the stratum must be distinguishable from adjacent beds.

See: bed thickness,  competent,  dipping bed,  lamination,  progradation,  retrogradation,  sediment,  strike,  superposition,  true stratigraphic thickness,  true vertical thickness