ACCUMULATION (from the Latin word "accumulatio", which means "accumulation" * EN: accumulation, aggradation; DE: Akkumulation, Speicherung, Aufspeicherung; FR: accumulation; ES: acumulacion; RU: аккумуляция) in geology is the accumulation of the mineral substances or organic residues at the bottom of the water bodies and on the surface of the land. The process of accumulation is opposite to the process of denudation and is depending on it.

The areas of the accumulation are mostly the lowered spaces, most often of the tectonic (downfolds, depressions, and others), and also of the denudation (valleys, basins) origin. The thickness of the accumulated sediments depends on the intensity of the denudation and the activity of the subsidence.

They distinguish the accumulation on the land (gravitational, fluvial, glacial, glacier water, marine, lacustrine, eolian, biogenic, volcanogenic) and under the water (underwater landslides, coastal-marine, deltaic, reefogenic, volcanogenic, chemogenic, and others). The formation of the various types of the exogenous mineral deposits (including the placer deposits) is associated with the accumulation processes.