alluvium

n. mud or sand deposited by flowing water, sediments deposited by a river or flowing waters

Alluvium (from the Latin, alluvius, from alluere, "to wash against") is soil or sediments deposited by a river or other running water. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel.Flowing water associated with glaciers may also deposit alluvium, but deposits directly from ice are not alluvium (see glacial till).A river is continually picking up and dropping solid particles of rock and soil from its bed throughout its length. Where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up. Areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium.
See more at Wikipedia.org...

Noun
1. clay or silt or gravel carried by rushing streams and deposited where the stream slows down
(synonym) alluvial sediment, alluvial deposit, alluvion
(hypernym) sediment, deposit
(hyponym) placer
(substance-meronym) alluvial soil

n. alluvium, mud or sand deposited by flowing water

n. Holocene period, earliest geological period in the Earth's history