You searched for: “diluvium”
diluvium (s) (noun); diluviums, diluvia (pl)
The sediments or deposits of topsoil, sand, gravel, stones, etc. on the bottom of a river as the result of the flow of rivers, or the melting of glacial ice: The diluvium in the tributary was layered because of the fast currents of the rapids.
The layers of glacial diluvium are often very dense; sometimes, indicating accumulations that have taken place over centuries.