The process of denudation continuously active over the surface of the earth by the factors like rain. river. glacier and wind. This process of denudation separates the rock material, dust particles, vegetation, animal residue, etc, which are transported along with flow of water and are deposited on the floors of sea or ocean. Thus the matter, accumulated over the sea floors form layer over the layer of such matter. These layers are compressed as they are overlying one another over a long period. Eventually rocks are formed showing many layers, so these are called Stratified Rocks'.
Water of rain, river, sea, etc. play an important role in the formation of stratified rocks. That is why these are also called 'Alluvial Rocks' Minerals like limestone, coal, mineral soil, gypsum, etc. are available from stratified rocks.