Diagenesis : the natural processes by which loose sediments on the floor of water basins are transformed into sedimentary rock under the conditions of the upper zone of the earth’s crust.
The concept of diagenesis was introduced by the German geologist W. von Gümbel (1888), who included within the concept all the changes in the sediment from its initial form to its conversion into metamorphic rock. Later the concept of diagenesis was narrowed so as to denote only the conversion of sediment into sedimentary rock proper (the German geologist J. Walther, the Soviet geologist A. E. Fersman, and others). Subsequent transformations of sedimentary rock belong to the stages of katagenesis and metagenesis.