Diagenesis refers to all physical, chemical, and biological changes that accompany the first stage of lithification, exclusive of surface alteration (weathering) and metamorphism. Diagenesis is the agent that transforms unconsolidated sediment into solid rock (sedimentary rock) through a combination of compaction, recrystallization, dehydration, replacement, dissolution, and cementation processes. Diagenesis virtually begins when a detrital grain is sedimented and begins its interaction with the pore waters and overburden. Diagenesis ends when these processes grade into metamorphism, and sedimentary textures and structures (such as bedding, grading, bioturbation, etc.) are lost.
Diagenetic processes thus usually take place at low temperature (<200 °C) and pressure (<3 kbar) and mostly result in minor to moderate changes in the rock’s mineralogy and texture. (In exceptional cases, however, the original constituents are completely replaced.) Commonly, clays, silica minerals,...