Lithifikaation

Lithifikaation, commonly spelled lithification, is the geological process by which loose sediment is transformed into coherent sedimentary rock. It is a component of diagenesis, the suite of chemical, physical, and biological changes that occur after deposition and before metamorphism. Lithification typically occurs at shallow crustal levels where temperatures remain low and pressures are moderate.

The two primary mechanisms are compaction and cementation. Compaction results from overburden weight, squeezing out pore fluids and reducing porosity. Cementation occurs when minerals precipitate from groundwater and bind grains together; common cements include calcite, silica (quartz), and iron oxides. Some rocks also lithify through recrystallization or by early cementation with clays and other minerals, which can alter porosity and grain contacts.

The mineralogy and porosity of lithified rocks are controlled by sediment composition and diagenetic fluids. Siliciclastic sediments typically form sandstones or siltstones; carbonate sediments can lithify into limestones or dolostones through cementation and recrystallization. Metasomatic exchanges or dissolution and re-precipitation during burial can modify mineral content and texture.

Timescales for lithification range from thousands to millions of years, depending on burial rate, climate, and fluid chemistry. Environments include river channels, alluvial fans, deltas, continental shelves, lakes, and deserts. The resulting rocks preserve sedimentary structures and fossils, providing records of past environments and conditions.