Lithified

Lithified describes sediments that have been transformed into solid rock through lithification, the set of processes by which loose grains become coherent rock. Lithification is part of diagenesis and typically occurs after burial when sediments are compacted and cemented, and may involve mineralogical changes within the rock.

The principal mechanisms are compaction and cementation. Compaction arises from overburden pressure as grains are squeezed closer together and pore waters are expelled, reducing porosity. Cementation occurs when minerals precipitate from pore fluids and bind the grains together; common cements include silica (quartz), calcite (calcium carbonate), and iron oxides. Recrystallization and other diagenetic alteration can modify mineral structures and porosity as fluids circulate during burial.

Lithified rocks include sandstone, siltstone, mudstone, and conglomerates in which the original mineral grains are bound by cement or interlocking recrystallized minerals. Limestone and dolostone are lithified carbonate rocks commonly formed from skeletal grains or precipitated carbonate minerals. Coal forms from peat through compaction and chemical changes, a process sometimes described as lithification of organic material.

Time scales range from thousands to millions of years, depending on burial depth, fluid chemistry, and tectonic conditions. The degree of lithification directly affects porosity, permeability, strength, and weathering behavior, with significant implications for groundwater flow, hydrocarbon reservoirs, and sedimentary geology.