Lithificationcompaction

Lithification is the process by which loose sediments are transformed into solid sedimentary rock. A central component of lithification is compaction, the mechanical reduction of porosity and the consolidation of grains under the weight of overlying sediments. As burial depth increases, grains are pressed closer together and pore fluids are expelled, reducing pore space and increasing grain-to-grain contact.

Alongside compaction, cementation often seals the sediments. Chemical precipitation from circulating pore water binds grains together, forming cement minerals such as calcite, quartz, or iron oxides. Diagenesis encompasses these lithification processes and related changes, including pressure solution, recrystallization, and the growth of authigenic minerals, which can modify porosity and rock texture without triggering metamorphism.

Factors such as grain size and sorting, mineralogy, burial depth, and fluid chemistry influence the rate and style of lithification. Clastic rocks form by varying degrees of compaction and cementation: sandstone may develop quartz or calcite cement, while mudstone often shows stabilization of clay minerals with cement reducing porosity.

The result of lithification is changes in porosity and permeability, shaping the rock’s mechanical properties and its potential as a reservoir or aquifer. Lithification is a diagenetic process, occurring at relatively low temperatures and pressures after deposition, generally over timescales ranging from thousands to millions of years depending on burial rate and tectonic conditions.