Diagenoituneet

Diagenoituneet (Finnish for “diagenetized”) refers to rocks or sediments that have undergone diagenesis, the set of physical, chemical, and biological changes that transform loose sediments into sedimentary rock after deposition, prior to significant metamorphism.

Diagenesis operates at relatively low temperatures and pressures, typically at shallow burial depths, but can be influenced by groundwater chemistry, microbial activity, and pressure-solution processes. It includes mechanical compaction, cementation by minerals such as quartz, calcite, or clays, dissolution and secondary porosity, replacements, and clay-mineral transformations. These changes can alter texture, mineralogy, porosity, and permeability, and may preserve fossils while recording depositional conditions.

Diagenesis is distinct from metamorphism, which involves higher temperatures and pressures and leads to recrystallization and deformation characteristic of metamorphic rocks. In sedimentary basins, diagenesis is often categorized as early (near-surface) and burial diagenesis, with later maturation sometimes referred to as catagenesis in petroleum systems.

Examples of diagenitized rocks include sandstones cemented by quartz or calcite and carbonates with sparry calcite, dolomite, or clay-mineral cements. Diagenetic signatures such as stylolites, grain overgrowths, or pore-fluid–driven mineral changes help geologists interpret sediment origin, diagenetic history, and reservoir quality for groundwater or hydrocarbons.