Digenesis

Diagenesis is the physical and chemical changes that occur in sediments after deposition, but before metamorphism. It encompasses a broad range of processes, including compaction, cementation, recrystallization, dissolution, and authigenesis. These transformations alter the original composition, texture, and mineralogy of the sediments, ultimately lithifying them into sedimentary rocks. Diagenesis occurs at low temperatures and pressures compared to metamorphism, typically within the Earth's crust and closer to the surface.

Digenesis meaning with examples

• The sandstone's porosity was significantly reduced by diagenetic cementation, primarily from silica and calcite. This process occurred over millions of years after the original sand grains were deposited at the bottom of the ancient sea.
• Researchers studied the diagenetic history of shale, focusing on the transformation of organic matter into hydrocarbons due to burial and temperature changes within a sedimentary basin.
• Analysis of a limestone core revealed evidence of extensive diagenetic alteration, including recrystallization of the original carbonate minerals and formation of secondary dolomite.
• Understanding diagenetic processes is critical for interpreting the geological history of sedimentary rocks and for predicting the characteristics of subsurface reservoirs, like for oil.