Definition - What does Diagenesis mean?
Diagenesis is a process by which the sediments and the existing sedimentary rocks undergo physical and chemical change by compaction, cementation, etc., and by solution into different sedimentary rocks during and after rock formation. Diagenesis does not include changes that occur as a result of weathering. Diagenesis only takes place after the lithification of existing sedimentary rocks or after sedimentation occurs.
Petropedia explains Diagenesis
Diagenesis is extensively used in geology and its literal meaning is across generation. From million years ago when the animals and plants were buried during sedimentation, the organic molecules in the corpse such as lipids, carbohydrates, proteins and lignin humic compounds breaks down into smaller molecules for decomposition due to increase in pressure and temperature. The transformations occur with slow decomposition process into two primary products, i.e., Kerogens and Bitumen.
Regarding hydrocarbon generation, Diagenesis can be divided based on hydrocarbon genesis and coal genesis into early diagensis (Eodiagenesis), Middle age Diagensis (Mesodiagenesis) and Late Diagensis (Telodiagenesis).