The phytol sidechain of chlorophyll provides a source of phytol which is used to form both pristane and phytane. Phytane forms in a reducing environment with a dihydrophytol intermediate and pristane forms in oxidizing environments through a phylenic acid intermediate. The sources of geoporphyrins in sediments are pigments that contain the porphin skeleton. These pigments are important in the plant and animal kingdom. They have been related to the chlorophyll and hemin molecules.
Hydrocarbons are isotopically lighter than the carbon from related sediments.
Methane is mostly generated by the splitting of C-C bonds in kerogen or in petroleum. Thus, the methane generated is enriched in 12 C, compared to heavier hydrocarbons and kerogen.