Bulk Geochemical Characterization and Classification of Organic Matter: Elemental Analysis and Pyrolysis

The classification of kerogen into Types I, II and III was first introduced by Tissot et al. (1974), based on an extrapolation of Van Krevelen’s work on coals to dispersed kerogen in other lithologies (Van Krevelen, 1961, pp. 113-20). The kerogen types are ‘defined’ by the atomic ratios of hydrogen and carbon, and oxygen and carbon, as determined by elemental analysis (Durand and Monin, 1980). A cross-plot of these parameters (now referred to as a ‘Van Krevelen diagram’, Fig. 21.1) can show both the composition of the organic matter and the way this is gradually modified during maturation, biochemical oxidation or weathering (by loss of water, carbon dioxide and hydrocarbons).