LAUSR

Abstract Vitrinite reflectance is perhaps the most widely used property to calibrate paleothermal histories, and the most common model for that purpose is Easy%Ro. This paper reviews the origin of Easy%Ro as a simplification of Vitrimat. Weaknesses of the original versions are discussed, as are historical attempts to improve them. New versions of Vitrimat and Easy%Ro are presented that use substantially higher frequency factors and activation energies, and variations of these versions are derived for vitrinite itself and hydrogen-rich macerals and bitumen. The Vitrimat models are based on the original premise that reflectance correlates primarily with H/C ratio and secondarily with O/C ratio. With this approach, the reflectance of different types of organic matter is automatically calculated based on the initial composition of that organic matter. This general approach may also serve as a pathway with appropriate cross-reaction terms to calculate suppression of true vitrinite reflectance matured in oil-prone rocks containing significant concentrations of liptinite.