2020 年 126 巻 11 号 p. 655-661
Vitrinite reflectance Ro is commonly used as a paleotemperature proxy for rocks. Among various models used to reconstruct paleothermal histories, EASY%Ro, a set of ordinary differential equations to describe the maturation of vitrinite, has been widely used since 1990. Approximations of EASY%Ro solutions employing specific paleothermal histories have been used in the field of structural geology to estimate maximum paleotemperatures Tmax. However, comparisons of those approximations with results obtained with EASY%Ro have not been reported in scientific literatures, and the errors on the approximations and the limitations of their use to determine Tmax remain undocumented. Here, we performed such comparisons and found that the use of those approximations can lead to considerable deviations from the results obtained with EASY%Ro. We then derived new approximations of EASY%Ro solutions for four representative paleothermal histories that provided estimates of Tmax within 3 °C of those obtained with EASY%Ro. We also describe the Jacobian of EASY%Ro, which can be used to propagate errors from Ro to Tmax. We expect that the four approximations provided herein will be useful, although we recommend using EASY%Ro itself if greater precision or particular paleothermal histories other than those assumed in this study are required.