Abstract
The organic maturity of four samples from the Recent marine sediments in Japan Sea off southwestern Hokkaido was evaluated by means of statistical Thermal Alteration Index (stTAI). The scale of stTAL was determined by the brightness or grey level, of pollen of Pinus, Podocarpus, Abies, Picea and Tsuga using a microscope (Ujiie, 1996b). The maturity of these samples lies below the lowest limit of vitrinite reflectance (Ro=0.30%). stTAI is a useful parameter to evaluate early maturation, especially of very immature sediments which can not be measured by vitrinite reflectance.
