COLOUR ALTERATION OF FOSSIL POLYPODIISPORITES AND MATURATION OF THE ORGANIC MATTER OF JINGGU BASIN

The relationship between colours of fossil Polypodiisporites,a widespread fossil spore in Cenozoic of Yunnan, and the maturation of organic matter could be employed to infer the stages of petroleum generation and evolution, and to indicate the favourable horizons and areas for petroleum prospecting. The study indicates that the colour of Polypodiisporites can be darker one grade over that of other sporo-pollen within the same rock specimen, though they all were subjected to the same palaeotemperature.For the Tertiary of the Jinggu Basin, the relationship between the colour of Polypodiisporites and the organic matter maturity is as follows. For yellow-orange section, the colour index ranging from 2.6-3.0, corresponding to vitrinite reflectance 0.42% and palaeotemperature of less than 60℃, indicates an immature stage of organic matter. The brown-black section, colour index 3.5-5.9, reflectance 0.58-0.8%, palaeotemperature 60-110℃, indicates the mature stage with the greatest potential of oil-generation. The effects of the amount of organic matter on the colour of sporo-pollen have also been discussed in the paper.