GEOCHEMICAL CHARACTERISTICS OF MAIN SOURCE ROCKS IN THE NANPANJIANG BASIN

Based on the study of depositional environment,black argiloid of the Middle and Lower Devonian is the most important source rock,and the source rocks of Carboniferous,Permian and Middle and Lower Triassic are accessory in the Nanpanjiang Basin.120 samples from 6 shallow wells indicate that,source rocks of the Middle and Lower Devonian have a total carbon content varying from 0.37% to 3.63% with an average of 1.65%.They are sapropelic and over-mature in thermal evolution.Biomar-kers of source rock reflect the marine source features of Paleozoic with higher content of lower carbon number compounds such as pregnanes and tricyclic terpanes in almost all samples because of the very high source maturation.