There have been carried out many studies on the C/N ratio of recent sediments. but few studies on ancient sediments. The relationship of carbon and nitrogen for nine-teen samples of marine kerogen shales of Tertiary age in Japan was examined. consequently carbon and nitrogen showed an approximatly logarithmic linear functional relation as have been showed in recent sediments by G. ARRHENIUS.
The ratio C/N from muddy siltstone group of “Onnagawa formation” was found to be higher, the mean being 27, than 14 of Trask's mean value from past sediments, and each sample of this group indicated that there is litte difference in nitrogen concentration but higher in carbon concentration in comparison with some of the other examined samples. The present auther thinks that this high ratio C/N wouldbe based on elemental carbon concentration in total organic carbon of each sample of that group.
From the above mentioned point of view, a new attempt waa propsed by the present auther, to discriminate the carbon in highly condensed form (nearly elemental organic carbon, namely charcol, graphite, coal) from the total organic carbon of the sedimentary rock.