The fact has been established that, as the quantity of organic matter in a rock increases, the chloroform-bitumen content of the organic matter decreases. The writer's researches showed that, as the oil fraction in the chloroform bitumen increases, the chloroform-bitumen content in the organic matter regularly decreases. Therefore, a greater quantity of oil fraction in the chloroform bitumen, together with a comparatively smaller quantity of chloroform bitumen in the organic matter, serves as positive criterion for considering the sediments as better source rocks.

Additional conclusions from the writer's study are: (1) the presence of numerous hydrocarbon accumulations, particularly of oil, in wholly lithologic (stratigraphic) traps is a positive criterion in the recognition of source rocks; (2) high content of organic nitrogen in sediments is a positive criterion for source rocks; whereas (3) high content of humic acid is a negative criterion; (4) relatively higher specific gravity and increased content of higher molecular-weight paraffins and heavier higher-boiling-point fractions in oils suggest that the oil deposit is nearer its source rock; and (5) plant matter is of great importance as a source of hydrocarbons.