Figures 1 and 2 show that maximum bitumem generation does not coincide with maximum oil generation as is sometimes assumed in the natural system. maximum bitumen generation is defined in the figures by a broad peak for the woodford shale and a relatively sharp peak for the phosphoria generation starts at alower thermal stress stress in the phosphoria retort shale than in the woodford shale. this difference cannot be explained by differences in the initial maturity levels of the two samples and suggests that the kinetics for oil generation may not be the same for same for all amorphous type ii kerogens.