Figure F37. Oxygen and hydrogen indices for samples from the lower Aptian organic-rich horizon (OAE1a) (Table T13, )—labeled as upper, middle, and lower—plotted on a modified van Krevelen diagram. The characteristics of organic-rich samples from the Aptian at Sites 463 and 866 in the mid-Pacific are also shown. The size of the data points is proportional to organic carbon contents. The lines designated I, II, and III represent the evolutionary trends with thermal maturation of the three major kerogen types (Tissot et al., 1974).

Figure F37. Oxygen and hydrogen indices for samples from the lower Aptian organic-rich horizon (OAE1a) (Table T13)—labeled as upper, middle, and lower—plotted on a modified van Krevelen diagram. The characteristics of organic-rich samples from the Aptian at Sites 463 and 866 in the mid-Pacific are also shown. The size of the data points is proportional to organic carbon contents. The lines designated I, II, and III represent the evolutionary trends with thermal maturation of the three major kerogen types (Tissot et al., 1974).