Figure F31. Oxygen and hydrogen indices for samples from the lower Aptian organic-rich horizon (OAE1a) (Table T12) plotted on a modified van Krevelen diagram. The characteristics of organic-rich samples from Site 1207 and 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 content. The lines designated I, II, and III represent the evolutionary trends with thermal maturation of the three major kerogen types (Tissot et al., 1974). OI = oxygen index, TOC = total organic carbon.

Figure F31. Oxygen and hydrogen indices for samples from the lower Aptian organic-rich horizon (OAE1a) (Table T12) plotted on a modified van Krevelen diagram. The characteristics of organic-rich samples from Site 1207 and 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 content. The lines designated I, II, and III represent the evolutionary trends with thermal maturation of the three major kerogen types (Tissot et al., 1974). OI = oxygen index, TOC = total organic carbon.