40Ar-39Ar dating of rocks drilled at sites 60-458 and 60-459

From conclusions based on other artificially disturbed samples (Ozima et al., 1979), we suggest that the reference isochron age (33.6 Ma) approximates the age of the sample.

A basalt from deeper in Hole 458 gives an isochron age of 19.1 ± 0.2 Ma, which is slightly younger than the plateau age of 21.4 ± 1.0 Ma. Both ages are, however, considerably younger than the age of fossils in the overlying sediments (30 - 34 Ma). The age discrepancy may be explained if the 40Ar-39Ar age represents the age of secondary minerals, which formed later.