Six whole rocks from the basaltic lava series drilled in the Vavilov basin have been analyzed by 39Ar-40Ar stepwise heating method. One sample from the upper part of the Hole 655B basement gave a plateau-age at 4.3 ± 0.3 Ma whereas the other ones showed disturbed age spectra caused by alteration processes. The weighted averages of ages measured at low and intermediate temperatures on these five samples are concordant (1) one to each other and (2) with independent estimates deduced from paleontological and paleomagnetical arguments. Ages of 4.3 ± 0.3 Ma and from 3 to 2.6 Ma may represent reasonable estimates of the crystallization ages of the basaltic lava series of the Holes 655B and 651A, respectively. These ages must be taken with caution because they correspond to argon released from secondary phases characterized by low argon retention.

40Ar/39Ar = radiogenic 40Ar/39Ar from K, 37Ar/39Ar = 37Ar from Ca/39Ar from K. The values are corrected for K- and Ca-derived Ar isotopes. The errors are quoted in 1 sigma. We used the decay constants recommended by Steiger and Jager (1977, doi:10.1016/0012-821X(77)90060-7).

Supplement to: Feraud, Gilbert (1990): 39Ar-40Ar Analysis on Basaltic Lava Series of Vavilov Basin, Tyrrhenian Sea (Ocean Drilling Program, Leg 107, Holes 655B and 651A). In: Kastens, KA; Mascle, J; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 107, 93-97