(Table 1) Sr isotopes on carbonates at DSDP Hole 62-463

Study of 12 carbonate oozes from Deep Sea Drilling Project Hole 463, in the Mid-Pacific Mountains, suggests mean values of 0.70690 ± 0.00029 (2-sigma) and 0.70712 ± 0.00030 (relative to 0.71014 for the NBS 987 Sr isotope standard) as representing the Sr isotope composition of the Barremian and early Aptian seas, respectively. Two additional values of less than 0.7064 are the least radiogenic values known from the Phanerozoic and may be a consequence of the introduction of Sr depleted in the heavy isotope from massive submarine volcanic activity, which followed the initiation of the latest oceanic spreading episode in the Oxfordian.