Host: Abstracts of Annual Meeting of the Geochemical Society of Japan
Name : Abstracts of Annual Meeting of the Geochemical Society of Japan
Number : 72
Date : September 07, 2025 - September 19, 2025
Pages 196-
The Ontong Java Plateau (OJP), located in the southwestern Pacific, was formed by the largest volcanic activity of the Cretaceous period and has long been considered the trigger for the Oceanic Anoxic Event 1a (OAE1a). However, recent Ar-Ar dating suggests that the basaltic eruptions of the OJP and the Manihiki Plateau occurred up to 10 million years after OAE1a (Davidson et al., 2023). On the other hand, some studies report that the ages of volcanic ash layers and fossil assemblages in surrounding marine sediments are consistent with the timing of OAE1a (Matsumoto et al., 2023), leaving the causal relationship between OJP formation and OAE1a unclear. In this study, we plan to conduct mineral separation on the freshest and coarsest-grained tholeiitic basalts (114-116 Ma) and alkaline basalts (111-112 Ma) collected off Malaita Island. We aim to verify the consistency between Ar-Ar dating and Re-Os mineral isochron ages.
