Relationships Between the Ontong Java Plateau and its Neighboring Ocean Basins: Insights Into Plateau Formation

The Ontong Java Plateau (OJP) in the western equatorial Pacific is the largest flood basalt province, or large igneous province (LIP), known in the oceans. Of controversial origin, the ca. 122 Ma OJP is flanked by ocean basins that are either demonstrably (Nauru and East Mariana) or presumably (Lyra) older, or presumably younger (Stewart and Ellice). To investigate structural and stratigraphic relationships between the OJP and these neighboring ocean basins, we have examined all available seismic reflection data from the region. Overall, acoustic basement is typically smooth and continuous between the OJP and the Nauru and Lyra basins, suggesting that ca. 122 Ma lavas flowed from the OJP into these older basins. However, where individual or linear chains of seamounts affect the transition between the OJP and Nauru Basin, in particular where the main OJP and its eastern salient merge, structural and stratigraphic relationships are more complicated. Similarly, relatively young Caroline hotspot activity along the northern flank of the OJP has likely disrupted formerly smooth and continuous acoustic basement extending between the OJP and the East Mariana Basin. The eastern salient of the OJP is deformed by normal faults, as well as affected by volcanism, along its southern flank where it adjoins the Stewart Basin, suggesting that the Stewart Basin formed after the OJP by NNE-SSW extension. Stratigraphic and structural relationships between the eastern salient of the OJP and the Ellice Basin are somewhat ambiguous, characterized by smooth acoustic basement in places, and volcanic activity in others, but overall suggest that the Ellice Basin is older than the OJP. We propose that lava flows originating from vents and fissures on the central OJP may have flowed more than 1500 km into the older ocean basins to the east, north, and west of the OJP.