Ontong Java Plateau Eruption Younger Than Previously Believed

New high-precision argon isotope dating of the Ontong Java Plateau indicates that it is 10 million years younger than previously thought, according to Peter Davidson and colleagues. The Ontong Java Plateau is part of a massive underwater volcanic eruption – possibly the largest in Earth's history – that took place in the Cretaceous Period in the equatorial western Pacific Ocean. This huge igneous emplacement has been proposed as the cause of Ocean Anoxic Event (OAE) 1a – a short period of severely reduced oxygen in the ocean - but the new dates for the eruption suggest it happened after OAE 1a. Some researchers think that events like OAE 1a are caused by huge submarine volcanic events that flood the oceans with carbon dioxide and nutrients, leading to explosive biological growth and subsequently a sharp reduction in oxygen. Davidson et al. determined new dates for the Ontong Java Plateau through 40Ar/39Ar dating of plagioclase mineral separates from drill sites and dredge locations along the plateau. The new ages range from 116.85 to 107.05 years ago, which make them about 10 million younger than previous estimates, and well after the timing of OAE 1a at 120 million years ago. The Ontong Java Plateau may be implicated in another anoxic event called OAE 1b, which occurred between 114.5 and 110.4 million years ago, the authors say.