A younger and protracted emplacement of the Ontong Java Plateau.

The submarine volcanic emplacement of the Ontong Java Plateau (OJP) is the suggested cause of Ocean Anoxic Event 1a (OAE 1a). However, no precise timing and duration exists for the formation of OJP, and its connection to OAE1a relies mainly on proxies in the sedimentary record. We provide high-precision Ar/Ar data from OJP drill and dredge sites that considerably improve OJP's eruptive history.