ABSTRACT

Volcanic eruptions that formed Ontong Java Nui (OJN) during the Aptian (~120 Ma), Early Cretaceous, triggered substantial environmental perturbations, including global warming and oceanic anoxic event (OAEs) 1a. However, the precise transition of OJN eruption styles and the influence of each volcanic phase on Earth's environment remains poorly understood. Here, we present Pb isotopic evidence for the OJN as the source of tuffaceous sedimentary sequence deposited on nearby Magellan Rise. Furthermore, we reviewed geochemical and lithological data around OAE1a, and updated the discussion on how the OJN emplacement influenced the earth environment. Our results point to explosive OJN eruption during the earliest phase of OAE1a based on compiled geochemical and lithological data. Stratigraphic variations in Pb isotopic compositions during this volcanic phase indicate a transition in OJN volcanism, from Kwaimbaita/Kroenke-like magma eruptions that formed the lower part of OJN to Singgalo-like magma eruptions that formed the upper part. Based on previously reported isotopic (Os and C), mineralogical, and geochemical data, this short (~250 kyr) explosive volcanic phase, indicated by the Pb isotopic signal, was accompanied by extensive volatile emissions and corresponds to the onset of the previously documented early to mid-Aptian environmental perturbations (global warming, OAE1a, and the nannoconid crisis).