Ontong Java Plateau

The Ontong Java Plateau lies in the western Pacific, northeast of Papua New Guinea, and is the world's largest oceanic plateau.¹ Its crust is unusually thick, reaching up to 30 kilometers, compared to typical oceanic crust of about 7 kilometers. The plateau formed during two major volcanic pulses: the main phase at ~120 million years ago (Early Cretaceous) and a smaller phase at ~90 million years ago.² The origin is debated, with the mantle plume hypothesis being the most widely accepted, although some propose a meteorite impact or a combination of processes. Geochemical analyses of basalts recovered from the plateau show a depleted mantle source, distinct from mid-ocean ridge basalts, supporting a deep mantle origin.²

The emplacement of the Ontong Java Plateau coincided with the Selli oceanic anoxic event (OAE 1a) in the Aptian stage, suggesting a causal link.² The massive release of volcanic gases, including carbon dioxide and sulfur dioxide, likely triggered global warming, ocean acidification, and widespread anoxia, leading to a major marine extinction event.⁴ The plateau's formation may have also affected sea level and ocean circulation patterns, with long-term effects on the Cretaceous climate.² Studies of sediment cores from the plateau have provided evidence of these environmental perturbations, including carbon isotope excursions and changes in marine biota.⁴

Since the late Miocene, the northern edge of the Ontong Java Plateau has been colliding with the Solomon Islands arc, a process that is currently ongoing.³ This collision is causing the plateau's thick crust to resist subduction, leading to the obduction of oceanic crust and the uplift of the Solomon Islands.³ Seismic imaging reveals that the plateau's crust is being thrust under the arc, but with significant deformation and the formation of a forearc basin.⁵ The collision provides a modern analog for ancient orogenic belts, such as the Himalayas, and is a key site for studying the mechanics of plate tectonics.³ The region is also seismically active, with frequent earthquakes and tsunamis, posing hazards to local populations.⁵

Beyond its size, the Ontong Java Plateau hosts several notable features. The plateau is home to the largest known submarine landslide, the Ontong Java landslide, which covers an area of over 100,000 square kilometers. The plateau's basalts contain unusual high-magnesium compositions, indicating high degrees of mantle melting.² The plateau also influences the modern oceanography, as its shallow bathymetry deflects deep ocean currents, affecting nutrient distribution in the region.¹ Additionally, the plateau is a target for scientific ocean drilling, with several Ocean Drilling Program (ODP) legs having recovered cores that are crucial for understanding LIP formation. The name "Ontong Java" derives from the Ontong Java Atoll, which lies on the plateau's western edge, and the term "plateau" was first used in the 1960s based on bathymetric surveys.¹

Large igneous province (LIP)

A massive accumulation of igneous rock resulting from volcanic activity, covering areas of hundreds of thousands of square kilometers.

Mantle plume

A column of hot, buoyant rock rising from deep within the Earth's mantle, which can cause volcanic activity at the surface.

Oceanic anoxic event

A period when the oceans become depleted of oxygen, leading to widespread extinction of marine life.

Obduction

The process by which one tectonic plate is thrust over another, often resulting in the emplacement of oceanic crust onto continental crust.