Ontong Java Plateau

Ontong Java Plateau
Name	Ontong Java Plateau
Type	Large igneous province
Location	Pacific Ocean, north of Solomon Islands
Coordinates	3°S 160°E
Area km2	1,900,000
Region	Oceania
Age	Early Cretaceous
Period	Barremian–Aptian
Primary rock	basalt

Ontong Java Plateau is one of the largest Large igneous provinces on Earth, located in the western Pacific Ocean north of the Solomon Islands and west of Kiribati. The plateau covers roughly 1.5–2.0 million square kilometers and is composed predominantly of thick sequences of basaltic lava flows and intrusive sills. It formed during the Early Cretaceous and is a focal feature for studies of mantle plume dynamics, plate reconstructions, and Cretaceous paleoceanography involving many institutions such as the Woods Hole Oceanographic Institution and Scripps Institution of Oceanography.

Geology and Structure

The Plateau exhibits an exceptional thickness of volcanic strata with massive piles of flood basalt flows overlain by pelagic sediments, intersected by a network of mafic sills and dikes. Bathymetric and seismic surveys by research vessels from NOAA and the Geological Survey of Japan show crustal thicknesses up to 30–40 km and major structural boundaries adjacent to the Solomon Sea and Manihiki Plateau. The Ontong Java Plateau is juxtaposed to other Pacific plateaus including the Manihiki Plateau and Hikurangi Plateau, and its margins record faulting associated with interactions with the Pacific Plate and microplates such as the Woodlark Plate.

Formation and Origin

Competing hypotheses attribute the origin to a giant mantle plume head, a deep mantle thermochemical anomaly, or a combination involving plate tectonic stresses and plume-lithosphere interaction. Proponents cite similarities with plume-generated provinces like the Deccan Traps and Siberian Traps, while alternative models reference recycled components observed in isotopic signatures akin to material implicated in Hawaii and Iceland geochemistry. Plate reconstructions link the event to Early Cretaceous dispersal episodes that also influenced plates such as the Farallon Plate and continental fragments like East Gondwana.

Age and Duration of Volcanism

Radiometric ages obtained from deep-drilled basalts, including samples recovered during Integrated Ocean Drilling Program expeditions and earlier Deep Sea Drilling Project legs, cluster in the Early Cretaceous, approximately 122–116 million years ago, contemporaneous with chronologies for the Aptian and Barremian stages. Some studies suggest a brief, intense eruptive pulse, while others infer protracted magmatism with episodic rejuvenation potentially extending into the mid-Cretaceous, comparable to duration estimates for the Paraná and Etendeka province.

Geochemistry and Petrology

Basalts from the Plateau display high-MgO tholeiitic affinities and variable trace-element patterns, including enriched light rare earth element signatures and high incompatible element concentrations. Isotopic systems such as Sr–Nd–Pb–Hf indicate a heterogeneous source with components resembling enriched mantle (EM) and recycled oceanic lithosphere signatures also observed in studies of Kerguelen Plateau basalts. Petrological models invoke high degrees of partial melting of a mantle plume mixed with metasomatized mantle domains; intrusive sills host differentiated gabbros analogous to layered intrusions studied at locales like Bushveld Complex.

Tectonic and Paleogeographic Significance

The Ontong Java event had major implications for Early Cretaceous plate motions and paleogeography, affecting configurations of the Pacific Plate, breakup of Gondwana fragments, and the evolution of regional basins including the Solomon Basin and Nauru Basin. Its emplacement likely modified lithospheric stress fields that influenced the nucleation of fracture zones and seafloor spreading centers, with consequences for adjacent marginal basins near New Guinea and island arcs such as the Vanuatu arc. Correlations with the Manihiki and Hikurangi plateaus are central to retrodictions of Cretaceous superplume activity.

Biological and Climatic Impacts

Rapid emplacement of massive volcanism is hypothesized to have released voluminous greenhouse gases, aerosols, and trace metals that could perturb Early Cretaceous climate and ocean chemistry, with potential links to oceanic anoxic events recorded in radiolarian and foraminiferal assemblages from sites investigated by University of Tokyo and University of California, Santa Cruz teams. Paleoecological shifts documented in marine microfossils coincide with stratigraphic horizons correlated to the plateau and bear relevance to global events such as minor carbon isotope excursions and paleo-productivity changes similar to those associated with other large igneous provinces like the Caribbean Large Igneous Province.

Exploration and Research History

Interest in the Plateau dates to mid-20th century bathymetric mapping by agencies including the United States Geological Survey and later seismic and drilling programs under the Deep Sea Drilling Project and the International Ocean Discovery Program. Key contributions came from researchers at institutions such as Lamont–Doherty Earth Observatory, Curtin University, and the National Institute of Water and Atmospheric Research, who combined geophysical mapping, petrology, and geochronology. Recent multidisciplinary expeditions continue to refine models using tools from geochemistry and geophysics and collaborations with organizations like the International Marine Research Community.

Category:Large igneous provinces