Oceanic Plateau Overview and Look Ahead

Oceanic plateaus result from fundamental processes in the Earth's interior, and have been implicated as instigators of major worldwide environmental changes. Although the plate tectonics paradigm successfully explains volcanic activity on the Earth's surface associated with seafloor spreading and plate subduction, it does not elucidate the massive flood volcanism that produces oceanic plateaus. Temporal correlations between flood basalts and environmental phenomena such as mass extinctions and oceanic anoxic events (OAEs) are well documented, yet the underlying mechanisms causing these global catastrophes are only beginning to be grasped. Focused investigations of oceanic plateaus have targeted the two largest features globally, the ~120 Ma Ontong Java Plateau (Pacific Ocean) and ~120-95 Ma Kerguelen Plateau/Broken Ridge (Indian Ocean), and the ~145-130 Ma Shatsky Rise (Pacific Ocean). These three features constitute the only oceanic plateaus where igneous basement has been drilled at more than one site. Multiple models - plume, bolide impact, and upwelling eclogite - have been proposed for Ontong Java's origin. The feature correlates temporally with OAE-1a, and interpretation of Sr, Os, and Pb isotopic systems during the time of OAE-1a points to a close linkage between the two, with CO2, Fe, and trace metal emissions from the massive magmatism potentially triggering the event. The Kerguelen Plateau/Broken Ridge is a composite feature that includes flood basalts, depleted mid-ocean ridge basalt (MORB)-related asthenosphere, and continental lithosphere. Models for the Shatsky Rise include mantle plume and fast seafloor spreading. Future studies of oceanic plateaus have the potential to transform our understanding of the Earth system through investigating: 1) magma (and hence mantle source) variability through times; 2) the nature of melting anomalies, i.e., compositional vs. thermal, that produce oceanic plateaus; 3) the precise durations of oceanic plateau events; 4) modes of eruption, i.e., constant effusion over one to several million years, or several discrete pulses over the same time interval; and 5) relationships among oceanic plateaus, OAEs, extinction events, and other major environmental changes (e.g., ocean acidification and fertilization). Increased knowledge of all will contribute to understanding and forecasting regional and global environmental changes during the Anthropocene. Advancing knowledge of oceanic plateaus and the Earth system requires integrated multi-disciplinary and cross-disciplinary approaches involving mantle geodynamics, plume modeling, petrology, geochemistry, environmental impacts, paleoceanography, micropaleontology, physical volcanology, geophysics, and tectonics. Oceanic plateaus must be studied in concert with oceanic (volcanic divergent margin) and continental counterparts to better understand emplacement mechanisms and environmental effects of their formation.