LIP Reading: Recognizing Oceanic Plateaux in the Geological Record

Basaltic oceanic plateaux are important features in the geological record. Not only do they record ancient mantle plume activity, but they also are believed to be important building blocks in the formation of the continental crust. In this paper we review the salient features of two Cretaceous oceanic plateaux (the Ontong Java and the Caribbean-Colombian): thick sequences of predominantly homogeneous basalt; the occurrence of high-MgO basalt, including komatiites; and an apparent absence of sheeted dyke complexes. In addition, pyroclastic deposits may be scarce. We then explore ways of distinguishing plateaux from basaltic sequences erupted in different tectonomagmatic settings: continental flood basalt provinces; island arcs; back-arc basins; ocean islands and mid-ocean ridges. Using these criteria, potential Archaean and Proterozoic oceanic plateaux are reviewed and identified. Finally, we explore how these remnant oceanic plateaux became incorporated into the continents, by reviewing the proposed accretion mechanisms for the Cretaceous Caribbean-Colombian oceanic plateau, on the basis of evidence from South America and the tonalites of the southern Caribbean island of Aruba.