Abstract

It is widely accepted that the thickened oceanic crust of the Caribbean plate, its basaltic accreted margins, and accreted mafic terranes in northwestern South America represent the remnants of a single ca. 90 Ma oceanic plateau. We review geologic, geochemical, and paleomagnetic evidence that suggests that the Caribbean-Colombian oceanic plateau in fact represents the remnants of two different oceanic plateaus, both dated as ca. 90 Ma. The first of these plateaus, the Caribbean Plateau, formed ca. 90 Ma in the vicinity of the present-day Galapagos hotspot. Northeastward movement of the Farallon plate meant that this plateau collided with the proto–Caribbean arc and northwestern South America <10 m.y. after the plateau's main phase of formation. Paleomagnetic evidence suggests that the second of these plateaus, the Gorgona Plateau, formed at 26°–30°S, possibly at the site of the present-day Sala y Gomez hotspot. Over the next ∼45 m.y., this plateau was carried progressively northeastward on the Farallon plate and collided in the middle Eocene with the proto–Andean subduction zone in northwestern South America. The recognition of a second ca. 90 Ma Pacific oceanic plateau strengthens the link between plateau formation and global oceanic anoxic events.

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