Late Cretaceous subduction initiation on the eastern margin of the Caribbean-Colombian Oceanic Plateau: One Great Arc of the Caribbean (?)

Abstract

Detailed mapping on the Leeward Antilles islands of Aruba, Curacao, Bonaire, and La Blanquilla has led to a reassessment of their stratigraphic, magmatic, and structural evolution. In general, each island preserves its own distinct sequence of geologic events. The Cretaceous geology of Aruba and Curacao consists of a mafic igneous complex, long interpreted to represent exposures of the Caribbean-Colombian Oceanic Plateau (CCOP), intruded by 89–86 Ma arc-related plutons and dikes. The rocks on both islands that are interpreted as remnants of the CCOP underwent a period of subaerial erosion in the Late Cretaceous, but subsequently their geologic histories diverge significantly in terms of their stratigraphic and structural evolution. Mapping on Bonaire has resulted in a major revision to the Cretaceous bedrock geology. Instead of a single stratigraphic unit (Washikemba Formation) the island contains two stratigraphic units separated by a northwest-trending fault. The southwest side of the fault consists of an arc-related Early to Late Cretaceous volcaniclastic section cut by shallow level intrusions, whereas the northeast side is composed of Early to Late Cretaceous epiclastic/hemipelagic strata that are locally cut by small arc-related mafic intrusions. La Blanquilla represents the southernmost exposure of the Aves Ridge which is a remnant arc separated from the modern arc of the Lesser Antilles by the Grenada back arc basin. The bedrock geology consists of two Late Cretaceous arc-related plutons. The geologic evolution of the Leeward Antilles when combined within a broader context of Caribbean tectonics leads us to a tectonic model involving three distinct arcs rather than a single “Great Arc” of the Caribbean as an explanation for the geodynamic evolution of the CCOP and its fringing arc system.