LATE CRETACEOUS SUBDUCTION INITIATION on THE EASTERN MARGIN OF THE CARIBBEAN-COLOMBIAN OCEANIC PLATEAU (CCOP): ONE GREAT ARC OF THE CARIBBEAN (?)

The stratigraphic, magmatic and structural evolution of the Leeward Antilles islands of Aruba, Curaçao, Bonaire, and La Blanquilla, in conjunction with previous investigations of Caribbean geology, suggest an alternative model for the Cretaceous tectonic evolution of the Caribbean fringing arc system. Aruba and Curaçao contain a mafic igneous complex interpreted as representing exposures of the Caribbean-Colombian Oceanic Plateau (CCOP) intruded by 89-86 Ma arc related plutons and dikes. The geologic evolution of Aruba and Curacao is comparable to accreted terranes in Colombia and Ecuador. There Late Cretaceous plutonic rocks and volcanic strata were emplaced into or erupted onto the CCOP. The Ecuadorian, Colombian and Leeward Antilles are interpreted as lateral equivalents of a single Late Cretaceous arc that was constructed on the CCOP. We call this the Ecuadorian-Colombian Leeward Antilles arc (ECLA). There is no evidence for an older Early Cretaceous arc substrate for the ECLA and thus available data indicates Late Cretaceous (~90 Ma) subduction initiation along the southeastern edge of the CCOP.

A number of investigations have concluded that the Ecuadorian and Colombian part of the ECLA collided with the South American margin in the latest Cretaceous (~75 Ma). Following collision, the collided arc and its CCOP basement were obliquely subducted beneath the South American margin giving rise to a post collisional arc that persisted into the Eocene. The Leeward Antillean islands of Aruba and Curacao were not involved in the collision. Curacao did not undergo deformation at ~75 Ma but instead received deep water turbidites derive from both the collided arc and the South American continental margin (i.e. the collision zone). Our U-Pb ages from detrital zircon and ⁴⁰Ar/³⁹Ar r ages from detrital hornblende form the basis of this interpretation. There is neither a deformational nor sedimentary record of this time interval preserved on Aruba. The Leeward Antilles part of the ECLA does not appear to have been directly involved in the accretionary event and thus must have been located North of the collision zone.

In our view, the Late Cretaceous ECLA was linked to the Greater Antilles arc via a Subduction Termination Edge Propagator (STEP fault) that ultimately became the subduction zone that generated the volcanic arc that constitutes the Aves Ridge. La Blanquilla, the only exposure of the Aves Ridge, is composed of two arc related plutons. An older 76 Ma pluton which was intruded by a 59 Ma pluton. During collision of the Ecuadorian-Colombian segment of the ECLA with the South American margin subduction propagated to the North along the STEP forming another arc system between the Greater Antilles and the collided ECLA. The 76 Ma pluton on La Blanquilla may represent the initiation of arc magmatism on what is now the Aves Ridge. The 59 Ma pluton is close in time to the opening of the Grenada Basin when the Aves Ridge became a remnant arc. This marks the inception of the remnant arc/back arc basin/active arc triad represented by the Aves Ridge, Grenada Basin, and Lesser Antilles.

Bonaire has an Early Cretaceous to Paleogene geologic history distinct from the other islands of the Leeward Antilles, and is most likely an arc fragment derived from the Greater Antilles. We suggest that it was derived from the eastern end of the Greater Antilles arc at the junction of the STEP fault that linked the Greater Antilles to the ECLA. Complex tectonic interactions at this junction resulted in the transfer of Bonaire to the proto-Caribbean Plate. Its journey ended when it became attached to the northern South American margin in the Paleocene/Eocene as indicated by the fluvial sediments of the Soebi Blanco Formation with a continental margin provenance.

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 that a single “Great Arc” of the Caribbean as an explanation for the geodynamic evolution of the CCOP and its fringing arc system.