Abstract

Two neighbouring areas of tholeiitic basalts, dolerites, isotropic gabbros and tonalites in eastern Jamaica are recognized as the upper section (~2.5 km thick) of an ophiolite. Limestones associated with this Bath-Dunrobin Formation contain a fauna of Upper Campanian and Lower Maestrichtian age. The basalts are overlain by a thick sequence of Maestrichtian volcaniclastic rocks and are faulted against a blueschist terrain. Since its emplacement the ophiolite has been subjected to uplift and major left-lateral strike-slip tectonism beginning in the Eocene. Recognition of this subduction zone complex and regional considerations of island arc polarity necessitates that ocean crust must have been consumed by a southward-dipping subduction zone. The overlying late Cretaceous/Palaeogene arc stretched from Guatemala through Jamaica to Oriente Province, Cuba. This arc separated the Yucatan Basin to the N, where active spreading accompanied subduction, from the Colombian Basin and the southern Nicaraguan Rise to the SE, where tholeiitic magmatism (B") penetrated older ocean crust. The Bath-Dunrobin Formation probably represents ocean crust from the Yucatan Basin obducted during the Maestrichtian. The major ophiolite terrains of Guatemala and Oriente, Cuba are by inference also derived from a proto-Yucatan Basin.

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