Abstract

New geologic, petrographic, and radiometric evidence (52 ages) from the Sierra Nevada suggest that plate tectonics controlled the complex Mesozoic evolution of the Caribbean continental margin.

The triangular Sierra Nevada massif is bounded by the Oca fault, Santa Marta–Bucaramanga fault, and Cesar lineament. During the Tertiary, dextral and sinistral movement of 65 and 110 km, respectively, occurred along the Oca and Santa Marta–Bucaramanga faults; subsequently, several thousand meters of uplift produced the present geomorphic setting.

Three metamorphic terranes are present; they differ petrographically and geochronologically and are separated by the Sevilla and Cesar lineaments (geosutures). The youngest terrane consists of three northeast-trending regional metamorphic; belts (Permian-Triassic gneiss, Jurassic schist, and Cretaceous-Paleocene green schist) that formed in successive subduction zones northwest of the Sevilla lineament. Tertiary plutons intrude this terrane.

Most of the Sierra Nevada massif consists; of l,300-m.y.-old granulite terrane overlair by unmetamorphosed Paleozoic and Permian(?)-Triassic rocks and intruded by four northeast-trending belts of plutons that filled successive dilational rifts. These plutonic belts become younger, shallower, and more potassic in a southeastward direction. Extensional disruption, with transform separations up to 46 km, culminated with Middle Jurassic emplacement of two belts of composite batholiths and extensive ignimbritic eruptions. These events are related to the same southeast-dipping subduction zone that produced the Jurassic schist in the youngest metamorphic terrane.

The third metamorphic terrane consists of younger(?) Precambrian amphibolite-grade rocks overlain by Silurian phyllites and unmetamorphosed Paleozoic and Mesozoic rocks that are typical of the Cordillera Oriental.

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