Structural evolution of the northernmost Andes, Colombia

Abstract

The primeval Guayana shield of northern South America is older than the metamorphism of the eugeosynclinal Imataca Complex of southeastern Venezuela which took place at least 3,000 m.y. ago. Metamorphism and two granitic magma cycles we~ded the shield area into a stable craton between 2,250 and 1,850 m.y. (Guyanese). To the west and probably to the north the shield rocks are younger; in Colombia the oldest known rocks are about 1,350 m.y. old (Orinocan). This P.recambrian crust extends well into the Andean Cordillera and appears to have provided a platform for ensialic miogeosynclinal sedimentation during much of Phanerozoic time.