SPEED, R. C., Northwestern University, Evanston, IL, R. M. RUSSO, Carnegie Institute of Washington, Washington, D.C., and K. A. FOLAND, Department of Geological Sciences, Ohio State University, Columbus, OH

ABSTRACT: Cenozoic Oblique Collision of South American and Caribbean Plates: New Evidence in the Coastal Cordillera of Venezuela and Trinidad

The hinterland of the Caribbean Mts. orogen in Trinidad and Venezuela contains schist and gneiss whose protoliths are wholly or partly of continental provenance. The hinterland lies between the foreland thrust belt and trranes. The terranes are alien to continental South America (SA) and may have proto-Caribbean or Caribbean plate origins. The hinterland rocks were widely thought to come from sediments and granitoids of Mesozoic protolithic ages and to be of Cretaceous metamorphic age. Such rocks are now know to be of at least two or more types, as follows: (1) low grade, protoliths of pre-Mesozoic basement and shelfal cover of uncertain age range, inboard locus, Oligocene to mid-Miocene metamorphic ages younging eastward (Caracas, Paria, and Northern Range belts), and (2) higher grad including high P/T, varied protoliths of uncertain age range, Cretaceous and (?)early Paleogene metamorphic ages (Tacagua, Araya, Margarita). The geometry, protoliths, structures, and metamorphic ages of type 1 parautochthoneity and an origin as a thickened wedge of crust-cored passive margin cover. The wedge grew by accretion between about 35 and 20 Ma during oblique transport toward the foreland. The diachroneity of metamorphism implies, as does the timing of foreland deformation, that the wedge evolved in a right-oblique collision between northern SA and terrances moving wholly or partly with the Caribbean plate since the Eocene. Type 2 rocks probably came with the terranes and are products of convergent zone tectonics, either in the proto-Caribbean plate. The hinterland boundaries a e brittle thrusts that are out of sequence and imply progressive contraction from mid-Cenozoic to the present.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.