Tectonic Evolution of the Central Part of the Venezuelan Coast Ranges

Abstract
Palinspastic reconstructions of the central part of the Venezuelan Coast Ranges combined with sedimentary data indicate that deep water marine deposits accumulated in east-west-trending troughs which were located successively farther south through time. From north to south, four such troughs are recognized. Regional metamorphism accompanied downbuckling in the two northern troughs, and allochthonous material slid southward into the two southern troughs. The emplacement of the allochthonous sequences is thought to be due to gravity sliding promoted by uplift in the north and downwarping in the south. Metamorphic grade and estimated sedimentary thicknesses suggest that the amount of downwarping decreased through time as the troughs migrated southward. In the eastern part of the East Venezuela Basin, this trough migration is reflected in the southward displacement of depositional axes between Late Cretaceous and Pliocene time. The structure of the Venezuelan Coast Ranges is interpreted as resulting from a linear downwarped zone, followed by an upwarped zone immediately to the north, migrating southward across the northern edge of the Guayana Shield at a rate of 1 to 2 km per m.y. from Jurassic until latest Tertiary time.