Abstract U/Pb zircon and 40 Ar/ 39 Ar hornblende ages of medium- to high-grade metamorphic basement rocks from La Vela Bay in the Falcon Basin and of granitic gneiss rocks from a basement inlier in the southeastern Guajira Peninsula, northwestern Venezuela, measured by laser ablation–inductively coupled plasma–mass spectrometry and sensitive high-resolution ion microprobe, document the presence of Meso- to Neoproterozoic crust related to the Putumayo orogen, which probably correlates with the Chibcha terrane, in Colombia. Metawackes, metapelites, and granitic gneisses from these localities showed a high-grade metamorphism peak between 1.0 Ga and 0.98 Ga. Ages of inherited zircon cores of 1212 ± 11 Ma, 1214 ± 10 Ma, 1227 ± 9 Ma, 1366 ± 38 Ma, 1519 ± 9 Ma, and 2707 ± 8 Ma, are interpreted as relicts of detrital igneous grains that were originally incorporated from the Amazon craton into the sedimentary protolith. In addition, 40 Ar/ 39 Ar ages of hornblende crystals in metapelites preserve younger events between 923 Ma and 916 Ma, which indicate cooling under 530°C after the granulite facies peak. Radiometric ages presented in this study support the idea that these basement rocks probably formed part of a single orogenic belt in western South America, that formed in an active margin located in the northwestern part of the Amazon craton, which gave rise to a continental collision with Baltica during the Neoproterozoic assemblage of Rodinia.

The Cordillera of eastern Venezuela is a south-vergent fold-thrust belt of Neogene age formed on the South American plate and its Atlantic passive margin series by right-lateral transpression during the relative eastward migration of the Caribbean plate. Together with the topographically high Serranía del Interior, the Maturín subbasin is the easternmost onshore segment of the Venezuelan Cordillera, its foothills, and its foreland. Oilfields and data coverage of the Maturín subbasin abundantly document the compound sediment wedge, its structure, and its sedimentary and tectonic evolution. In the Monagas foothills, décollements at the base of the Miocene are responsible for the formation of a complex accretionary wedge. Deeper structures in the Monagas foothills involve the Mesozoic assemblages that were emplaced by thrusting following the emplacement of the Carapita accretionary wedge. Apparent “out of sequence” relations at the surface of the Serranía del Interior and in the shallow subsurface of the Maturín subbasin are due to the interference of late deeper structures with the earlier structures of the accretionary wedge. Six alternative structural interpretations range from basement-involved to non–basement-involved décollement tectonics. These hypotheses imply varying amounts of shortening along the Serranía to foreland ranging from 9% to 66% or 15–115 km oblique component of the El Pilar fault.

The igneous and metamorphic rocks of Venezuela may be classified in three geographic units: a southern Precambrian Shield, an intermediate belt of Paleozoic age and a northern border of Mesozoic to Tertiary age. The shield is exposed in the south; it extends northward under a sedimentary cover to an inferred contact with the metamorphosed Paleozoic or Mesozoic-Tertiary rocks. South of this contact, in the eastern states of Anzoátegui and Monagas, the shield's oldest known sedimentary cover is of Cretaceous age; to the west, it is of Cambrian age. A graben is identified in the State of Guarico, located approximately along the contact of the Paleozoic basement with the Precambrian Shield. It contains a 2,390 m (7,840 ft) column of sedimentary rocks of Carboniferous and Jurassic age, not previously identified in the Barinas-Apure and Eastern Venezuela basins. Preliminary interpretation of recently acquired aeromagnetic data indicates that this feature forms part of a much longer graben, hitherto not known, which may extend westward from near Barcelona, Anzoátegui, to the Colombian border at approximately 70° 00' West Longitude, 7° 10' North Latitude, a distance of 600 km (375 mi).