TRANSPRESSIONAL TECTONICS OF NORTHERN SOUTH AMERICA

Along the northern margin of Venezuela from Colombia to Trinidad, lies an east-west range, (1,000 x 150 miles) which has been interpreted as an “Orogenic Float” developed by the interaction between oceanic crusts and the South-America´s passive margin during late Cretaceous to Neogene times from west to east. These two distinct subduction zones play important roles in the geodynamic context: the “B” subduction of Lesser Antilles (west polarity) and coeval “B” Colombo-Venezuelan subduction (south polarity). Following, some examples that illustrate atypical structural styles formed in these domains: - The Barbados Accretionary Prism evolves over oceanic crust to the east and progressively rides continental crust towards the south. The prism is currently being disrupted by gravitational tectonics associated with the Orinoco Delta edifice. - The south vergent Mid-Miocene Serrania del Interior shows differential uplift due to remobilization of Miocene shales along its leading edge. - Orogenic collapse of the igneous-metamorphic “Caribbean allochthonous belt” and transpression superimposed to the Neogene sequence are caused by a transfer system between the two “B” subduction zones. - The Falcón anticlinorium resulted from partial inversion of a Neogene flexural basin, as opposed to the prevalent pull-apart model. It is actually overthrusted to the north, following the Present-day Colombo-Venezuelan Accretionary Prism. - Comments will be made on both the geodynamic setting of wrench tectonic models, e.g. the Boconó and Oca lineaments and “opposing” northwest vergence of the Mérida and Perijá folded belts. Implications for exploration will be discussed for all these structural styles.