The Tertiary evolution of the north-eastern Venezuela offshore is dominated by Paleogene (Middle Eocene-Oligocene) extension and Neogene transtension, interrupted by Oligocene to Middle Miocene invasions. The pre-Tertiary basement of the northeastern offshore of Venezuela consists of a deeply subducted accretionary complex of a Cretaceous island an: system that formed far to the west of its present location. The internal structure of this basement consists of metamorphic nappes that involve passive margin sequences, and as ophiolites.

The Paleogene extension is mainly an arc-normal extension associated with a re- subduction boundary. It is limited to La Tortuga and La Blanquilla basins. All of these basins are north of and not directly related to El Pilar fault system. On a reconstruction, these Paleogene extensional systems were located to the north of the present Maracaibo basin.

By early Miocene, the leading edge of the now overall transpressional system had migrated to a position north of the Ensenada de Barcelona. This relative to South America's eastward migration is responsible for the Margarita strike-slip fault and the major invasions that began during the Oligocene and lasted into the Middle Miocene

The Bocono-El Pilar-Casanay-Warm Springs fault and the La Tortuga-Coche-North Coast fault systems are exclusively Neogene with major transtension occurring during the Late Miocene to Recent. They act independently from the earlier Paleogene extensional system and are responsible for the large Neogene transtensional basins of the area, the Cariaco trough, the northern Tuy Cariaco and Paria sub-basins, and the Gulf of Paria basin.

This latest phase is characterized by strain partitioning into strike slip faults, a transtensional northern domain and a transpressional southern domain, which is responsible for the decollement tectonics and/or major inversions of the Serrania del Interior and its associated Monagas foreland structures. Part of the latest phase (Middle Miocene-Recent) is the formation of a large arch that corresponds to the Margarita-Testigos-Grenada zone, which was subjected to mild lithospheric compression during the Pliocene.

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