Map of tectonic provinces. The final results provided by this study, enabled the separation of the Pirital block in two different sub-blocks: Pirital-Cerro Corazon block and Manresa block. (Map modified after Cobos, 2002, and Chaplet, 2001.)

Strike section showing the different tectonic sheets laterally. Note that the Pirital-Tala thrust systems (system in blue) are composed of various thrust families separated by lateral ramps. This explains the differences between dip sections that lie in different tectonic sheets. This new interpretation of the Pirital block enabled us to develop the proposition of a new lateral ramp within the Pirital block, delimiting two laterally different tectonic provinces: the Pirital-Cerro Corazon block and the Manresa block .

Tectono-Stratigraphic Interpretation

Seismic stratigraphy and biostratigraphic data allowed the documentation of three main unconformities , each one of which dates the emplacement of the three thrust systems interpreted in this study. The oldest unconformity, dated early Miocene, documents the emplacement of the first tectonic pulse recognized. High frequency-short wavelength asymmetric anticlines characterize the structural style for this period of deformation. Currently, most of these structures are exposed to the north, in the outcropping ranges. To the south, in the subsurface, they are buried below a thick column of foreland sediments and form the giant oil fields typical of the Northern Monagas foredeep. Middle Miocene sediments onlapping erosional truncations (Fig. 18) provide evidence and timing for a second tectonic event. The thrust system (Pirital thrust system), associated with this event, intercepted, uplifted, folded, and reactivated the previous thrusts, exposing some of the oldest faults in outcrops to the north and burying the rest of them in subsurface to the south. The basal detachment of the Pirital thrust system has been interpreted to lie within pre-Cretaceous rocks. Thus, more than 5 km of Cretaceous and pre-Cretaceous strata have been folded, uplifted, and transported to the south for more than 40 km of average displacement. Upper Miocene strata onlapping middle Miocene sediments give evidence for the emplacement of a third thrust system, with its basal detachment interpreted to lie at the top of the basement, system in green. Major thrusts reactivated and deformed the Pirital structure, causing the rotation and uplifting of the Pirital high and the creation of the Morichito basin. It is also proposed in this study that some of the major faults within the Monagas basin, such as the Urica fault and the San Francisco fault, constitute the lateral ramps of this last major event.