Print this pagePato-Onado Area Structural Style Venezuelan Eastern Basin
GRUBER, IRAIMA R., and HUMBERTO JOSE SANCHEZ
The Pato-Onado Area comprises a belt limited by the Anaco thrust 
fault
and
the Norte de Monagas deformation front.
The delineation of structural styles that dominate the fault patterns is
determinant for the location of oil-bearing sands.
At the begining of the basin development there existed a Cretaceous-Paleocene
passive margin. During this period the sedimentary column was exposed by tilting
of the basin to the north, and over this eroded surface, the transgressive sands
of the Oligocene Merecure formation were deposited. During the upper Oligocene-
mid-Miocene period, tectonic elements typical of passive margins were developed,
including east-west oriented normal faults dipping south. During this period the
transgressive lower and middle section of the Oficina Formation was deposited
from the north. The presence of normal faults dipping north are associated with
the foreland-type Maturin sub-basin, and were generated by the transcollision of
the Caribbean plate with the South American plate during Mid-Miocene. In late
Miocene, the compressive activity to the north caused the reactivation of the
normal faults, although not enough to cause inversion of the blocks, only
folding. At the same time the Freites formation was deposited. During the
Pliocene-Pleistocene period, erosion of the compressive province to the north
supplied the clastics of the Las Piedras and Mesa formations, which represent
the final basin fill, where a compressive regime
is still acting.