NEW INSIGHTS INTO THE SEDIMENTARY ARCHITECTURE OF THE FALCóN BASIN (ONSHORE VENEZUELA)

The sedimentary basins from the northern South American margin contain the major oil reserves of America. These hydrocarbon reserves are comparable to those of the Middle East. The Falcón Basin is a poorly studied example of an oblique collision-related basin, formed during the Cenozoic in the northwestern Venezuela, which was inverted during the Middle Miocene to present. To reconstruct the basin geometry and to understand the tectono-sedimentary evolution of the Falcón Basin, the Oligocene to lower Miocene sedimentary successions of both northern and southern basin margins were studied by means of facies analysis and sequence stratigraphy. The northern flank of this back-arc basin is characterized by a kilometre-scale prograding delta system, which interfingers with transgressive carbonate deposits represented by coral biostromes, passing basinwards to packstones and rudstones dominated by coralline algae and larger foraminifera. In the northern margin the subsidence was controlled by planar normal faults without block-rotation, forming a stepped basement geometry dipping to the basin. The southern flank is represented by transgressive siliciclastic marine deposits integrated by black shales, turbidite sandstones and occasionally, glauconitic sandstones; and regressive isolated carbonate banks dominated by reworked larger foraminifera and coralline algae. In the southern margin, the subsidence was controlled by listric normal faults with block rotation and sedimentary bodies dipping towards the fault. Isolated carbonate banks were developed upon submarine block-fault mountains. Similar Oligocene-Miocene carbonate ramps developed on structural highs are major reservoir rocks in offshore Venezuela (Perla giant gas field).