A very long (736 km) and ultra-deep (PSDM 40 km) seismic section, oriented in the dip direction (NE-SW), was re-interpreted from a previously published interpretation. The main differences regarding these two versions concern the nature of the continental-oceanic boundary, the dimensions of the underlying rift sections situated in the continental slope area and the petroleum potential of the Drift Supersequence in the ultra-deep waters.

The line was re-interpreted using the modern concepts of rupture and break-up of mega-continents, presently used by the petroleum industry worldwide. The petroleum-rich passive continental margins are nowadays classified into two end-members: magma-poor or sedimentary passive margins and volcanic passive margins. The analysis performed indicated that the Pará-Maranhão Basin can be classified as a typical magma-poor passive margin developed during the oblique dextral separation between South America and Africa.

The original thickness of the continental crust below the shallow waters of the basin is in the order of 32 km. The Moho reflection is easily observable and shallows up gradually to depths around 12-13 km where it forms a small plateau before meeting the top of the crystalline basement. The continental crust tapers significantly and forms a narrow band of hyper-extended crust (circa 30 km wide) before being broken by a clear stretch of exhumed mantle (around 30 km wide). Oceanic crust follows in a typical tabular shape with thicknesses between 5-6 km. At the northeastern end of the line, the Moho dips deeply under the Ceará Rise, suggesting a typical continental crustal profile for this feature. In being so, the Ceará Rise could be interpreted as a significantly large micro-continent.

The results of this interpretation indicate a high potential for the Drift Supersequence in ultra-deep waters where the thickness of sediments reaches 8 km. Strong and large bright spots surround a structural high situated upon the exhumed mantle, buried underneath edifices of volcanic intrusions. Their seismic facies suggest turbidites filled with fluids deposited around a syn-tectonic high. Older generation seismic lines did not have resolution to highlight these leads. The shallow gravitational cells in deep waters also overlie high potential deeper Drift Supersequence sections. Besides unravelling the crustal structure underneath the Pará-Maranhão continental margin, this interpretation also expanded horizontally and vertically the prospectable area of the basin. It proved that petroleum potential may exist beyond the termination of the continental crust, upon the exhumed mantle.

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