ABSTRACT

Interpretation of more than 30,000 and 75,000 km of high-quality, modern seismic data from the Niger Delta (ND) and Gulf of Mexico (GOM), respectively, has revealed fundamental kinematic and stratigraphic similarities between these two highly prolific, unstable continental margins. They are characterized by (1) Mesozoic oceanic crust formation and subsequent rapid subsidence; (2) early deposition of a thick section (salt in GOM, mud in ND) that later developed into a ductile substrate; (3) an early phase of compressional deformation demonstrated by a distal fold belt (GOM) and imbricate thrusts (ND); (4) massive amounts of synsedimentary extensional strain accommodated by flow in the ductile substrate; (5) mappable Tertiary sequences and systems tracts; and (6) good evidence of deep-water reservoir sandstones, in basin-floor fans and lowstand slope-fan systems tracts. In both margins, the early Tertiary was dominated by seaward progradation of a growth-fault-modified, unstable, ramp-type continental margin. In contrast to the horizontal salt, which largely obscures the deep structure in the GOM, in the ND, diapiric overpressured shale permits seismic imaging of the deep structure. Oceanic crustal relief, corroborated by gravity data, has had a major influence on the structural and stratigraphic development of the ND, whereas in the GOM, the oceanic crust appears to be much smoother in current data. We suggest a new model of the Niger delta, emphasizing the interplay between deep canyon formation with deposition of lowstand systems tracts and intervening paralic and deltaic complexes during highstands. In the GOM, we attribute the scarcity of analogous deep canyon cuts to differences in sedimentation rate between the two margins.

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