--> Nested Submarine Canyon Complexes on the Flanks of the Niger Delta: A Structural Model, by E. Duncan, P. Ventris, K. Koleoso, and R. Lilletveit; #90986 (1994).

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Abstract: Nested Submarine Canyon Complexes on the Flanks of the Niger Delta: A Structural Model

Edward Duncan, Paul Ventris, Kazeem Koleoso, Ragnhild Lilletveit

Large, vertically persistent, submarine canyon systems appear to be characteristic on the flanks of major deltaic headlands. As these systems are generally assumed to represent important sediment conduits to the deep-water, they are considered attractive exploration targets, helping prediction of basin-floor fan targets. Genetic models of canyon evolution generally invoke deep fluvial incision during eustatic lowstands or shelf edge instability, exacerbated by headward erosion during highstands.

Using seismic and well data from modern and ancient canyon systems of the Niger delta, this contribution proposes an alternative, dominantly structural genetic model. Lateral variations in rates of thin skinned extension around a basin margin, together with flexural loading due to the thick deltaic succession, create zones of extensional faulting and enhanced subsidence on the delta flanks, orientated perpendicular to depositional strike. Gravitationally driven deformation creates linked and starved half-grabens and crestal collapse grabens. Where sedimentation does not keep pace with this subsidence, dip orientated, basinward opening canyons result.

Some lithostratigraphic features previously described as canyon infills can be reinterpreted within this model as areas where aggradation keeps pace with enhanced subsidence. As such, these features need not have had significant topographic expression during their development. Indeed the modern distribution of mangrove swamps around the Niger delta may be controlled by such subsidence axes.

A tectonic origin implies that lowstand, fluvial incision is not a pre-requisite for canyon initiation and they need not, therefore, represent conduits for fluvially derived, coarse clastics to deep-water basin-floor fans.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994