--> Do Stratigraphic Variations Influence Fault Zone Architecture in Deep-Water Fold-Thrust Belts? by Rob Butler, Bill McCaffrey, and Richard Morgan; #90052 (2006)
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Do Previous HitStratigraphicNext Hit Variations Influence Previous HitFaultNext Hit Zone Architecture in Deep-Water Fold-Thrust Belts?

Rob Butler1, Bill McCaffrey1, and Richard Morgan2
1 University of Leeds, Leeds, United Kingdom
2 VeritasDGC, Crawley, United Kingdom

In thrust system analysis, Previous HitfaultNext Hit zones are commonly modelled as discrete surfaces, with surrounding rock deformation explained by combination of Previous HitfaultNext Hit shape and displacement gradients. However, high resolution 3D seismic data from the compressional parts of gravitationally-driven fold belts on continental margins show more complex Previous HitfaultNext Hit zone architectures. While in some settings Previous HitstratigraphicNext Hit cut-offs against inferred faults are crisply imaged, in others there are significant zones, up to 1km wide, within which there is substantial amplitude loss. In many instances these represent zones of closely-spaced subsidiary faults, separating Previous HitfaultNext Hit-bounded slices of strata, together with distributed strain; adjacent stratal reflectors may be deflected into the Previous HitfaultNext Hit zone. These non-discrete Previous HitfaultNext Hit occurrences entail different predictions for structural development, the evolution of horizon dips (and hence the geometry of growth strata), and for the connectivity of the Previous HitfaultNext Hit zone itself. We use insights from outcrop analogues (Marnosa Arenacea, northern Apennines of Italy; Gres du Champsaur, French Alps) to aid Previous HitinterpretationNext Hit of thrust zones from deep-water Niger delta in 3D seismic volumes. The key feature controlling the width, structural complexity and arrangement of Previous HitfaultNext Hit-bounded sandstone lenses in outcrop (and that may enhance vertical permeability in subsurface settings) is the propensity of buckling. This in turn is favoured by well-layered, alternating sand-shale sequences. The scale of buckling and cyclic thrusting and folding are strongly influenced by the gross stacking patterns of sand that in turn effect the fold amplification. Thus locally calibrated Previous HitstratigraphicNext Hit knowledge may be used to predict Previous HitfaultTop zone architecture and vice versa.