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Simon Higgins, StatoilHydro (Norway)
Benjamin Clarke, StatoilHydro (Norway)
Richard J Davies, Durham University (United Kingdom)
Joe Cartwright, Cardiff University (United Kingdom)
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The structural evolution of a fold and thrust belt is investigated through the analysis of a single, isolated fold imaged using 3D seismic data over part of the deep water Niger Delta. Numerous thrust faults, of similar and opposing dip, link and transfer displacement through transfer zones within the structure creating a central structural culmination and causing the vergence to vary along strike. These linkages vary in spatial extent and have distinctly different styles. Fault heave and shortening measurements are presented for each instance as displacement-length profiles and strike projections with reference to a simple fold comprising a single fault plane. Syn-kinematic growth packages are used to chart fold and fault growth through time and allow for an understanding of the early structural growth history. This evidence forms the basis for a model of fold and thrust fault growth for toe-of-slope compressional settings. Several detachment folds initiate with individual structural culminations and grow towards each other by lateral propagation along strike. Numerous faults nucleate at various stratigraphic levels along the length of the structure on both flanks producing an asymmetric fold shape. Analysis of lateral fold tip structures suggests the faults propagate some distance above the detachment. Continuing fault development results in the migration of the point of maximum displacement, observed in a given 2D section, downwards towards the detachment. Folds coalesce and faults link along strike, resulting in structural culmination migration to a single central apex and the formation of synthetic and antithetic thrust fault linkages. The bulk shortening profile resembles that of an individual fault and fold indicating component structures have acted as a coherent unit since inception. Final fault and fold geometries display fluctuating fault heave values and a smoother shortening profile that suggests deformation by folding compensates for deficits in fault heave along strike.
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