Internal geometry and growth history of a thrust-related anticline in a deep water fold belt

Abstract

Although 3D seismic imaging has become a fundamental tool for the analysis of extensional fault geometries and their development, it has not been utilised to the same degree to investigate the structure and growth history of thrust faults. Here, the structural evolution of a fold and thrust belt is investigated through the analysis of an isolated fold imaged in the deep water Niger Delta. A quantitative description of thrust fault displacement through transfer zones is presented to investigate the internal structure of a complex fault-related fold, while syn-kinematic growth packages are used to chart fold growth through time, so as to also understand the early growth history. Results reveal that a number of initially separate folds coalesced along the axial trends into a single structural culmination. Numerous thrust faults with similar and opposing dip, link and transfer displacement within the structure as it changes vergence along strike. The distribution of bulk deformation along the fault-related fold is simple, systematic and similar to that observed for extensional fault systems. Deficits in fault heave, both in the form of perturbations on non-linking or aggregated profiles, and displacement minima within transfer zones, are compensated to some degree by an increase in fold-related strain. Despite this accommodation, fold amplitude or crest elevation is largely unaffected by variations in fault heave. The observations for this isolated fold should be widely applicable to fold and fault development in more complex areas.