Quantitative analysis of fault-and-fold growth in a transtensional basin: the Sørvestsnaget Basin, Western Barents Sea

The growth of faults and folds in basins formed under transtension has been less studied than that in their extensional counterparts. In this study, we capitalize on 3D seismic reflection data to investigate the evolution of faults and folds that evolved coevally during suborthogonal partitioned extension and shortening, respectively, in the Sørvestsnaget Basin, Western Barents Sea. We use quantitative techniques to constrain the distribution of normal fault throw, shortening accommodated by folds and thrusts, and stratigraphic thickness variations, to analyse the relative temporal and spatial evolution of faults and folds. Our results show that normal faults display a similar evolution to those occurring in extensional basins, where they grew by lateral- and dip-linkage of individual fault segments as well as upward propagation. Notably, we show that shortening-related fold growth affected the fault growth patterns, skewing their throw distributions, and shifting the location of accommodation away from the evolving folds. Thus, fold amplification caused lateral migration of normal fault hanging-wall depocentres. Our results shed new light on fault-and-fold growth processes in transtensional basins and contribute to an improved understanding of the structural evolution of basins forming along sheared continental margins, which has economic implications for sheared-margin basins targeted for hydrocarbon exploration.