Abstract 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.

Abstract An exploration well was drilled as a wildcat targeting high-pressure and high-temperature gas condensates within Jurassic-age reservoir sandstones offshore Norway. The well, drilled to a depth of more than 5000 m (16,404 ft) subsea with bottom-hole temperatures up to 176 °C and mud pressures up to 93 MPa, was successfully tested. As part of a comprehensive logging and coring program, oil-base mud EARTH Imager℠, Baker Hughes/Baker Atlas data were acquired in the discovery well. The objectives of the wellbore imaging were to determine the structural dip, confirm the presence or absence of (seismic and subseismic) faults, support detailed core sedimentology studies, and determine the orientations of depositional or architectural elements. This contribution summarizes the acquisition and interpretation of the borehole images. Structural dip and an apparent low density of faulting interpreted from the images were consistent with the predrill structural interpretation. Comparison of the core and images assisted in the characterization and orientation of the depositional architecture.