From isolated buildups to buildup mosaics: 3D seismic sheds new light on upper Carboniferous-Permian fault controlled carbonate buildups, Norwegian Barents Sea

Carbonate buildups are a common feature of many ancient carbonate platforms, and were especially abundant during the Palaeozoic. Our present understanding of buildup distribution, and the ability to better predict their location, is however hampered by the fact that maps of buildups rarely show evidence of widespread spatial organisation and indeed their distribution often appears chaotic. A previously unrecognized pattern of buildup distribution has been revealed by three-dimensional (3D) seismic data recently acquired from the Loppa High, Norwegian Barents Sea. Here, syn-rift Carboniferous-Permian buildups are not isolated but are instead linked into a mosaic of laterally extensive ridges. The buildups' location is controlled by the intersection of three trends of syndepositional faults. Systematic organisation of buildup height, width, density and external form across the study area appears to have been controlled by changes in accommodation space driven by differential subsidence. The buildups were remarkably long-lived and developed over an interval of 35 Ma. Despite this longevity, buildup location remained relatively static and true to the underlying pattern of basement faults, indicating that their progradation was likely restricted by a combination of factors including limited highstand production, their depositional relief <420 m, steep flanks and/or differential subsidence. Study of the buildups' internal seismic geometries, and analogy to well-exposed onshore buildups, indicates that they are composite features, developed through the repeated recolonization of antecedent bathymetric seafloor highs following hiatuses related to both subaerial exposure and drowning. The picture of interconnected buildup mosaics described for the first time here provides important new insights as to the spatial and internal organisation of carbonate buildups and has potentially far-reaching implications for the interpretation of buildups in areas where good 3D control is poor or unavailable.