Paleogene drainage system evolution in the NE Faroe–Shetland Basin

Abstract

Incised drainage systems can provide a record of the timing, duration and magnitude of ancient vertical crustal motion. The NE Atlantic underwent rapid uplift at c. 56 Ma, resulting in widespread incision and the formation of Paleogene unconformities across the Faroe–Shetland Basin. We used 3D seismic data to map a newly identified incised drainage system in the northern Faroe–Shetland Basin that formed during this period of uplift and compared it with similar incision surfaces in the region. The c. 30 km × 50 km erosional surface is a composite feature, comprising the Upper Thanetian Unconformity, which was rejuvenated and eroded by the younger Flett Unconformity, and records prolonged regional uplift during the late Thanetian–earliest Ypresian punctuated by a phase of subsidence. The drainage system was influenced by igneous intrusions, resulting in the diversion of channels around forced fold structures. Several preserved palaeoshorelines occur close to the basinward limit of the incision surface, recording progressive back-stepping of the shoreline and marine transgression during early Ypresian subsidence. The drainage system may have supplied ‘clean’ sand, eroded from the North Shetland Platform, to the Flett Sub-basin, with the potential to form high-quality reservoir units. Such sands may have been concentrated along shorelines coeval with the drainage system, but potentially were also delivered further out into the basin.