Cretaceous revisited: exploring the syn-rift play of the Faroe–Shetland Basin

Abstract

Abstract Improved seismic imaging of the deep structures in the Faroe–Shetland Basin has revealed a complex Mesozoic rift system with shifting block polarity along the West Shetland Platform. Newly acquired seismic data has led to the focus of hydrocarbon exploration on structurally defined Mesozoic traps and has re-opened exploration in the deeper stratigraphic sections beyond the stratigraphic, Paleocene deep-water play. In the study area, rift geometry changes from symmetrical (south) to asymmetrical (north), the latter creating a large-scale seaward-dipping flexure. The polarity shift may link up with deep-seated basement structures (rift-oblique lineaments) segmenting the rift zone. The initial rifting along the West Shetland Platform strongly influenced the depositional setting and lateral distribution of the Lower Cretaceous sediments. During rift initiation in the Early Cretaceous faulting took place along numerous small faults, which eventually linked up, creating a set of basin master faults in the main rift phase. Sand derived from rivers and longshore currents on the West Shetland Platform was transported down the axis of relay ramps and filled the juvenile rift basins. These sediments formed thick onlapping wedges, reflecting the continuous creation of accommodation space and the overall transgressive nature of the syn-rift and early post-rift succession. In this period, rift basins were elongated, which to some extent hindered cross-rift transport of coarse material except at relay ramps and rift-oblique lineaments. As fault movements ceased, the rift topography was levelled out and allowed gravity-driven systems to reach further into the basin, overstepping former cross-rift barriers. Lower Cretaceous syn-rift sediments are well exposed at several localities along the margins of the northern North Atlantic including onshore NE Greenland. The close analogy to the syn-rift structural setting imaged in the west of Shetland seismic succession may provide valuable information on structurally controlled depositional systems, reservoir architecture and properties.