Tectonic and climatic control of Triassic sedimentation in the Beryl Basin, northern North Sea

The Beryl Basin (Embayment) occupies a central position along the Viking Graben of the northern North Sea and has been a hydrocarbon play since the early 1970s. Detailed analysis reveals a complex half graben that was established during a rift-phase of development that occurred in the Early Triassic (Teist Formation), after which, a long period of thermal subsidence (Lomvi and Lunde Formations) provided accommodation for in excess of 1000 m of sediment. The Teist Formation sediments are complex, they include shales, sands and conglomerates, and their superimposition on Zechstein salts is indicative of both uplift and the development of a moderate relief. They give way to the comparatively clean and occasionally pebbly sands of the Lomvi Formation, for which an analysis of both bedding and texture suggests deposition by a westerly-directed river system draining the hanging-wall ramp. The Lunde Formation records the spreading influence of a bajada/playa complex and its eventual conversion to a more persistent lake. The growing importance and eventual dominance of the succession by lacustrine sediments gives clear indication of a change in climate, and this has been attributed to the rapid northward drift of Pangea during the Triassic period.