northern North Sea











Tertiary of the West Shetland Platform

During the Early Tertiary, the continental margin of NW Europe experienced intense volcanic activity in response to the onset of sea floor spreading in the North Atlantic. Most activity was concentrated in the interval between 61 and 55 Ma. Tow buried strata-volcanoes, Erlend and West Erlend, occur at 62ºN, and a thick basalt and dolerite sill runs along the edge of the West Shetland Platform, covering an area of 750x100 km.

Offshore oil exploration and 3D seismic surveys have added greatly to our understanding of the impact of ocean spreading on the Shetland area. Throughout the Tertiary Shetland shed sediment to the West Shetland Basin. The main pulse of uplift and erosion occurred between 60 and 54 Ma, with tilt of Shetland towards the Moray Firth. The main river valleys incised into the platform can be detected on seismic surveys. In the Faeroe-Shetland Basin, the drainage system can be mapped over an area in excess of 700 km2. Individual valleys obtain a maximum vertical relief of around 100m and widths of between 3 and 5km. The dominant north-north-east directed drainage pattern reflects the underlying Mesozoic basin margin slope (Underhill and Biskopstø, 2001). The Palaeocene-Eocene sediments are mainly shallow marine sands.

Around 4 million years ago, the shelf was tilted slightly towards the NW, implying modest uplift of the Shetland land area (Stoker et al, 2005).