At the opening of the Tertiary chalk sedimentation continued on the northern North Sea. Starting around 63 Ma, the East Shetland Platform was uplifted and tilted towards the south-east. Rapid erosion of Devonian and Permo-Triassic sandstones generated sands that were transported by large river systems to deep water submarine fans. These sands are up to 1 km thick in parts of the Viking Graben.

The Balder Formation records the most intense phase of Tertiary volcanic activity seen in the North Sea and may be the product of an outburst of volcanic activity triggered by the start of ocean floor spreading between Faeroe and Greenland.. In the lower part of the unit there are hundreds of individual volcanic ash layers, mostly only millimetres to centimetres thick but forming a total thickness of over 8 m at the northern end of the North Sea Basin, and known informally as the Balder Tuff. This ash unit is an important marker throughout the North Sea as it produces a distinctive gamma or sonic bow on well logs. The total ash thickness declines toward the south-east, but ashes are found as far away as southern England, Germany and Denmark. The ashes are of theoleiitic-basalt composition and were probably erupted from a large volcano, somewhere along the North Atlantic rift, north-west of Britain.