In the Cretaceous period sea levels rose globally and much of low-lying Scotland was covered by a warm shallow sea. Within these seas thick layers of chalk were laid down, up to 1400 metres in the central North Sea. 

Although much of Scotland was covered in this layer of sediment and chalk most of these rocks were eroded during the later Tertiary and Quaternary periods. Today only very small outcrops of Cretaceous rocks occur in Scotland. Marine Upper Cretaceous sediments are found on Mull and at Morvern, where 13 m of Cenomanian green sands are overlain by 8 m of pure white sandstone. These pure quartz sands are mined at Loch Aline for high quality glass sand.

At the end of this period the Cretaceous-Tertiary extinction occurred when 65% of all life on Earth was extinguished

The bull's eye marks the location of the Chicxulub impact site.   The impact of a 10 mile wide comet caused global climate changes that killed the dinosaurs and many other forms of life.  By the Late Cretaceous the oceans had widened, and India approached the southern margin of Asia. The approximate position of Scotland is indicated by Red Arrow. [Copyright C.R. Scotese, Paleomap Project]

The K/T Extinction