At this stage, the coal swamps of the north-western shore of the island had subsided below the sea so that the Kellaways clay was formed in fairly deep water and the Kellaways sand was blown and washed from what had become the hot desert land.
As the coal swamps on the northern shore of the island receded, they were replaced by the formation of Kellaways clay in deeper waters. The Kellaways sand was then transported to the now-arid land that had become a desert.