Between 15 and 30 degrees latitude north and south of the equator lie the majority of the world’s deserts. Arran drifted through a similar latitude between 290 and 250 Ma years ago during the Permian.

Wind blown sediment and sediment deposited by flash floods are typical of the desert environment. The latitude alone was not the sole reason for the desert like climate on Arran during the Permian; the supercontinent Pangea had a more or less contiguous ring of mountains around its outer margins. This helped to restrict the movement of moisture laden air into the continental interior. For nearly forty Ma years Britain was a desert just like sub-Saharan Africa is today

Great dunes of wind blown sand moved across Arran, creating a vast and desolate landscape. Flash floods would cause more violent movements of sediment, and the dune sands are often interbedded with breccias. The finest example of aeolian sandstone can be seen at the Corrie shore (NR 963518) overlying the Coal Measures of the Carboniferous. These rock exposures demonstrate the large scale cross bedding associated with dune sandstones.

If examined with a hand lens, one may note that the grains of sand are exceptionally rounded and smooth. They also have a frosted texture, gained through the constant reworking of the sediment by the wind.