Carboniferous 362-290 Ma ( Arran at the8 degrees North)

Carboniferous rocks reflect a time when tropical conditions prevailed with occasional igneous activity. Expansive shallow seas, deltas and swamps covered the Midland Valley of Scotland and repeated fluctuations in sea level gave rise to the Milankovitch cycles of sedimentation typified by the Period.

Arran, being on the edge of such a basin, has a variable thickness of Carboniferous rocks from the east to the west due to changes in rates of basin linked subsidence. Although better represented on the mainland, nearly 900m thickness of Carboniferous rocks on Arran can be seen in the northeast along the shore at Corrie. The first sandstones and conglomerates of the Period, known as the Kinneswood Formation, lie on the errosive base of the Old Red Sandtone. The famous locality at Hutton's unconformity, is where Carboniferous rocks of the Kinneswood Formation overly Dalradian Rocks (unconformity is shown above).

Moving south along the shore the basalt lavas and agglomerates of the Clyde Plateau Volcanic Formation eventually give way to the fossiliferous sandstones, organic rich mudstones and limestones for which the Carboniferous is so well known. Arran, however, does lack the coal measures so ubiquitous in the Carboniferous of the mainland. The only known coal on Arran outcrops on the shore at Laggan and was once mined for the production of salt.