Abstract Carboniferous rocks occupy much of the Midland Valley of Scotland, but are commonly obscured at surface by Quaternary deposits. The succession occupies an ENE-trending graben bounded by the complexes of the Highland Boundary Fault to the NW and the Southern Upland Fault to the SE. Onshore, the graben is about 90 km wide and extends some 150 km from the Ayrshire coast and Glasgow in the west to the Fife and East Lothian coasts in the east (Fig. 43). The basins within the graben are associated with a succession of Carboniferous rocks more than 6 km thick. The Highland Boundary and Southern Upland faults were active and helped to control sedimentation, initially during the Tournaisian as sinistral strike-oblique slip faults and subsequently in the Visean to Westphalian a regime of dextral strike-oblique slip deformation (Browne & Monro 1989; Ritchie et al. 2003; Underhill et al. 2008). Isolated exposures also occur on the Isle of Arran and at Machrihanish in Kintyre. The Midland Valley of Scotland was separated from basins to the south (Tweed and Solway Firth basins and the Northumberland Trough; see Chapter 13) by the Lower Palaeozoic rocks of the Southern Uplands Block, which formed a positive, mainly emergent area throughout the Carboniferous. However, this was breached during the Carboniferous by narrow NW-SE-trending basins, for example Stranraer and Sanquhar to Thornhill.