Abstract Carboniferous rocks within this region occupy a broadly east-west trending graben, referred to as the Northumberland Trough within Northumberland (Bewcastle to the North Sea coast) and the Solway Basin in the vicinity of the Solway Firth, where much of the succession is obscured by Permo-Triassic strata (Fig. 40). The graben is bounded to the south by the Maryport-Stublick-Ninety Fathom Fault System, which forms the northern boundary of the Lake District and Alston blocks (see Chapter 12). The Carboniferous rocks are broadly separated from the Midland Valley of Scotland (Chapter 14), to the north, by the Lower Palaeozoic rocks of the Southern Uplands, which formed an emergent upland area throughout much of the Carboniferous, with local deposition within small basins. At the eastern onshore extent of the Southern Uplands a relatively condensed Carboniferous succession was deposited upon the Cheviot Block. All of the regional stages of the Carboniferous are present at outcrop, though strata of Stephanian age have not been proved biostratigraphically. The oldest Tournaisian strata occur at outcrop along the northern margins of the Northumberland Trough-Solway Basin, represented by continental and peritidal deposits, typically separated by volcanic rocks (Inverclyde Group). These strata extend offshore in the North Sea (Chapter 15), linking directly with the outcrop of Inverclyde Group present within the Midland Valley of Scotland. In the Northumberland Trough-Solway Basin, the Inverclyde Group passes southwards into, and is overlain by, a lower to middle Visean heterolithic clastic and non-marine carbonate and fluvio-deltaic succession (Border Group).

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.