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.

Abstract Carboniferous rocks are now most extensively preserved in central Scotland, the Borders and the offshore areas east of Scotland. Preservation is patchy and successions are generally thin and incomplete in the offshore areas west of Scotland, the Highlands and Southern Uplands, which all tended to remain positive throughout much of the period. However, Carboniferous cover was formerly much more extensive than at present, as demonstrated by a series of isolated outliers with attenuated successions in the Western Highlands and Islands and the Southern Uplands. Most of the cover in these areas was stripped off during the latest Carboniferous uplift and erosion. The basal junction with the Upper Devonian is arbitrary, because it is drawn at the first appearance of calcareous soil profiles (calcretes) within an unfossiliferous fluvial and aeolian succession, but it is usually conformable and coincides with a widespread change to a slightly wetter climate (Paterson et al. 1990; and Chapter 8 ). Progressive overlap took place at various horizons including the early Carboniferous, the base of the Namurian and the Early Westphalian. Figure 9.1 shows Scotland and the adjacent offshore areas, with onshore Carboniferous outcrops, major structures and the principal localities mentioned in the text, and Figure 9.2 shows the onshore outcrops in central and southern Scotland in greater detail. Preserved Carboniferous strata tend to be thin in the west and thickest in the east, with thickening in local basins (Browne et al. 1985). Figure 9.3 shows the chrono- and lithostratigraphical divisions

Abstract Archibald Geikie played a fundamental, but largely unrecognized, role in the establishment of the Scottish oil shale industry by providing James ‘Paraffin’ Young with the critical information about the location, thickness and probable geographical extent of organic-rich shales during their field visit in 1858. Young subsequently used the observations to determine where to buy leases for commercial oil shale extraction and production before any competitors emerged. Geikie acquired his critical knowledge of the area whilst preparing the first map and memoir of the Edinburgh area published in 1859 and 1861, respectively. In 1866, Young’s Paraffin Light and Mineral Oil Company Limited opened the Addiewell works, the largest oil shale works in the world at the time. By the late 1860s, there were over 120 works distilling oil in Scotland, mostly from the shales of the Lothians. Eventually, more than 22 million gallons of crude oil a year were produced in the Midland Valley in an industry that employed c. 40 000 people. Although the Scottish oil shale industry eventually closed in the 1960s, Geikie’s legacy lives on through a better understanding of the geology of the Midland Valley and the renewed interest in extracting oil and gas from the shales buried beneath.

Abstract Following an adventitious oil flow into a coal mine in 1847 in the Riddings area of the county of Derbyshire in the English Midlands, the young Scottish chemist James Young carried out seminal work into the development of oil refining technology. In Derbyshire, by the end of 1848, he set up an early refinery to exploit this oil commercially by distillation, producing both lighting and lubrication fractions which he sold directly to end customers. His findings in Derbyshire led him to move on to investigate production and refining of oil from coal by destructive distillation, technology for which he gained his global reputation; Young’s patented technology was adopted by the commercial refineries that were to follow in many countries as the world’s oil fields sprang to life.

Abstract Twenty-one new 40 Ar/ 39 Ar step-heating experiments on mineral separates from intrusive and extrusive Carboniferous and Permian igneous rocks in the Midland Valley of Scotland yielded 17 concordant experiments with a relative age precision better than 1% (2σ). These ages resolve inconsistencies between existing K-Ar dates on the same samples and their stratigraphical constraints correlated to recently published timescales. The precise 40 Ar/ 39 Ar dates are stratigraphically constrained to stage level and can contribute to Carboniferous timescale tie points at the Tournaisian-Visean boundary, within the Visean and at the Carboniferous-Permian boundary. Situated in the extending Variscan foreland, two distinct phases of extension-related transitional-alkaline volcanism have been resolved in the Dinantian: the Garleton Hills Volcanic Formation in the eastern Midland Valley near the Tournaisian-Visean boundary, 342.1 ± 1.3 and 342.4 ± 1.1 Ma; and the Clyde Plateau Volcanic Formation in the western Midland Valley during the mid-Visean, 335 ± 2329.2 ± 1.4 Ma. Alkaline basic sills near Edinburgh, previously thought to be Namurian, appear to be coeval with the Clyde Plateau Volcanic Formation at 331.8 ± 1.3–329.3 ± 1.5 Ma. The new ages allow correlation between these short-lived Dinantian magmatic pulses and extensional and magmatic phases in the Northumberland-Solway and Tweed basins to the south. After late Westphalian, end-Variscan, compression and a regionally important tholeiitic intrusive phase at c. 301–295 Ma, alkaline magmatism related to post-Variscan extension occurred in the central and western Midland Valley during the latest Carboniferous or Permian from 298.3 ± 1.3 to 292.1 ± 1.1 Ma. This correlates well with post-Varsican extension and magmatism observed across the NW European foreland from 300 to 280 Ma.

Abstract Extensional tectonics to the north of the Variscan Front during the Early Carboniferous generated fault-controlled basins across the British Isles, with accompanying basaltic magmatism. In Scotland Dinantian magmatism was dominantly mildly alkaline–transitional in composition. Tournaisian activity was followed by widespread Visean eruptions largely concentrated within the Scottish Midland Valley where the lava successions, dominantly of basaltic–hawaiitic composition, attained thicknesses of up to 1000 m. Changing stress fields in the late Visean coincided with a change in the nature of the igneous activity; subsequently, wholly basic magmatism persisted into the Silesian. As sedimentary basin fills increased, sill intrusion tended to dominate over lava extrusion. In the Late Carboniferous (Stephanian) a major melting episode, producing large volumes of tholeiitic magma, gave rise to a major dyke swarm and sills across northern England and Scotland. Alkali basaltic magmatism persisted into the Permian, possibly until as late as 250 Ma in Orkney. Geochemical data suggest that the Carboniferous–Permian magmas were dominantly of asthenospheric origin, derived from variable degrees of partial melting of a heterogeneous mantle source; varying degrees of interaction with the lithosphere are indicated. Peridotite, pyroxenite and granulite-facies basic meta-igneous rocks entrained as xenoliths within the most primitive magmas provide evidence for metasomatism of the lithospheric mantle and high-pressure crystal fractionation.