Permian and Triassic, Southern Uplands

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Stone, P, McMillan, A A, Floyd, J D, Barnes, R P, and Phillips, E R. 2012. British regional geology: South of Scotland. Fourth edition. Keyworth, Nottingham: British Geological Survey.

Introduction

Palaeogeographical reconstructions from the Ordovician to the Cretaceous. P912314.
Distribution of depositional environments across the south of Scotland and northern England during Permian and Triassic times. P912358.
Outcrops of Permian and Triassic strata in the south of Scotland and north-west England. P912359.
Correlation chart for the Permian and Triassic successions of the south of Scotland and north-west England. P912360.

Late in Carboniferous times, a major continental collision far to the south of southern Scotland produced the Pangaea supercontinent, and in the process drove the Variscan Orogeny. As a peripheral effect, the Carboniferous basins that had formed across southern Scotland and northern England were inverted, their strata uplifted, folded and faulted. The Permian Period commenced (at about 299 Ma) with the erosion of these strata, at a time when Britain lay, as a part of Pangaea, in tropical latitudes about 10 degrees north of the Equator (P912314e). Pangaea continued to drift slowly northward and by Triassic times (from about 251 Ma) the south of Scotland region had moved to about 30 degrees north. The palaeogeography is summarised in P912358. Desert conditions prevailed throughout this interval, creating depositional environments that included sandy dunefields, alluvial plains, ephemeral lakes and mudflats. There was localised volcanic activity early in the Permian, evidence for which is now best preserved in the Thornhill Basin.

Permian and Triassic continental clastic sedimentary rocks were formerly referred to the ‘New Red Sandstone’. Early descriptions of the ‘New Red Sandstone’ of the Dumfries Basin date back to the 1850s, with the desert red beds long known for their vertebrate trackway trace fossils. However the strata of southern Scotland lack biostratigraphically diagnostic fossils and so are difficult to date with any precision. Further, because the Permo-Triassic sedimentary basins in which they were deposited are tectonically and geographically isolated (P912359), a separate lithostratigraphical nomenclature has been established for each basin. For the exclusively Scottish basins these local schemes are now all included within the Stewartry Group. The large Carlisle Basin spans the border between southern Scotland and north-west England, and for this sequence the lithostratigraphy developed for the extensive English outcrop is extended across the border into the relatively small Scottish outcrop along the northern margin of the basin. Only general correlation is possible between the wholly Scottish and the trans-border successions (P912360).


Bibliography

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Brookfield, M E. 1978. Revision of the stratigraphy of Permian and supposed Permian rocks of southern Scotland. Geologischen Rundschau, Vol. 67, 110–149.

Brookfield, M E. 1979. Anatomy of a lower Permian aeolian sandstone complex, southern Scotland. Scottish Journal of Geology, Vol.15, 81–96.

Brookfield, M E. 1980. Permian intermontane basin sedimentation in southern Scotland. Sedimentary Geology, Vol. 27, 167–194.

Brookfield, M E. 2004. The enigma of fine-grained alluvial basin fills: the Permo-Triassic (Cumbrian Coastal and Sherwood Sandstone groups) of the Solway Basin, NW England and SW Scotland). International Journal of Earth Science (Geologischen Rundschau), Vol. 93, 282–296.

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Holliday, D W, Holloway, S, McMillan, A A, Jones, N S, Warrington, G, and Akhurst, M C. 2004. The evolution of the Carlisle Basin, NW England and SW Scotland. Proceedings of the Yorkshire Geological Society, Vol. 55, 1–19.

Holliday, D W, Jones, N S, and McMillan, A A. 2008 Lithostratigraphical subdivision of the Sherwood Sandstone Group (Triassic) of the north-eastern part of the Carlisle Basin, Cumbria, and adjacent parts of Dumfries & Galloway, UK. Scottish Journal of Geology, Vol. 44, 97–110.

Holloway, S. 1985. The Permian. 26–30 in Atlas of onshore sedimentary basins in England and Wales: post-Carboniferous tectonics and stratigraphy. Whittaker, A (editor). (Glasgow: Blackie and Son.)

McKeever, P J A. 1994. A new fossil vertebrate trackway from the Permian of Dumfries and Galloway. Scottish Journal of Geology, Vol. 30, 11–14.

Stone, P. 1988. The Permian successions at Ballantrae and Loch Ryan, south-west Scotland. Report of the British Geological Survey, Vol. 9, No 2, 13–18.