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| Old Red Sandstone continent | |
|---|---|
| Name | Old Red Sandstone continent |
| Period | Devonian |
| Type | former continent |
| Notable basin | Orcadian Basin, Old Red Sandstone Supergroup |
| Orogenies | Caledonian orogeny |
| Lithology | sandstone, conglomerate, shale, siltstone |
Old Red Sandstone continent is an informal palaeogeographic term for the landmass represented by the widespread Devonian Old Red Sandstone deposits across northern Europe and beyond. The term connects sedimentary basins and structural features exposed in regions such as Scotland, Norway, Greenland, and eastern North America, and is central to understanding the Devonian stratigraphic record, the Caledonian orogeny, and the evolution of early tetrapods and vascular plants. Research on the continent interweaves work by figures like Roderick Murchison, Adam Sedgwick, and institutions such as the British Geological Survey.
The Old Red Sandstone continent developed in the wake of the Caledonian orogeny and the closure of the Iapetus Ocean, forming a peneplain and intramontane basins across Laurentia, Baltica and Avalonia sutured during the Late Silurian–Early Devonian collisions. Continental interiors and foreland basins accumulated thick non-marine sequences deposited in fluvial, lacustrine and alluvial-fan systems tied to post-orogenic subsidence and regional flexural loading related to the Variscan orogeny to the south and the continuing influence of the Proto-Atlantic margins. Tectonic frameworks recognized by mapping campaigns of the Geological Survey of Norway and the United States Geological Survey link basin architectures from the Midlothian and Shetland basins to exposures in East Greenland and the Gaspé Peninsula.
Stratigraphic successions within the Old Red Sandstone realm include formations and groups such as the Old Red Sandstone Supergroup in Britain, the Gedinnian–Frasnian sequences in Norway, and coeval units in Newfoundland and Spitsbergen. Lithologies are dominated by red-bed sandstones, conglomerates and siltstones with intervening shales and local volcanic units, recording syndepositional faulting, braided-river channels and playa deposits. Key local stratotypes include the Kirkton Formation, the Burray Sandstone Formation, and the Oxburgh Beds, each correlated through biostratigraphy using fossils studied by paleontologists affiliated with institutions like the Natural History Museum, London and the Smithsonian Institution.
Palaeogeographic reconstructions place the Old Red Sandstone continent at low to mid-latitudes during the Devonian, adjacent to Laurentia and Baltica within the equatorial to subtropical belt described in syntheses by Alfred Wegener-inspired plate models and later refined by researchers at the Paleomap Project. Strike-slip faulting, basin inversion and thermal subsidence produced isolated lacustrine depocentres such as the Orcadian Basin and the Garth Basin; these link with margins exposed in Scandinavia, Shetland, Iceland and the Canadian Shield through paleomagnetic and structural studies conducted by teams from Uppsala University and the University of Edinburgh.
Devonian climates recorded by Old Red Sandstone facies span semi-arid to seasonal humid regimes, inferred from palaeosol profiles, evaporite pseudomorphs and sedimentary cyclicity studied by researchers at the University of Cambridge and the University of Aberdeen. Fluvial architecture and channel-fill deposits indicate high-energy braided systems, whereas laminated lacustrine shales and dolomitic horizons preserve low-energy freshwater basins analogous to modern closed basins studied by ecologists at the Royal Society. Palynological and isotope studies published in journals associated with the Geological Society of London and the International Union of Geological Sciences constrain Devonian atmospheric oxygen and carbon dioxide trends that influenced terrestrialization events documented by field teams from the University of Oslo and the University of St Andrews.
Fossil assemblages in Old Red Sandstone deposits include iconic Devonian fishes such as Dunkleosteus-grade arthrodires, sarcopterygians like Eusthenopteron, early tetrapodomorphs including Ichthyostega-grade forms, extensive rhyniophyte and progymnosperm floras, and freshwater invertebrates documented in collections at the Natural History Museum, London, the National Museum of Scotland and the Canadian Museum of Nature. Vertebrate and plant fossils from locales like Scotland’s Midland Valley, Møre district, East Greenland and Newfoundland underpin models of early terrestrial ecosystems and colonization pathways explored by researchers affiliated with the Royal Society of Edinburgh and the Smithsonian Institution. Trace fossils, including tetrapod trackways, and microfossil assemblages inform palaeobiogeographic links with contemporaneous faunas in Laurentia and Avalonia.
Old Red Sandstone units have provided building stones used historically in urban centres like Edinburgh and Bergen, and are reservoirs for groundwater exploited by communities documented in regional planning archives such as those of the Ordnance Survey. Conglomerates and sandstones host local aggregate and dimension-stone quarries operated by firms registered with national bodies like the British Standards Institution, while organic-rich shales and isolated coalified horizons have been evaluated for hydrocarbon potential in basin studies by the Norwegian Petroleum Directorate and the Geological Survey of Canada. Geotourism and heritage designations managed by agencies including Historic Environment Scotland and Riksantikvaren highlight Old Red Sandstone landscapes.
The study of Old Red Sandstone sequences shaped 19th-century geology through debates between geologists such as Roderick Murchison and Adam Sedgwick and later syntheses by workers including Charles Lapworth and Archibald Geikie, influencing stratigraphic principles codified by the International Commission on Stratigraphy. Twentieth- and twenty-first-century research integrating sedimentology, palaeontology and plate tectonics has been driven by universities and surveys including the University of Cambridge, the University of Oxford, the British Geological Survey, Uppsala University and the Smithsonian Institution. Ongoing multidisciplinary projects funded by bodies like the Natural Environment Research Council and the European Research Council continue to refine models of Devonian terrestrialization, basin evolution and global biotic transitions recorded in Old Red Sandstone successions.