The Old Red Sandstone of Britain and Ireland : a review

The Old Red Sandstone (ORS) is an informal term which is given to continental, predominantly siliclastic, strata of late Silurian to early Carboniferous age which were deposited across the continent of Laurussia at sub-tropic to tropical latitudes. The coincidental development of land plants had a major impact on the atmosphere and global climate by lowering atmospheric carbon dioxide levels, which profoundly affected the style of alluvial sedimentation during this interval, by stabilising flood plains and facilitating the development of soils. The ORS also provides examples of syn- to post-orogenic deposition related to the Caledonian Orogeny, which was affected by synchronous tectonism and volcanism. The influence of Variscan tectonics on basin deformation and tectonism is also evident in the ORS sequence. In October 2014, a symposium was held, organised by the South Wales Geologists’ Association, entitled The Old Red Sandstone: is it Old, is it Red and is it all Sandstone? The event consisted of talks and posters on topics associated with the Old Red Sandstone deposits, principally of Wales and the Welsh Borders and the Scottish Borders in the UK, and included a series of field trips. Seven of the speakers have contributed manuscripts which are presented in this volume. These include papers discussing fossil fish and plant assemblages, the Fforest Fawr Geopark, Old Red Sandstone building stones, and soft sediment deformation. A brief report on the event and acknowledgements is also included.