An introduction to the South Wales Pennant Formation: its origin, outcrop and conservation

Abstract

In the South Wales coalfield the Pennant Formation is widely distributed and is responsible for controlling much of the landscape seen today. The typical scarp and slack features of the northern margin are complimented by central, relatively high plateau areas that are typically incised by substantial rivers and streams to form a complex network of valleys. The Pennant Formation of South Wales has been generally accepted as being composed of relatively monotonous sequences of coarse sandstone, with several thin uneconomic coal seams. This Pennant lithology is very different to that of the underlying Productive Coal Measures (Langsettian to middle Bolsovian) where the sequences are dominated by mudstones and thick coals deposited in extensive marginal swamp forests. The change was primarily due the northerly advancing Variscan causing uplift and erosion of the landmass to the south of the South Wales Coalfield Basin. Exposures of these strata are extensive and provide the ideal setting for the establishment of a UNESCO Geopark.