The Ludlovian and Downtonian Rocks of the Knighton District, Radnorshire

The Knighton district displays a thick “ basin facies ” succession of over 6000 feet of Ludlovian rocks, which has been divided into five groups. The Old Red Sandstone, above the basal Platyschisma helicites Beds, is divided lithologically into Yellow, Green, and Red Downtonian. Correlation is made with successions in other Welsh Borderland areas. Conditions of deposition of the Ludlovian rocks are considered. The Ludlovian succession shows two distinct faunas separated by a group of very poorly fossiliferous strata, apparently representing conditions unfavourable to the development of benthonic forms. Structurally the most notable feature is a disturbed belt some 3½ miles wide, which occupies the western part of the area. It comprises a set of NE.–SW. folds associated with strike-faulting and much fracturing. The belt can be traced north-eastwards and south-westwards considerably beyond the limits of the Knighton district.