Welded Tuffs in the Borrowdale Volcanic Series, English Lake District, with a Note on Similar Rocks in Wales

Abstract

Abstract Compact “streaky” rocks, from the Borrowdale Volcanic Series, English Lake District, are diagnosed in part as welded tuffs. Original glass is completely replaced, but similarity to welded tuffs elsewhere is shown by the dacitic-rhyodacitic composition, lack of bedding, and development of columnar jointing. The deposition of welded tuffs, as nuée ardentes, or incandescent tuff flows, is discussed.