Geological notes and local details for geological sheet SS91SE (Tiverton)

Abstract

This report describes and provides an initial interpretation of the bedrock and superficial geology of 1:10, 000 Geological Sheet SS 91 SE Tiverton (Devon). The geology of the area consists of Carboniferous sandstones and mudstones, which belong to the Bude Formation (Culm), in-turn these are unconformably overlain by Permian sandstone and breccias. The sandstone, typically a fine-grained sandstone or sandy mudstone, is informally called the ‘Tidcombe Sands’, whilst two breccias can be recognised and distinguished on the basis of clast morphology and lithology – the Chevithorne Breccia and Cadbury Breccia. Previous studies suggest that the ‘Tidcombe Sands’ and Chevithorne Breccia intercalate to the north of Tiverton, whilst present mapping to the south of the town reveals that the sands are also inter-digitated with the southern Cadbury Breccia, and the latter is derived from the southwest. Resting unconformably upon the Permian strata are thick accumulations of Palaeogene and Quaternary deposits. These include terrace deposits and alluvium associated with the rivers that drain the sheet, and a significant distribution of blanket head, regolith and colluvium