A lithostratigraphical framework for onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain and the Isle of Man

Abstract

This report presents the proposed BGS lithostratigraphical framework for the onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain (England, Scotland and Wales) and the Isle of Man. The objective of the report is to provide a practical framework to aid future Quaternary correlation, mapping and research, and a stratigraphical scheme capable of use in a wide variety of applications. An overview of the framework was published by McMillan et al. (2005). A framework that utilises the full hierarchy of the stratigraphical code (supergroup, group, subgroup, formation and smaller units) is proposed. Although the framework is built around the formation, the primary unit for mapping and correlation, it is recommended that some classes of lithogenetically-defined deposits are not accorded formational status. However, at group level the scheme embraces all Quaternary and Neogene (Tertiary) superficial deposits, thus enabling a coded lithostratigraphical superscript to be applied to every Quaternary map symbol defined in the BGS Specifications for the preparation of 1:10 000 scale geological maps (Ambrose, 2000). The map specifications are based upon the lithogenetic classification of Quaternary deposits, as outlined in BGS Rock Classification Scheme (RCS) for artificial and natural superficial deposits (McMillan and Powell, 1999). In parts of Great Britain lithostratigraphical mapping at formation level can be regarded only as a long-term objective. Products such as lithostratigraphical maps, cross-sections and three-dimensional models may therefore be regarded as an evolving layer in the geological model. The unified lithostratigraphical framework for onshore Quaternary deposits is designed to be of use for regional mapping and correlation and may also be of relevance for regional hydrogeological and geotechnical applications. For example the lithostratigraphical classification can be used to enhance geological and hydrogeological domains maps and models depicting landform–sediment associations (McMillan et al., 2000). The current report is based upon a review of published literature (including BGS geological maps and reports), and expert local knowledge. Extensive reference is made to the Geological Society (London) Special Report No. 23 — A revised correlation of Quaternary deposits in the British Isles (Bowen, 1999)