BGS classification of lithodemic units : a classification of onshore Phanerozoic intrusions in the UK

This report presents a classification of mapped onshore igneous intrusions of the UK that were emplaced during the Phanerozoic Eon, and which are represented in the BGS DiGMapGB-50 model and its equivalent in Northern Ireland. It represents the first significant step towards a comprehensive, unified classification of lithodemic units in the UK, to complement well-advanced efforts to produce a full classification of lithostratigraphical units (set out in the BGS Stratigraphical Framework report series). The structure of the classification and the procedure for assigning formal names to intrusive units follow the proposals of Gillespie et al. (2008). In that scheme, 34 different types of individual intrusions and groupings of intrusions are arranged in a hierarchical parent–child association spanning six formal ranks (Figure 1); Rank 1 is taken to be the ‘highest’ and Rank 6 the ‘lowest’. A further eight types of lithodemic unit are used to classify mapped units that consist mainly of intrusive rock but have a ‘mixed’ character, encompassing a significant proportion of non-intrusive rocks (Figure 1).