BGS Lexicon of Named Rock Units

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Dataset Description:

The BGS Lexicon of Named Rock Units is a database of almost 20,000 BGS definitions to terms that appear on BGS maps and publications.  The contents are dynamic and edited regularly as mapping progresses and knowledge of the rocks improves.  It is a replacement for the previous ‘BGS.Dic_Strat’ database/dictionary that was created to store unique codes on BGS paper maps.

Entries in the database include the following data fields:

  • Rock unit name
  • Rank, parent unit, and parent unit rank
  • Age and lithology
  • Lower and upper boundaries
  • Thickness
  • Geographical extent
  • Stratotypes

All entries also include a code to describe the level of information that is held:

  • Formal (F) and Informal (I) – fully defined (about 25% of all entries)
  • Partial (P) – some elements are lacking from a full definition
  • Code Pending (CP) – entries which are not yet defined
  • Code Only (C) – units not scheduled for definition

Searches can be undertaken by:

  • The name (or part name) of the rock unit
  • Computer code
  • Preferred map code
  • Maximum age of rock unit


Dataset Thumbnail:


Dataset Specification:

Product Name

BGS Lexicon of Named Rock Units

Data Provider

British Geological Survey (BGS)




Great Britain

Data Structure





Geological reference guide


BGS Licence

Update Frequency


Dataset Resources:

Product site