All users are advised that our latest digital mapping is available to view via our onshore GeoIndex and offshore GeoIndex pages and may differ significantly from the maps delivered via this portal. Further details about our digital vector data mapping is available via BGS Geology datasets. Alternatively, users can request this data via GeoReports or our custom 1:50 000 geological maps service.
Basic-scale geological mapping was recorded in the field using 1:10 560 or 1:10 000 Ordnance Survey base maps cut up to fit a standard field-mapping case. While mapping was undertaken at this scale, the published output was primarily the one-inch 1:50 000 geological maps. A small number of maps for key areas, such as London and the coalfields maps, were printed and published; however, the majority of maps at 1:10 560 and 1:10 000 are manuscript and remain unpublished. As public records, they were all made available at the various BGS offices around the country for public consultation.
The manuscript maps went though a long process. Initially drawn up by a field geologist, the maps would proceed through an approval process until a map was finally approved as a ‘Standard’ or ‘Clean’ (in Scotland) copy. The collection in the maps portal is the full range of maps held by BGS irrespective of approval status and so should not be regarded as the definitive geological maps.
Users should expect some variability between versions of the same map. The maps have been developed over an extended period of time, following an evolving range of survey working practices. The following points should be considered.
- Ordnance Survey base six-inch 1:10 000 map series sheet bounds: initially based on County Series and later New Series or New Meridian sheets, most maps since the late 1940s have been captured on the Ordnance Survey 1:10 560 or 1:10 000 sheets on National Grid sheetlines (a few areas continued on County Series sheets if National Grid topographic maps were not available)
- Many sheet areas have undergone revisions or partial revisions of the geology. These revisions were often created on separate sheets, but some sheets may contain multiple episodes of mixed generations of mapping
- Sheets may have undergone none, partial or full approval for publication (at the time of survey)
- A wide variety of physical formats and media are represented in the maps, from paper maps that were hand-coloured using watercolour paints, pencils or crayons to formally lithoprinted maps (either uncoloured or coloured). Some maps will be dyeline ‘masters’, photographic reproductions, electrostatic or digital plots
A more detailed account of the BGS 1:10 560 or 1:10 000 paper geological maps, with examples, can be found on Earthwise: BGS maps – their characteristics and history.