Geology of the Llanidloes area: Information sources

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This page is part of a category of pages providing a summary of the geology of the Llanidloes district (British Geological Survey Sheet 164).
Links to other pages in this category can be found at the foot of the page.

Authors: Wilson, D, Burt, C E, Davies, J R, Hall, M, Jones, N S, Leslie, A B, Lusty, P A J, Wilby, P R, and Aspden, J A.

Further geological information held by the British Geological Survey relevant to the district and adjoining areas is listed below. Searches of indexes to some of the collections can be made on the Geoscience Data Index (GDI) system, available online at BGS Catalogue of geological maps, books and data is available on request or may be viewed on the website. Maps and other publications may be purchased online ( or through the BGS sales desks, and can be consulted at the BGS libraries.

Enquiries concerning geological data for the district should be addressed to the Manager, National Geological Records Centre (NGRC), BGS, Keyworth. Geological advice should be sought from Geology and Landscape Wales, British Geological Survey, Columbus House, Greenmeadow Springs, Tongwynlais, Cardiff CF15 7NE, Tel: +44 (0)2920 521962. The BGS hydrogeology enquiry service (wells, springs and water borehole records) can be contacted via the BGS website or at Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX0 8BB. Tel: +44 (0)1491 838800. Fax:+44 (0)1491 692345.


Original 1:63 360 scale geological maps are out of print, but can be provided as facsimiles or can be consulted at the BGS library, Keyworth. Unpublished 1:25 000 scale geological maps, listed below, are available on request. Groundwater vulnerability maps are published by the Environment Agency from data commissioned from BGS and The Soil Survey and Land Research Centre, and are available from BGS sales desks and The Stationary Office (020 7873 0011).

Many BGS products and data are available in digital form under licensing agreement, details of which are available from the Intellectual Property Rights Manager, BGS, Keyworth. Digital datasets include those covering geochemistry, geophysics, geohazards, hydrogeology, borehole logs and mapping and allow the information to be used in GIS applications.

Geological maps

The district was originally surveyed at the scale of 1:63 360 by W T Aveline, H W Bristow, A C Ramsay and A R Selwyn, and published as part of Old Series sheets 56, 57, 59 and 60 in 1848 and 1850. The Central Wales Mining Field was surveyed at the 1:10 560 scale by O T Jones of the University of Wales in 1917–18, and part re-surveyed by D Williams in 1940. Small areas along the western and eastern margins of the sheet were surveyed at 1:10 560 scale by R Cave between 1965 and 1972. The southern margin of the sheet was surveyed at 1:10 000 scale By R Cave, J R Davies, C J N Fletcher, A J Reedman and R A Waters between 1986 and 1989 as part of the BGS Rapid Mapping Programme. The remaining area was surveyed at 1:20 000 scale in 2006 by J A Aspden, C E Burt, J R Davies, M Hall, N S Jones, A B Leslie, T H Sheppard, P R Wilby and D Wilson utilising previously published and unpublished data; the work was undertaken as part of the GeoCymru Project, supported by a grant from the Welsh Assembly Government.

1:1 500 000
Tectonic map of Britain, Ireland and adjacent areas, 1996.

1:625 000
Bedrock Geology of the UK: South Map, 2007.
Quaternary Geology: South Sheet, 1977.

1:250 000
52N 04W Mid Wales and Marches, Solid, 1990.
Geological Map of Wales (Solid Geology), 1994.

1:50 000
Sheet 164, Llanidloes, Bedrock and Superficial Deposits, England and Wales, 2009.

1:20 000, 1:10 000 and 1:10 560 The component BGS maps of the district at this scale are listed below, along with the surveyors’ initials and the dates of survey.

Map number Surveyor Dates
SN 87 CJNF, AJR, JRD 1986–89
SN 88 RC, JRD 1965, 2006
SN 89 RC, JRD, JAA 1965, 2006
SN 97 JRD, RAW 1986–89
SN 98 DW, NSJ, ABL 2006
SN 99 JAA, THS, JRD 2006
SO 07 RC, JRD, MH, CEB 1986–89, 2006
SO 08 RC, MH, CEB, 1986–9, 2006
SO 09 RC, PRW 1988, 2006

Geophysical maps

1:1 500 000
Earthquakes 1980–2008, British Isles and adjacent areas, 2009.

1:1 000 000
Gravity Anomaly Map, 48ºN-54ºN, 6ºW-0ºE, Southern Britain, 1998.
Magnetic Anomaly Map, 48ºN-54ºN, 6ºW-0ºE, Southern Britain, 2004.

1:625 000
Gravity Anomaly Map of the UK: South Sheet, 2007.
Magnetic Anomaly Map of the UK: South Sheet, 2007.

Hydrogeological maps

1:625 000
Sheet 1: England and Wales, 1977.

Groundwater vulnerability maps

1:100 000
Sheet 27: Dyfed, 1990.
Sheet 28: Powys 1990.

Geochemical atlases

1:250 000
Stream waters in Wales, 2000.
Stream sediment and soil: Wales, 2000.

Books, reports and other publications

Books, reports and other select publications relevant to the district are listed in the References.

Documentary collections

Records of boreholes and site investigations pertaining to the district are available for consultation at NGRC in BGS, Keyworth. Index information, including site references, is held in digital format and can be viewed through the GDI, available on the BGS website.

Material collections

Material collections from the district are available for inspection at BGS, Keyworth, and include petrological hand specimens, thin sections and fossils. Index data for petrological specimens and for fossils is listed in the Britrocks and Palaeosaurus databases, respectively. These may be searched through the GDI on the BGS website.

Geology of the Llanidloes area - contents