The BGS Lexicon of Named Rock Units — Result Details

Brendon Formation

Computer Code: BREN Preferred Map Code: Bre
Status Code: Full
Age range: Visean Stage (CV) — Visean Stage (CV)
Lithological Description: Dark grey, locally siliceous, mudstone with laminae and thin beds of siltstone. Scattered packets of blue-grey to grey-green coarse grained greywacke sandstone with interbedded dark grey mudstone. There are locally distributed units of tuff and basaltic lava. As mapped and defined, this formation may include parts of previously contiguous and coeval formations. Further work is needed as this formation may represent a collection of mud-prone Dinantian lithologies brought together tectonically.
Definition of Lower Boundary: The lower boundary is not seen; all observed contacts are tectonic.
Definition of Upper Boundary: The upper boundary is not seen; all observed contacts are tectonic.
Thickness: 450m+, but more or less due to thrusting.
Geographical Limits: Launceston/St Mellion areas (SX 33 73), between Bodmin Moor and Dartmoor, east Cornwall.
Parent Unit: Teign Valley Group (TEVY)
Previous Name(s): Brendon Formation (BREN)
Lydford Formation (LYDD)
Greystone Formation [Obsolete Name And Code: Use BREN] (GSTN)
Culm Measures And Upper Devonian Slates (-1386)
Middle Culm Measures (-719)
Upton Wood Formation (-4491)
Alternative Name(s): Tredorn Slate Formation
Stratotypes:
Partial Type Section  Roadside exposures between Brendon Farm and Spur House, 3km southeast of Callington. Horizon of exposed beds within the Formation is unknown. Unpublished description in Whiteley (1983). 
Reference(s):
Reid, C, Barrow, G, Sherlock, R L, MacAlister, D A and Dewey, H, 1911. The geology of the country around Tavistock and Launceston. Memoir of the Geological Survey of Great Britain, Sheet 337 (England and Wales). 
Ussher, W A E, 1907. The Geology of the country around Plymouth and Liskeard. Memoir of the Geological Survey of Great Britain, Sheet 348 (England and Wales). 
Isaac, K P, 1983. The tectonic evolution of the eastern part of south-west England: Tectonothermal denudation and weathering histories. Unpublished PhD Thesis, University of Exeter. 
Stewart, I J, 1981a. The structure, stratigraphy and conodont biostratigraphy of the north eastern margin of Bodmin Moor and adjacent areas. Unpublished PhD Thesis, University of Exeter. 
Leveridge B E, Holder, M T, Goode, A J J, Scrivener R C, Jones N S and Merriman, R J. 2002. Geology of the Plymouth and south-east Cornwall area. Memoir of the British Geological Survey, Sheet 348 (England and Wales). 
Whiteley, M J. 1983. The geology of the St Mellion outlier, Cornwall and its regional setting. Unpublished PhD thesis, University of Exeter. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E335 E336 E337 E338 E348