The BGS Lexicon of Named Rock Units — Result Details
Middle Devonian Slates
| Computer Code: | MDVS | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Mid Devonian Epoch (DM) — Mid Devonian Epoch (DM) | ||
| Lithological Description: | Very variable over the area of outcrop, and within local areas. The cleaved mudstones (shales) are generally light to dark grey in colour with a greenish tinge in many districts, and everywhere weathering buff or buff-green. Commonly calcareous, especially in the upper part; absence of micaceous shales and sandy shales dintinguish them from the Lower Devonian shales. At Hope's Nose (near Torquay), a thickness of approximately 61 m of shales are seen above Lower Devonian grits and thin-bedded limestones at the top of the cliff. At Mudstone Sands, south of Berry Head, 60m of shales are overlain by limestone. | ||
| Definition of Lower Boundary: | Commonly a thrust contact with a variety of other Devonian and Carboniferous rock types. | ||
| Definition of Upper Boundary: | Commonly a thrust boundary, juxtaposing the mudstones against other Devonian and Carboniferous rock types. Seen at some localities to be overlain by limestone; transition is gradual with calcareous mudstones common towards the top of the sequence. | ||
| Thickness: | Not known. | ||
| Geographical Limits: | In a band of varying width, trending approximately east-west across south Devon and Cornwall: from Newton Abbot (in south Devon) [SX 8582 7166] to Trevose Head (on the north Cornwall coast) [SW 8474 7630]. Modern nomenclature includes rocks of Middle Devonian age - see 'alternative names' section. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | none recorded or not applicable | ||
| Alternative Name(s): | Trevose Slate Formation [Obsolete: use SAH] Bedruthan Formation Rosenum Formation Saltash Formation Nordon Slate Formation [Obsolete: use NOSL] |
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| Stratotypes: | |||
| none recorded or not applicable | |||
| Reference(s): | |||
| Ussher, W A E. 1903. The Geology of the country around Torquay. Explanation of sheet 350. Memoirs of the Geological Survey. | |||
| Ussher, W A E, by Lloyd, W. 1933. The Geology of the country around Torquay. Explanation of sheet 350. Memoirs of the British Geological Survey. | |||
| Ussher, W A E. 1912. The Geology of the country around Ivybridge and Modbury. Explanation of sheet 349. Memoirs of the Geological Survey. | |||
| Ussher, W A E, Barrow, G and MacAlister, D A. 1909. The Geology of the country around Bodmin and St. Austell. Explanation of sheet 347. Memoirs of the Geological Survey. | |||
| Reid, C, Barrow, G and Dewey, H. 1910. The geology of the country around Padstow and Camelford. Explanation of sheets 335 and 336. Memoir of the British Geological Survey, England and Wales. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E350 | |||