The BGS Lexicon of Named Rock Units — Result Details
Morte Slates Formation
| Computer Code: | MSL | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Frasnian Age (DR) — Famennian Age (DA) | ||
| Lithological Description: | Smooth silvery, greenish-grey and purplish grey slates. Locally silty with a few fine-grained sandstones and scattered thin, discontinuous limestones, which are most common in the lower part of the sequence and in the rocks at Morte Point [SS 4400 4545]. | ||
| Definition of Lower Boundary: | Junction with the underlying Ilfracombe Slates is seen clearly on the coast. The top beds of the Kentisbury Slates are comprised of silvery grey, smooth calcareous slates with current-bedded sandstones (at [SS 5021 4714]); the lowest beds of the overlying Morte Slates at [SS 4972 4720] are described as bluish grey or silvery grey slates which are commonly silty. The junction between the Kentisbury Slates and the overlying Morte Slates forms a clear topographical feature inland. | ||
| Definition of Upper Boundary: | Overlain by the Pickwell Down Sandstones. The top of the Morte Slate Formation is marked by a persistant keratophyric tuff band up to 8 m thick which is massive and strong where fresh, and forms a distinct topographic feature. The lower boundary is distinguished by change from the grey cleaved mudstones of the Morte Slates to the massive, slightly foliated fine- to coarse-grained tuff of the lower beds of the Pickwell Down Sandstones. | ||
| Thickness: | Between 600 to 1500 m. | ||
| Geographical Limits: | Along the north Devon coast from the south of Ilfracombe [SS 5009 4720] to south of Woolacombe [SS 4570 4312], and in a band inland trending WNW-ESE through Arlington [SS 6200 4100] across the Brendon Hills; outcrop terminates 1.5 km east of Baompton Ralph [ST 0840 3204], where the Morte Slates pass below Permian rocks. An outlier of Morte Slates exists to east around Broomfield [ST 2310 3220], with other small outliers to the north. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | Ilfracombe Slates
(IFSLS)
|
||
| Alternative Name(s): | Brendon Hill Beds Upper Morte Slate [Obsolete] Sticklepath Slate |
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| Stratotypes: | |||
| Type Area | Morte Point, north of Woolacombe. Edmonds et al., 1979. | ||
| Reference(s): | |||
| Weaver, T. 1838. Geological Relations of North Devon. Proceedings of the Geological Society, Vol. 2, 589. | |||
| Evans, J W. 1922. The geological structure of the country round Combe Martin. Proceedings of the Geologists' Association, Vol.33, 201-228. | |||
| Edmonds, E A, Whittaker, A, and Williams, B J. 1985. Geology of the country around Ilfracombe and Barnstaple. Memoir of the British Geological Survey, Sheets 277 and 293 (England and Wales). | |||
| Edmonds, E A, Williams, B J and Taylor, R T. 1979. Geology of Bideford and Lundy Island. Memoir of the Geological Survey of Great Britain, Sheets 292 with 275, 276, 291, and part of 308 (England and Wales). | |||
| Webby, B D. 1966. Middle-upper palaeogeography of north Devon and west Somerset, England. Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 2, pp 27-46. | |||
| Hicks, H. 1896. On the Morte Slates and associated beds in north Devon and west Somerset. Quarterly Journal of the Geological Society, London, Vol. 52, pp 254-272. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E277 | |||