The BGS Lexicon of Named Rock Units — Result Details

Hyner Mudstone Formation

Computer Code: HYMU Preferred Map Code: notEntered
Status Code: Full
Age range: Famennian Age (DA) — Tournaisian Stage (CT)
Lithological Description: Hard dark blue-grey or bluish green-grey, generally mottled, silty shales and mudstones. Calcareous bands and nodules, and calcareous shales and mudstones occur near the top, together with a calcareous siltstone (locally yielding trilobite and pelagic ostracod faunas). Within the metamorphic aureole of the Dartmoor Granite, calc-flints and hornfels are developed and siliceous nodules are characteristic of the lower parts of the Formation.
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: The upper boundary is taken at the gradational incoming of grey and green micaceous shales of the overlying Trusham Mudstone Formation above the dark blue or bluish green mottled shales and calcareous beds of the Hyner Mudstone Formation. Commonly this boundary cannot be detected in the metamorphic aureole of the Dartmoor Granite.
Thickness: 250m+
Geographical Limits: Middle Teign Valley (SX 84 85), eastern Dartmoor, south Devon.
Parent Unit: Not Applicable (-)
Previous Name(s): Hyner Shale Formation [Obsolete Name And Code: Use HYMU] (HYSH)
Hyner Formation (-3484)
Hyner Shale (-4719)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Road section (B3193) east of Christow, middle Teign valley, south Devon. 44m of locally fossiliferous mudstones in the uppermost part of the Formation; the boundary with the overlying Trusham Mudstone Formation is exposed. Selwood et al. 1984 
Reference(s):
Selwood, E B, Edwards, R A, Simpson, S, Chesher, J A, Hamblin, R J O, Henson, M R, Riddolls, B W and Waters, R A. 1984. Geology of the countryside around Newton Abbot. Memoir of the British Geological Survey, Sheet 339 (England and Wales). 
Chesher, J A, 1968. The succession and structure of the Middle Teign Valley. Proceedings of the Ussher Society, Vol.2, 15-17. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable