The BGS Lexicon of Named Rock Units — Result Details

Nethybridge Psammite Formation

Computer Code: NETH Preferred Map Code: NETH
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Pale to dark grey, buff weathering, flaggy, feldspathic psammite, with subsidiary micaceous psammite, semipelite and quartzite. Locally more micaceous in parts and also contains thick quartzite beds. Lenticular calc-silicate pods widespread but not abundant in the psammites.
Definition of Lower Boundary: Presumed gradational boundary with underlying siliceous psammites, quartzites and graded psammites, semipelites and pelites of Pityoulish Formation.
Definition of Upper Boundary: Grades upwards and laterally into siliceous psammites and quartzites of the Knockando Quartzite Formation, and into psammite and quartzite members of the Tormore Psammite Formation.
Thickness: 2000 to 5000m
Geographical Limits: In a large, irregular triangular area of the Abernethy Forest and the Spey Valley around Cromdale. To the northwest the formation extends across the Ericht - Laidon Fault (Spey Valley) and terminates against the Grampian Shear Zone and the Grantown Pluton (granite). To the south it is underlain by the Pityoulish Formation that crops out east of Loch Pityoulish and on Craigowrie and Meall a' Bhuachaille Hills. It is also truncated by the Cairngorm Pluton and to the east passes up into higher units of the Grampian Group in the Water of Ailnack section, the Braes of Abernethy and the Haughs of Cromdale.It is probably equivalent to the Coylumbridge Formation to the southwest. To the northeast it passes laterally into a thicker succession that includes much of the Dallas Psammite Formation, the Knockando Quartzite Formation, and parts of the Tormore Psammite Formation (the Rynaballoch Psammite Member and parts of the Cromdale Hills Quartzite Member).
Parent Unit: Grampian Group (GRAM)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  River Dulnain, north side of roadbridge. [Highton, 1999]. 
Reference Section  Large quarry close to Broomhill House. [Highton, 1999]. 
Highton, A J, 1999. Solid geology of the Aviemore district, Memoir for 1:50000 geological sheet 74E [Scotland]. London: The Stationery Office. 97pp. 
Mendum, J R and Stephenson, D. In preparation. Geology of the Glenlivet and Glenbuchat district. Memoir of the British Geological Survey, Sheets 75W and 75E. (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S074 S075