The BGS Lexicon of Named Rock Units — Result Details

Arnisdale Psammite Member

Computer Code: MAAP Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Psammite, commonly massive and thick-bedded, typically >50 cm, commonly brown to orange-brown. Commonly strongly recrystallised and lacking sedimentary structures. Locally cross-bedding and slump folds occur. Locally thin semipelite beds.
Definition of Lower Boundary: The Arnisdale Psammite Member locally forms the lowest member of the Lower Morar Psammite Formation: its lower boundary is relative sharp against the Basal Pelite Formation (MABP), or directly upon its basement formed by Lewisianoid Gneiss, typically of the Western Glenelg Gneiss (WGG).
Definition of Upper Boundary: The Arnisdale Psammite Member is stratigraphically overlain by the Rubha Ruadh Semipelite (MARRS) via a highly transitional contact of interbedded psammite and semipelite, indicating a broad fining upwards trend.
Thickness: none recorded or not applicable
Geographical Limits: The Arnisdale Psammite Member has been mapped and defined on the Knoydart peninsula, where it forms part of the local Morar Group sequence. The unit probably thins out to the south towards Morar. The unit also occurs on the northern side of Loch Hourn. It is currently not known how far to the NE the unit can be traced into Glenshiel and Kintail. It is also uncertain whether the Morar Group psammite near Glenelg are part of the Arnisdale Psammite Member (c.f. Ramsay & Spring, 1962).
Parent Unit: Lower Morar Psammite Formation (MALP)
Previous Name(s): Armisdale Psammite (-5240)
Main Striped Group (-5241)
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Peach, B N, Horne, J, Woodward, H B, Clough, C T, Harker, A and Wedd, C B. 1910. The geology of Glenelg, Lochalsh and the south-east part of Skye (Explanation of One-Inch Map 71). Memoir (Sheet) of the Geological Survey of Great Britain (Scotland). (Edinburgh: His Majesty's Stationery Office.) 206pp. 
Ramsay, J.G. and Spring, J., 1962. Moine stratigraphy in the Western Highlands of Scotland. Proceedings of the Geological Association, 73: 295-326. 
Richey, J.E. and Kennedy, W.Q., 1939. The Moine and sub-Moine series of Morar, Inverness-shire. Bulletin of the Geological Survey, Great Britain, 2: 26-45. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S071