The BGS Lexicon of Named Rock Units — Result Details

Glen Effock Schist Formation

Computer Code: GES Preferred Map Code: SYMB
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Dominant semipelite, but with considerable psammite and pelite. Psammites micaceous but fairly massive, rarely gritty. Greenish feldspathic semipelite with high magnetic susceptibility and associated micaceous psammites locally abundant near the base of the Formation. Beds of white quartzite with specks of green mica occur, particularly near the top of the Formation. Calc-silicate rocks are extremely rare.
Definition of Lower Boundary: First incoming of dark, greenish, biotitic and feldspathic semipelite with layers showing high magnetic susceptibility at top of Tarfside Psammite Formation.
Definition of Upper Boundary: Gradational transition with incoming of muscovite-staurolite-schist and increase in proportion of gritty psammite and decrease in proportion of greenish feldpathic semipelite at base of overlying Glen Lethnot Grit Formation.
Thickness: Apparently 2500m thick in Greenburn - Colmeallie area (NO5578 to NO5977), but this figure is probably inflated by tectonic thickening.
Geographical Limits: Arcuate belt 4-5km wide in the southern parts of Sheets 65E and 66W from c. NO 3876 to NO 6280.
Parent Unit: Southern Highland Group (SOHI)
Previous Name(s): Glen Effock (Pelite) Group [Obsolete Name And Code: Use GES] (DCGE)
Glen Effock Schists (-280)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  For main lithologies: Crags on south side of Glen Effock (Easter Cruys, Mid Cruys, Wester Cruys and Craig of Corriedoune) with some exposure in Water of Effock. 
Type Area  For Craig Dullet lithology: Upper part of crags of Graig Dullet. 
Reference(s):
Harte, B, 1979. The Tarfside succession and the structure and stratigraphy of the eastern Scottish Dalradian rocks. "In" Harris, A L, Holland, C H and Leake, B E. Geological Society of London Special Publication No.8, p.221-228. 
Smith, C G, Goodman, S and Robertson S. 2003. Geology of the Ballater district. Memoir of the British Geological Survey, Sheet 65E (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S066 S065 S066