The BGS Lexicon of Named Rock Units — Result Details

Greenan Sandstone Formation

Computer Code: GNNS Preferred Map Code: GNNS
Status Code: Full
Age range: Brigantian Substage (CX) — Pendleian Substage (CE)
Lithological Description: Sandstone, purple-grey weathering distinctive orange-purple, medium- to coarse-grained, parallel and cross-laminations, thin layers of purple-red and green mudstone; basal breccia of metamorphic clasts.
Definition of Lower Boundary: Unconformable on Dalradian Supergroup metamorphic rocks
Definition of Upper Boundary: Not exposed, faulted out.
Thickness: At least 550m, probably to more than 1000m
Geographical Limits: The Milltown Segment of the Fintona Block and south side of Greenan Mountain, County Tyrone.
Parent Unit: Not Entered (?)
Previous Name(s): Greenan Formation (-937)
Alternative Name(s): none recorded or not applicable
Type Section  South flowing stream on the south side of Greenan Mountain. Exposes basal epiclastic breccia and succeeding sandstones with green mudstones clasts. 
Reference Section  Broad outcrop of Greenan Formation southeast of the Castle Archdale Fault, Long sections in the higher parts of the sandstone sequence are exposed in numerous northward-flowing streams. 
Type Area  Four small streams draining the south side of Greenan Mountain. Partial exposyre of the basal breccia, the lowest sandstones, and with all localities containing dateable green/blue mudstone horizons. 
Mitchell, W I and Owens, B, 1990. The geology of the western part of the Fintona Block, Northern Ireland: Evolution of Carboniferous basins. Geological Magazine, Vol.127 (5), 407-426. 
Simon, J B, 1984. Sedimentation and tectonic setting of the Lower Old Red Sandstone of the Fintona and Curlew Mountain district. Irish Journal of Earth Sciences, Vol.6, 213-228. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable