The BGS Lexicon of Named Rock Units — Result Details

Drosgol Formation

Computer Code: DRF Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Hirnantian Age (OH) — Hirnantian Age (OH)
Lithological Description: Dark grey, brown to buff weathering, massive, homogenous mudstones with thick beds of sandstone locally, and evidence of penecontemporaneous slumping and dewatering.
Definition of Lower Boundary: Conformably overlies the Nant-y-Moch Formation, the boundary being either gradational or sharp, and taken at the point where thinly interbedded mudstones and sandstones give way to massive mudstones.
Definition of Upper Boundary: Taken at the top of the well bedded Pencerrigtewion Member, where it gives way to massive disturbed mudstones of the Bryn-glas-Formation, the boundary being gradational and apparently conformable, although likely to be a syndepositional slide plane.
Thickness: 290 to 405m
Geographical Limits: Not specified.
Parent Unit: Not Available (!)
Previous Name(s): Drosgol Beds (-4621)
Drosgol Grits (-4622)
Drosgol Group (-2765)
Alternative Name(s): none recorded or not applicable
none recorded or not applicable
Jones, O T. 1909. The Hartfell-Valentian succession in the district around Plynlimon and Pont Erwyd (north Cardiganshire). Quarterly Journal of the Geological Society of London, Vol.65, 463-536. 
Cave, R and Hains, B A. 1986. Geology of the country between Aberystwyth and Machynlleth. Memoir of the British Geological Survey, Sheet 163 [England and Wales]. [London: HMSO.]. 148pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: