The BGS Lexicon of Named Rock Units — Result Details

Middle Coldwell Beds [Obsolete Name And Code: Within CDW]

Computer Code: MCW Preferred Map Code: MCw
Status Code: Index Level
Age range: Homerian Age (SH) — Gorstian Age (SG)
Lithological Description: Consists of variable proportions of fine-grained, blue-grey, calcareous siltstones with interbedded laminated siltstone and silty mudstone. The calcareous divisions form pronounced ridges with marked cleavage.
Definition of Lower Boundary: Taken at base of calcareous siltstones overlying coarse siltstones or fine-grained sandstones of the Lower Coldwell Beds.
Definition of Upper Boundary: Transitional, taken at incoming of non calcareous laminated siltstones of the Upper Coldwell Beds.
Thickness: c. 30 metres, at type section, lateral variation (+-) 10 metres.
Geographical Limits: Not defined.
Parent Unit: Windermere Supergroup (WIN)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Coldwell, near Hawkshead, Cumbria, Sheet 38 (Ambleside). 
Reference(s):
Marr, J E. 1878. On some well defined Life Zones in the lower part of the Silurian (Sedgwick) of the Lake District. Quarterly Journal of the Geological Society, Vol.34, p.871-885. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E039