The BGS Lexicon of Named Rock Units — Result Details

Cornbrook Sandstone Formation

Computer Code: COS Preferred Map Code: CoS
Status Code: Full
Age range: Pendleian Substage (CE) — Arnsbergian Substage (CG)
Lithological Description: Comprises conglomerate and pebbly quartzitic sandstones, coarse- to fine-grained. The sandstones are orange or brown, locally stained red, and thick-bedded. Thin mudstone beds, bluish grey or green. locally red, with seatearths and thin coals. The base of the formation comprises of a massive conglomerate with clasts up to 25 cms in diameter of quartz and quartzite, and subordinate slate, with sandstone from the Old Red Sandstone Group, and Dinantian limestone.
Definition of Lower Boundary: The pebbly sandstones of the Cornbrook Sandstone Formation are considered to rest unconformably upon limestones of the Oreton Limestone Formation at the type locality of Cornbrook Dingle, although the exposed contact is faulted, and upon the Devonian St Maughans Formation (Lower Old Red Sandstone Group at the reference section in Benson's Brook.
Definition of Upper Boundary: At Benson's Brook, the boundary has been considered to occur where thick seatearths and sandstones of the Pennine Coal Measures Group rest unconformably upon thick sandstones and conglomerates of the Cornbrook Sandstone Formation (Dixon, 1917). In contrast, the boundary has been argued to be faulted at this locality (Jones and Owen, 1961).
Thickness: From 55m to 215m
Geographical Limits: The Clee Hills area of Shropshire [SO 60 75].
Parent Unit: Millstone Grit Group [See Also MIGR] (MG)
Previous Name(s): Cornbrook Sandstone (-2715)
Millstone Grit (-2071)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Stream section at Cornbrook Dingle [SO 602 758 to SO 604 755], south of the Ludlow-Cleobury Mortimer road (A4117): about 215 m thick succession, base faulted, top not seen. Jones and Owen, 1961. 
Reference Section  Benson's Brook, on the southern slopes of Titterstone Clee, which displays a complete thickness of 55 m, including the base and the top of the unit. Jones and Owen, 1961. 
Reference(s):
Dixon, E E L. 1917. The geology of the Titterstone Clee Coal Field. Transactions of the Royal Society of Edinburgh, Vol.51, 1064-1071. 
Turner, N and Owens, B. 1993. Palynological evidence for an early Namurian age of the Cornbrook Sandstone Formation. Proceedings of the Yorkshire Geological Society, Vol.49, 189-196. 
Dixon, E E L. 1910. The geology of the Titterstone Clee Hills. Geological Magazine, Vol.7, 458-460. 
Jones, D G and Owen, T. 1961. The age and relationship of the Cornbrook Sandstone. Geological Magazine, Vol.98, 285-294. 
Cleal, C and Thomas, B A. 1996. British Upper Carboniferous stratigraphy. Geological conservation review series No. 11. [London: Chapman and Hall]. 
Dixon, E E L. 1911. The geology of the Titterstone Clee Hills. Report of the British Association (for 1910), 611-613. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E166 E181