The BGS Lexicon of Named Rock Units — Result Details

Chalk Rock Member

Computer Code: CKR Preferred Map Code: CkR
Status Code: Full
Age range: Turonian Age (KT) — Turonian Age (KT)
Lithological Description: Very hard chalk and chalkstone, some nodular, including mineralized hardground surfaces and marl seams.
Definition of Lower Boundary: The base is taken at the diffuse lower limit of cementation of the lowest bed of chalkstone at this level.
Definition of Upper Boundary: The upper boundary is taken where the Hitch Wood Hardground is developed, at the flint nodule horizon that marks the base of the overlying nodular chalk unit. In other areas, at the Pewsey Hill Hardground or the Ogbourne Hardground.
Thickness: About 0.5 m up to 4 to 5 m where fully developed.
Geographical Limits: Known throughout the Southern Province and in the Chiltern area of the Transitional Province, eastwards to south Norfolk. Noted at 55 sites throughout the "Transitional" and Southern provinces in Bromley and Gale (1982).
Parent Unit: Lewes Nodular Chalk Formation (LECH)
Previous Name(s): Chalk Rock Formation [Obsolete Name and Code: Use CKR] (-2702)
Chalk Rock [Obsolete Name and Code: Use CKR] (-2091)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Ogbourne Maizey. Old farm west of Ogbourne Maizey, 3 km north of Marlborough, Wiltshire. The six hardgrounds that make up the full succession are visible in this quarry within 5 m of section. 
Partial Type Section  (For Hitch Wood Hardground). Hitch Wood. Small roadside pit below Hill End Farm, near Hitch Wood, west of Stevenage, Herts. 
Reference(s):
Gale, A S, Wood, C J and Bromley, R G. 1987. The lithostratigraphy and marker bed correlation in the White Chalk (Cenomanian-Campanian) of southern England. Mesozoic Research, Vol.1, 107-118. 
Bromley, R G and Gale, A S. 1982. The lithostratigraphy of the English Chalk Rock. Cretaceous Research, Vol.3, 273-306. 
Whitaker, W. 1861. On the Chalk-Rock, the topmost bed of the Lower Chalk in Berkshire, Oxfordshire and Buckinghamshire. Quarterly Journal of the Geological Society of London, Vol.17, 166-170. 
Jukes-Browne, A J and Hill, W. 1904. The Cretaceous Rocks of Britain, Vol.3. The Upper Chalk of England. Memoir of the Geological Survey of Great Britain. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E175 E188 E189 E204 E205 E206 E220 E221 E237 E238 E239 E253 E254 E255 E327