Computer Code: |
TRK |
Preferred Map Code: |
TRk |
Status Code: |
Full |
Age range: |
Turonian Age (KT)
— Coniacian Age (KO) |
Lithological Description: |
Hard cream limestone with scattered brownish phosphatic nodules commonly green-coated at the top. Mineralised hardground or chalkstone bed. |
Definition of Lower Boundary: |
The base is conformable within the Kensworth Nodular Chalk Member at an indistinct boundary marking a significant increase in nodularity between 2 and 3 m above the uppermost hardground of the Chalk Rock Member. |
Definition of Upper Boundary: |
The upper boundary is conformable at the hardground surface marked by the change from mineralised hard chalkstone to soft white smooth chalk. |
Thickness: |
0.8 to 1.0 m in Cambridgeshire. 0.3 m to 1.0 m in to Chilterns, to which areas it is essentially confined. |
Geographical Limits: |
The Chilterns within Hertfordshire and possibly Buckinghamshire. |
Parent Unit: |
Kensworth Nodular Chalk Member (KNCK)
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Previous Name(s): |
none recorded or not applicable
|
Alternative Name(s): |
none recorded or not applicable
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Stratotypes: |
Reference Section |
Quarry faces at Kensworth (Leighton Buzzard). The full succession through the underlying Chalk Rock Member to 5m above the Top Rock Bed is visible. See Shephard Thorn et al. (1994). |
Type Section |
Uppermost quarry face in the Reed Pit near Royston in Cambridgeshire. The full succession of the bed is visible. |
Reference Section |
Quarry faces at Hitch Wood Hill End (Hitchin). See Hopson et al. (1996, p.55, Figure 17). |
Reference(s): |
Penning, W H and Jukes-Browne, A J, 1881. Geology of the neighbourhood of Cambridge. Memoir of the Geological Survey, Old Series Sheets 51SW and part 51NW (England and Wales). |
Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp. ISBN 0 852725175 |
Bromley, R G and Gale, A S. 1982. The lithostratigraphy of the English Chalk Rock. Cretaceous Research, Vol.3, 273-306. |
Hancock, J M. 1989. Sea-level changes in the British Region during the late Cretaceous. Proceedings of the Geologists' Association, Vol.100, 565-594. |
Brighton, A G. 1928. Notes on the Middle and Upper Chalk of the Cambridge District. Geological Magazine, Vol.65, 368-371. |
Worssam, B C and Taylor, J H. 1969. The geology of the country around Cambridge. Memoir of the Geological Survey of Great Britain, Sheet 188 (England and Wales). |
Hopson, P M, Aldiss, D T and Smith, A. 1996. The geology of the country around Hitchin. Memoir of the British Geological Survey, Sheet 221 (England and Wales). |
Shepard-Thorn, E R, Moorlock, B S P, Cox, B M, Allsop, J M and Wood, C J. 1994. Geology of the country around Leighton Buzzard. Memoir of the British Geological Survey, Sheet 220 (England and Wales). |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E206
E220
E221
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