Computer Code: |
CHOS |
Preferred Map Code: |
ChO |
Status Code: |
Full |
Age range: |
Aptian Age (KP)
— Aptian Age (KP) |
Lithological Description: |
Very fine-grained, poorly sorted, glauconitic sand with some beds of medium-grained sand, more clayey sands and thin ferruginously cemented beds. |
Definition of Lower Boundary: |
The lower boundary is unconformable on various Jurassic formations. |
Definition of Upper Boundary: |
The upper boundary is marked by the upward change from sand to extremely clayey glauconitic sand and sandy clay of the Bedchester Sands Member, or, in its absence, to the sandy clay of the Gault. |
Thickness: |
Between 0 and about 10 m. |
Geographical Limits: |
Across the northern part of the Shaftesbury Sheet (313), southeastern part of the Wincanton Sheet (297) and onto the Salisbury Sheet (298), beyond which it has not been mapped to date. |
Parent Unit: |
Folkestone Formation (FO)
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Previous Name(s): |
none recorded or not applicable
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Alternative Name(s): |
none recorded or not applicable
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Stratotypes: |
Type Area |
There is an extensive outcrop between Child Okeford and Bedchester. |
Reference Section |
Old sandpit, north of Piper's Mill, Bedchester (Jukes-Browne, 1891). Where most of the member may be seen. See Bristow et al. (1995, 93-94). |
Reference Section |
Borehole (ST 81SW/22) 600m north of Child Okeford Church (4.4 - 8.6m). Shows a full local succession of the member. Bristow et al. (1995, p.93). |
Reference(s): |
Bristow, C R, 1991. Geology of Sheet ST 81 (Shillingstone-Compton Abbas, Dorset). British Geological Survey Technical Report WA/91/03. |
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales). |
Hopson, P M, Wilkinson, I P and Woods, M A. 2008. A stratigraphical framework for the Lower Cretaceous of England. British Geological Survey. British Geological Survey Research Report, RR/08/03. |
White, H J O. 1923. The geology of the country south and west of Shaftesbury. Memoir of the Geological Survey of Great Britain, Sheet 313 (England and Wales). |
Jukes-Browne, A J, 1891. Notes on an undescribed area of Lower Greensand or Vectian in Dorset. Geological Magazine, (3), Vol.8, p.456-458. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E313
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