The BGS Lexicon of Named Rock Units — Result Details

Broom Formation

Computer Code: BROM Preferred Map Code: notEntered
Status Code: Full
Age range: Aalenian Age (JA) — Aalenian Age (JA)
Lithological Description: Pale grey to brown, coarse-grained, poorly sorted, conglomeratic sandstone with mudstone clasts. In some areas it is dominantly medium- to coarse-grained, often carbonate-cemented sandstone with carbonaceous streaks. Cross-bedding locally occurs. Sandy mudstone units with burrows, including Arenicolites, and ferruginous, and oolitic sandstones occur locally.
Definition of Lower Boundary: The Broom/Drake formational boundary is characterised by a gradational downward change from medium- to coarse-grained sandstones to mudstones. There is a down-section increase in gamma-ray values.
Definition of Upper Boundary: The upper boundary is marked by a downward change from very fine- to fine-grained sandstone (Rannoch Formation) to coarse grained or pebbly sandstone (Broom Formation). Where the Rannoch mudstone unit is present at the base of the unit, there is a down-section change from micaceous mudstones to coarse-grained sandstones. In some areas where Broom-like and Rannoch-type facies are interbedded, the top is taken at the top of the highest coarse-grained or pebbly sandstones. The upper boundary is always marked by a down-section decrease in gamma values.
Thickness: Up to c. 50 m.
Geographical Limits: East Shetland Basin, North Sea quadrants 2, 3, 210, and 211.
Parent Unit: Brent Group (BRNT)
Previous Name(s): Basal Sand (-5178)
Basal Sand Bed (-5179)
Broom Sub-Unit (-5180)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  North Sea well 211/19- 5 between 3250 and 3255.5.5 m below KB (Richards et al., 1993). 
Reference Section  North Sea well 2/05- 3 between 3447.5 and 3462.5 m below KB (Richards et al., 1993). 
Type Section  North Sea well 211/29- 3 between 2818 and 2829 m below KB (Deegan and Scull, 1977). 
Reference Section  North Sea well 210/24- 2 between 2228 and 2244.5 m below KB (Richards et al., 1993). 
Reference Section  North Sea well 211/11- 1 between 3139.5 and 3161 m below KB (Richards et al., 1993). 
Reference(s):
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. 
Bowen, J M. 1975. The Brent Oil-Field. In: Woodland, A W (ed.) Petroleum and the contineental shelf of North-West Europe, 353-361. [Heyden & Son, London] 
Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G (eds.). Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. 
Richards, P C. 1992. An introduction to the Brent Group: a literature review. In: Morton, A C, Haszeldine, R S, Giles, M R and Brown, S (eds.) Geology of the Brent Group. Special Publication of the Geological Society, London, No.61, 15-26. 
Giles, M R, Stevenson, S, Martin, S V, Cannon, S J C, Hamilton, P J, Marshall, J D and Samways, G M. 1992. The reservoir properties and diagenesis of the Brent Group: a regional perspective. In: Morton, A C, Haszeldine, R S, Giles, M R and Brown, S (eds.) Geology of the Brent Group. Special Publication of the Geological Society, London, No.61, 289-327. 
Brown, S, Richards, P C and Thomson, A R. 1987. Patterns in the deposition of the Brent Group (Middle Jurassic) UK North Sea. In: Brooks, J and Glennie, K W (eds.) Petroleum Geology of North West Europe, 899-913. [Graham & Trotman, London] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable