The BGS Lexicon of Named Rock Units — Result Details

Finstall Member

Computer Code: FNSTL Preferred Map Code: notEntered
Status Code: Full
Age range: Anisian Age (TA) — Anisian Age (TA)
Lithological Description: The dominant lithology is planar and trough cross-bedded, irregularly bedded and structureless, pale red-brown and greenish grey sandstones. Subordinate lithologies are red-brown and grey-green mudstone and siltstone. The sequence shows repeated fining-upward cycles, from sandstone to mudstone; there is commonly an intraformational conglomerate at the base of each cycle and the upper beds of sandstone are commonly parallel laminated. Sedimentary structures include ripple marks, flute casts, slump structures, mudcracks and convolute bedding. Micaceous bedding planes are common. Bioturbation occurs in the lower part of the member and plant remains and Euestheria have been found in the upper part in the reference section. Elsewhere the member has yielded acritarchs, miospores, plant remains, annelids, brachiopods, bivalves, Euestheria, ostracods, and remains of arachnids, fish, amphibians and reptiles.
Definition of Lower Boundary: The lower boundary is taken at the base of the cycle above the highest bed of extraformational conglomerate.
Definition of Upper Boundary: The upper boundary is taken at top of the highest significant (>1 m) bed of sandstone with large scale cross bedding.
Thickness: The thickest known sequence is 139.5 m, in the Sugarbrook No.3 Borehole; the minimum known thickness is 33.6 m, in the Longbridge Laundry Borehole [SP 0201 7847] (Powell et al., 2000).
Geographical Limits: The member has only been mapped in the Bromsgrove area of Worcestershire but is likely to extend westwards to Little Witley [SO 78 63], Worcestershire.
Parent Unit: Helsby Sandstone Formation (HEY)
Previous Name(s): Building Stones (-5112)
Alternative Name(s): none recorded or not applicable
Type Section  Disused quarry, Hadley, Worcestershire. 
Reference Section  Sugarbrook No. 3 Borehole. BGS Registered No. SO96NE/30, 67.3-206.8 m (Old et al., 1991). Scattered exposures in the Bromsgrove area, south and east of Kidderminster. 
Old R A, Hamblin, R J O, Ambrose, K, and Warrington G. 1991. Geology of the country around Redditch. Memoir of the British Geological Survey, Sheet 183 (England and Wales). 
Ambrose, K, Hough, E, Smith, N J P and Warrington, G. 2014. Lithostratigraphy of the Sherwood Sandstone Group of England, Wales and south-west Scotland. British Geological Survey Research Report, RR/14/01. 
Hull, E, 1869. The Triassic and Permian rocks of the Midland Counties of England. Memoir of the Geological Survey of Great Britain. 
Powell, J H, Glover, B W and Waters, C N. 2000. Geology of the Birmingham area. Memoir of British Geological Survey Sheet 168 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable