The BGS Lexicon of Named Rock Units — Result Details

Kersdown Chert Member

Computer Code: KSDC Preferred Map Code: notEntered
Status Code: Full
Age range: Asbian Substage (CR) — Brigantian Substage (CX)
Lithological Description: Dark grey to black laminated thin- to thick- bedded blocky cherts with interbedded shaly siliceous mudstones and a few partly silicified limestones. Scattered chert nodules occur within the limestones.
Definition of Lower Boundary: The lower boundary is taken at the incoming of abundant blocky chert with few limestones of the Kersdown Chert Member above the siliceous radiolarian shaly mudstones with some silicified limestones forming the lower part (Hayne Beech Beds) of the Bampton Limestone Formation.
Definition of Upper Boundary: The upper boundary is taken at the incoming of black shaly mudstones with limestones and minor cherts (Bailey's Beds), forming the upper part of the Bampton Limestone Formation, above the blocky cherts with few limestones of the Kersdown Chert Member.
Thickness: 7m
Geographical Limits: Between Brushford (SS 92 26) and Ashbrittle (ST 04 21), Somerset.
Parent Unit: Bampton Limestone Formation (BPLM)
Previous Name(s): Kersdown Beds (-2883)
Kersdown Chert Formation (-2884)
Middle Bampton Cherts (-3866)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Kersdown Quarry, Bampton, Somerset. The entire member, 7m thick, is seen, including lower and upper boundaries. 
Reference(s):
Whiteley, M J. 2004. Culm Trough. 477-504 in British Lower Carboniferous Stratigraphy. Cossey, P J, Adams,A E, Purnell, M A, Whiteley, M J, Whyte, M A and Wright, V P (editors). Geological Conservation Review Series, No 29. (Peterborough: Joint Nature Conservation Committee). 
Thomas, J M. 1962. The Culm Measures in north-east Devon. Proceedings of the Ussher Society, Vol. 1, 29-30. 
Webby, B D. and Thomas, J M. 1965. Whitsun field meeting: Devonian of west Somerset and the Carboniferous of north-east Devon. Proceedings of the Geologists Association, Vol. 76, 179-194. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable