The BGS Lexicon of Named Rock Units — Result Details

Barneil Member

Computer Code: BRNL Preferred Map Code: BRNL
Status Code: Full
Age range: Llanvirn Series (OE) — Caradoc Series (O4)
Lithological Description: Red bedded chert, associated with pillow lava.
Definition of Lower Boundary: The exact base of the Member is not clearly defined, as the cherts may be interbedded or overlie the lavas. An analogous situation is seen in the Marchburn Formation in the Northern Belt of the Southern Uplands, where lavas and cherts are interbedded with each other, and the cherts are similarly identified as late Llandeilo to early Caradoc, based on conodont evidence.
Definition of Upper Boundary: The lavas can be seen to be unconformably overlain by the Craighead Limestone Formation at Craighead Quarry.
Thickness: At least 50m
Geographical Limits: Craighead Inlier, Girvan.
Parent Unit: Craighead Volcanic Formation (CRV)
Previous Name(s): Balcreuchan Group, Part Of Arenig Volcanic Complex (Correlated With, But No Sp (-723)
Balcreuchan Group (Correlated With, But Not Named) (-3874)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  The area around Barneil, on the western and northern slopes of Craighead Hill, Girvan 
Reference(s):
Peach, B N and Horne, J. 1899. The Silurian Rocks of Britain, Volume 1. Scotland. Memoir of the Geological Survey of the United Kingdom. 
Lamont, A, and Lindstrom, M, 1957. Arenigian and Llandeilian cherts identified in the Southern Uplands by means of conodonts, etc., Transactions of the Edinburgh Geological Society, Vol. 17, 60-70. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S014 S008