The BGS Lexicon of Named Rock Units — Result Details

North Campsie Pyroclastic Member

Computer Code: NCPY Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The member consists of pyroclastic material deposited largely in tephra cones, as ashfall tuffs and lapilli tuffs and reworked volcaniclastic sedimentary rocks derived from the erosion of coallescing tephra cones. Typically, finely stratified tuffs pass upwards into coarse, unstratified spatter deposits and agglomerates. The lower agglomerates are composed largely of accidental and accessory material, including large blocks (up to 2 m) of basalt, smaller lava fragments and rare sandstone boulders. Higher agglomerates tend to be composed of essential tephra and scoria bombs in an upward progression that is typical of tephra cones. Impersistent tongues and lenses of highly vesicular basaltic lava occur locally.
Definition of Lower Boundary: Rests unconformably on Inverclyde Group strata of the Clyde Sandstone Formation.
Definition of Upper Boundary: Overlain conformably or locally disconformably by the Campsie Lava Member of the Clyde Plateau Volcanic Formation.
Thickness: Unspecified and probably highly variable. Since fragmental rocks that form subaerial tephra cones are indistinguishable from those occupying necks, it is possible that some of the tephra is actually neck agglomerate.
Geographical Limits: Continuous along lower parts of the northern escarpment of the Campsie Fells, from Canny Tops [NS 551 833] in the west to Gonachan Cottage [NS 629 860], on the south side of the Endrick valley, in the east.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): North Campsie Tephra Deposits (Associated With The North Campsie Linear Vent System) (-1082)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Corrie of Balglass on the north side of the Campsie Fells; 2.5 km of cliffs, reaching a height of up to 200 m. Craig, 1980 
Reference(s):
Hall, I H S, Browne, M A E and Forsyth, I H. 1998. Geology of the Glasgow district. Memoir of the British Geological Survey, Sheet 30E (Scotland). 
Craig, P.M. 1980 The Volcanic Geology of the Campsie Fells area, Stirlingshire. Unpublished PhD thesis, University of Lancaster. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S030 S031