Langhill Lava Member
Langhill Lava Member (LHLA), Campsie Block, Carboniferous, Midland Valley of Scotland
Langhill Lava Member is part of the Clyde Plateau Volcanic Formation.
Name
Previously named the Langhill Lavas (Forsyth et al., 1996)[1].
Lithology
The Langhill Lava Member consists of four flows of typically fine-grained, platy-jointed basaltic-trachyandesite (mugearite). The only exposures are in the River Carron (NS 773 845) 500 m north-east of Langhill. The lowest lava has a relatively coarse grain size and is about 15 m thick, with well-developed columnar jointing. The other lavas are very fine grained and intensely jointed. At least one of these has an autobrecciated base, consisting of buckled and disrupted tabular blocks of the lava.
Stratotype
The type area is the eastern part of the Kilsyth Hills (NS 7750 8442 to NS 7616 8539) (Forsyth et al., 1996)[1]. A reference section is the River Carron, eastern Kilsyth Hills, north-east of Glasgow (NS 7726 8454 to NS 7749 8439) (Craig, 1980)[2].
Lower and upper boundaries
The member overlies plagioclase-microphyric trachybasalt of the Campsie Lava Member, but the nature of the contact is unknown.
The Langhill Lava Member is overlain by the Gargunnock Hills Lava Member, but the nature of the contact is unknown. The lithological change is to mostly plagioclase-macrophyric basalt to hawaiite (‘Markle’ type) with some plagioclase- and olivine-microphyric basalts (‘Jedburgh’ and ‘Dalmeny’ types).
Thickness
Some 35 m.
Distribution and regional correlation
The member is restricted to the eastern part of the Kilsyth Hills (Forsyth et al., 1996)[1]. The rocks mostly crop out on the northern side of the Carron Glen (NS 7750 8442 to NS 7616 8539) with the outcrop extending locally to the base of the valley (NS 7739 8450) and on to the southern side (NS 7709 6446).
Age
Mid Visean (Arundian to Asbian).