| Computer Code: |
SKDL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Asbian Substage (CR) |
| Lithological Description: |
The Skiddaw Lava Member consists predominantly of plagioclase-macrophyric basalt (of 'Markle' type) and composite lavas with some plagioclase-microphyric basalt (of 'Jedburgh' type). In the east of the outcrop [NS 6572 9122], the member includes a composite lava composed of massive, rounded bodies mostly of macroporphyritic basalt, but also includng near the centre of the lava some transitional plagioclase-microphyric to olivine-microphyric basalts, in a matrix of slaggy, highly vesicular microporphyritic basalt. |
| Definition of Lower Boundary: |
The basal basalt of the member unconformably overlies sedimentary rocks, including sandstone, siltstone and mudstone of the Clyde Sandstone Formation, of the Inverclyde Group. |
| Definition of Upper Boundary: |
The Skiddaw Lava Member is overlain unconformably by the Slackgun Volcaniclastic Member. The lithological change is from transitional plagioclase-macrophyric to plagioclase-microphyric basalt lava or composite basalt lava to a dull red 'bole' reflecting prolonged weathering of the lavas below. |
| Thickness: |
0-37 m |
| Geographical Limits: |
The member is restricted to the northern and western Fintry Hills and to the north-western Gargunnock Hills, north-east of Glasgow. These rocks crop out from below Double Craigs [NS 6304 8712] north-north-west towards Skiddaw [NS 622 891] and then north-east, to the north-west side of Lees HIll [NS 6577 9122]. |
| Parent Unit: |
Clyde Plateau Volcanic Formation (CPV)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
In the northern and western Fintry Hills, and in the north-western Gargunnock Hills, north-east of Glasgow. Francis et al., 1970. |
| Reference Section |
Slackgun, north-western Gargunnock Hills, north-east of Glasgow. Francis et al., 1970. |
| Reference(s): |
| Francis, E H, Forsyth, I H, Read, W A and Armstrong, M. 1970. The geology of the Stirling district. Memoir of the Geological Survey of Great Britain, Sheet 39 (Scotland). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S039
|
