Salsburgh Volcanic Formation
Salsburgh Volcanic Formation is part of the Bathgate Group
From the type section. The term was first applied by Browne et al. (1999).
The Salsburgh Volcanic Formation consists of highly altered basaltic lavas with sporadic interbeds of limestone, mudstone, tuff and tuffaceous mudstone and tuffaceous sandstone.
The type section is from 1114.65 to 1216.15.m depth in the Salsburgh 1A oil well (BGS Registration Number NS86SW/89) (NS 8166 6487) north-west of Shotts (see Browne et al., 1999, fig. 2, col. 6).
Lower and upper boundaries
The Early Devonian trachytic rocks at the base of the Salsburgh 1A oil well (see above) have been interpreted as intrusive feldspar-macrophyric microgranodiorite (or rhyodacite). The contact between the latter and the overlying Salsburgh Volcanic Formation had previously been accepted as an unconformity, but now could be reinterpreted as intrusive (Phillips and Browne, 2000).
The top of the formation is a conformable transition to the cyclical sequence of mainly sandstones with siltstones and mudstones of the West Lothian Oil-Shale Formation, Strathclyde Group. In the type section, a limestone correlated with the Burdiehouse Limestone rests directly on the Salsburgh Volcanic Formation.
The maximum known thickness of the formation is 102.m in its type section, where the base was apparently not reached (Phillips and Browne, 2000).
Distribution and regional correlation
The formation is only known in its type section (see above).
- Browne, M A E, Dean, M T, Hall, I H S, McAdam, A D, Monro, S K, and Chisholm, J I.1999.A lithostratigraphical framework for the Carboniferous rocks of the Midland Valley of Scotland.British Geological Survey Research Report, RR/99/07