Bathgate Hills Volcanic Formation

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Bathgate Hills Volcanic Formation (BHV), Carboniferous, Midland Valley of Scotland[edit]

Bathgate Hills Volcanic Foramtion is part of the Bathgate Group

Name[edit]

From the Bathgate Hills, West Lothian. The name was first used by Smith et al. (1994)[1] to replace earlier terms such as ‘Bathgate lavas’. It was formally defined by Browne et al. (1999)[2].

Lithology[edit]

The Bathgate Hills Volcanic Formation consists of lavas, tuffs and volcaniclastic sedimentary rocks. The lavas are mostly relatively primitive, silica-undersaturated rocks with a restricted range of composition. The ‘basic’ rocks are commonly nepheline-normative basanites. The lavas are mostly basalt and basanite and olivine-clinopyroxene-microphyric basalt with rare microporphyritic hawaiite. Weathered ferruginous palaeosols (red boles) are developed. The volcanic rocks interdigitate and interact with clastic sedimentary rocks of various formations.

Genetic interpretation[edit]

The formation was produced by long-lived series of episodes of volcanic activity. The depositional environment was mainly terrestrial, at times into water, at times into hot springs.

Stratotype[edit]

The type area comprises natural exposures in the Bathgate Hills (NS 98 75). A reference section, in which twenty-six lavas interdigitate with clastic sedimentary rocks, is in the Rashiehill Borehole (BGS Registration Number NS87SW/22) (NS 8386 7301) from 791.6 to 1110.4.m depth.

Lower and upper boundaries[edit]

The base of the formation is taken at the lithological change from underlying clastic sedimentary rocks, to lavas, tuffs or volcaniclastic sedimentary rocks or at an upward change from the petrologically wider range of volcanic rocks that form the Clyde Plateau Volcanic Formation, as in the Rashiehill Borehole (see above). In the former case the boundary is gradational and is taken where volcanic rocks predominate over sedimentary rocks. The top is likewise gradational.

The formation is laterally equivalent to, and interdigitates with, the West Lothian Oil-Shale (Strathclyde Group), and Lower Limestone, Limestone Coal, Upper Limestone and Passage formations (Clackmannan Group).

Thickness[edit]

Up to 319 m maximum in the Rashiehill Borehole (see above).

Distribution and regional correlation[edit]

The main outcrop is in the Bathgate Hills, West Lothian where the rocks crop out in a belt from Bathgate to Bo’ness on the coast. The formation has been proved under younger rocks as far west as Rashiehill.

Age[edit]

Visean to Namurian (Asbian to Arnsbergian)

References[edit]

  1. Smith, R A, Stephenson, D, and Monro, S.1994.The geological setting of the southern Bathgate Hills, West Lothian, Scotland.Transactions of the Royal Society of Edinburgh: Earth Sciences. Vol. 84, 189–196.
  2. 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