Westphalian, Midland Valley of Scotland
|Cameron, I B, and Stephenson, D. 1985. British regional geology: The Midland Valley of Scotland. Third edition. Reprint 2014. Keyworth, Nottingham: British Geological Survey.|
The Westphalian succession in the Midland Valley consists of the Lower, Middle and Upper Coal Measures. During the Lower and Middle Coal Measures sedimentary conditions were similar to those in the Limestone Coal Group of the Namurian Series, but the Upper Coal Measures are more arenaceous and show evidence of increasing aridity in the upper part. The rocks are mudstones, sandstones and siltstones with seams of coal and seatclay and rarely of ironstone deposited in cyclic sequence. A few thin marine bands occur which are important for correlation. Coal seams are well developed in the Lower and Middle Coal Measures and up to 20 seams have been worked extensively. The sediments in the Upper Coal Measures are secondarily reddened and coal seams are mostly destroyed by oxidation.
The strata were deposited in a fluvio-deltaic environment in which the marine influence was restricted to a few short-lived intervals. Although subsidence was considerable in order to receive the large amount of sediment brought into the area, sedimentation kept pace to the extent that the water depth was never great and the depositional surface was always close to sea level. However, the degree of subsidence varied greatly from place to place with the contemporaneous formation of local basins and differential subsidence across lines of faulting.
The rock sequence consists of the repetition, in whole or in part, of a sedimentary cycle which commonly has a mudstone at the base and a root-bed and coal at the top. Beds of sandstone, siltstone and mudstone may appear in the cycle in a number of combinations below the root bed. Marine horizons are rare, but strata with non-marine bivalves or ‘mussels’ are not uncommon. The cycles range in thickness up to about 30 m but average 10 m. There is considerable variety, within these limits, between one cycle and another and laterally within a single cycle.
Apart from fragmentary plant material, the most abundant fossils present are the non-marine bivalves (mussels) which in conjunction with the marine bands, form the basis of correlation both within and between coalfields. The Vanderbeckei and Aegiranum marine bands contain species unique to the individual horizons and to the equivalent bands elsewhere in western Europe. This suggests that the depositional facies was uniform over a very large area in Westphalian times. The presence of these bands in Scotland allows the recognition of Westphalian A, B and C of the western European classification (P915556).
In the Upper Coal Measures evidence of marine conditions is scarce and confined to the lowermost parts of the sequence. Mussels become scarce compared with their occurrence in the Middle Coal Measures.
The base of the Lower Coal Measures is drawn at a locally convenient horizon in each coalfield area since the Subcrenatum Marine Band, which marks the base of the Westphalian, has not been recorded in Scotland. Its horizon probably lies within the upper part of the Passage Group. The base of the Middle Coal Measures is defined as the base of the Vanderbeckei (Queenslie) Marine Band and the base of Upper Coal Measures is drawn at the top of the Aegiranum (Skipsey’s) Marine Band.
The distribution of the Westphalian outcrops is shown on P915536 which shows that the sequence is now only preserved in a few separate areas. The outcrops shown offshore in the Firth of Clyde and the Firth of Forth are known from geophysical data and a few boreholes. Knowledge of the succession in these areas is meagre. The generalised successions in the various coalfields are shown on P915537 together with the stratigraphical classification and the names of some of the principal coals.
Bibliography (for all Carboniferous)
Belt, E. S., Freshney, E. C. and Read, W. A. 1967. Sedimentology of Carboniferous cementstone facies, British Isles and eastern Canada. J. Geol., Vol. 75, pp. 711–721.
Brand, P. J. 1977. The Fauna and Distribution Of The Queenslie Marine Band (Westphalian) In Scotland. Rep. Inst. Geol. Sci., No. 77/18.
Brand, P. J. 1983. Stratigraphical palaeontology of the Westphalian of the Ayrshire Coalfield, Scotland. Trans. R. Soc. Edinburgh: Earth Sci., Vol. 73, pp. 173–190.
Brand, P. J. , Armstrong, M. and Wilson, R. B. 1980. The Carboniferous strata at the Westfield Opencast Site, Fife, Scotland. Rep. Inst. Geol. Sci., No. 79/11.
Bott, M. H. P. and Johnson, G. A. L. 1967. The controlling mechanism of Carboniferous cyclic sedimentation. Q.J. Geol. Soc. London, Vol. 122, pp. 421–441.
Browne, M. A. E. 1980. Stratigraphy of the lower Calciferous Sandstone Measures in Fife. Scott. J. Geol., Vol. 16, pp. 321–328.
Currie, E. D. 1954. Scottish Carboniferous goniatites. Trans. R. Soc. Edinburgh, Vol. 62, pp. 527–602.
Davies, A. 1972. Carboniferous rocks of the Muirkirk, Gass Water and Glenmuir areas of Ayrshire. Bull. Geol. Surv. G.B., No. 40, pp. 1–49.
Davies, A. 1974. The Lower Carboniferous (Dinantian) sequence at Spilmersford, East Lothian, Scotland. Bull. Geol. Surv. G.B., No. 45, pp. 1–38.
Forsyth, I. H. 1978. The lower part of the Limestone Coal Group in the Glasgow district. Rep. Inst. Geol. Sci., No. 78/29.
Forsyth, I. H. 1979. The Lower Coal Measures of central Glasgow. Rep. Inst. Geol. Sci., No. 79/4.
Forsyth, I. H. 1982. The stratigraphy of the Upper Limestone Group (E1 and E2 stages of the Namurian) in the Glasgow district. Rep. Inst. Geol. Sci., No. 82/4.
George, T. N. 1978. Eustasy and tectonics: sedimentary rhythms and stratigraphical units in British Dinantian correlation. Proc. Yorkshire Geol. Soc., Vol. 42, pp. 229–254.
George, T. N. , Johnson, G. A. L., Mitchell, M., Prentice, J. E., Ramsbottom, W. H. C., Sevastopulo, G. D. and Wilson, R. B. 1976. A correlation of Dinantian rocks in the British Isles. Spec. Rep. Geol. Soc. London, No. 7.
Goodlet, G. A. 1957. Lithological variation in the Lower Limestone Group of the Midland Valley of Scotland. Bull. Geol. Surv. G.B., No. 12, pp. 52–65.
Greensmith, J. T. 1965. Calciferous Sandstone Series sedimentation at the eastern end of the Midland Valley of Scotland. J. Sediment. Petrol., Vol. 35, pp. 223–242.
Hill, D. 1938-41. Carboniferous rugose corals of Scotland. Palaeontogr. Soc. (Monogr.) Lumsden, G. I. 1964. The Limestone Coal Group of the Douglas Coalfield Lanarkshire. Bull. Geol. Surv. G.B., No. 21, pp. 37–71.
Hill, D. 1965. The base of the Coal Measures in the Douglas Coalfield, Lanarkshire. Bull. Geol. Surv. G.B., No. 22, pp. 80–91.
Hill, D. 1967. The Carboniferous Limestone Series of Douglas, Lanarkshire. Bull. Geol. Surv. G.B., No. 26, pp. 1–22.
Hill, D. 1967. The Upper Limestone Group and Passage Group of Douglas, Lanarkshire. Bull. Geol. Surv. G.B., No. 27, pp. 17–48.
Hill, D. and Calver, M. A. 1958. The stratigraphy and palaeontology of the Coal Measures of the Douglas Coalfield. Bull. Geol. Surv. G.B., No. 15, pp. 32–70.
Hill, D. and Wilson, R. B. 1978. Stratigraphical classification of the Carboniferous succession of central Scotland. C.R. 8e Congr. Int. Stratigr. Geol. Carbonif., Vol. 2, pp. 27–36.
McLean, A. C. and Deegan, C. E. 1976. A synthesis of the solid geology of the Firth of Clyde region In McLean, A. C. and Deegan, C. E. (editors). The solid geology of the Clyde sheet (55°N/6°W). Rep. Inst. Geol. Sci., No. 78/9.
Monro, S. K., Loughnan, F. C. and Walker, M. C. 1983. The Ayrshire bauxitic clay: an allochthonous deposit? In Residual Deposits, pp. 47–58. Wilson, R. C. L. (editor). Spec. Publ. Geol. Soc. London, No. 11.
Muir R. O. 1963. Petrography and provenance of the Millstone Grit of central Scotland. Trans. Edinburgh Geol. Soc., Vol. 19, pp. 439–485.
Mykura, W. 1960. The replacement of coal by limestone and the reddening of Coal Measures in the Ayrshire Coalfield. Bull. Geol. Surv. G.B., No. 16, pp. 69–109.
Mykura, W. 1967. The Upper Carboniferous rocks of south-west Ayrshire. Bull. Geol. Surv. G.B., No. 26, pp. 23–48.
Neves, R., Read, W. A. and Wilson, R. B. 1965. Note on recent spore and goniatite evidence from the Passage Group of the Scottish Upper Carboniferous succession. Scott. J. Geol., Vol. 1, pp. 185–188.
Neves, R., Gueinn, K. J., Clayton, G., Ioannides, N. S., Neville, R. S. W. and KruszeWska, K. 1973. Palynological correlations within the Lower Carboniferous of Scotland and northern England. Trans. R. Soc. Edinburgh, Vol. 69, pp. 23–70.
Ramsbottom, W. H. C. 1977. Major cycles of transgression and regression (Mesothems) in the Namurian. Proc. Yorkshire Geol. Soc., Vol. 41, pp. 261–291.
Ramsbottom, W. H. C. 1977. Correlation of the Scottish Upper Limestone Group (Namurian) with that of the North of England. Scott. J. Geol., Vol. 13, pp. 327–330.
Ramsbottom, W. H. C., Calver, M. A., Eagar, R. M. C., Hodson, F., Holliday, D. W., Stubblefield, C. J. and Wilson, R. B. 1978. A correlation of Silesian rocks in the British Isles. Spec. Rep. Geol. Soc. London, No. 10.
Read, W. A. and Dean, J. M. 1967. A quantitative study of a sequence of coal-bearing cycles in the Namurian of central Scotland, 1. Sedimentology, Vol. 9, pp. 137–156.
Read, W. A. and Cole, A. J. 1971. Some Namurian (E2) paralic sediments in central Scotland: an investigation of depositional environment and facies changes using iterative-fit trend-surface analysis. J. Geol. Soc. London, Vol. 127, pp. 137–176.
Smith, A. G., Hurley, A. M. and Briden, J. C. 1981. Phanerozoic palaeocontinental world maps. (Cambridge: Cambridge University Press.)
Thomson, M. E. 1978. IGS Studies of the geology of the Firth of Forth and its approaches. Rep. Inst. Geol. Sci., No. 77/17.
Weir, J. and Leitch, D. 1936. The zonal distribution of the non-marine lamellibranchs in the Coal Measures of Scotland. Trans. R. Soc. Edinburgh, Vol. 57, pp. 697–751.
Wilson, R. B. 1966. A study of the Neilson Shell Bed, a Scottish Lower Carboniferous marine shale. Bull. Geol. Surv. G.B., No. 24, pp. 105–128.
Wilson, R. B. 1967. A study of some Namurian marine faunas of central Scotland. Trans. R. Soc. Edinburgh, Vol. 66, pp. 445–490.
Wilson, R. B. 1974. A study of the Dinantian marine faunas of south-east Scotland. Bull. Geol. Surv. G.B., No. 46, pp. 35–65.
Wilson, R. B. 1979. The base of the Lower Limestone Group (Viséan) in North Ayrshire. Scott. J. Geol., Vol. 15, pp. 313–319.
Wilson, R. B. 1983. Note on the correlation of the Upper Limestone Group (Namurian) in south Ayrshire. Scott. J. Geol., Vol. 19, pp. 183–188.