Page:VCH Warwickshire 1.djvu/41

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GEOLOGY conformity by the so-called Lower Permian rocks. The Coal Measures lie in a syncline or trough, the axis of which extends in a north and south direction, and on all sides the beds dip towards this line. The northern part of the coalfield is bounded by faults or lines of fracture, along which the rocks on either side have been relatively shifted, so that here various newer rocks, the ' Permian ' and Trias, abut against the Coal Measures. Mr. Fox-Strangways thinks it unlikely that the Coal Measures will be found to extend continuously under the Trias into the Leicestershire coalfield. In the other direction however they extend southwards under the ' Permian ' of Baxterley, and come to light again as a small ' inlier ' at Arley. South of Bedworth both the Coal Measures and ' Permian ' are covered unconformably by the Trias, and the seams have been worked through this last as far south as the Craven Colliery, three miles north-east of Coventry. Beyond this the outcrops are said to curve round towards the south-west. 1 It becomes an interesting and important question as to whether or not these coals extend continuously under the Trias towards South Staffordshire. There is no reason to doubt that the Coal Measures of the Warwickshire coalfield and those of South Staffordshire were originally deposited in one and the same basin, for in both districts the measures thicken towards the north-north-west, and in the opposite direction the coals approach each other by the thinning out of the intermediate beds, and tend to combine into one or two seams of abnormal thickness. It thus, in Professor Lapworth's 2 words, ' becomes a matter of high probability that the Thick Coal of South Staffordshire extends more or less continuously under the Red rocks of North Warwickshire, possibly from Hawkesbury to Smethwick.' At the same time it must be borne in mind that land apparently lay to the south and south-east during Coal Measure times, and in that direction the coals may be expected to die out ; again, it is always possible that there may be local unconformities and ' wash-outs ' within the Coal Measures themselves, and it is just possible that areas of post-Carboniferous folding and denudation may lurk concealed and unsuspected under the unriven cloak of Trias. According to Professor Lapworth 3 the Warwickshire Coal Meas- ures may be grouped in descending order as follows : 4. Grey and red sandstones and shales, with one or more bands of Spirorbis limestone. 3. White and yellow sandstones and shales. 2. Red and green brick-clays and marls. i. Grey sandstones and dark shales with five workable coal seams, and beds of fireclay and ironstone. The base of the series was first worked out in detail in 1886 by Mr. Strahan. 4 He found the lowest beds to consist locally of buff or 1 Howell, 'The Warwickshire Coalfield,' Mem. Geol. Survey, p. 22. 2 Proc. Geol. Assoc. xv. (1898), 369. 3 Ibid. p. 368.

  • Geol. Mag. (1886), p. 540 et seqq. ; also Geol. Survey map, sheet 63 S.W. new ed. (1886).