1006 DR R. KIDSTON, MR T. C. CANTRILL, AND MR E. E. L. DIXON. 



7 yards of clod, has been shown on the Survey map ; above it the Spirorbis-limestone, 

 was detected at many points by Mr Daniel Jones. * 



Murchison in 1839 was aware that in the Coalbrookdale Coal Field two groups of 

 Coal Measures are present : a newer group, containing a thin band of Spirorbis-lime- 

 stone and several sulphur coals similar to those of the Shrewsbury and Lebotwood 

 Coal Fields, and an older group, in which the chief coal-seams and ironstones are 

 contained ; but he appears to have inferred that in the Forest of Wyre Coal Field 

 only the newer group is represented. It has long been known that this inference 

 was incorrect. 



The researches of Mr Daniel Jones,! begun in 1868 in connection with the first 

 Royal Commission on Coal Supplies, materially advanced our knowledge. He cor- 

 related the sweet coal-seams with those of the Clee Hills, Coalbrookdale, and South 

 Staffordshire, and traced throughout most of the district the Spirorbis-limestone, 

 known to be associated with the sulphur coals in the Shrewsbury, Lebotwood, and 

 Coalbrookdale Coal Fields. He was thus enabled to indicate the broad geographical 

 distribution of the Sulphur Coal Group and Sweet Coal Group respectively, and 

 established the fact that their distribution is anomalous. In the north, at Chelmarsh, 

 and generally from Bridgnorth to Billingsley, the Sulphur Coal Group, as we have 

 seen (p. 1004), rests directly on the Old Red Sandstone. This is the case in the 

 south-west also, from Bayton to Abberley. But in the intermediate district, from 

 Billingsley to Baveney Wood, it is the Sweet Coal Group that rests directly on the 

 Old Red Sandstone. To explain this anomaly, Mr Jones applied the theory of a 

 great wash-out or denudation of Coal Measure date, basing this view on Marcus 

 Scott's conclusion that in Coalbrookdale the Sulphur Coal Group is unconformable 

 to the Sweet Coal Group, the plane of unconformity or wash-out being known as 

 the Symon Fault. On this hypothesis, the Wyre Forest district, after the formation 

 of the Sweet Coal Group, was subjected to an extensive denudation, with the result 

 that the Sweet Coal area was reduced to a small isolated patch or outlier, which 

 owed its preservation to the protection afforded by the basaltic intrusion of Kinlet. 

 Over this outlier of Sweet Coal Measures the Sulphur Coal Measures were then 

 laid down unconformably. The outcrop of the Sweet Coal Group between Billingsley 

 and Baveney Wood was thus regarded as the exposed western margin of this outlier, 

 the rest of the outlier being buried under the Sulphur Coal Group ; though it was 

 known to extend eastward as far at least as Highley, where the sweet coals had 

 been worked for some years at a considerable depth vertically below the sulphur 

 coals. That this supposed outlier does not extend as far south as the Dowles Valley 

 was thought to be established by the fact that a series of deep bore-holes there had 

 proved a great thickness of Coal Measures, but had one and all failed to prove work- 



* Trans. Manch. Geol. Soc, vol. x (1870-71), p. 37. 



t Geol. Mag., 1871, pp. 200-208, 363-371 ; ibid., 1873, pp. 138, 348. Colliery Guardian, vol. xxii (July-Dec. 

 1871), pp. 580, 605, 633, 659. Trans. Fed. Inst. Mm. Eng., vol. vii (1893-4), pp. 287-301, 577-580 ; vol. viii 

 (1894-5), pp. 356-360. 



