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XIII.—The Formation of Rock Joints and the Cleat of Coal

Published online by Cambridge University Press:  15 September 2014

P. F. Kendall  and
Henry Briggs
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Extract

The occurrence in coal seams of planes of division, generally approximately at right angles to the stratification, has been known for centuries. Owing to the important part these planes play in the lay-out of workings, miners have found it necessary carefully to pay heed to their direction and character. They long ago observed, for example, that, in the majority of seams, there are main divisions or “cleats” and secondary divisions or “cross-cleats,” and that these systems intersect at an angle of generally 80 to 90 degrees. It was also seen that cleats are always best developed in the bright parts of bituminous coal, and that they are less distinct, more widely spaced, or even non-apparent in durain and in cannel. When the dull and bright parts are finely laminated, however, the cleat planes pass through the mass without interruption. Sparry inclusions (ankerites) are very common in the cleats of bright coal and equally rare in dull coal; occasionally the inclusions extend a little way into the roof, and then the existence of associated cleat in the roof is particularly easy to detect.

Type
Proceedings
Information
Proceedings of the Royal Society of Edinburgh , Volume 53 , 1934 , pp. 164 - 187
Copyright
Copyright © Royal Society of Edinburgh 1934

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References

page 164 note * Stainier, X., Ann. Soc. Scient. Bruxelles, vol. 1, 1930, B, p.34.Google Scholar

page 165 note * All bearings are to the true meridian, unless otherwise stated.

page 165 note † Kendall, P. F., “On Cleat in Coal Seams,” Geol. Mag., February 1914, p. 49CrossRefGoogle Scholar.

page 166 note * “Geological Facts to Elucidate the Ashby de la Zouch Coalfield,” 1834.

page 166 note † Coal Fields of the Lothians, Edin., 1839, p. 16.

page 167 note * “On the Structure of Crystalline Rocks,” Mining Almanack, 1849.

page 167 note † Brit. Assocn. Report, 1856, p. 369.

page 167 note ‡ Illustrations of Yorkshire, vol. ii, 1836.

page 167 note § J. B. Jukes, Student's Manual of Geology, 2nd ed., 1862, p. 207.

page 167 note ║ Étude Synthétiques de Géologie Expérimentale, Paris, 1879, p. 303.

page 168 note * P. F. Kendall, loc. cit.; Kendall and Wroot, Geology of Yorkshire, 1924; H. Briggs, Colliery Engineering, January 1932.

page 168 note † Collier, A. J., “The Arkansas Coal Field,” U.S. Geol. Surv. Mem., 1907, p. 48Google Scholar.

page 169 note * 23rd Ann. Rep. Dept. of Geol. and Nat. Resources, Indiana, p. 25.

page 169 note † “Notes on Cleat in the Scottish Coalfields,” Trans. Inst. Min. Engs., vol. lxx, p. 115.

page 169 note ‡ Coal Age, vol. xxvii, p. 576.

page 170 note * Jukes, op. cit., p. 207.

page 172 note * The order of importance of the planes is indicated on the map by the numerals 1, 2, and 3.

page 172 note † L. R. Wager, Q.J.G.S., vol. lxxxvii, 1931, p. 392.

page 173 note * Geol. Mag., vol. x, 1883, p. 397.

page 173 note † Data collected by Mr F. S. Steart.

page 173 note ‡ Data collected by Mr A. C. Graham.

page 173 note § Briggs, and Kemp, , Trans. Inst. Min. Engs., vol. lxxvii, 1929, p. 5; Colliery Engineering, January 1932, p. 15.Google Scholar

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page 174 note † Geology, vol. i, 1886, p. 283.

page 175 note * Structural and Field Geology, 1908, p. 152.

page 175 note † Principles of Structural Geology, New York, 1931, p. 132.

page 175 note ‡ See also J. B. Jukes, op. cit., p. 210.

page 176 note * See, e.g., Daubrée, Études Synthétique de Géologie Expérimentale, Paris, 1879; E. M. Anderson, “The Dynamics of Faulting,” Trans. Edin. Geol. Soc., vol. viii, 1905, p. 38; C. K. Leith, Structural Geology, New York, 1913; Briggs and Morrow, “The Rationale of Faulting and Subsidence,” Trans. Inst. Min. Engs., vol. lxxiii, 1927, p. 465; C. M. Nevin, op. cit.

page 177 note * E.g., Versey, Proc. Yorks. Geol. Soc., N.S., vol. xxi, p. 203.

page 178 note * Becker, G. F., Trans. Amer. Inst. Min. Engs., vol. xxiv, 1895, p. 136.Google Scholar

page 178 note † Nevin, an advocate of the tension theory of joint formation, argues (op. cit., p. 143) that the sheet ought to crack along CD, i.e. at right angles to the direction of maximum tension. Clearly, he omitted to look at the other side of the pane! The glass, which persists in breaking in both directions, should itself have been sufficient to demonstrate the defectiveness of both the argument and the theory it seeks to uphold.

page 179 note * Briggs, Colliery Engineering, January 1932, p. II.

page 179 note † Manual of Geology, 2nd ed., 1862, p. 214.

page 181 note * Q.J.G.S., vol. lxxxvii, 1931, p. 392.

page 182 note * It appears from Wager's map (loc. cit.) that on the north side of the North Craven fault, the joints are rotated parallel with the fault near Ingleborough and at right angles to it near Grassington. The circumstances preclude large lateral movements in opposite directions on the same side of the fault, and at first sight the observation appears to give the death-blow to the theory of transcurrent shift. We have, however, to bear in mind, first, that the limestone possesses two sets of joints at 90°, and, second, that the subsidiary set may locally assume the rôle of the “master” series. It seems not unlikely then that, at Grassington, the joints depicted by Wager are “end” joints abnormally developed.

page 183 note * See Nàdai's Plasticity (McGraw-Hill Co., 1931), the latest and most authoritative treatise on the mechanics of matter in the plastic state.

page 183 note † Leith, C. K., Structural Geology, New York, 1913, p. 63.Google Scholar.

page 183 note ‡ Few anthracites possess a true cleat; but occasionally in South Wales, and more frequently in Pennsylvania, anthracite seams are to be found that still retain the cleat of the lower-rank coals from which they were derived.

page 183 note § The words “direct” or “continuous” are used as in electrical terminology in contradistinction to “alternating.”

page 184 note * The words “direct” or “continuous” are used as in electrical terminology in contradistinction to “alternating.”

page 185 note * Op. cit., p. 7.

page 186 note * Kendall, P. F., “Physiography of the Coal Swamps,” Presidential Address, Geology Section, Brit. Assoc. Report, 1922, p. 71Google Scholar.

page 186 note † Zentralbureau der International Erdmessung, Berlin, No. 38, 1921.

page 186 note ‡ Jour. Geol., vol. xxvii, 1919, p. 585.

page 186 note § Bull. Nat. Research Council, Washington, No. 78, 1931, p. 68.