June 20, 1913. ______________________________________________________________________________________________________________________________ ] 348 THE COLLIERY GUARDIAN. and the Top Hard coal of Nottinghamshire (Barnsley coal of Yorkshire) 1,000ft. higher in the sequence, retain well-marked characters over a large part of the coalfield. Measures Below the Top Hard (Barnsley) Coal.—The middle coal measures, which are over 3,000 ft. in thick- ness, can be conveniently regarded as consisting of two sub-groups in relation to the Top Hard or Barnsley coal which, apart from its persistence and strongly marked characters, is the one chiefly sought for in the concealed coalfield. The more important coals are the Silkstone, Middleton Main, Tupton, Deep Hard (Parkgate), and Deep Soft ranging from 3 to 6 feet in thickness. These form the backbone of the mining industry in the exposed coalfield, but in the concealed coalfield they have scarcely been touched, except at Clifton Colliery, south of Nottingham. Nearly the complete sequence is considered to have been proved in the boring at Edwalton, and possibly at Owthorpe and Clipston. The upper beds have been pierced for a few hundred feet by most of the shafts and borings between Nottingham and Selby. Over a large part of the coalfield the Silkstone coal is the most important seam, but it becomes a worthless mixture of shale and coal in the north where, according to Green, it is represented by the Blocking or Barcelona coal. Numerous dirt partings also make their appear- ance towards the southern margin of the coalfield where, for this reason, the seam is generally called the The complete sequence has been definitely proved only at Oxton and Maltby, where the upper coal measures are certainly present and where the Top Hard or Barnsley coal has been proved beyond all question. But over a large part of the fields except to the north- east of Nottingham (Gedling, Thurgarton), the upper coal measures and some of the middle coal measures were removed by denudation before the deposition of the permiau and triassic rocks. Since the amount of this destruction of the coal measures and their arrangement cannot be determined beforehand, owing to the unconformity of the permian and triassic rocks, it is important to ascertain not only the composition of the coals, but also the characters of the associated strata and by what means they may be identified. This investigation, however, has not as yet reached a com- pletely satisfactory stage, and in some of the borings, notably at Barlow and Selby, the identification of individual coals could not be determined, but in others, as at Oxton and Thorne, the Mansfield marine bed proved a reliable index. Top Hard, Barnsley or Warren House Coal.—This is the most important seam of the middle coal measures, no other approaching it in value, except, perhaps, the Silkstone coal in Yorkshire. Its superiority mainly depends upon the presence of a band of hard semi- anthracitic coal, known as “ Hards,” which furnishes a first-class steam coal. In addition, other parts of the The Top Hard coal can be traced at the surface and has been followed in colliery workings across the county border, and in Yorkshire as far north as Wakefield, where it is known as the Barnsley coal. In the neigh- bourhood of Barnsley it reaches a thickness of 9ft., and, what is most important, to fully this amount in the recent sinkings at Maltby, Brods worth, Bentley, and in the boring at Thorne, tn the shafts at Bentley Colliery the seam consists of :— Ft. in. Soft coal 4 1 Parting 0 41 Hard coal 2 9 Soft 2 North and north-east of Wakefield the seam becomes split up by dirt partings, and is known as the Warren House. North of the Calder, and in the valley of the Aire, the dirt partings become thinner and less numerous with a decided improvement in the quality of the coal. Numerous examples of changes in the composition of West iooo. Derwent Valley Fl RTrerit ----i____ Fig. 4.—Diagrammatic Sections to illustrate the Probable Structure of the Coalfield in the North (A) and in the South (B). Blackshale coal and less frequently the Clod coal. The seam yield house, manufacturing and, to a less degree Middleton Main coal, sometimes regarded as the ! gas coal. So great is the value of this composite seam, equivalent of the Silkstone coal, becomes of importance j that some of the older collieries, in which it has been in the northern part of the coalfield. The Deep Hard nearly exhausted, find it more profitable to lease fresh (Parkgate) coal, though variable in thickness and areas and to sink new and deep pits rather than continue quality, and liable to somewhat extensive washouts, the old shafts down to the seams lying below. The pro- can be recognised over the entire coalfield, and is a gressive and important development of the concealed valuable seam. In the Doncaster district, about 30 or coalfield in the district of Doncaster hinges upon the 40 feet below the Barnsley seam, a coal named the existence of the Barnsley coal, and south of Doncaster on Dunsil, from 4 to 5 feet in thickness, has been proved the presence of the Top Hard coal. In Nottingham- at Bentley Colliery and in the boring at Thorne. At rr’~~ —o1 —t Bentley it is stated to be of excellent quality. The fauna and flora, though more abundantly represented and more evenly distributed, include the forms found in the lower coal measures. A few species, such as Carbonicola robusta, die out; and others, such as Anthracomya modiolaris, make their appearance towards the summit. Not infrequently the shells of Carbonicola acuta and C. aquilina are massed together in bands from 3 to 4 feet in thickness, forming- the well-known “ mussel ” or “ cockle ” bands of the miner. At present marine shells have been found only in one bed, 300 ft. above the Deep Hard coal in the Clay Cross district, and between 300 to 400 feet in the Chesterfield area, and there is good evidence to show that this represents the sole incursion of sea water during the deposition of these measures. Measures above the Top Hard (Barnsley) Coal.—In the middle coal measures below the Top Hard coal some of the coals and sandstones can be traced through Derbyshire and Nottinghamshire into and over a large part of Yorkshire. The Top Hard or Barnsley coal has an equally wide extension, but it is difficult to correlate the coals occurring above this seam in Derbyshire and Nottinghamshire with those in Yorkshire. Of recent years the inspection of borings and sinkings has proved the constant presence of a band of argillaceous limestone resting on a tfiin coal and succeeded by shales containing a highly specialised fauna. This composite band, here called the “ Mansfield Marine Bed,” always maintains the same character and has been found in all the borings and sinkings from Gedling Colliery, near Nottingham, to the OWTHORPE Fig. 5.—Sections illustrating the Coal j Measures Below the Trias at Owthorpe I and Clipston. i CLIPSTON shire the Top Hard coal varies in thickness from a little over 2 ft. to over 6 ft. in thickness. It gives the following average section :— Coal, soft...... ............. „ rifl-jr ..... „ best hard ........ „ soft .... „ list .... „ soft .... The lower part of the seam consists locally of cannel from 1 to 2 feet in thickness. A thin seam, Comb, Combe or Coombe coal occurs at varying distances above the Top Hard. Sometimes it is only separated by a dirt parting, but the name is also given to a seam several feet above the Top Hard, where it probably represents the coal called the Barnsley Rider in Yorkshire. South of the Trent the Top Hard is only known for certainty at Clifton Colliery, where it is 5 ft. 11 in. thick, but it here lies so close beneath the water-bearing Bunter sandstone that it is unworkable. North of the Trent the Top Hard, varying greatly in thick- ness from place to place, and though occasionally subjected to somewhat extensive washouts, may with great certainty be regarded as extending from its outcrop in the Erewash and Bother valleys eastward as far as the Trent. A local opinion exists that the thickness of the seam decreases eastwards, an opinion based mainly upon a gradual decrease as it is followed to the east in the workings of several collieries between Annesley and Bestwood. But considering the local variations in the thickness of the Top Hard in Derbyshire and Notting- hamshire the arguments brought forward for a general easterly a ttenuation of this valuable seam hardly | justify the condemnation of an area so important as the boring at Thorne 12 miles north-east of Doncaster.' one bordering the navigable portion of the Trent. Ft. 1 1 2 0 0 1 in. 0 0 0 4 01 2 the Barnsley coal could be quoted even in different parts of the same colliery workings. Such variations in thick- ness, composition, and quality may be expected to occur in the concealed area, though so far, in the Doncaster district, the coal remains wonderfully uniform. j The nature of the roof, always an important factor, i becomes especially so in deep workings where the cost of maintenance is necessarily higher than in shallow pits. Between Nottingham and Mansfield the roof, in the collieries bordering the concealed area, or in shafts sunk through the magnesian limestone, is always a blue ' or dark blue shale (bind) generally containing nodules of ironstone. North of Mansfield the shale roof becomes gradually more sandy (stone bind), and occasionally (Whitwell) it is described in the records as being a sandstone rock. In Yorkshire the roof of the Barnsley coal at the outcrop is not infrequently sandstone, but in pits sunk to the deep it is often a shale or sandy shale. In the deeper explorations at Bentley and Thorne it consists of shales with beds and nodules of ironstone. Several genera and numerous species of plants are frequently very abundant in the roof shales, and by the working miner they are considered to be indicative of this horizon. Between Annesley and Gedling, in Nottinghamshire, the following shells have been obtained by Mr. R. D. Vernon* in the shales above the Top Hard and Coombe coals:—Naiadites modiolaris (J. de C. Sow.); N. carinata (J. de C. Sow.); N. triangularis (J. de C. Sow.); N. quadrata (J. de C. Sow.); Carbonicola aquilina (J. de C. Sow.); C. similis (Brown); C.nucularis (Hind); Anthracomya modiolaris (J. de C. Sow.); A. williamsoni (Brown). At Brodsworth Colliery Lingula mytiloides has been recorded from a thin band of blue shale lying 111 ft. above the Barnsley coal. (To be continued}. * “ Report on the Fossil Fauna and Flora of the southern portion of the Derbyshire and Nottinghamshire Coalfield?’ Rep. Brit. Assoc, for 1910 (1911), pp. 827-38.