June 9, 1916. THE COLLIERY GUARDIAN. 1089 □ YORK KPWORTf iese (a.) I<* 640 (t.h. * OiESTERFIELD V 'ILLEUTOH MANSFIELD NOTTINGHAM BOO (C H) 1034 (TH) SHIREOAKS Ci A 64 fc.Wj 1370 (T.H) —Dip uv Coal Measure-8 proved/ undergrouad- Svadrues. $ | $ AiVLtcLuve#. ---Faults ------. Contours of Coal Measure surfaae uv feet below 0.D All depths areg overt/ in- feet below 01) -(cm) depth/ to Coal Measures (t.h.) depth- to Top Bard- Coal, (b.) depth- toBarnsley Coal. © Collier les fc.) o- Borings (b.h.) * “““■ Radi-vags & Stations 1895 (B.) SHERWO 5 47(7:^ 172 (C.fif.) IwARSOP C qEDWALTON MARKET WTBUJUTQN Map Showing Positions of Shafts and Borings in the Concealed Area. The evidence provided by pits and borings on the south beyond the area of the map, suggests that on the south-east this east-and-west Mansfield anticline is cut off by a sharp north-easterly and south-westerly synclinal trough which contains unprofitable red and green measures belonging to. the upper coal measure series^ such as were proved at Oxton and Thurgarton. The published evidence from the Kelham boring which is also just south of the boundary of the map may be interpreted as suggesting that this trough through Farns- field is followed by an eastward rise of the measures in the district to the east of it. In following the axis of the eastward swell of the contours between Tibshelf and Rufford along a line of latitude immediately south of Mansfield, one must not lose sight of the existence of the north-western and south-eastern syncline through Barlow and Chesterfield. This Chesterfield syncline contains measures above the Silkstone, coal, and flanks the Brimington anticline on the south-west. Possibly it is the disturbance of this trough line encroaching upon the Brimington anticline which brings the Top Hard coal within the faulted syncline of Williamthorpe, and produces the curious outline of the outcrop of that coal from the upper valley of the Doe, round by North Wingfield, to Grassimoor, in . the valley of the Rother. South of Holmwood, the Williamthorpe syncline is supposed to lose itself in faults, and Dr. Gibson has suggested that beyond it the Brimington anticline may reassert itself, and “ pass between the 'borings at Oxton and Thurgarton and that of Kelham.* From the trend of the contours, it would seem that the only place for any continuation of the Brimington anticline south of Stainsby is the crest line through Sutton and south of Mansfield, which the writer has already discussed. From Silver Hill and Teversal northwards to Staveley, the contours of shallow depths trend steadily to the north-west, and are very close together, a dip of almost 1 in 2 being indicated about Glapwell, the workings of which flank the southern end of the main Brimington anticline. Through Ireland, Markham, and Bolsover pits, the line of the Dronfield-Staveley syncline (which is its north-eastern neighbour) is continued, but the effects of this are complicated and somewhat reduced by a subsidiary anticline through Oxcroft and between Shirebrook and Warsop, which separates it from the main trough that passes south of Creswell to Lang- with, and in the deepest part of which the new pit at Welbeck seems to have been sunk. The wide bay in the outcrop of the Top Hard coal about Renishaw is on the line of the anticline of Norton Ridgway. The line of this disturbance continues north of Barlborough, through Whitwell, and in its relations with the Dr onfield-Langwith syncline, determines the southerly or south-easterly dip of the coal at Creswell and Southgate. Steetley lies on the northern flank of this disturbance, and the’crowding of the —300, —400, and —500 yard contours to the west of that pit suggests that its acuteness has not decreased south-eastwards. Waleswood, Aston, Beighton, Fence, Handsworth, Orgreave, Tree ton, High Hazels, and Tinsley Park pits lie among contours quite as regularly as any spot levels determined for the plane at the base of the permian. Norwood, West Kiveton, and Kiveton Park are deeper than would be estimated from a knowledge of the depths in Yorkshire, and evidently lie south of their proper posi- tion as determined by producing south-eastwards the straight-line contours drawn among the pits of Rother - vale. The effect is as of -an anticline along the line of the Sheffield-Worksop railway, and a comparison of the depth at Shireoaks with depths at Steetley and at Manton suggests that the displacement due to such an anticline increases rather than diminishes eastwards. Between the county boundary of Yorkshire and the neighbourhood of Sheffield the regularity of the shallower contours has already called for comment. In this area the Top Hard coal thickens northwards, and, becoming more bituminous, is counted worthy of the name of the “ Barnsley bed.” In this district the dip near the out- crop is steeper than the average, and the widening out of the spaces between the deeper contours is particularly marked. The direction of the strike is some few degrees more westerly than in any other district shown upon the map. The deeper contours shown have had to be drawn between spot-levels that are very far apart, and the experience gained at Thurcroft causes one to expect that, when the details become known, bends and other irregularities, perhaps of considerable amplitude, will be required to represent the true underground geometry of the central and eastern parts of the district. Through Sheffield, by Rotherham to Hooton Roberts and Conisborough, ranges the well-known disturbance always referred to as the disturbance of the ‘‘Don faults.” This is a belt of country more than a mile in width, across which a proved succession of not very con- siderable faults and very important variations in the amount and direction of the dip accomplish the equiva- lent of a vertical displacement of the measures by some 400 or 500 yds. Usually, in alluding to this displacement, one lays stress on the throw of the faults known respectively as the “Northerly” and the “Southerly” Don faults; but when, after an inspection of mining plans and a study of the ground, a number of horizontal sections across them to true scale has been made, the greater general importance of steep dips compels notice ; and one concludes that the whole disturbance is better regarded as the steep and somewhat broken middle limb of a monoclinal fold. A geometrical plotting of the depths at Holmes, Car House, Aldwarke Main, Roundwood, Thry- bergh Hall, Denaby Main, and Gadeby Main collieries also gives evidence in favour of the same view, which has therefore been adopted in the making of the map. From the map it will be seen how regularly the average slopes continue, despite the faults, and by it a proper emphasis is placed upon the general steep south-easterly dip within the faulted zone. The axis of the synclinal trough related to the Don faults disturbance appears to range somewhat north of east through Rotherham Main and° between Sil verwood and Maltby Main. The behaviour of the dip at Maltby and the great depth of Yorkshire Main Colliery might suggest that the centre of the trough occurs somewhere between Maltby and Doncaster; but the dip at Rosisington Main and the depths given by borehole information at Armthorpe and South Car make it probable that the main deep * Concealed Coal Field Memoir, p. 39.