DISLOCATIONS NEAR WOLVERHAMPTON, DUDLEY PORT, ETC. 503 



flats), instead of dipping under the New Red Sandstone, rise gently as they approach 

 it \ nay, further, they taper away and deteriorate in quality, until they are successively 

 intercepted by the line of fracture which brings them into contact with the red ground. 

 As the face of this fault sinks to the west or W.N. W. at an angle of 45°, it follows, that 

 the inferior measures or "blue flats" range 800 yards further to the west than the 

 uppermost bed of coal. (PI. 29. f. 13. and PI. 37. f. 3.) 



Knowing that the Wenlock limestone has been proved at several points beneath the 

 bottom beds of the Wolverhampton field, and seeing the tendency of that rock to 

 bulge out in other parts of the tract, and to throw the strata- into troughs, we can 

 easily suppose, that this anomalous appearance of the coal measures rising against, in- 

 stead of dipping under the New Red, has been produced, either by an upcast or swell 

 of the Silurian rocks, or by the elevation of some point of trap rock, similar to that 

 observed near Sandwell. This inference, indeed, is countenanced by the structure of 

 the opposite flank of the field near Wallsall, where the Silurian rocks rise to day at 

 angles of 40° to 50°, and trending from north-east to south-west, constitute what is 

 termed the ' ' great limestone fault " ; which throwing off the coal measures, as represented 

 (PI. 37. f. 3.), may there be called the natural edge of a basin. Again, as the elliptical- 

 shaped Silurian masses of Sedgeley, the Wren's Nest, and Dudley rise in steep ridges 

 and domes, the coal measures on their flanks are naturally cut off, and in several cases 

 the coal is also bent up on their lower edges at high angles. These sudden expansions 

 of the inferior rocks, have necessarily produced great flexures in the overlying coal 

 measures, throwing them into irregular troughs of unequal sizes. It must, however, 

 be always recollected, that when viewed as a whole, the tract, so far from being a basin, 

 is merely made up of undulating broken masses, the sides of which are lost on all sides 

 beneath the New Red Sandstone 1 . 



The irregular elevations of the inferior rocks are necessarily accompanied by dislo- 

 cations, some of which extend for considerable distances through the adjacent coal-field. 

 The most powerful faults in the richest part of the Dudley field range from north-east 

 to south-west the direction of its major axis. Two of these, running parallel to each 

 other, produce a deep and narrow trough of coal of 84 yards in width, the base of which 

 is 100 yards beneath the thick coal on the south-eastern side, and 80 yards beneath it 

 on the north-western. The edges of this trough coincide precisely with the direction 

 of the axis of elevation of the Wallsall limestone, and the result is, that on the chief 

 upcast side, the same limestone throws up the coal measures, thus proving that the 

 forces which determined the protrusion of the Wallsall ridges, produced also the sub- 

 terranean upcast of Dudley Port. The transverse section (PI. 37. f. 1 .) explains the 



1 I am the more desirous of directing attention to these general relations of the coal-field, because Dr. Buck- 

 land in his Bridgewater Treatise has given a section by Mr. Jukes, PI. 65, which though true as respects a 

 portion of this tract, ought not to lead to the belief, that this coal-field, like ordinary coal basins, is on the 

 whole supported on its flanks by older rocks. (See my sections, PI. 37. figs. 1 & 3.) 



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