3^4 



NA TURE 



[August i8, 1904 



premising, liowever, that by Permian 1 mean tlie Magncsian 

 Limestone series, and not the " Permian of Salopian l.V|)e," 

 which is now known to be partly of Triassir but principally 

 of Carboniferous age. In the course of the investigation 

 we shall find reason to conclude that several at least of (he 

 iiiovements followed old axes of disturbance, lines of weak- 

 ness dating from an early period in the history of the habit- 

 able globe ; and, again, that some of the latest disturb- 

 ances of which we have cognisance were but renewals of 

 movement along the same general lines. 



One of the most clearly proved examples of pre-Permian 

 faulting in the Carboniferous rocks occurs in the White- 

 haven Coalfield. The fault forms the south-eastern limit 

 of the Coal Measures, and has been precisely located for a 

 distance of six miles. In its course towards the south-west 

 it passes under five outliers of Permian rocks, and finally 

 is lost to sight under the Permian and Trias of St. Bees. 

 The dislocation in the Carboniferous rocks amounts to about 

 400 yards, but the Permian rocks have not been even 

 cracked ; though broken and displaced by numerous faults 

 of later date, they pass undisturbed over this great dis- 

 Icjcation, the movement along it obviously having ceased ' 

 iiefore they were deposited. Phis fault forms part of the 

 upheaval which brought the older rocks of Cumberl;md 

 and Westmorland to the surface, and in that sense it may 

 be said to form the north-western frontier of the Lake 

 District. 



On the norlh-eastern side also of the Lake District the 

 Permian rocks rest upon uptilled Carboniferous strata, but 

 I he axis of upheaval runs in a north-north-westerly direc- 

 lion and defines what we may regard as the north-eastern 

 Irontier. .\long this frontier much movement has taken 

 place in post-Permian times, but the unconformable rela- 

 (ions of the Permian and Carboniferous rocks enable us to 

 (li-.tinguish that part of the tilting which intervened between 

 the two periods. On the south-eastern frontier also the 

 I '.irboniferous rocks had been upheaved and denuded before 

 ihe Permian sandstones were laid down. K huge fault, 

 .dong which Carboniferous rocks have been jammed from 

 I he east in a multitude of plications against Silurian, runs 

 from Kirkby Stephen by Dent to Kirkby Lonsdale, and 

 ihence trends south-eastwards by Settle. It is highly prob- 

 .ible, though it has not been proved, that this fault is of 

 |)re-Permian age. That the Pendle axis which upheaves 

 the Lower Carboniferous rocks between Settle and Burnley 

 is pre-Permian is placed beyond doubt by the fact that an 

 outlier of Permian rests upon the denuded crest of the 

 anticline near Clitheroe. 



The south-western frontier is defined by a still more 

 marked unconformable overlap by the Permian strata, which 

 here pass over the edges of the lowest members of the 

 Carboniferous series and come li> rest upon the Lake District 

 recks. 



VVe have thus defined the sides of an oblong tract which 

 was upheaved in the period we are considering. The older 

 rocks forming the northern part of that tract had already 

 had imposed upon them a dominant north-easterly strike by 

 a pre-Carboniferous movement of great energy. As a result 

 also of that and other movements they had been subjected 

 10 vast denudation, not only in the Lake District, but 

 ihroughout the north-west of England generally. But 

 while it is doubtful whether any of the physical features 

 I hen produced have survived, it seems to be beyond dispute 

 ih.it it was in consequence of the pre-Permian movements 

 that the older rocks of the Lake Di.strict were freed from 

 I heir Carboniferous covering, and that to this extent the 

 district may be said to have been blocked out in pre-Permian 

 times. The detailed sculpturing resulted from later move- 

 ments, with which we are not now concerned. 



During this same period there rose into relief that part 

 of the Pennine axis which runs between Lancashire and 

 Yorkshire. The doming up of the Lower Carboniferous 

 rocks and the wildness of the moorlands which characterise 

 I heir outcrops have impressed all who have had occasion 

 to cross from the one populous coalfield to the other, and 

 have gained the name of the " backbone of England " for 

 this jinticlinal axis. Whether, however, it can be regarded 

 • IS one axis or as the result of several movements is doubtful, 

 but not material for our present purpose. Regarded as a 

 geological structure it is not continuous with that part of 



NO. 18 I 6, VOL. 70] 



the Pennine axis which runs along the north-eastern frontier 

 of the Lake District. 



Passing westwards from the Pennine axis we cross the- 

 deep and broad Triassic basin of Cheshire, which may be- 

 regarded as the complement of the dome of elevation of 

 Derbyshire, io the west of this, again, we reach a part 

 of North Wales which was more or less shaped out by the- 

 earth-movements which came into action between the 

 Carboniferous and Permian periods. Two leading faults- 

 traverse the district. The one runs in a north-north-westerly 

 direction across Denbighshire and introduces that little bit 

 of " Cheshire in Wales " known as the Vale of Clwyd. 

 Though there has been some later movement along this, 

 fault, it was in the main pre-Triassic, which statement, in 

 view of the perfect conformity between the Permian and 

 Trias, amounts to saying that it was pre-Permian. The 

 other passes across Wales in a north-easterly direction along 

 the Dee Valley at Bala, and reaches the Triassic basin 

 between Chester and Wrexham. The date of this fault has 

 not been worked out in detail, but the fact that it is- 

 associated with a pre-Triassic anticline, where it reaches 

 the Triassic margin, proves that it is in part at least of 

 pre-Triassic age. In Anglesey also there has been strong, 

 post-Carboniferous folding in the same N.E.-S.W. direction- 

 It is to be noticed, further, that the Carboniferous rocks 

 maintain their characters to their margins on the flanks, 

 of the Clwydian Hills and other ranges of Silurian rocks- 

 in North Wales. Both along the coast, and even in a 

 little outlier preserved near Corwen by an accident of fault- 

 ing, they show a persistence of type and of detail in 

 sequence which could hardly have been maintained had the- 

 Silurian uplands existed in Carboniferous times. The 

 inference that the uplands of Denbighshire and Flintshire 

 are the result of post-Carboniferous upheaval is strengthened 

 by the fact that the Carboniferous rocks reposing on their 

 flanks are tilted at an angle which would carry them over 

 their tops. This part of North Wales, therefore, presents 

 a history corresponding in its main events with that of 

 the Lake District. It had undergone elevation and denuda- 

 tion in pre-Carboniferous times on a scale so vast that: 

 rocks showing slaty cleavage and other indications of deep- 

 seated metamorphism had been laid bare. But in both 

 cases it was in consequence of the post-Carboniferous move- 

 ments that the leading physical features as they exist to- 

 day began to take shape. 



in both these regions pre-Carboniferous movements had 

 been extremely active. For example, an axis of compres- 

 sion and upheaval ranges from N.E. to S.W., involving 

 the Lake District, the Isle of Man, and .-\nglesey. It 

 belongs to the Caledonian system of disturbances which is 

 developed on a large scale further north, and which sufliced 

 here to cause slaty cleavage and presumably the extrusion 

 of the Shap granite. I mention this pre-Carboniferous axis 

 to point out that it offers an explanation of the direction 

 taken by the post-Carboniferous disturbances of White- 

 haven, Pendle, .Anglesey, and possibly Bala. With the ex- 

 ception of the last-named they lie well within the region 

 affected, and alone among the post-Carboniferous axes 

 take that particular direction. 



The Pennine axis ends as a physical feature in South- 

 Derbyshire and North Staffordshire on the margin of a 

 deep channel filled with Triassic marl, which extends west- 

 wards from Nottingham into Shropshire. In this part of 

 England there springs into existence a remarkable series 

 of disturbances tending to radiate southwards. The 

 westernmost of these is the great fault which forms the 

 western boundary of the North .Staffordshire Coalfield. 

 Recent work by Mr. W. Gibson has shown that the vertical 

 displacement of the Coal Measures amounts to no less than 

 qoo vards, but that it is far less, though recognisable, in the 

 Trias, proving that the disturbance was in the main pre- 

 Triassic. The fault ranges from Macclesfield in a south- 

 south-westerly direction, is lost to view under the Trias 

 near Market Drayton, but it is recognisable further on in 

 the great dislocation which passes along the western side 

 of the Wrekin, and thence through Central Shropshire by 

 Church Stretton to Presteign in Radnorshire, and thence 

 into Brecknock. 



The second is the Apedale Fault of the North Stafford- 

 shire Coalfield. In working the coal this disturbance has 



