Marr : The Rigidity of North-west Yorkshire. 69 



west now submerged beneath the sea, though rocks older than 

 the Coniston Limestone are seen near Dalton and at Black 

 Combe. Movement along the same lines recurred later. We 

 find a mass of Carboniferous Limestone running southward 

 from Kendal, with older slate rocks on either side of it. 



Though the Craven fault forms the southern limit of the 

 rigid block of North-west Yorkshire, there is no doubt that 

 the movements belonging to the system affect the disturbed 

 rocks far away to the west of that part of the fault-system 

 which bounds the rigid block. 



The nature of the rigid block may be summed up in the 

 following words. It is a resistant tract of earth-crust, composed 

 of Carboniferous rocks resting unconformably upon more 

 ancient rocks, the nucleus consisting of crystalline rocks of 

 Archaean type and probably of that age. Around this block 

 the Coniston Limestone has been bent down on the north, 

 west, and south, and possibly to the east, though of this we 

 have no evidence, owing to the covering of newer rocks. Away 

 from the block, on three sides, rocks newer than the Coniston 

 Limestone are found, and are folded in various degrees, owing 

 to earth-stresses acting at various periods. The block itself 

 is surmounted, as stated, by Carboniferous rocks, which are 

 nearly horizontal, though fractured here and there, and affected 

 by an occasional buckling, as between Brough-under-Stainmore 

 and Barnard Castle. The rocks are, however, tilted slightly 

 eastward, and accordingly we are now presented with a tract 

 of country sloping gently to the east and abruptly terminated 

 to the west and south by steep slopes, the fault-scarps. This 

 general condition of rigidity has survived through all the 

 vicissitudes of earth movement, submergence and emergence, 

 deposit and erosion since the beginning of Carboniferous times, 

 and possibly, as far as the core of the block is concerned, from 

 a still earlier date. 



Having now dealt with the nature of the block, we may 

 proceed to consider the. effect of its existence upon other 

 events. Unique as the structure is as regards Great Britain 

 in its scale and its simplicity, it has given rise to occurrences 

 which are similarly unique in this country. 



The river-drainage is generally recognised as an ordinary 

 consequent drainage, the streams running to the east and 

 west from the top of the watershed. Owing to the easterly tilt 

 of the block, the law of unequal slopes is exemplified here, the 

 streams flowing westward with steeper grade, being engaged 

 in capturing the headwaters of those whose courses are in an 

 easterly direction. Some of the details of this have been 

 worked out along that portion which is bounded by the 

 Pennine Fault ; and along the tract east of the Dent fault, it 

 is known that the Clough flowing westward has captured the 



lr21 Feb. 1 



