480 PROP. E. J. GARWOOD ON THE LOWER CARBONIFEROUS [DeC. 1912^ 



lower stage of the sub-zone almost everywhere throughout the 

 country. In the Eastern Districts the beds belong to the Yoredale 

 type of Phillips and the Geological Survey. The base of the sub- 

 zone is, for convenience, taken at the lowest sandstone which there 

 overlies the Melmerby or Knipe Scar Limestone, as it ushers in the 

 change in lithological character. The upper limit of the sub-zone 

 is much more difficult to define, and in one district at least (ther 

 Pennine District) the sub-zone persists well up into beds mapped 

 as Millstone Grit by the officers of the Geological Survey. The 

 separation of these beds into two divisions represented by the 

 symbols D., and D^ in other areas, cannot be satisfactorily attempted 

 at present in the North- Western Province. This is due to the 

 almost complete absence of Cyatliaxonia Eeds, examples of this 

 genus being extremely rare and confined, so far as is knoW'D, to 

 local occurrences in the Westmorland Pennine District ; while no 

 beds referable to the Pendleside Series have been met with in the 

 districts described. 



Another difficulty is introduced by the marked difi'erence in the- 

 lithological and palseontological characters presented by the higher 

 beds of the Bihimo^thylluon Zone in the Eastern and Western Dis- 

 tricts respectively. Unfortunately, these beds have been denuded 

 from the greater part of the Western Districts, so that the exact 

 areas originally occupied by the two types and the character of 

 the passage from one to the other cannot now be definitely stated. 

 Of the portions still remaining, the northern and eastern outcrops, 

 forming the Shap-Ravenstonedale and Pennine Districts, belong to 

 the 'Yoredale' type, while the Southern and Western Districts belong 

 to what w^e ma}', for convenience of description, call the Western or 

 'Kirkby Lonsdale' type. These two types are now separated over the 

 greater part of the area by a wide tract of Lower Palaeozoic rocks, 

 although the eastern margin of the Kirkby Lonsdale District lies 

 within 2 miles of the Yoredale rocks of Casterton Pell, from which, 

 however, it is separated by the Dent and Craven system of faults. 



It is no part of the object of this communication to enter into a 

 detailed discussion of the causes which produced this diff'erence in 

 the character of these two types. The writer, however, has long 

 been of the opinion that, although the change from the Yoredale 

 type of deposits, now found north of the Craven Paults, to that 

 found on the south side must originally have been a gradual one, 

 the close proximity of these two types east of Kirkby Lonsdale at 

 the present day suggests that here, at all events, the two types have 

 been brought into their present positions by tectonic movements. 

 This view w^as expressed by Dr. Marr as long ago as 1899, for 

 he remarked in his work on the Limestone Knolls in the Craven 

 District of Yorkshire that 



'the Mkldle Craven Fault, in fact, appears to be a thrust-plane inclined 



downward towards tlie north if the fault be a thiaist the disposition 



of the rocks is perfectly explicable if ray interpretation of the structures- 

 south of the fault be true, the.se structures require thrusting to account 

 for them.' (Q. J. G-. S. vol, 1y, ] 809, pp. 352-53.) 



