546 PK0E. G. A. LEBOUK AND DK. J. A. SMTTHE ON [Aug. I906, 



iron and phosphorus in the rock immediately overlying the shales 

 of the Lower Series, thus : — 



Analysis (1) of samples from the actual base, and (2) of samples 

 from about 6 feet above the base. 



(1) (2) 



FeO trace none 



Fe 3 l-43°/ 0-91% 



P 2 5 0-07% none. 



IY. Conclusions. 



From the various facts recited in the foregoing pages, it seems 

 inevitable to conclude that: (1) the beds to which we have referred 

 as the Lower Series suffered a considerable amount of denudation 

 before the Upper Series or Table-Rocks Sandstone was deposited, 

 and that this denuded surface occupied a large area ; (2) that after 

 the deposition and consolidation of the Upper Series, a movement 

 took place which thrust that series northwards over the shales and 

 other beds of the Lower Series. 



The actual amount of denudation, and the consequent time-value 

 of the unconformity, we have as yet no means of appraising. The 

 actual amount of horizontal displacement or overthrusting we have 

 also, unfortunately, no means of gauging. It seems clear, however, 

 that most, if not all, of the small faults, sharp folds, and other 

 disturbances affecting the Lower Series of beds, are the result of 

 the moving of the Upper Series over them, generally speaking along 

 the pre-existing plane of denudation. 



In this case, then, we may regard the thrust as one in which a 

 massive and compact set of rocks was dragged or pushed over a 

 previously-prepared floor chiefly composed of soft, clayey, and, so-to- 

 speak, specially-lubricated material, the nature of the rocks above 

 and below the unconformity providing the required line of least 

 resistance. Where the lubrication was least perfect accidents 

 happened. Thus at F a tongue of Upper Sandstone pierces the 

 shale beneath (see fig. 6, p. 536). At E, the sandstone has been 

 pressed against the hard Mussel-Band and reared up into a fine curl 

 (fig. 14, p. 547). 



At several spots the sandstone has ploughed into the shales, 

 hardening and sometimes slickensiding them, as for example on 

 the beach at C, where high-dipping sandstone can be seen resting 

 upon slickensided shale. 



The action referred to seems intimately connected with the 

 production of the stony ridges, which have been mentioned as 

 occurring at J, K, and M, and deserve special notice. These 

 ridges consist essentially of outcrops of sandstone belonging to the 

 basement-portion of the Table-Rocks Sandstone, but striking from 

 the base of the cliff, and transversely to it, for some 8 to 10 yards, 

 and intruded dip-wards into the shales of the Lower Series for a 

 distance of 4 to 8 feet. At first sight, these down ward- torn 

 apophyses of the Upper Sandstone present the appearance of dykes, 



