Vol. 55-] 



GEOLOGY OF NOETHER]^ AI^GLESEY. 



651 



strata ; in certain parts there is also extensive ^disruption of the 

 beds, resulting in the phenomena known as ' crush-conglomerates/ 

 These various effects will now be considered. 



(«) Contortions and Folds. 



In the south of the district the chloritic schists of Mynydd Mechell 

 are thrown into contortions which are everywhere visible in the 

 bare rocky hills which they occupy. The individual folds, though 

 small, are not as a rule sharp, nor do their axes seem confined to 

 one particular direction. In the north-east, stretching for several 

 miles along the coast between Amlwch and Point ^lianus and 

 extending southward to the bounding thrust, is another and more 

 sharply-contorted area, described by Ramsay and other writers. 

 Beds of the same character, and showing similar fine contortions, 

 occur elsewhere, as for example near Llanfair-y'nghornwy Rectory 

 (see fig. 4), where the beds have a beautiful damascened appear- 

 ance. Here, as in most cases, the axes of the folds slope in the 



Fig. 4. — Contorted green phyllites : ]Dart of rock-face in quarry 

 behind Rectory^ Llanfair-y^nghornwy. 



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same direction as the dip, and the inference from this general 

 southerly to south-westerly tilt of the crests of the anticlines is 

 that the region has been affected by a powerful push acting as a 

 whole from the north : a conclusion which is in harmony with the 

 general structure of the district, as developed in the first part of 

 this paper. 



Even where the dip is at first appearance quite steady, a close 

 examination or more favourable exposures will show in some cases 

 that small contortions interfere with the apparent steadiness. 

 An example of this may be seen in the Rhosbeirio Shales of 

 Bodewryd IN'ewydd quarry, and I have noticed a number of other 

 instances, some in the neighbourhood of the crush-conglomerates. 

 Between Trwyn Peu-careg and Cemlyn there is continual over- 

 folding to the south and consequent repetition of the beds : here too 

 are instances of folds in which the axes are almost horizontal. 



