1899] Barlow— Arch^an Conglomerates. 213 



the coarse material has been formed by the breaking apart of 

 small dyKes or apophyses of the intrusive rock. At one place in 

 Tudor, on lot 12, con. XIX, an exposure of the usual crystalline 

 limestone is seen in contact with the granitic-looking diorite. 

 The junction between the two rocks is exceedingly irregular 

 and jagged and re-entering angles of the limestone fill 

 up the interstices m the diorite. On the other hand arms 

 or points of diorite pierce the limestone and their continua- 

 tion outward is seen to have been broken in the stretching to 

 which the rock has been subjected, leaving a series of rounded 

 lumps of the intrusive rock extending out into the limestone and 

 entirely separated from the parent mass. In other instances, 

 possibly a little more remote from the batholite, the limestones 

 are often penetrated by a series of more or less parallel dykes, 

 most of which are pegmatitic in origin and structure. The 

 extreme deformation of these relatively much more brittle bands 

 or dykes produce autoclastir rocks which are undistinguishable 

 in many instances from the ordinary clastic conglomerates. 



The psuedo-conglomerates, however, that have perhaps 

 caused most confusion and misinterpretation are those which 

 possess a dark grey, often almost black micaceious matrix, in 

 which are embedded rounded or lenticular fragments, the most 

 abundant of which were evidently composed of some species of 

 fine-grained granite. (See Plates, VI, VIII and XIX.) In pre- 

 vious descriptions covering this and adjacent areas, precisely 

 similar occurrences have been invariably described as ex- 

 cellent examples of undoubted clastic conglomerates, while 

 the lenticular outlines of many of the contained fragments 

 was referred to as interesting evidence of the intense squeez- 

 ing and stretching to which the whole rock-mass had been 

 subjected. All the exposures of rocks of this kind ex- 

 amined in the area covered by our map-sheet, furnished little 

 or no evidence in contradiction of such a theory while the 

 apparent identity of the coarse fragments with material com- 

 posing certain plutonic masses in the immediate neighborhood, 

 seemed to lend additional support to such a view. On the other 



