2 16 The Ottawa Naturalist. [February 



connection in origin with ordinary pegmatite. Stretching prim- 

 arily develops a series of oblique transverse lines or joints which 

 gradually widen with an increase in the amount of dynamic 

 action. At times narrow arms or remnants may be seen connect- 

 ing the severed portions of the once continuous band, but these 

 gradually disappear. The breach becomes wider, the space thus 

 created being filled with the more plastic schist, until finally, and 

 in the same way as in the case of those autoclastics with 

 the limestone matrix, the extreme of deformation is reached 

 when the resulting rock seems perfectly indistinguishable from 

 an ordinary clastic conglomerate. 



EXPLANATION OF TLATES. 



The illustrations are half-tone reproductions from photographs, taken by Mr, 

 Joseph Keele and the author. 



Plate VI. — Autoclastic rock or pseudo conj^lomerate ; from lots 13, con. XIX of 

 Tudor township in the County of Hastings, Ont. 



The matrix is a dark grey, in places almost black micaceous schist pierced 

 by dykes of a micro-granitite, which more brittle than the enclosing matrix have 

 become autoclastic by stretching. In places the original continuity of these 

 more or less parallel igneous dykes is still preserved, but in most instances the 

 rock bears a marked resemblance to occurrences, which have usually been des- 

 cribed as "stretched conglomerates." 



Plate VII— Pseudo-conglomerate (autoclastic) ; from lots 12 con. XIX of Tudor 

 township. The enclosing matrix is a dolomitic limestone which has undergone 

 complete recrystallization. The supposed pebbles, which occur as a series 

 of rudely parallel and detatched lumps, weathering out from the surrounding lime- 

 stone were at one time fairly continuous bands and their identity in origin with 

 igneous dykes may be plainly seen by reference to the large and unbroken 

 pegmatitic dyke, which is shewn in the same illustration. 



Plate VII, Fig. 2. — Pseudo-conglomerate (autoclastic) ; lot 18, con. Ill of Wolla- 

 ston on the road between Coe Hill and The Ridge P.O. The euclosing matrix 

 is again a dolomite, but the fragments which were at first believed to be pebbles 

 are more diverse in composition ; granite is the most abundantly represented, 

 but diorite, amphibolite, pegaiatife and quartz were also noted. The irruptive 

 plutonic masses in the immediate vicinity shew a corresponding diversity in 

 composition. 



LATE VIII, Fig. I . — Autoclastic rock ; from lot 13 con. XIX of Tudor. The 

 matri.x is the dark grey mica-schist already mentioned, probably tufaceou in 

 origin, pierced by small parallel dykes of micro-granitite. The oblique trans- 

 verse lives representing small breaks, characteristic of the first stages in this pro- 

 cess of deformation or stretching may be noticed in the more elongated individuals 

 while in the same illustrations other portions of the rock resembles very closely 

 ordinary clastic conglomerate. 



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