On a Palaeozoic Serpentine CoiigloTiierate. 3 



ment Gap. On both sides of the spur in this vicinity and 

 extending on in a south-easterly direction, the serpentine rocks 

 can be ti-aced. They appear to have been subjected to a consid- 

 erable amount of mechanical deformation, so that a well defined 

 foliated structure has been induced. The general trend of the 

 planes of foliation is from the north-west to the south-east, and 

 coincides generally with the strike of the Ordovician rocks. 

 Local variations, however, were observed and further on where 

 the chrome iron ore occurs the foliation was more easterly. 

 That the rocks have been subjected to considerable movement, 

 and probably torsion also, is shown by the polishing and slicken- 

 siding of the serpentine laminae. Smoothed and rounded 

 boulders were abundant on the slopes of the spur and several 

 were found which showed distinct grooving and striation, and 

 apart from this feature the shape of many of the boulders was 

 even more suggestive of ice action. These boulders were traced 

 to parallel bands in the serpentine, the general features of which 

 are of considerable interest. 



The matrix is for the most part serpentine and contains 

 rounded boulders up to six inches and more in length. The 

 included rocks are of various kinds, those noted being, quartzite 

 and other indurated rocks, micaceous schist and basic igneous 

 rock. The boulders of the latter are for the most part either 

 wholly or partially serpentinised. These are the softest rocks in 

 the deposit and are the only ones that showed marked striations. 

 Between the larger boulders, a finer grit is frequently found and 

 the component particles of this portion of the deposit consist 

 chiefly of rounded grains which are now serpentine. Some of 

 the pebbles show distinct evidence of movement in the matrix 

 and consequent slickensliding due to the abrasion by the finer 

 grit. Mechanical deformation is well shown by one of the 

 serpentine boulders which shows a structure similar to that 

 induced by the squeezing of a partially dry ball of putty. 



The grooving, and particularly the shape of many of the 

 boulders when examined in the hand specimens, would suggest at 

 once the ice origin of the material, but when the subsequent intense 

 pressure, movement and torsion indicated in the rocks is taken 

 into account the value of striation at any rate becomes less import- 

 ant. It is possible, however, as indicated by the shape of many 



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