140 THE GEOLOGY OF TASMANIA— THE PRE-CAMBRIAN. 



highest peak of the Surve3^or's Range. Looking thence 

 towards the north, the eastern portion of the s.ummit of 

 the Frenchman's Cap is seen to be folded into gentle 

 anticlines and synclines, and to have been fractured. 

 The other portions of the horizon appear to have re- 

 mained unaffected, and to be nearly horizontal. The 

 massive layers so plainly visible on the north-western 

 and western faces of Algonkian Mountain appear quite 

 undisturbed by folding forces, and dip at a low angle 

 towards the south-west. 



Between these remaining summits of the ranges the 

 quartzite schist stratum has been removed by denuda- 

 tions, and the subjacent schists are exposed. 



The horizon of quartzite schist rests unconform.ably 

 upon the quartz-schist and mica-schists, which show a 

 much more intense folation. This unconformity is 

 clearly &een on travelling along the top of the Sur- 

 veyor's Range; The higher peaks of this range (which 

 lies between the Jane and Acheron Rivers) are of the 

 more massive variety, and the abrupt change into the 

 highly contorted schists of the main mass of the range 

 is most noticeable. 



The existence of plainly horizontal layers of the rock 

 overlying the contorted schists is a strong argument for 

 not only the presence of a marked unconformity, but 

 also for a long period of erosion between the tune of 

 foliation of the lower schists and that of the deposition 

 of the upper quartzose sediments, which have since 

 been rendered slightly schistose. 



Confirmatory evidence must be obtained throughout 

 this region before these views can be fully accepted ; 

 but the writer is strongly of the opinion that there is a 

 distinct unconformity present in the district, and that 

 two distinct periods of sedimentation are represented, 

 and that a protracted period of erosion has intervened 

 between the deposition of the lower and upper members. 

 The greater degree of contortion displayed by the lower 

 series may be accounted for by the fact that these rocks 

 have suffered plication before the upper horizon was 

 formed. 



If it be granted that there are two such distinct 

 series among the Pre-Cambrian sediments in Tasmania, 



