30 NOTES ON THE GEOLOGY OF CKADLE MOUNTAIN DISTRICT, 



the Pleistocene glacial deposits. A little recent alluvium 

 IS also present. The general disposition of the first three 

 series is roughly indicated in Mr. Johnston's official 

 Geological Map of Tasmania of 1884, the earliest chart to 

 which the writer has had access. A more accurate repre^ 

 sentation is found in the map given by Jeffrey Smith, 

 "based on information supplied by the Geological Survey 

 of Tasmania." (2). 



The Pre-cambriaix rocks of the region have been 

 briefly described by Messrs. Waller (5) and Ward. (4) The 

 latter remarks that at Barn Bluff they strike a few de- 

 grees north of west. Between here and the Forth River 

 the strike, according to Waller, is nearly east and west. 

 In the immediate vicinity of Cradle Mountain the writer 

 found the strike to be between E.N.E.-W.S.W. and 

 N.N.E.-S.S.W., the former direction predominating to the 

 north-east of the mountain ; while to the north-west, along 

 the Dove River, rocks have been observed striking west of 

 north. Evidently there is a great bend in the Pre-cam- 

 brian fold-axes in this region. The rocks are intensely 

 folded ; numerous sharp anticlines and synclines are 

 visible. The dips are nearly vertical, and easterly dips 

 are usually steeper than those directed towards the west, 

 while the latter are more common. These facts suggest 

 that overfolding has occurred under the influence of a 

 thrust directed from the west. 



The rocks present are all of sedimentary origin. They 

 include dark grey phyllite, coarsely crystalline mica-schist, 

 micaceous quartz-schist, felspathic quartz-schist, and 

 schistose quartzite, showing abundant evidence of recrystal- 

 lisation, and, indeed, passing locally into vein-like masses 

 of quartz. True veins of quartz traverse the other rocks, 

 occurring lenticularly in the bedding-planes or running 

 obliquely thereto. Four samples have been examined 

 microscopically; the following are brief descriptions of the 

 same, using the terminology adopted by Grubenmann (^) : 



1461. Puckered Phyllite (helicitic texture). This 

 consists of a granoblastic ground, mass of 

 quartz-grains, with wavy bands of finely-di- 

 vided carbonaceous matter, sericite, and' 

 bleached biotite, the whole more or less stained 

 with limonite. 



(2) A Naturalist In Tasmania. London, 1309. 



(3) See Bibliography No. 21. 



(4) L. K. Ward. Contributions to the Geology of Tasmania. Syste- 

 matic Geology. The Pre-cambrian. Proc. Roy. Soc. Tas. 1909. 



(5) Die krystallinen Schiefer. Second edition, 1910. 



