28 NOTKS ON MT. ANNE AM) THE WELU UIVKU VALLEY. 



in Tasmania, typical of juvenile drainage. The main 

 streams have cut through the diabase sill and extended their 

 valleys considerably in the softer rocks below. They have 

 thus captured the drainage of very considerable areas of 

 country, and in widening their valleys have isolated rem- 

 nants of the old plateau which stand out as erosion residuals, 

 Mt. Anne being one of the best examples of this type of 

 mountain in Tasmania. [Sir Edgeworth David has asked 

 whether the topography has been all caused by differential 

 erosion and suggests faulting as responsible for the escarp- 

 ments east of Mt. Anne. The writer had this possibility 

 in view, but could find no evidence of large scale faulting. 

 and respectfully submits that erosion is responsible for the 

 present topography. But the possibility of a fault scarp 

 running up the west side of the Weld, past Mt. Stephen 

 (Tim Shea), west of the Vale of Rasselas, and even to the 

 west of the Cradle Plateau, should be borne in mind in 

 future investigations.] In eroding their valleys the rivers 

 have removed later sediments from and exposed the early 

 Palaeozoic topography, which, as Mr. Ward has remarked, is 

 now exerting an influence on present topography (Ward, 

 1909). An interesting example of this is to be seen at the 

 mouth of the Weld, where several miles of Cambro-Ordo- 

 vician quartzites with an already developed topograjjhy are 

 being exposed from beneath the sandstones. The topography 

 of the western portion of the area has been moulded by 

 glaciers during the Pleistocene Ice Age, the work of which 

 will be dealt with later. The rivers are at present engaged 

 in removing the morainal dams of the lakes and other re- 

 mains of the glaciers. 



3. STRATIGRAPHICAL GEOLOGY. 



(a) Pre-Cambrian. 



The highly foliated quartz-mica schists, ordinarily 

 referred to the Proterozoic [the Algonkian of Ward and 

 Twelvetrees], with which the Arthur and P^rankland Ranges 

 are made up do not appear to cross to the east of the Huon 

 unless Scott's Peak [which was not examined] consists of 

 these rocks, but this is unlikely. Mr. R. M. Johnston in his 

 Geology of Tasmania placed the rocks of the western ranges 

 in this system, and Mr. Twelvetrees describes the junction 

 with the quartzites visible north of Mt. Wedge (Twelvetrees, 

 1908), but in the area being described the junction appears 

 to be obscured beneath the glacial deposits of the Huon 

 Valley. The Geological Map of Tasmania issued by the 



