PROCEEDINGS OF SECTION C. 387 



5.— NOTES ON THE GEOLOGY OF THE YOU YANGS, 



VICTORIA. 



By ERNEST W. SKEATS, D.Sc, F.G.S., Professor of Geology and 

 Mineralogy, University of Melbourne. 



[With Three Plates.] 



INTRODUCTIOX. 



About 30 miles from Melbourne, in a direction a little south of west, 

 a bold line of hills, known as the Youangs or You Yangs, rises abruptly 

 irom the level surface of the volcanic plains. The railway line between 

 Melbourne and Geelong passes within a short distance of them, and the 

 culminating point, marked on the Government map as Wurdi Youang, 

 or Station Peak (l,154;t.), is clearly visible from Melbourne and from 

 Geelong (12 miles). To those entering Port Philip by boat the clear-cut 

 ridge forms the most conspicuous object during the passage up the har- 

 bor. The highest point — Station Peak — provides a magnificent and 

 extended view over the Melbourne Basin and the Western District of 

 Victoria, and this hill was the first on which a white man set foot in 

 Victoria, Captain Flinders making the ascent in April, 1802. 



I can find no written description of the geology of the rocks of the 

 You Yangs. The general geological relations of the area are, however, 

 clearly shown in the maps of the Geological Survey of Victoria, quarter- 

 sheets 19 and 20. The area was mapped by Daintree and C. S. Wilkin- 

 son in 1861, under the direction of Selwyn, the Government Geologist, 

 and the maps were published in 1863. 



PHYSICAL GEOGRAPHY AND GENERAL GEOLOGICAL RELATIONS. 



The physical geography of the district is simple, for one is concerned 

 mainly with two features — the hills and the plains. The hills are 

 entirely granitic. From the southern extremity the exposed area of 

 granite stretches northwards for about three miles, and then divides, 

 one narrow outcrop continuing northwards for about another three 

 miles, while the main mass extends in a north-west direction for about 

 seven miles. Outlving masses which occur beyond this extremity, and 

 others to the north and to the west-south-west of the main mass, are 

 no doubt connected beneath the basalt plain. The age of the granite 

 cannot b^ defiuitelv fixed. It is probably Post Ordovician, since it has 

 altered rocks which are probably of that age. Denudation subsequent 

 to the intrusion has now exposed the granite at the surface, and only 

 at the south-west extremity of the area are any of the altered Palaeozic 

 sediments preserved. These are shown on the geological survey map 

 as a narrow fringe of highly metamorphosed sandstones and mudstones, 

 forming the south-west margin of a small low-lying projecting part of 

 the southern end of the granite. The present hill is, therefore, a residual 

 mass or monadnock, which owes its preservation to the superior power 



