Serpen fine Area and Rhyolife!^. '^53 



IG, 1907. The official report is not yet available. Last year 

 some opportunity was afforded at the University for the chem- 

 ical and petrological examination of some of the rocks and 

 minerals collected. This was further supplemented by some 

 valuable chemical analyses by Mr. G. Ampt, B.Sc, who formed 

 one of the party on the 1907 trip. Mr. Ampt's analyses were con- 

 ducted in the Chemical laboratory of Melbourne University 

 This year, though time has been somewhat limited, some fur- 

 thei" petrological research has been carried out in the Geological 

 laboratory, and considerable help has been afforded b}^ Professor 

 Skeats, whose personal knowledge of the district made his 

 advice particularly valuable. 



IV. — The Serpentine Area. 



(a) Physiographica] features : — 



The lower palaeozoic area covers probably 40 or 50 square 

 miles to the west of Mt. Wellington, and occupies the basin of 

 the upper Wellington river. A large basin is here in process of 

 formation. The crown of a great anticlinal fold of the over- 

 lying upper palaeozoic rocks has been denuded, exposing the 

 underlying slates. Tliese have yielded to denuding agencies 

 more rapidly than the overlying sandstones and rhyolitic lavas, 

 so that the slate region is marked by a great immature basin 

 filled ^vith lower, but still precipitous, hills, surrounded by an 

 amphitheatre of high and imposing scaq^s of the upper palaeo- 

 zoic rocks. The eastern wall rises particularly steeply to an 

 elevation of over 5000ft., and is formed of a great pile of acid 

 lavas of Mt. Wellington. The basin extends northwards to the 

 east of Tamboritha, towards the headwaters of the Wellington, 

 and southwards to a transverse east and west ridge joining 

 the Avon and Macallister Avatersheds. The western wall is 

 broken by the gorge through which the Wellington issues to- 

 wards the Macallister. 



The valleys are deeply incised int;> the slates, and are the 

 characteristio narrow Y-shaped mountain valleys, with ver}' 

 restricted alluvial flats. 



Tliree important streams drain this basin, the upper Wel- 

 lington and two tributaries. The central one is the Barrier 

 Creek, which flows from the springs issuing at the base of the 



