[Peoc. Roy. Soc. Victoria 28 (N.S.). Ft. II., 1916]. 

 Art. XI. — Notes on (he Geology of the Coburg Area. 



By G. A. COOK, J3.Sc. 



i Kt-niot Research Scholar in Geology, University of Melbourne). 



(Communicated by Professor E. W. Skeats). 



(With Plate XVII.) 



Head 12th August, 1915 . 



Introduction. 



The area that will he discussed in tin's paper is about four square 

 miles of country to the east and north of Pentridge Stockade* It 

 has been mapped by the Geological Survey of Victoria on quarter 

 sheets (Nos. 1 X.E. ami 1 N.W.), hut the independent mapping of 

 the writer shows slight differences from that of the quarter sheet. 

 (For this independent mapping the contours were obtained from a 

 map published by the Metropolitan Board of Works.) 



The following stratigraphical horizons occur : — 



Palaeozic - Silurian sediments. 



! Basic dykes. 

 Tertiary sands. 

 Sub basaltic gravels and sands. 

 Newer Basalt. 

 Recent - River alluvium. 



Physiography. 



The area constitutes a portion of the peneplain around Mel- 

 bourne, and is drained by the Merri Creek. The country is of an 

 average height of 200 feci above sea level. To the West and North 

 basalt occurs, and forms a nearly uniformly flat plain, the highest 

 level of which is about 240 feet. Through this basalt plain in the 

 North, the Merri Creek follows a rather sinuous course, flowing 

 between narrow V-shaped valleys, and over rapids and miniature 

 waterfalls, with an average grade of 1 in 170. These are all 

 characteristics of a stream young in development. To the South, 

 however, where the stream is flowing through Silurian or along 

 the junction of Silurian and basalt, the grade flattens to 1 in 480, 



