Physiography oj Wervihee Area. 271 



For the first six miles the Werribee flows south, parallel to the 

 Eastern Moorabool. Just below the Greendale fault line it flows 

 on to newer basalt, and thus continues past Ballan ; the valley here 

 is shallow and insigniflcant. It turns easterly at Ballan, and 

 thence flows in a young V-shaped valley about 150 feet deep, cut 

 into tiie volcanic plain. Between Ballan and its junction with 

 Pyke's Creek, the bed exposes a variety of rocks such as might be 

 expected hereabouts only in the Ballan sunkland : small patches of 

 Ordovician sandstones, permo-carboniferous glacials, buried river 

 gravels, etc. In several places it bisects deej^er portions of the 

 basalt, of which a better knowledge may some day give material 

 for the mapping of the pre-basaltic river-beds there. 



Where the river passes at the foot of Mt. Darriwill, a tunnel 

 has been made to lead water through to the adjoining valley into 

 the storage reservoir of Pyke's Creek. Half a mile or more before 

 the Werribee joins Pyke's Creek, it has almost cut through a tongue 

 of thicker basalt, giving a fine exposure of a pre-basaltic valley, 

 cut in the underlying granodiorites. The present river course here- 

 is tortuous, probably due to meanders inherited from its original 

 channel in the basalt plain, and exaggerated as the river 

 deepened. 



From Pyke's Creek downward, the grade is much steeper, cutting 

 through the granodiorites and Ordovician beds on which it has been 

 superimposed. These hard rocks have caused the river to give all 

 its attention to downward erosion, and we pass into a precipitous 

 gorge. For the next three miles, to the eastern end of " the 

 Island," this gorge grows deeper, and here the steep-graded 

 Myrniong Creek enters on the northern side. 



From this point onward foi- about two and a-half miles, the river 

 turns and twists through a gorgd of great scenic beauty. The land 

 on the left bank of this area, adjoining the river, bas been pro- 

 claimed a public park. An excellent section showing tlie stiucture 

 here has been prepared by Mr. C. C. Brittlebank, and published in 

 the Monthly Progress Report of the Victorian Mines Department, 

 May, 1899. Steep cliffs nearly 800 feet high occur, showing fine 

 exposures of the great anticlines and synclines of the Ordovician. 

 the junction of the latter with the granodiorite, old glacial valleys 

 and striated *' pavements," and many other features which com- 

 bine to make this gorge an area greatly favoured by Victorian 

 geologists. It has been described as '' scientifically, tlie most 

 famous place in Victoria." 



