284 Charles Fenner : 



and east 24^S. No evidence for this was especially looked for in 

 the field, but Hobbs (ref. 32, p. 56) suggests that the ** master- 

 joints " of a crushed block are intersected by another set at about 

 45° to the first. (See also Fig. 242, ref. 32, the " pattern " of the 

 stream shown in Hobb's figure has a peculiar resemblance to that of 

 Back Creek). 



Korobeit Creek rises near Mt. Blackwood, and has been influ- 

 enced in its upper parts by the Blackwood basalts. It flows south 

 and west through Ordovician, later tertiary gravels, and older 

 volcanics (including tuft's), in a wide valley that was perhaps 

 already chosen in pre-newer basaltic times, joining Pyke'a Creek at 

 the reservoir. This concludes the account of Pyke's Creek and its 

 tributaries. 



(e) Myrniong Creek. — This stream is wholly post-newer basaltic. 

 Its ancestor, the '' ancient Myrniong," flowed down from where Mt. 

 Blackwood now is, entering the ** ancient Werribee " not far from 

 the point where the Myrniong junctions with the present Werribee 

 This old valley was filled by a newer basalt flow (Fig. 21), and the 

 ■"twin streams" of the Myrniong and Korkuperrimul Creeks 

 arose one on either side. The head valleys of the Myrniong are in 

 Ordovician rocks, and are at first somewhat steep, but soon widen 

 out. The stream flows south, keeping the lava flow of Mt. Black- 

 wood on its eastern bank, and with a variety of older rocks on its 

 western side. At the village of Myrniong, in response to a west- 

 ern bend in the basalt tongue, it also turns westward, and then 

 south. It then enters granitic rocks, which being much decom- 

 posed are here, less resistant than the newer basalts. About a mile 

 south of Myrniong it cuts an old basalt-filled river-bed, and 

 thence continues flowing directly towards the Werribee. A little 

 distance further along the stream again meets a deeper tongue of 

 basalt, filling an old valley in the granite, and this gives rise to a 

 most peculiar, though small, physiographic feature, shown in Fig. 

 34. 



This peculiar loop in the Myrniong occurs where it comes in con- 

 tact with the basalt, which it has not yet quite cut through. It 

 takes a long course through this basalt, doubling right back on 

 itself as shown in the figure. High clifts occur where the hachures 

 art darkest. The country rock here is granitic, and just over a 

 low ridge, a few hundred yards from the southernmost point of the 

 loop, is the gorge of the Werribee, 300 or more feet deeper. Why 

 the Myrniong chose to turn here, across this very resistant obstruc- 

 tion, and to flow to the Werribee in the present long loop-like 

 <:ourse, is difficult to say. It would have been much easier and 



