Physiography of Werrihee Area. 2^S 



of the scarp, we must admit the possibility of the fault having: 

 occurred during the newer basalt period. The lavas along the- 

 southern part of the scarp, east of Maude, etc., must have been 

 poured out, prior to the faulting, while those near Bacchus Marsh 

 may have, in part, been poured out during its formation. Pro- 

 fessor Skeats, as already! quoted. (ref. 47, p. 208), suggests that the- 

 scarp may have been formed " during the eruptive period," while- 

 Mahony (ref. 39, p. 377), refers to the possibility that " the newer 

 basalts mark the close of the last great movement which elevated the 

 marine K a i no z o ic s . " 



The scarp at Bachus Marsh was viewed by Professor W. M. 

 Davis, during 1914, and discussed by him with Dr. Summers. Tlie 

 latter gentleman informs me that the Professor's suggestion was 

 that, if a fault, it was post newer basaltic, since a basalt flow could 

 not, from its mobile nature, have clothed the scarp as it appears to- 

 day. This expression of opinion, from so great an authority, must 

 be accounted as valuable evidence against a pre-newer basaltic age, 

 especially when the available evidence of the sections examined so- 

 strongly favours the belief that the newer basalt sheet was present 

 when the fault occurred. 



It must be admitted that the appearance of the slope, where the 

 rocks are exposed on the right bank of the Parwan (Note 16, Quar- 

 ter Sheet 12 N.E.), (see Fig. 32), gives an impression that the 

 basalt " flowed " over the slope. It may be that in these tertiary 

 clays and sands, with their strong covering " roof " of basalt, we 

 did not get a sharp line of fracture in all places, but rather a zone 

 of fracture, in places of a monoclinal nature, to the slopes of 

 which the basalt sheet accom.modated itself by movements along its 

 very abundant joints and cracks. (Fig. 7b.) However, the sum of 

 the evidence, as already shown, favours a post-newer basaltic 

 origin. 



Notwithstanding our lack of knowledge concerning the rate of 

 erosion in tlie various rocks, it is permissible to say that the physio- 

 graphic evidence also points to a comparatively late age for the 

 scarp. 



Other hypotheses have been put forward regaiding the origin of 

 this scarp — that it was an old sea clift' (ref. G), a river cliff, etc. 

 These ideas were kept in view when examining the scarp, and there 

 has been found not the slightest evidence in favour of any other 

 explanation than that of faulting. To briefly recapitulate the facts 

 as seen in the field, we may once more take a 'rapid survey of the 

 whole line. 



