Physiography of Werrihee Area. 221 



Where the Werribee river cuts the scarp, soft tertiary materials 

 ^abound, and the wide, soil-covered valley slopes do not provide any 

 ;good sections. A point east of Trig Hill, however, attracted the 

 attention of the survey in 1868 (ref. 56), and has also been 

 -examined and commented on by Mr. Hart. The usually level ter- 

 tiary beds here show an easterly dip, possibly due to "drag" 

 :along the fault line. Mr. Hart expresses somewhat the same idea 

 by calling it a " faulted monocline." (ref. 22, p. 268). 



A little further south there are three important sections : — (i.) 

 on the right bank of the Dog-Trap Gully, above the railway line, 

 (ii.) on the right bank of the Parwan, where it crosses the scarp 

 preferred to in 1868; note 16, Quarter Sheet, 12 N.E.), and (iii.) 

 in the cutting where the road passes over the eastern ridge into the 

 Parwan Valley, a short distance to the south of the last point. The 

 sum of the observations at these three points was that the basalt 

 -capping the higher block along the edge is now very thin, that the 

 tertiaries remain on the whole level-bedded close to the edge of the 

 scarp, and that the junction between the two thence descends steeply 

 ■eastward. These relations are diagrammatically shown in Section 8b. 

 The " Parwan Creek " shown in this section indicates the small 

 valley cut into the alluvial and basalt by the lower Parwan. east 

 of the scarp. 



The Dog-Trap Gullv is of further interest, inasmuch as it 

 •exposes along its left bank tlie side of a thick body of basalt that 

 apparently fills an old valley which once existed there. 



Section 8c shows tlie typical relations of the scarp face further 

 south along the eastern wall of the Brisbane Ranges. The relations 

 immediately at the foot of the scarp are somewhat hidden by 

 alluvium, but stream sections show the volcanic sheet, in places, 

 continuing up to the scarp. We cannot be sure that it does con- 

 tinue everywhere sharply up to the edge of the Ordovician, but a 

 shaft sunk by the Geological Survey (Quarter Sheet 12 S.E.), in the 

 alluvium about one and a-half miles east of the scarp, bottomed on 

 basalt at 42 feet. If the basalt of the lower plains, at this point, 

 ever existed on the top of the higher Ordovician block, we might 

 expect to find evidence of this fact in the alluvium lying on the vol- 

 •canic sheet near the base. In this connection it is of interest to 

 note that Wilkinson's survey party, in 1863, in the shaft just 

 referred to, found and recorded basalt boulders at depths of 13 ft. 

 '6in,, 26 ft. 6 in., and 28 ft. 9 in. It is of course possible that these 

 boulders were derived from' the denudation of the low basaltic hills 

 to the east of tlie scarp, and carried thence by stream action. 



