Oeoloyy of the Dlaniotul Creek Aren. 329 



likely. Near the margin of the basalt in several places, but 

 especially near the northern limit at Greensborough, good examples 

 of fossil wood have been found. The structure iias been remaik- 

 ably well preserved in some examples. A section of the wood was 

 examined by Prof. Kwart. He informed me that he felt sure 

 that the wood belonged to the eucalyi)ts, l)ut that one section was 

 not sufficient to correlate it with existing species. The sands are 

 frei[uently horizontally bedded, and some sections show good cur- 

 rent bedding. The gravels which were foi'merly the position of 

 the valleys now frecjuently occur as ridges elevated above the sur- 

 roundings. The reason for this is twofold. (T) the basalt has pro- 

 tected the gravels, and even in places where the basalt is not now 

 pi-esent. it may formerly have covered them. (2) the resistant 

 character of the gravels in themselves. Small amounts of gold 

 occur in the sands and gravels throughout the area, and they have 

 been worked at several places with indifferent results. Just to the 

 east of the main road from (Treensborough to Diamond Creek, near 

 the southern limit of the basalt, over .£1000 worth of gold was won 

 in about seventeen years. The sands were also extensively used 

 in the construction oi the Maroondah aqueduct. 



Basalts. 

 The basalts occur in the extreme east and west of the area; one 

 small patch occurs about one mile to the east of Diamond Creek. 

 The writer has separated them on peti-ological grounds into 3 types. 



1. Fine grained aphanitic basalt. 



2. Medium to coarse grained basalt and dolerite. 



3. Garden Hill basalt, medium to fine grained in character. 

 No field .separation of these types was possible. The tirst 

 type is well exemplified in a quarry off the main road near the 

 northern limit of tlie l)asalt at Greensborough, and also in a quarry 

 just to the south-east of Garden Hill. In both quarries the basalt 

 is clearly the basal member, and has filled up the prebasaltic 

 stream valleys. In both cases also columnar structure indicative 

 of fairly rapid cooling has been developed. The columns are ver- 

 tical and cleanly cut. The second type is a rather coarse grained 

 basalt or dolerite. i It is the average type throughout the area, and 

 it overlies the finer grained type near Greensborough and Kangaroo 

 Grounds. 



The third type, as the name suggests, is typically developed afc 

 Garden Hill, Kangaroo Grounds. It is medium to fine grained 



1 Chamberlin and Salisbury. Processes and Results, p. 398. 



