Volcanic 'Tuff of Pe/ark Marsh. 9 



ing hills? The ejected lumps of the older underlying rocks alone 

 testify to the presence of a not distant source. On the eastward 

 •outward slope of the lake near the cemetery, a well put down 

 passed through about 80 feet of tuff before striking water, but half 

 .a mile or so further east, poor " buckshot " country is encountered 

 resting on, it is said, a clay bed. Again, near the summit of 

 Mount Terang, another well was sunk, and a still greater thick- 

 jiess of tuff was met with. Mr. Merry also says that to the west and 

 south of the lake the good volcanic country is succeeded by 

 ** buckshot " and clay lands. The geological quarter sheet shows 

 what is called the *^ older volcanic series," giving place to " buck- 

 shot" gravel to the west, but to the north extending to the limits 

 of the quarter sheet. The title given to this series is badly 

 •chosen, and misleading, as it doesi not refer to the older basalts, 

 known a^ such since the time of the first geological survey of Vic- 

 toria, but to a section of the newer volcanic rocks belonging to a 

 much more recent period. Apart from the confusion occasioned 

 thereby, *' older " is an inappropriate term to employ, as the 

 basalt it is applied to, is in, part superficial, and at Lake Terang 

 mapped right up to its side, so that it must be younger than the 

 tuffs there, and Mahony and Grayson state that the basalts belong 

 to one cycle of. activity, no sharp line of demarcation separating 

 them. These authors^S have very properly in their paper substi- 

 tuted the terms " earlier " and " later " for the older and newer 

 •volcanic series of the quarter sheet. To the north of Lake Terang 

 we know that at the Pejark drain, distant about a mile, there is 

 at the most only two feet of tuff, and Mr. Merry ascertained that 

 between the drain and the lake the tuff or " sandstone " had been 

 • encountered in every well sinking and cellar excavation, increasing 

 in thickness as the lake was approached. The actual thickness of 

 the tuff bed on that side of the lake could not be found out. The 

 section behind the Mechanics' Institute shows a face of 10 feet. 

 This establishes the continuity of the Pejark and Lake Terang 

 tuffs, and makes it probable enough that they originated from the 

 same point, although of course, as already stated, they may have 

 blended to some extent to the west and north with the tuft's which 

 •emanated from the site of Lake Keilambete and from Mt. Noorat. 



As the tuffs of Lake Terang are unquestionably occupying their 

 -original place of deposition, and are continuous with, and thin 

 -out into, the Pejark beds, there seems no reason to attribute the 



18. Loc. supra cit., p. 4. 



