50 ./. T. Jatsoii : 



The Kangaroo Ground Older Basalt. 



The main portion of this basalt occupies a fairly extensive belt 

 of high country a few miles to the east of the Greensborough 

 basalts. As seen in the road cuttings, it is very vesicular, and con- 

 siderably decomposed in parts. In the former character it differs 

 from the Greensborough Older Basalts, as the latter, so far as ob- 

 served, are generally dense. 



Beneath the basalt are some gravels, grits and sands, which have 

 in places been worked for gold. These sediments, together with 

 their silicified products, quartzites, can be noticed at the edges of 

 the basalt on the noi'thern and eastern sides of the main outcrop. 

 Quartzite boulders are found in other parts, and in the township 

 of Kangaroo Ground there is a rather extensive outcrop, which 

 also apparently underlies t?ie basalt. 



An actual section of the basalt covering the sediments is seen to 

 the east of the small quarry reserve in Allotment 16, Section III., 

 Parish of Nillumbik. The basalt cap here is only a few yards in 

 diameter, but it rests on grits and gravels of an exposed thickness 

 of about 16 feet, so that any doubt as to the relations of the two 

 rocks is set at rest. 



The Geological Surey has marked on the parish map of Nillumbik 

 the " probable course of lead " under the basalt, thus indicating a 

 belief in the existence of an old buried river channel. The basalt 

 at Kangaroo Ground certainly in parts lies on a very uneven sur- 

 face, as may be seen on the main road running north to the town- 

 ship from Eltham. By Weller's Temperance Hotel, at the foot of a 

 long hill, the basalt outcrops and overlies gravels, w^hilst towards 

 the top of the same hill going north it rests on Siluri.m rocks. In 

 this uneven surface, it appears to differ much from the Greens- 

 borough Older Basalts. Elsewhere, however, in the vicinity, the 

 general surface on which both the basalt and gravels lie seems 

 moderately level. 



The question of the age of the Kangaroo Ground l)asalt is not 

 easily answered. The writer, in his paper already referred to on 

 the physiography of the Yarra Basin, regarded this rock (through 

 adapting the current ideas of its age as that of the typical Older 

 Basalt of Royal Park, etc.), as a monadnock on the Nillumbik Pene- 

 plain, and therefore older than the latter. The cap of Kainozoic 

 sands and gravels around Melbourne rests on the ]>eneplain, and is 

 therefore younger or at least coincident with the final stage of for- 

 mation of the peneplain. Considering the Greensborough gravels 

 and sands as part of this cap, makes the Older Basalts of the same 



