fPRor. Roy. Soc. Victoria, 26 (N.S.), \'t. I., 1913]. 



Art. IV. — Oil the Occurrence of a Felsitic Dyke and Associated 

 Breccias at Sugar Loaf Hill (Mont Park), near 

 Heidelberg. 



HV 



J. T. JUTSON 

 ((jleological Survey of Western AiLstralia). 



AND 



FREDERICK CHAPMAN, A.L.S., etc. 

 (National Museum, Melbourne). 



(With Plate VI., and one Text Figure). 

 [Read loth April. I91.S . 



Introduction. 



Sugar Loat' Hill is an elongated hill running about north-north- 

 west, and is -440 feet above sea level. It lies a little to the north of 

 Heidelberg, and constitutes a prominent landmark, from whicii a 

 fine panoramic view can be obtained. 



As already pointed out by one of us (J.T.J.i) the hill is a mouad- 

 nock on the Nillunibik Peneplain. 



Previous literature. 



References to this hill are few. Selwyn, in the map accompany- 

 ing his report on the geological survey of the Yarra basin and 

 Western Port ,2 has mapped it as a " siliceous dyke of red jasper 

 and white quartz rock." On Quarter-Sheet 2 S.E. (Aplin, 1808), 

 it is noted that on tlie hill there are outcrops of a " hard and Hinty 

 ' breccia,' composed of angiilar and here and there a few semi- 

 rounded pieces of sandstone and altered shale." and the suggesticm 

 is made that this breccia has, in all proliability. tilled a pre-existing 

 fissure in the bed rock. 



Mr. T. S. Hart, M.A., in his " Volcanic Hocks of the Melboui-ne 

 District, "3 inclines to the opinion that Sugar Loaf Hill was onte 

 the bottom of a lava-filled valley, that the lava has been removed. 



1 Proc. Roy. Soc Victori.i, vol. xxiii. (N.S.), pt. ii., 1911, p. .'<0'2. 



2 " The Basin of the River Yarra and part of the Northern, North Kastern and Kastern Hraiii- 

 atfe of Western Port Bav." Votes and Proceedings, l,e«:. Council, Victoria, 18.i5-6, vol. ii., pt. i. 



3 Vict. Nat., vol. xi., 1894, pp. 74-78. 



