METAMORPUIC ROCKS OF THE OMEO DISTRICT, GIPPSLAND. 209 



Isolated mountains similar to these and pi'obably of the same 

 great age are to be found to the westward of the area. 



The age of the Snowy River porphyries is fixed by the Silurian 

 sediments, which are inferior to them, and the Middle Devonian 

 marine limestones, which, for instance, at Gelantipy rest upon 

 them. 



At Bindi, in the Omeo district proper, examples of this series 

 can be studied where the quartz porphyries and fragmental beds 

 pass upwards by gradatures into purely marine limestones, charged 

 with organic remains of the Middle Devonian age.* 



These Middle Devonian formations are succeeded at Mount 

 Tambo by a great thickness of coarse conglomerates, shales and 

 grits, which I have provisionally referred to the Upper Devonian, 

 and which close the geological record in the Omeo district, 

 excepting the few Cainozoic basalts before referred to. 



In speaking of the Snowy River porphyries I mentioned certain 

 mountain masses of porphyritic rocks which are connected with 

 them, and I also said that similar masses ai'e to be found to the 

 westward of them. At Bairnsdale, where such a mountain 

 (Mount Taylor) occurs, its approximate age is fixed by the capping 

 of Upper Devonian rocksf which rest upon its denuded summit. 

 It seems to me probable that the other isolated mountains of the 

 same character may be referred to this geological age. In the Omeo 

 district such occurrences are to be found at the boixler of the 

 metamorphic area, and subsetjuent to the formation of the 

 crystalline schists. 



These masses of generally porphyritic rocks may for the purposes 

 of this paper be spoken of as younger plutonic, and they are 

 incidents in the great sequence of plutonic and metamorphic 

 phenomena with which the crystalline schists of Omeo are 

 connected. 



It will be perhaps well, before speaking in the following section 

 of a similar occurrence of younger plutonic rocks within the 

 Omeo area, to shortly describe a typical example of the extreme 



* I may take this opportunity to refer to a difference of opinion which has arisen between 

 Mr. James Sterling, F.G.S., and myself as to these quartz porphyries, and to their relations 

 to the Hindi beds. In my description of the Tambo beds I described the Bindi limestones 

 as having- been laid down ujion the red quartz porphyries of the locality which I regarded 

 as belonging to the Snowy River I'orphjries. In a paper read before the Geological 

 Society of Australasia (Transactions, Vol. 1. Pt. I. p. IS) Mr. Sterling says that the Bindi 

 limestones "together with shales, sandstones and conglomerates inferior to them, have 

 been cut off from the main mass by an eruptive mass of quartz porphyry, which has not 

 only transmuted and absorbed the sandstones and conglomerates along the line of contact, 

 but has indurated and otherwise alteied the limestones into subcrystalline white and grey 

 marbles." After this was published Mr. Sterling kindly invited me to visit the locality 

 with him, and we together carefully examined his supposed intrusive contact. I found 

 that the relations of the Bindi beds to the quartz porphyries are precisely analogous to 

 those of the Buchan beds to the quartz poqihyries and diabase rocks of that locality. The 

 Bindi beds were deposited upon the quartz porphyries, and are connected with them by a 

 short series of fragmental beds, which become increasingly calcareous in passing upwards. 

 Samples which I collected of the quartz porphyries and of the fragmental beds lying upon 

 them proveii, upon microscoiiical examination of thin slices, to be quite liormal in their 

 character. 



t Geological Survey of Victoria, Progress Report, III. p .210. 







