566 Jenkins— Geology of Victoria. 



II. — On the Tertiary Deposits of Victoria. 

 By H. M. Jenkins, F.G.S.i 



THE geology of Victoria is better known than that of any other 

 British colonj^ the existence of gold-bearing deposits in different 

 localities having led to the establishment of a Grovernment Geological 

 Survey about twelve years ago. The labours of this survey, under 

 the able direction of Mr. Selwyn, have made known to us, in a 

 general way, the geological structure of the whole colony, and a 

 more detailed survey is now in active progress. 



The marked contrast to our knowledge of the geological features 

 of Victoria is our comparative ignorance of its palasontology. 



Under these circumstances Mr. Selwyn has sent the author for 

 determination a large series of Tertiary fossils from the beds which 

 he has mapped as Miocene and older Pliocene ; and as they present 

 some points of very great interest to the palseontologist, he gave 

 an account of the localities whence they had been obtained, as a 

 preface to a report on the fossils, which he hoped to lay before the 

 Association on a future occasion. 



One point of great importance, depending on the correct interpre- 

 tation of the age of these Tertiary strata, is the date of the payable 

 gold-drifts of Victoria. Their age relatively to other deposits has 

 been tolerably well made out by Mr. Selwyn ; but, as a matter of 

 scientific interest, their antiquity in relation to changes in the climate, 

 and in the fauna and flora of the region, has still to be determined. 



The most varied section of the marine Tertiary beds of Victoria is 

 exhibited on the coast west of Cape Otway, a headland situated 

 southwest of Port Philip Bay, where the Tertiary deposits were 

 accumulated in a trough of Mesozoic carbonaceous sandstone be- 

 tween Castle Cove and Cape Otway ; and the Tertiary beds were 

 afterwards contorted and then denuded ; and the trough, now 

 deeper and probably narrower, was refilled with the Post-pliocene 

 false-bedded sandstone. 



It is of great importance to determine the relations of these beds, 

 as one of them has yielded the Trigonia semiundulata (M'Coy), a shell 

 of Secondary type, quite different from the recent species, and more 

 comparable with the T. costata of the Oolites. 



About twenty miles west of Castle Cove, and nearly five miles 

 beyond Moonlight Head, another series of Tertiary deposits occurs, 

 resting, as before, on the Mesozoic sandstone. 



West of the Gellibrand river the Miocene beds rise from beneath 

 Post-pliocene calcareous sandstone, dipping to the eastward ; that is, 

 in the opposite direction to those on the other side of the river's 

 mouth. They extend along the coast for nearly forty miles, but 

 their stratification and divisions are much obscured by the fallen 

 masses of the more recent Tertiary sandstone. The most important 

 bed is a dark, slate-coloured, stiff clay, very rich in fossils, and 



1 Eeud before the Britisli Association (Section C.) Norwich, August, 1868. 



