Aet. XVII. — Notes on Post Tertiary Strata in South- 

 Western Victoria. 



By John Dennant, F.G.S. 



[Kead 11th November, 1886.] 



I. — Dune Limestone, Recent. 



Amongst the prevailing tertiary strata in the counties of 

 FoUett and Normanby there are certain deposits of still later 

 age, which, though limited in extent, are, from their mode 

 of occurrence, of great geological interest. They may be 

 arranged chronologically into two distinct sets of beds, the 

 most recent of which will be first considered. 



If the traveller leaves Portland to go to the pleasant little 

 watering-place at Cape Bridge water, he is struck by the 

 sight of an outcrop of rock dipping at various angles amongst 

 the consolidated sand dunes through which the road winds. 

 The strata are very abundant along the coast from Portland 

 to the border of the colony, and for many miles farther west 

 in South Australia. They are met with also for a short 

 distance inland, but chiefly in quarries, being usually hidden 

 from view on the surface by a thin covering of drift sand. 

 The only use of the rock is as a rough kind of building 

 stone, where other materials are not available. Churches, 

 schools, &c., constructed of it are generally pointed off with 

 a finer kind of stone, and these have, for bush edifices, quite 

 a passable appearance. Being of a very porous nature, the 

 blocks of stone used need to be thick to avoid damp; but 

 even then this defect renders it undesirable for dwelling- 

 houses. 



The strata are highly laminated, the weathered edges break- 

 ing off* into leaves as thin as flags of roofing slate, with the 

 laminations, of course, always parallel to the bedding planes. 

 These, however, are seldom horizontal, the most characteristic 

 feature of the beds being their constantly changing dip, not 

 only in direction, but also in amount. The highest observed 

 inclination was 30 degs., but between this and deg. almost 

 any angle may be found. 



Locally the rock is called sandstone, from its coarse 

 appearance, but it is essentially a carbonate of lime, the 

 silica obtained from a sample analysed being as low as 4 per 



