16 On the Caves Perforating Marble 



In concluding this sketchy article on the caves, a few 

 remarks on the beds they perforate may be interesting. It- 

 has been shown with reference to the Limestone Creek 

 marble beds that the surface outcrops, and also those within 

 the caves, are intersected with thin yellow seams parallel 

 to the bedding planes, and it is conjectured that these seams 

 can hardly be due to the percolation of surface waters 

 holding colouring matter in solution, because of their regu- 

 larity and parallelism. Whether the intense subterranean 

 heat, which it is probable caused the metamorphism of the 

 calcareous sediments into crystalline marbles, has obliterated 

 all traces of bedding at a depth, and so produced a homo- 

 geneous mass of saccharoidal marble, I am unable to suggest; 

 but in regard to the origin of the marbles the evidences are, 

 I think, in favour of their having assumed their crystalline 

 form during shrinkages in the earth's crust at the close of 

 the Silurian or at the beginning of the Devonian periods, 

 when the whole series of sedimentary rocks were inclined at 

 high angles — i.e., folded and bedded together by the dynamic 

 and metamorphic agencies of nature — and, after long-con- 

 tinued periods of subaerial or subaqueous denudation, were 

 again submitted to the influence of plutonic forces, during 

 which the fragmental porphyries which at present rest on 

 the upturned edges of the sediments were deposited. That 

 the latter are the results of either subaerial ash, or sub- 

 aqueous tuff, grouped round such probable volcanic centres 

 as Wombargo and Cobboras mountains,* is, I think, evident 

 enough from their lithological character and their strati- 

 graphical position. It is hardly probable that- the deposition 

 of the porphyries over the palaeozoic sediments would cause 

 such extensive metamorphism of the calcareous beds ; in 

 fact, the proof that such is improbable is seen at Stony 

 Creek, for here the unaltered fossiliferous beds are in direct 

 contact with the overlying porphyries, while the crystallisa- 

 tion of the rock masses appears to increase with the depth 

 below the surface. 



In my examinations of the Stony Creek marble beds I was 

 fortunate in finding some fossils, which Professor M'Coy has 

 been good enough to examine, and has identified one shell, 

 spirigina reticularis, which he states is one of the few 



* Vide A. W. Howitt in Progress Beport, Geological Survey of Victoria, 

 1876, p. 200. 



