Palaeozoic Geology of Victoria. 



75 



K)f the area. A narrow, incomplete ring of black clierty graptolite 

 slates of Upper Ordovician age. almost surrounds the inlier, but on 

 the northern side along a portion of the contact the Silurian sedi- 

 jnents rest directly against the Serpentine. The whole series is 

 intensely crushed and contorted, and so are the Upper Ordovician 



MORrZ()NT;(L 



^"^'"^ Seer. 



Secfior %howinq relation of Cambrian Inlic*- To surroundmij Rocks 

 Dolo<3lrooURivpr 



rocks. As all the successive formations have been subjected to 

 periods of folding and compression along a north-westerly direction, 

 they have a similar strike, and small vertical sections of contacts 

 •do not yield conclusive evidence of unconformity. The mapping, 

 however, of the boundaries gives more satisfactory information in 

 this direction, and everywhere the lithological and palaeontological 

 break is quite sudden. 



The Serpentine. — The extent and general features of this rock 

 with its associated minerals, Chromite and Corundum, were de- 

 scribed in a previous paper (13), but the age and relationship to 

 the surrounding rocks had not been definitely established. The 

 Serpentine was then regarded by me as the oldest rock occurring 

 in this region, and was put down as Pre-Upper Ordovician. This 

 view is still upheld, but it is now possible to further restrict its age 

 to Pre-Upper Cambrian. The Serpentine was shown previously 

 (13) to be of the nature of an altered intrusive rock, originating 

 from both pyroxenites and peridotites. Various rocks are found 

 •directly in contact with it, for example, serpentinous grits, con- 

 glomerate and finer sediments derived from the denudation of the 

 serpentine, also associated diabase tuffs in which there are dcfi- 

 Tiitely interbeddcd lenticular limestone deposits of Upper Cambrian 



