Palaeozoic Geology of Victoria. 77 



age; elsewhere Upper Ordovician slate or Silurian sandstone and 

 shale directly overlie the Serpentine. Nowhere has there been 

 observed any rock showing contact alteration. The conclusion^ 

 therefore, is clear that not only is the Serpentine the oldest rock 

 but there is a stratigraphical break between it and the next oldest 

 rock, the Upper Cambrian, sufficient to allow of considerable denu- 

 dation previous to the deposition of the Upper Cambrian. The in- 

 tense shearing and foliated character of much of the Serpentine has 

 been previously referred to (13). It is generally recognised that 

 a certain amount of such structure frequently found in Serpentine 

 is due to intense expansional forces generated by the increase in 

 volume, which accompanies the mineralogical change from pyroxene 

 and olivine into Serpentine. Additional stresses, however, of an 

 intense character due to general compressional earth movements 

 have further deformed these rocks, and have largely contributed to 

 their schistose character. 



A very useful and comprehensive summary of the state of our 

 knowledge concerning the Heathcotian Series is given by 

 Professor Skeats in the "Volcanic Rocks of Victoria" (18). It 

 includes references to various Serpentines and associated rocks in 

 Victoria, some of which have been doubtfully referred to by various 

 gieologists as Pre-Ordovician. Further interesting information 

 and statements concerning Can:ibrian occurrences generally in Aus- 

 tralia are discussed by Professors David and Skeats in the Federal 

 Handbook, in the section dealing with the geology of the Common- 

 wealth (20). Serpentine has been shown to occur in a number of 

 widely-separated localities frequently associated with cherty and 

 diabasic rocks, notably at Waratah Bay, near Casterton and the 

 Limestone River, Benambra. These rocks have been doubtfully 

 included by some authorities in the Pre-Ordovician Series, but 

 though little is known concerning the relationship td the surround- 

 ing rocks, the definite fixing of the age of the Wellington Serpen- 

 tine adds a little more weight to the conjecture that these other 

 occurrences may be correlated with the Pre-Ordovician. 



It is interesting to note as previously referred to by Professor 

 Skeats (18) that near Heathcote the diabase at its margin passes 

 into a rock allied to Serpentine, known as Selwynite, containing 

 chromite and corundum, an association also found in the Welling- 

 ton area. 



The Garvey Gully Series. — Tliese rocks were recognised in part 

 in my previous paper (13), under the heading of " Sediments com- 

 posed largely of Serpentine Detritus, and were doubtfully in- 



