134 PROCEEDINGS OF SECTION C. 



are now fully exposed. The Giant Rock and its neighbour, the 

 Little Rock, are also only exposed on account of dissection by a 

 tributary of the Konong-Wootong Creek. 



Outline of the Geology. — The area round Coleraine and Casterton 

 is undoubtedly one of the most interesting in Victoria, notwith- 

 standing the fact that the relationship existing between the various 

 formations are masked by the later tertiary deposits. 



Archcean. — The oldest rocks in the area are a series of crystalline 

 schists and gneisses which form part of the Archaean Series. One 

 exposure of these rocks is in a creek section a little to the north of 

 Carapook, where biotite gneisses and schists intersected by veins 

 of graphic granite and coarse pegmatite are well seen. Near Wando 

 Dale station quartz and mica schists with tourmaline pegmatites 

 are exposed along the Wando River. Further exposures are found 

 along the Glenelg River, and similar schists and gneisses also occur 

 to the south of Mt. Stanley near Bushy Creek. 



Granite rocks are fairly extensively developed near Harrow 

 and Balmoral, but at present there is no evidence as to their age, as 

 in no place have they been observed in contact with deposits other 

 than the Archaean, Permo-carboniferous and Tertiary. All that can 

 be stated with certainty is that they are intrusive into the Archaean 

 gneisses and are pre-Permo- carboniferous. It is quite possible that 

 these granite rocks belong to the upper part of the archaean and 

 correspond to the Great Granitoid series of Chamberlin and Salis- 

 buryi, the schists and gneisses corresponding to the Great Schist 

 series of the same authors. 



Ordovician.— At the Hummocks serpentine and chert occur, 

 and these, as stated by Professor Skeats^, possibly belong to the 

 same horizon as the cherts and diabases of Heathcote — i.e., they are 

 basal Ordovician. At Lower Steep Bank Rivulet, Nolan's 

 Creek, and along the Glenelg the rocks exposed are similar 

 in every way to normal Ordovician sediments, and both 

 Ferguson^ and Stirling* have pointed out that they differ entirely 

 from the gneisses and schistose rocks. Unfortunately, no junction 

 between the two types has been observed, so that definite field 

 evidence is not forthcoming, and so far no fossils have been obtained 

 from the sediments. At present they are included in the Ordo- 

 vician, as the intense folding points to at least a Lower Palaeozoic 

 age, and the geographical position of the area suggests Ordovician 

 rather than Silurian. Of course there is the possibihty that these 

 sediments may be Cambrian or pre-Cambrian, the only evidence 

 against such a suggestion being their association with the cherts 

 and serpentine which elsewhere appear to be not older than 

 basal Ordovician. 



1 Chamberlin and Salisbury: "Earth History," Vol. II., p. 142. 



2. Op. cii., p. 179. 



3. Op. cit., p. 59. 



4. Op. cit., p. 86. 



