Bucks of the Howqua River. 63 



^he quartz. Secandary silicification is apparent in some sections. 

 No ferromagnesian minerals were noted. (Slides 26, 28, and 34.) 



3. Conglomerates. — This bed often passing into pebbly sand- 

 . stones generally overlies the rhyolite almost everywhere in this 

 series. It is well developed at Mount Timbertop, where it passes 

 ■up into the normal sandstone. 



4. The sandstones are generally of a coarse texture, often flaggy 



and micaceous, and with a reddish colour. They form as a rule 



thick beds which alternate with a purplish to chocolate coloured 



•shale, which sometimes has the appearance of an oxidised ash bed. 



The shales generally provide good grazing country. The colour, 

 texture and generally low angle of dip of these rocks render them 

 readily distinguishable from' the older rocks in the field. Their 

 influence on the tojjography, too, is distinct. 



The alternation of hard and soft beds more or less horizontally 

 • disposed gives the hills in general a table topped and ledged charac- 

 ter, so well shown in the neighbourhood of Mansfield. 



Summary and Conclusions. 



The area examined covers about 60 square miles of mountainous 

 country, previously unmapped. It lies about 20 miles to the south- 

 east of Mansfield, and forms a portion of the central highland 

 region of Victoria. Physiographically it consists of an area of 

 high relief in an advanced stage of deep dissection. The original 

 plateau character is almost completely obliterated. Deep valleys 

 <v'ith permanent streams separated by steep narrow ridges occupy 

 the whole of the region. Small remnants of an overmantel of flat- 

 lying rhyolite and sediments are preserved, providing a topo- 

 :graphic contrast to the outline of the highly folded older rocks. 



The area lies in the drainage basin of the Upper Goulburn, and 

 the development of this river system as a whole is intimately con- 

 nected with interesting tectonic and structural questions. 



The main problem dealt with in the area concerns tlie occur- 

 rence of diabasic rocks and cherts closely similar to those of Heath- 

 cote, and their relations generally with reference to the Heath- 

 cotian problem in Victoria. 



The lithological resemblances are most striking, both with regard 

 to the diabase and its alteration products. The cherts occupy a 

 similar relationship, and in each case contain ProfoajioiKjia. Con- 

 tact alteration features are absent, and the rocks for the most part 

 ihave the character of altered lavas and tuffsi of submarine origin. 



