Palaeozoic Geology of Victoria, 91 



Should more detailed work later fail to discover any Silurian 

 rocks to the east of the Upper Palaeozoic belt, it would seem to 

 -point to the possibility of an old eastern shore line of the Silurian 

 sea, which is now buried beneath the latter rocks of this area. 



The whole Palaeozoic history of this belt, with its succession of 

 ■sedimentary and volcanic events emphasises that it has represented 

 a major tectonic and structural zone throughout Palaeozoic times. 



The two areas where the Upper Palaeozoic rocks have received most 

 attention from me are the vicinity of Mt. Wellington and the Mac- 

 -allister valley, at Rickey's Creek. These two areas will be con- 

 sidered separately. 



Wellington Area. — The position and extent of these rocks within 

 the area discussed is shown on the map, and their relationship to 

 the underlying rocks is indicated in sections, numbered 1, 2, 3 and 

 4. It will te seen that they rest unconformably on the Silurian and 

 older rocks, and in general the beds dip at low angles with a 

 marked absence of the sharp repeated folds of the older series. 



On the western side of the map it is seen that the beds dip uni- 

 formly westerly (W.S.W.), and on the Wellington side the dip is 

 easterly. These two directions have been proved to form part of a 

 large anticlinal fold at least fifteen to twenty/ miles in width. The 

 -axis hasi a direction of about N.N.W. and lies between Mt. Tambo- 

 ritha and Mt. Wellington. The southern portion has suffered much 

 denudation, with the result that within the area examined, the 

 crown of the fold has entirely gone, revealing the underlying older 

 rocks, which have, in turn, been much dissected during the present 

 cycle of erosion. The two limbs of the folds are preserved with 

 their steep scarp slopes opposing one another, forming, especially 

 in the case of Mt. Wellington, bold and precipitous cliffs. (Photo. 

 ■3.) 



The rock succession is very constant over the whole area, though 

 the thickness of the individual beds is subject to some variation, 

 and in general the observations of Murray (9) and Howitt (4) in 

 other portions of this region, indicate the same succession and 

 -featurtes. 



The basal beds almost everywhere consist of i-eddisli conglome- 

 rates, breccias, or breccio-conglomerates, with pebbly sandstone 

 and red shaly bands developed locally. The pebbles and boulders 

 •consist chiefly of quartz and quartzite, with some indurated shale 

 •and cherty slate. 



One feature of importanc(i is the occurrence also of acid igneous 



