Palaeozoic Geology oj Victoria. 139 



period corresponds closely with the general direction of the Palaeo- 

 zoic trend lines. This arrangement led Howitt to postulate the 

 idea that the volcanoes of this epoch were disposed along a meri- 

 dional fissure, and though the actual position of the sites of these 

 ancient volcanic vents still remains to be located, the view certainly 

 offers the most probable explanation of the features as a whole. 



This zone would appear also to have been successively fractured 

 at later periods. The occurrence of the iron ores appears to be asso- 

 ciated with one of these lines. The marked shearing re- 

 sulting in the production of porphyroids is another phase, and 

 the origin of the basins in which the limestones occur, though per- 

 haps referable mainly to warping and erosion, may possibly be asso- 

 ciated also with some trough faulting. Howitt has also referred to 

 ctrtain persistent features along the eastern side of the Snowy 

 River Porphyries, coinciding wdth the valley of the SnoAvy River, 

 suggesting the existence of a powerful meridional fault. Other 

 parallel faults coinciding Avith the Limestone Creek and Buchan 

 River are also suggested. (3, p. 189.) 



The age, however, of these fault and fracture lines, and, in fact, 

 their exact position also, is very indefinite. Some may be post- 

 Palaeozoic, and it is even probable that if not originating in Kaino- 

 zoic times, the plateau building period that produced the existing 

 highlands has caused- renewed movement along some of these major 

 f aultis. 



The undulations and' gentle folding of the Middle Devonian lime- 

 stones show that the fold movement, though less intense than in 

 earlier times, still continued, and the same feature is shown by the 

 structure of the Upper Palaeozoic rocks of the Wellington region. 



Summary. 



The principal features to be emphasised as a result of the con- 

 sideration of the areas under discussion may be briefl}^ enumerated 

 as follows. — 

 1. Wtllmyton District. 



(1) The general structure of the Wellington-Dolodrook region 



is anticlinal, passing from a broad, simple fold in the 

 case of the uppermost rocks to' complex repeated folding 

 in the case of the underlying old rocks. 



(2) The periods of folding have l>een renewed from time to time, 



possibly on four successive occasions, but the trend of all 

 the fold lines has persisted in a toleral)ly constant direc- 

 tion, varying between north-w^est and north-north-west. 



