. Palaeozoic Geology of Victoria. 131 



shown that the Mansfield-Wellington belt has had a particularly 

 varied history, and it contrasts strongly with the belt to the east,, 

 whicli is almost entirely Ujiper Ordovician, and which we may call 

 the Dargo-Ovens zone. To the west, on the other hand, the- 

 rcK.-ks are chiefly Silurian, overlying Upper Ordovician. With 

 regard to the eastern limits of this area, it is perhaps significant 

 that it corresponds closely with the Cambrian outcrop in the Wel- 

 lington district, and also the Howqua-Mansfield and Dookie locali- 

 ties fartlier norih, in the vicinity of which rocks doubtfully re- 

 ferred to as the Heathcotian Series occur; while on the western side 

 forming the boundary in part, between a Lower Ordovician region 

 to the west, there is the important Mt. William-Colbinabbin line 

 of Heathcotian rocks. These boundaries, or geological frontiers, 

 may, therefore, represent certain critical lines in the past earth, 

 history, along which the struggle for mastery between conflicting^ 

 earth forces has been repeatedly renewed and fought out. 



Successive Distribution of Land and Water. 



In considering the piobable distribution of land and water 

 throughout Palaeozoic times, we c'an only be guided by the known 

 outcrops of the various formations, and fresh discoveries at any 

 time are liable to modify our views, but the sub-parallel arrange- 

 ment and the restriction of particular formations to certain belts 

 or areas strongly suggest a successive alternation of land and 

 water, which might be brought about by a long continued progres- 

 sive Avave-like undulation of the earth's crust. 



If we consider a succession of east and west sections through Vic- 

 toria during the Palaeozoic history, representing them diagram- 

 matically to show the relative position of land and water, certain 

 interesting features are brought out. (Diagram No. 11.) 



With regard to the Cambrian times, our knowledge is far too- 

 fragmentary to enable us to form any reliable conception of the area 

 of the sea of that period, but the pre-Cambrian rocks of Western 

 A'ictoria may have formed the western limit, while on the east it 

 may have been the belt of crystalline rocks of thd Omeo zone, though 

 there is some doubt as to whether these rocks are really Archaean 

 or altered! Ordovician. 



At any rate, a probable view that seems reasonable would repre- 

 sent a wide Cambrian sea, occupying the greater part of the now 

 dry land of Victoria, with ancient land masses in the east and the- 

 west (Diagram No. 11, Fig. 1). 



Practically all the Cambrian rocks of Victoria so far known repre- 

 sent accumulations of submai'ine volcanic material of the nature of 



