134 E. 0. Teale: 



period. The sea never again transgressed in Palaeozoic times to^ 

 the extent of the early marine basins. (Diagram 11, Fig. 5.) In. 

 Middle Devonian times, the last marine deposits were formed in the 

 restricted basins or troughs in Eastern Victoria,' which were de- 

 pressed below sea level, and were partly filled by limestone and cal- 

 careous shales. 



The region of the depression coincided closely witli that occupied 

 by the volcanic zon^ of the Snowy River Series (Diagram 11, Fig. 

 6). The conditions of late Devonian and early Carboniferous were 

 essentially terrestrial, but were accompanied by the development of 

 several lacustrine basins, the greatest of which was the great Mans- 

 field-Wellington trough, and as previously indicated, the early sedi- 

 mentation was accompanied by rhyolitic effusions, and, later, by 

 basic lava flows. (Diagram 11, Fig. 7.) 



Types of Earth Movements. 



The general trend of all these Palaeozoic basins appears to have 

 been northerly, and the type of crust movement which most reason^ 

 ably explains the succession of basins, parallel, but laterally shifted 

 or restricted, is the conception of a slow wave-like undulation of the 

 earth's crust, the basin being reciprocal feature of the adjacent 

 land mass. It is possible to picture a prolonged progres- 

 sive movement of this type to proceed with or w^ithout marked 

 compressional or tangential movement. In the first case, the beds 

 of each successive formation would become highly folded, and in 

 the latter only slightly so. The idea does not preclude the pos- 

 sibility of periods of a itnucli augmented rate, with important, 

 fractures and displacements. 



An alternative view would be to consider the formation of a suc- 

 cession of basins such as here described, as being due mainly to the 

 differential movement of great blocks or earth segments along fault 

 planes, certain areas being alternately lifted and lowered. The 

 whole structure of the Palaeozoic rocks, however, favours the first 

 view, but it does not exclude the possibility and even the probability 

 of a certain amount of faulting and block movement as well, aud- 

 it would seem that as the Palaeozoic era drew to a close, after the 

 great Devonian convulsion, though the fold movement still pre- 

 dominated, that of the block type became more pronounced, and' 

 finally prevailed throughout Mesozoic and Kainozoic times. 



If the regional distribution of calcic and alkali igneous rock is 

 definitely related to fold and fault movement respectively as Marker 

 has contended, then in areas where both these types may have acted' 



