194 VOLCANIC ROCKS OF SOUTH-EASTERN QUEENSLAND 



VII. PETKOGRAPHIC PROVINCES. 



The conclusions to be derived from the above considera- 

 tions are — 



1. During the ? Lower Cainozoic period there was- 



an extensive basic to sub-basic sub-alkaline pro- 

 vince over most of the southern and western 

 portion of the area. 



2. During the ? Middle Cainozoic period there 



was an acid sub-alkaline sub-province, and at 

 least three acid to sub-acid alkaline sub-pro- 

 vinces, two of which, namely, those of the Main 

 Range and Mount Flinders, were probably 

 connected. 



3. During the ? Upper Cainozoic period there 



was a basic to sub-basic sub-alkaline province 

 over almost the whole area. 



In addition to this, during the ? Middle Cainozoic- 

 period, there was a sub-province in the Esk district, parti- 

 cularly characterised by an acid to sub-acid series of rocks 

 of a nature intermediate between the alkaline and sub- 

 alkaline but more allied perhaps to the latter. 



Relationship hefween the Volcanic Rocks and Earth 

 Movements. 



There is no evidence in this area of the folding move- 

 ments such as Harker^^ associates with the pacific or sub- 

 alkaline type of rocks ; but, on the other hand, faulting on- 

 an extensive scale is known to have taken place along cer- 

 tain lines. The main fault-lines are in a general north and' 

 south direction along the eastern escarpment of the Main 

 Range, and along a line to the west of Ipswich; there is a 

 possible extension of this latter fault-line in a north-east 

 and south-west direction to Mount Flinders. 



The Main Range faulting took place at some time sub- 

 sequent to the extrusion of the volcanic rocks of the upper 

 division, as they had been dissected by streams to a depth 

 of 1,500 feet at least, but whether faulting had occurred 



*^ Natural History of Igneous Eocks. 



