ON THE GEOLOGY OF WEST MORETON, QUEENSLAND. 149 



Limestone Hill (Ipswich) has been formed by a fissure 

 flow of basalt and it consists of a brown decomposed basalt, 

 white trap, silicified breccia which has been rebrecciated, 

 and basalt. 



Red Hill forms the western portion of the same flow, the 

 fissure running through the Golf Park. 



Age of Volcanic Rocks. 



Trachyte and basalt intrude and cap the Trias- Jura Ooal 

 Measures throughout the whole of the volcanic zone from 

 the Main Range to Redbank Plains and portions of the 

 Trias-Jura rocks can be found embedded in the volcanic 

 breccias at Mount French and Ivory's Rock. Thus at first 

 sight one would naturally conclude that the whole of the 

 volcanic eruptions were Post Trias- Jura. 



After very careful search along the Blenheim Greek 

 valley and also in the deep gullies at the base of Mount 

 Flinders and Mount Alford, water worn volcanic pebbles 

 were found embedded in an extensive bed of conglomerate 

 which occurs near the top of the Walloon Series. This 

 conglomerate is capped by grits and sandstones for a thick- 

 ness of about 150 feet. 



At the "Hip Roof" referred to above, a large piece of 

 volcanic tuff was found associated with basalt containing 

 fossil imprints of Trias-Jura plants. One specimen sub- 

 mitted to Mr. W. S. Dun for identification was stated to be 

 Taeniopteris Daintrei. There seems thus to be conclusive 

 evidence that at least some of the volcanic eruptions of 

 West Moreton were of Trias-Jura age. This agrees with 

 the evidence published by Andrews and Marks. 



Field evidence seems to support the conclusion that there 

 have been two distinct and separate series of volcanic 

 eruptions in the West Moreton District: — 



