98 



VOLCANIC AREA OF EAST MORETON, ETC., DISTRICTS, Q. 



To the comendite families belong, in addition to the Glass 

 House Mountain instances, the main masses of Mt. Coolum, Mt. 

 Cooroora and Mt. Cooran. The arrangement of the columns 



^Vertical columns 

 ' A \ Si-oprxc columns 



°y , /' ' ' * '* *"•'• • »"^\H riPl7 "' v '" ra I COLUMNS 



$' \ A' - - ' 



x y. x 



V X X A. X. ^j- 

 <, x_ X X X X \ 

 X X X X X x \ 

 X. X x x«. x. X % 



'X X X XXX 

 /v * X X X X > 

 X X X X X 



Fig. 17. -Section of Mt. Cooran, indicating the arrangement of the 

 columns in the comendite monoliths. 



of the last-mentioned is shown in Text fig. 17. Hemi-vitreous 

 varieties of comendite are met with in Coolum Mountain. Here 

 occur also highly vesicular varieties, with geodes full of mesolite 

 crystals. 



(3) Andesites and Dacite s. — As shown in a previous 

 paper, dacites newer than trachytes occur at Bankfoot House 

 among the Glass House Mountains (Plate xvi., fig.35). Similar 

 rocks occur around Mt. Wappa, and on the Nindherry Saddle in 

 the Yandina district. Dykes of a basic andesite cut the trachy- 

 rhyolites and quartz-porphyry at Battersby's, west of Tunbubudla 

 (Plate v., iii.). 



Andesitic rocks ranging from very basic to acidic, quartzose 

 varieties occur very abundantly in the Maroochy district, and are 

 associated with abundant tuffs and breccias. In most of the 

 railway cuttings between Nambour and Cooroy andesite or 

 its fragmentary equivalent is met with. Dykes of it often 

 intersect rhyolite dykes. 



