BY H. I. JENSEN. 95 



between Eumundi and Cooroy, numerous dacites, having close 

 affinities with the Cooroy mass, are found. 



(e) Volcanic Rocks. — It is advisable to discuss these under four 

 headings, (1) Trachy-rhyolites, (2) the Soda-Trachyte and Pantel- 

 larite Series, (3) Dacites and Andesites, (4) Basalts. 



(1) Trach y-rhy oli tes. — Under this heading I include 

 rocks having the colour of trachyte with the facies of rhyolite, 

 and whose exact nature the microscope only doubtfully reveals. 



Mt. Eerwah, 3 miles W.S.W. of Eumundi (Text fig 16), has two 

 peaks, the eastern 1.090 feet high, the western 1,290 feet, separated 

 bya saddle about 850 feet high. The western peak is composed of 

 rhyolitic or felsitic tuff and breccia, the eastern of trachyte. The 

 saddle and lower slopes of the mountain are decked with andesite 

 and andesitic breccia, and covered with dense vine-scrub. Nind- 

 herry Mountain and Mt. Wappa are composed essentially of a very 

 fine-grained rhyolite, surrounded by rhyolitic and dacitic tuffs 

 and breccias, and dacite lavas. The felsitic and andesitic tuffs 

 of Yandina contain sandstone inclusions and are therefore Post- 

 Triassic. Abundant rhyolite dykes occur in the Eumundi-Cooroy 

 railway cuttings, and some between Yandina and Nambour. 



Rhyolites occur in the Blackall Range at Lillingstone's Creek 

 (Text fig.15); on the Mapleton Tableland (Portions 69v. and 61v.) 

 west of Nambour, at an elevation of 1,000 feet and surrounded by 

 basalt; at the Bottle and Glass, and in the Tuchekoi Range. A 

 great portion of the Kenilworth district west of Mapleton and the 

 Bottle and Glass is covered with rhyolitic tuffs, breccias and 

 lavas, which partly cover Palaeozoic rocks and are covered with 

 basalt in places. In the Bottle and Glass they intrude Jurassic 

 sandstone. 



Mt. Tinbeerwah, near Tewantin,is composed of trachy-rhyolite, 

 and sends dykes into the surrounding coal-measure formation. 



Mt. Byron (1,600ft.), south-west of Mt. Mee, forms a large 

 trachy-rhyolite tableland. Dykes of the same rock intrude the 

 sandstones of the DAguilar Range, south of Mt. Mee; but 

 whether these trachy-rhyolites belong to the same era of eruption 

 as the felsitic tuffs of Brisbane, or to that of the Glass House 



