ON THE GEOLOGY OF WEST MORETON, QUEENSLAND. 147 



there is distinct evidence that the andesite intrudes and 

 caps the trachyte. 



Mount Alford (2,200 feet) about three miles to the east 

 of Mount Greville is composed of andesites, quartz-diabases 

 and devitrifled obsidians, etc., intruded by rhyolite dykes. 

 This mountain presents a fine field for research work and 

 holds the key to the volcanic sequence. It is hoped that a 

 -detailed examination will be made later. 



Mount Maroon (3,300 feet) about 12 miles to the E.S.E. 

 of Mount Alford is composed entirely of rhyolite. Two 

 features are here worthy of note (1) the occurrence of huge 

 vertical prisms 150 feet high on the northern side of the 

 summit, and (2) the presence of two small but very deep 

 elliptical lakes near Mr. Rose's Farm on the mount side. 

 These lakes are surrounded by rhyolite breccia and tuffs, 

 and have never been known to be dry. The larger one is 

 150 yards long by 75 yards wide. 



Mount Barney the culminating peak of southern Queens- 

 land, 4,625 feet high, is also composed of rhyolite, intruded 

 by basalt dykes. It is situated between Mount Maroon 

 and the McPherson Range. 



3. Rhyolites. 



A large rhyolite dyke intrudes trachyte at Johnston 

 Creek, about one mile to the west of Mr. Anderson's house 

 "Marraboola," in portion 92 V, Parish of Clumber. 



Glennie's Pulpit consists of the plug of rhyolite on the 

 north-western side of Mount Alford. It stands about 120 

 feet above the contour of Mount Alford, and is composed 

 of practically horizontal hexagonal prisms, pointing to a 

 vertical conduit for the molten magma. It is surrounded 

 by acid tuffs and breccias and represents a centre of 

 rhyolite eruption. 



