ON THE GEOLOGY OF WEST MORETON, QUEENSLAND. 145 



2,000 feet. From the south it appears as a huge inaccess- 

 ible pinnacle. The narrowest part of the summit is not 

 more than nine feet across, and a stone can be dropped on 

 the eastern side for a depth of at least 1,500 feet before 

 striking the rock face, while on the western side there is a 

 similar cliff of about 500 feet. From the summit of the 

 mountain an excellent view of the low lying Fassifern Block 

 can be obtained, and beyond the hills around Ipswich, which 

 bound the block on the east, the waters of Moreton Bay 

 are visible. 



Mount Greville (2,700 feet) the sentinel of " The Gap," 

 situated about five miles to the east of the Main Range, is 

 composed of grorudite, and its present contour is probably 

 due to the erosion of the mature rivers that formerly flowed 

 through Cunningham's and Spicer's Gaps. The northern 

 slope corresponds in contour with the southern slope of the 

 former, while the southern contour recalls the outlines of 

 the northern slope of the latter. 



The eastern side of Mount Greville is cleft by fissures 

 from 6 feet to 20 feet wide with precipitous walls from 100 

 feet to 200 feet in height. They have been formed by 

 basalt dykes which being less resistant than the grorudite 

 have been completely eroded. These clefts are studded 

 with magnificent palms, ferns, and orchids, and form one 

 of the most picturesque spots in Southern Queensland. 



Mount Edivards (2,300 feet) is composed of trachyte 

 intruded by basalt, and Mount French (1,800 feet) is com- 

 posed of comendite, tuffs and breccias. 



Spicer's Peak (4,100 feet) presents a section almost 

 identical with that of Mount Mitchell, and like the latter 

 has a vertical escarpment on the east. 



2. Andesites and Dacites. 

 A parasitic cone of andesite occurs along the old Warwick 

 Road which runs through Spicer's Gap (See Fig. 1). Here 



J— August 2, 1911. 



