ON THE GEOLOGY OF WEST MOKETON, QUEENSLAND. 139 



Mitchell and Spicer, and Mounts Roberts and Wilson. They 

 represent the U-shaped mature river valleys eroded to base 

 level, which have since been elevated to a height of about 

 2,700 feet above sea level. Cunningham's and Spicer's 

 Gaps still preserve a perfect U-shaped contour, the latter 

 being one and three quarter times the size of the former. 

 A magnificent view of these "gaps" can be obtained from 

 the western side of "Jump Up," a high ridge which runs to 

 the north of Mount Alford about six and a half miles to the 

 west of the township of Boonah. The gap between Spring 

 Bluff and Bald Mountain has been faulted to a depth of 

 about 500 feet below the uplifted peneplain, whereas Cunn- 

 ingham's, Spicer's and Wilson's Gaps are ou the edge of 

 the escarpment. These gaps have at the present time an 

 important influence upon the meteorology of the eastern 

 coastal plain. 



In Cainozoic times the Water Divide existed far to the 

 east of its present position, and four important western 

 flowing streams carved the U-shaped valleys of the afore- 

 said gaps to base level. The most northern of these rivers 

 followed somewhat the course of the Lockyer and Murphy's 

 Creeks and flowed through the Spring Bluff gap near 

 Toowoomba. Its tributaries on the left bank carved the 

 aggraded U-shaped valleys through which Blenheim Creek 

 and Laidley Creek now meander, and the rich agricultural 

 lands of the famous Lockyer District are the result of their 

 work. The second ri ver flowed west through Cunningham's 

 Gap, and one important tributary on the right bank is 

 represented by the magnificent V-shaped gorge of Reynold's 

 Creek, which cleaves Mount Edwards. This gorge is at 

 present about two miles long, its sides slope at an angle of 

 40°, and the summit of the V on the east is 1,000 feet above 

 the bed of Reynold's Creek, and that on the west 1,800 feet. 

 It much resembles the famous Upper Shoalhaven River 



