Sand Ridges in Western Australia. 



417 



Below this laterite waste, the bedrock of greenstone (a fine-grained 

 epidiorite or amphibolite) occurs. The sand can be traced to some 

 of the saddles of the ridge, through which it has passed, and spread 

 itself outward and downward on the eastern sides of the ridge. 

 Towards the northern end, the sand on one saddle has become 

 discontinuous, by erosion of some kind, with that lower down on 

 the eastern slope of the ridge, where it is now being removed by 

 stream action. Towards the southern end, at another saddle, a 

 small amount of sand has spread well over the saddle, but has 

 not, as a blown sheet, reached far down the eastern slope, as it is 

 being carried away by a small watercourse, along which it forms 

 a narrow thread. Still farther south the sand has spread out as a 

 wide, long mass and has merged into that which has worked around 

 the eastern side of the ridge from the sand plain to the south of 

 this ridge. Stream action has carried portions of this sand 

 farther east as narrow bands. Where the ridge is higher than 

 the passes, the sand flanking the ridge on its western side is at a 

 lower level than that at the passes. The outline of the sand at its 

 junction with the laterite thus shows a series of curves rising in 

 height as the passes are approached. 



These deposits of sand, which are clearly wind-blown, constitute, 

 on the eastern side of the laterite ridge, the " sand glaciers " of 

 Comet Vale, and this paper is, so far the writer is awaie, the first 

 record for such phenomena in Western Australia. 



QenercL/fs ecC S ecf/ons 



\ie^t 



Scisf 



f^f'X IThroua/t a- crest of fti^ Tncctn /ccf^er/'fe r/c/ye_ 



yfpst fast 



X ^ ^ 

 > ^ X X 



I 



'^^■Z ftfrouah ct ^0.5^ on t/jc main /a/'er/Ve r/c^oc 

 A A LcLfcrite cap XX (prems/ones 



llB/oY^n 3 an Us ^/^ Lctfer/'/^e WasA. 



Figs. 2 and 3. — Generalised sections acrcss th«* sloping sand plain and tlio 

 dissected hitrh lands, showing the relation of th«' sand to the crests and 

 passes of the main (western) laterite ridge. 



