On Certain Conglomerates near Sydenham. 53 



materials carried will be firstly river gravels or coast shingle as 

 the case may be, but among those from the river glaciated stones 

 may occur in two ways. It is noted on the Yukon, by the same 

 writer, that stones embedded in the clay on the banks become 

 ground on one side by the stranding of river ice, especially in. 

 spring floods while ice barriers still exist in the river. The 

 material also in the river may itself be largely derived form glaciers, 

 as the nature of the mudstone matrix would suggest in this case. 



The pebbles will naturally be more numerous in mudstones 

 because first the mudstone being more slowly formed than the 

 sandstone as a rule, more ice is likely to float across it while a 

 given thickness is deposited, and, secondly, because the current 

 being more gentle more of the ice is melted as it passes over it at 

 a slow speed. No indentation need be seen on the beds even if 

 they are laminated, for the stones may sink gently with ice still 

 attached. 



A minor arrangement of the pebbles as continuous bands may 

 readily occur by the drift ice being more abundant at certain 

 times or a tendency of the ice to accumulate at certain places. 



The character of the pebbly mudstones and sandstones is just 

 what might be expected off" a coast along which the climate was 

 such that considerable rivers could freeze to the bottom in winter 

 and much shore ice could be formed. Such a condition may be 

 associated with neighbouring general glaciation as at present in 

 Alaska, where glaciers occur south of the Yukon. The moderate 

 size of the largest boulders also favours this view. 



The formation of the heavy conglomerate under such conditions 

 may be due to ordinary current transport, and the erosion of the 

 underlying mudstones favours this view. The stranding of ice 

 would however assist, when by gradual melting at one place, a 

 heterogeneous mass of gravel of all sorts and sizes would readily 

 accumulate, and the stranding and the rocking of the stranded 

 masses might also have caused the erosion. 



The severe climatic conditions might also contribute to the 

 complete break in the fossil fauna which seems to occur about this 

 horizon. 



These evidences of glacial action occur at the localities Nos. 1, 

 2, 3 and 4, but I did not notice them at No. 7 (Keilor). 



