31 



In reaching a conclusion the following facts have to be 

 considered : — 



(1) The deposit is not an alluvial fan in the ordinary 

 acceptation of the term. A normal fan is built up by a 

 succession of flood deposits of corresponding features aa to 

 strength of current and alluvial sediments, forming a suc- 

 cession of fine and coarse sediments; but the Glen Osmond 

 alluviation, now under description, was unique, there was 

 nothing like it before or since in the geological history of the 

 creek. The sections exposed in the banks of the creek exhibit 

 the normal red clay, with occasional beds of sand or fine 

 gravel, typical of the Adelaide Plains, and in no case do 

 large angular blocks of 6tone show in these sections. This is 

 confirmed by well sinkings in the neighbourhood. Mr. 

 Baulderstone sunk a well on the ground where the stones 

 occur in great numbers, the first 60 ft. was in bluish and 

 reddish clays followed by 10 ft. of sand and gravel; no large 

 stones were met with in sinking, nor was bed-rock reached. 

 A well on the adjoining property gave a like result. 



(2) The stones consist of quartzites and slates, chiefly 

 the former, and can be definitely identified with beds of a 

 like character that outcrop in the Glen Osmond Gorge. 



(3) All the large stones are angular in outline and of 

 indefinite shape, often partly broken on the bedding plane 

 as though wrenched from their bed by strong force. 



(4) The stones lie in every possible position and are 

 confusedly mixed. Sometimes a large mass of slate is seen 

 wedged in between two quartzites. 



(5) The trail can be traced back from the Fullarton 

 Road, following the general direction of the creek to the 

 mouth of the gorge. Near the Fullarton Road it is about six 

 chains wide. 



The only explanation that can be given, consistently 

 with the evidence, is that of a torrential wash of extraordinary 

 force. To carry such a body of stone, including many rocks 

 of from three to six tons in weight, over a low gradient for 

 a mile, seems an almost impossible task for such a small 

 watercourse. The gathering ground is so limited, the rocks 

 are of the hardest kind, and the stream must have spread 

 out far beyond its ordinary banks. We must assume that a 

 cloud-burst, of local extent, but of exceptional intensity, 

 must have acted as the quarrying and transporting agent. 



It is self-evident that no such storm has occurred in 

 our neighbourhood since its occupation by Europeans. Whilst 

 this occurrence must be regarded as geologically "recent," it 



