FJtysiograpJty of the Glenelg River. 107 



Mr. T. S. Hartii believes tlie ]\[ain Divide of Victoria to have been 

 slowly uplifted along an east-west line, with trough faults on 

 either side. This elevation amounts to some 6000 feet in the extreme 

 east, and becomes gradually less westward, so that it seems most 

 likely that in the areai under consideration we have the last traces 

 of this great hoist as it gradually decreased to nothingness. To' 

 the south, at Portland, a proved depth of 2265 feet)^ of tertiary sedi- 

 ments indicates a very great subsidence there. 



If we picture the whole of the old Murray estuary as slowly 

 rising above sea-level, it is evident that the first part uncovered by 

 the sea would be the Dundas Highlands^ — our area C. We should 

 then have developed there the two sets of short consequent streams- 

 that still exist (see map). One set, Chetwynd, Pigeon Ponds^ 

 Mathers' creeks, etc., flowing north, and the other set, Dundas,. 

 Steep Bank, Wando, Koonong Wootong, etc., more or less southerly. 

 A certain amount of caj^ture in the region of their headwaters has 

 slightly but not materially affected these streams since then. (See 

 Fig. 2.) 



The remaining flatter part of the estuary floor would probably 

 rise a little more slowly, the sea apparently receding along a north- 

 west south-east coastline. Such a movement appears to be still 

 continuing, probably with minor oscillations, and is aided in its 

 reclamation work by the ridges and sand-dunes built by winds and 

 currents. The north-north-west trend of the parallel ridges and 

 swamps in that corner of South Australia is strongly suggestive of 

 this, and the part played by coastal dunes during the uprising is 

 evidenced by the occurrence, all through the areas concerned, of 

 patches of dune sand, sometimes very extensive, at other times blown 

 away and re-collec-ted in recent hollows. With the continued 

 recession of the sea, the northern streams would endeavour to make 

 their way north, probably a little west; while the southern streams 

 would gather to form two or three more or less uniformly south 

 flowing streams (see Fig. 2). Of these, the Glenelg would be one, 

 and a stream formed by the union of the Dwyer's Main Creek, and 

 the Upper Wannon would almost certainly be another. 



The sad lack of grade to the north would act against any definite 

 valleys being cut out and adhered to there, and we should probably 

 have our northern streams degenerating into chains of shallow 

 lakes, such as still occur in area B. The sister stream, the Wim- 



1 Proc. Roy. Soc. Victoria, December, 190y, and B.A.A.S., 1914. 



2 Quoted by H. Herman, Vict. Handbook, B.A.A.S., 1914, from Vict, boring records. 



