

642 RECORDS OF THE S.A. MUSEUM 
RIVER SYSTEMS OF THE SOUTH EAST OF SOUTH AUSTRALIA, 
As indicated by Tindale (1933) the predominantly underground drainage of 
this low level karst area has been an inrportant factor in the preservation of the 
relatively youthful appearance of the dunce ranges which serve as couvenient 
markers for the eustatic marine terraces, River drainage systems were always 
present and able to maintain a limited regime. Their flow was perhaps only great 
when subterranean capacity was overloaded and during the readjustment periods 
after changes of sea level had occurred. The courses of the streams when traced on 
the map reveal several interesting details: 
(a) The streams were antecedent to the formation of (he dune ranges. 
(b) Their headwaters are mature streams of the old Pliocene peneplaned 
land surfaee vast of Naracoorte, 
(e) During times when the terrace dunes were forming the stream mouths 
were often diverted along the eoast by the formation of off-shore and river mouth 
bars, 
(d) Normal trend of movement when diverted was northward. 
(e) Traces of drowned valleys of several streams can be detected running 
across the ancient Murray Gulf shelf to the continental margin. When more 
detailed bathymetric contour maps are available study of these valleys may yield 
important altitude data on submerged terraces, 
The principal streams of the area under consideration, other than the Glenelg 
and Murray Rivers, are the Reedy, Brown Cattle and Avenue Creeks, There are 
smaller ones south of Millicent with outlets to Lake Bonney. These streams are 
fed partly by excess of underground water and flow above ground chiefly during 
the wet winter season. 
For present purpose it is convenient ta trace the history of several of these 
streams during Mast Avenue and Reedy Terrace times and then to tie their 
courses in with streams further inland and those nearer the present seashore, 
During the early part of Reedy Terrace lime, Reedy Creeek flowed into the 
sea. at a joint just east of Matherleigh. Tts waters passed across the continental 
shelf off Cape Buffon. Shortly afterwards this mouth began to be barred and its 
flow diverted, step-by-step northwards behind developing fore dunes of Reedy 
Terrace. 
Tt is possible that this northward trend of movement of stream channels 1s 
characteristic of periods of building up of foreshore deposits in the South East, 
Re that as it may, Reedy Creek month at the end of Reedy Terrace time came to he 
at Blackford, after a step-by-step northerly migration of 50 miles. When this is 
understood Tt is lear that Reedy Creek Range and West Avenue Range are 
parts of a single dune series cut obliquely by the stream bed, Zeuner (1945) was 
