lix 



bold headland of "Wilson's Bluff, gradually change their 

 character, and at INoarlunga give place to sands and shingle. 



Again, the scarped ridge east of the main street of Gawler is 

 made up of coarse sands crowned by rounded gravel ; the sands 

 contain blocks of stone, resulting from consolidation of the 

 sands by carbonate of lime, "which yield a few marine fossils, 

 and also silicified stems, having a structure resembling that of 

 Casuarince and Eucalyptus. The process of silicification took 

 place subsequent to entombment in the marine or estuarine 

 beds, because the stems are not unfrequently found to be 

 drilled by Teredos. As we proceed towards the ranges, the 

 depressions in the Palaeozoic rocks are levelled up by more or 

 less angular gravel, either loose or consolidated into a compact 

 conglomerate ; whilst at higher levels on the foot hills of the 

 Adelaide chain evenly-bedded sandrock, mottled clayey sands, 

 and ironstone conglomerates occupy flat-topped heights, con- 

 spicuous by their scrub vegetation. If we trace the mottled 

 clays, which cover the fossiliferous limestone at Adelaide, 

 towards the north, we find that they are coterminous with beds 

 identical with those just described. Indeed, strata of this 

 character occur in patches of great or less extent from the 

 Hope Valley Reservoir, Teatree Gully, to Golden Grove, thence 

 to Gawler Town Hill, where they attain an elevation of 950 

 feet. They constitute the gold drifts of the Barossa and 

 Humbug Scrubs, and stretch away in a narrow band by 

 Lyndoch, Tanunda, and Nuriootpa. No other fossil remains 

 than silicified tree-stems similar to those at Gawler have been 

 met with in these Upland Miocenes. The amount of denuda- 

 tion that they have been subject to is immeasurable. They now 

 occur as disconnected patches, separated from one another by 

 deep ravines, and are only remnants of a long narrow incline 

 plane bounded on the east by the Adelaide chain, but whose 

 western confines are not extant, as in many places they form 

 the highest ground on the Gawler Hills. 



The littoral beds at INbarlunga conduct us to beds of a like 

 nature, and doubtlessly similar origin, forming the gold-field of 

 Echunga. In the same category must be placed the Tertiary 

 beds of Myponga Flat, the sandstones and ironstones at 

 Tankalilla, which there overlie marine Miocenes, the varied 

 sandy beds constituting the scrub-lands to near Cape Jervis, 

 among the hills to the north of Victor Harbour, along the 

 eastern slopes of the Adelaide chain, extending northward 

 along the valley of the Bremer to Callington. 



The character of the gravels and their relation to the marine 

 Miocenes must, in the absence of positive evidence to the con- 

 trary, be regarded as indicating a fresh-water origin. I may 

 remark in connection with the clays overlying the Miocene 



