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What once constituted the upper beds of the Cambrian 

 System on the Peninsula, of unknown thickness, has 

 entirely disappeared. Of those that are left the fossiliferous 

 beds, which form the highest members of the series, are near- 

 ing extinction ; the dolomitic limestones, which underlie the 

 latter, have a somewhat wider range, but come second in 

 their restricted areas ; the basal grits are a little more pre- 

 valent, again ; and the rest of the country, when cleared of 

 the more recent deposits, exposes the old Pre-Cambrian base 

 level. Here we have the evidences of a peneplanation which 

 began in early Palaeozoic times and has continued intermit- 

 tently to the present day ; the effects are seen in the few 

 broken and disconnected remnants of great geological systems 

 that have survived to tell the tale. 



(c) CAINOZOIC PENEPLANATION. 



From the close of the Cambrian period to middle 

 Tertiary times the geological history of the greater part of 

 Yorke Peninsula is a blank. Geological cycles may have 

 come and gone in this interval without leaving a trace behind. 

 A striking illustration of this is seen in the survival of an 

 outlier of the Permo-Carboniferous till in the southern por- 

 tions of the Peninsula. In this latter case favourable circum- 

 stances combined to preserve this fragment of a past age in 

 a local patch which otherwise would have been unrepre- 

 sented on the Peninsula. The occurrence of the Permo- 

 Carboniferous deposits, as stated, helps to bridge the long 

 interval and throws light on the geology of the Peninsula in 

 two ways : it proves that in late Palaeozoic times the land in 

 this region was certainly above sea level, and that the climate 

 was very cold. 



So far as we can judge from the evidences that are 

 extant this particular region remained above sea level from 

 the close of the Cambrian period until the great coastal 

 submergence of Australia which took place during the 

 Miocene period. At that time a great maritime strip of 

 country passed below sea level and received a thick layer of 

 sediments which in places amounted to 1,000 feet. Whether 

 so great a thickness of these beds ever existed on Yorke 

 Peninsula is difficult to say, probably not; but at present 

 they are reduced to near vanishing point. On the eastern 

 side of the Gulf fossiliferous sands and limestones of Pliocene 

 Age are commonly found resting upon the eroded surfaces of 

 the Miocene, but no remains of these beds have survived on 

 the Yorke Peninsula side, having been, apparently, planed 

 off by the denuding forces. Some indications of the under- 

 lying Miocene beds, however, still remain. On the slightly 



