186 



Introduction. 



Ardrossan, situated in the northern portions of Yorke 

 Peninsula, was the first locality in South Australia from 

 which Cambrian fossils were obtained. Mr. J. G. O. Tepper, 

 who was for several years State school teacher at Ardrossan, 

 obtained from the local limestones some trilobite remains 

 as well as examples of fossil "coral" (Archaeocyathinae) in 

 sea-worn pebbles of the same limestone on the beach. These 

 remains Professor Tate referred, tentatively, to the Lower 

 Silurian. ^) The so-called "corals" were handed to Mr. R. 

 Etheridge, of Sydney, for description, who recognized their 

 affinity with the Archaeocyathinae.' 2 ). 



Soon after the discovery of these interesting fossils Mr. 

 Tepper published two papers on the geology of the district/ 5 ) 

 including a geological plan and section illustrating the 

 occurrence and succession of tlie beds that had yielded the 

 remains. These papers, as the work of a pioneer, formed a 

 useful contribution to the subjects and, although subject to 

 correction, indicate careful observation. 



Yorke Peninsula contains many points of geological 

 interest. The basement rocks, so far as they are exposed, 

 form fragments of the old Pre-Cambrian peneplain and are 

 representative of the oldest Australian terrain known to us, 

 and although the covering, formed by subsequent deposits on 

 this primordial floor, is patchy and of no great thickness, it 

 carries the records of many strange vicissitudes in its geo- 

 logical history. It was submerged during the latter part of 

 the Cambrian period, following which is a blank, extending 

 through several geological periods, concerning which no 

 records have survived. It was above sea level in Permo- 

 Carboniferous times when a great ice-sheet covered the land, 

 leaving behind it great thicknesses of boulder clay and gritty 

 sandstones that have disappeared by denudation except where 

 protected in the deep-seated valleys of the southern portions 

 of the Peninsula. The Mesozoic Age has left no remains, 

 but a few isolated patches of the older Tertiary marine beds 

 prove that the land was again under sea level in middle 

 Tertiary times, and has apparently been above sea level and 

 subject to subaerial waste from that time to the present. 



U) Trans. Philos. Soc. (Roy. Soc.) S. Austr., vol. ii., p. xxix. 

 (1879); ibid., vol. hi., p. xiii. 



(2) Etheridge : Trans. Rov. Soc. S. Austr., vol. xiii., p. 10, 

 with Editorial Note by Tate." 



(3) Introduction to Cliffs and Rocks at Ardrossan, Trans. 

 Philos. Soc. (Roy. Soc.) S. Austr., vol. ii., 1879, p. 71, Sketch of 

 Geologv and Phvsical His. of Hund. of Cunningham, ibid., vol. iv., 

 1882, p. 61. 



