61 



Sketch of a Geological and Physical 

 History of Hundred Cunningham 



and neighbouring regions. 



[Abridged.] 



By J. a. Otto Tepper, F.L.S., Corr. Mem. 



[Read May 3, 1881.J 



The Palaeozoic rocks forming the bulk of the South Aus- 

 tralian mountain ranges, and consisting princij^ally of divers 

 hornblende and mica schists, clayslates, quartzites, and marbles, 

 have been — and still are to a great extent — a puzzle to geolo- 

 gists as to their correct position among geological for- 

 mations. This much, indeed, has been ascertained of late — 1. 

 That they form one great system of alternating (or inter- 

 changing) layers of immense thickness ; and 2. That this 

 system is certainly of Pre-Silurian age, true Silurian rocks — 

 as determined by the critical examination of Professor Tate, 

 P.Gr.S. — having been found by me overlying them near 

 Ardrossan, Y.P. 



Having resided for many years among these Pre-Silurian 

 rocks, and examined quarries, wells, mines, &c., where and 

 whenever opportunities offered, the impression has grown 

 strongly upon my mind (especially since studying Dawson's- 

 " Dawn of Life," and other works,) that they will ultimately 

 be proved to be Huronian or Laurentian, the description of the 

 non-fossiliferous Canadian rocks seemingly agreeing very well 

 with the general characteristics of ours. Mr. Scoular, in a 

 very interesting paper on the " Geology of Munno Para" 

 (Trans. Eoyal Soc, S.A., 1879-80, vol. III.), has treated their 

 general aspects so well, that it only need be mentioned here 

 that they generally exhibit very high angles of dip, denoting 

 enormous foliation by lateral pressure, as noted also in the 

 Canadian rocks. My own observations have been principally 

 made in the neighbourhood of the Barossa Ranges about 

 Lyndoch, Tanunda, Angaston, &c., but embrace also more 

 distant localities. Almost everywhere their anticlines have 

 been extensively removed by erosion, while, in most instances, 

 the synclines are buried deeply below later deposits. One of 

 the latter, however, is visible in the bank of the creek at 



