285 



The Field River, in its lower portion, cuts the beds transversely and sup- 

 plies some excellent geological sections. At a distance of about half a mile from 

 the coast a very striking overfold occurs in the left bank of the stream in the 

 form of the letter S (Howchin, W., 1904, pi. xxxviii.), and, a little higher up 

 the stream, the junction of the lower and upper series of the Palaeozoic rocks 

 can be seen. The Brighton limestone and associated beds are thrown down to 

 the west at a high angle of dip (as in the section at the Brighton quarries) 

 with the purple slates in superior order. Rising from beneath the limestone 

 are the impure siliceous limestones which, at about a mile from the beach, form 

 a commanding anticline, 100 feet in height (Howchin, W., 1904, pi. xxxvii.). 

 A curve in the stream at this point shows that the beds also roll on the line of 

 strike, forming anticlinal folds at right angles to the great anticline just 

 described. 



The main limestone makes a remarkable curve in its outcrop where it crosses 

 the Field River. From Brighton to Field River it follows a north and south 

 strike, but on reaching the stream, just mentioned, it curves to the eastward and 

 follows the left bank of the river till within about a mile of Reynella, where it 

 is faulted to the right bank, and at Reynella it resumes its approximate north 

 and south direction. In Sec. 521, a little east of the fault, just mentioned, the 

 stream cuts the beds, for a short distance, at a right angle, and as the beds are 

 not so highly pitched here as they are further to the westward, an excellent 

 opportunity occurs for studying the junction which the Adelaide Series makes 

 with the Purple Slate Series at this point ; the uppermost limestones of the 

 former pass up, gradually, into the purple slates of the latter. 



On the ^southern side of Field River the Cambrian purple slates (inter- 

 bedded with thin reddish quartzites) form the main sea-clifif, reaching a maximum 

 height of about 80 feet, and as the strike of the beds accords, approximately, 

 with the direction of the coast, the cliffs form nearly a straight line, and no 

 special rock features are brought into view for a considerable distance. The 

 beach, however, forms an excellent example of a marine platform, cut back by 

 the waves, with the truncated edges of the highly-pitched Cambrian beds standing 

 up in serrated ridges, like the furrows of a ploughed field. At a short distance 

 south of Hallett's Cove a fine example of a oo -shaped fold (occurring along the 

 strike of the beds) is seen on the beach (Howchin, W., 1918a, fig. 104, p. 118). 

 The best view is obtained from the top of the cliffs where the outlines of the 

 complex fold can be taken in at a glance. Southward from Hallett's Cove 

 the Cambrian beds maintain a comparatively even face (on the strike) forming 

 prominent cliffs. The exposed face forms the western limb of a rather acute 

 anticlinal fold, with a high pitch. 



At a distance of about one and a half miles from the Cove, a headland 

 known as Curlew Rock (or Curlew Point) occurs. It is situated near the east- 

 west district road that separates Sees. 581 and 577, Hundred of Noarlunga. 

 On the southern side of the headland the sea has cut back the Cambrian beds 

 for a considerable distance and has left the Curlew Rock as a semi-detached 

 fragment at the angle of divergence in the cliffs, and exposed a transverse 

 section of the folds that makes one of the most striking rock features along the 

 coast (Howchin, W., 1904, pis. xxxix. to xl.). The rock consists of numerous 

 alternations of thin purple quartzites with slaty partings that have become con- 

 torted in a most intricate fashion. The beds are in vertical position and the 

 flexures, which by weathering have been brought into strong relief, are defined 

 with the greatest detail. The folding can be studied in two directions — in the 

 direction of the dip, in the headland ; and in the direction of the strike, on the 

 beach, which is clear of sand, and shows the truncated edges of the Cambrian 

 rocks. 



