295 



platymodes, Tate ; and a specimen of Plesiastraea, which seems to differ from 

 each of the two species of this genus described by Tennison Woods. 



The cHffs opposite to the Rocky Point stack consist mostly of alluvium 

 which has been washed down on to the face of the soft and yielding Cambrian 

 slates, and has, at the same time, obscured the outcrops of the fossiliferous 

 Pliocene beds. They are no doubt continuous over this area, as some indications 

 of their presence can be detected in a place or two, but they make no very dis- 

 tinct feature in the cliffs until they are seen on the broad platform of the lower 

 cliff, immediately to the south of Rocky Point, as described below. 



Near the northern end of this platform there is a conspicuous exposure of 

 the fossiliferous Pliocene, forming a scarp about 15 feet in height, and is con- 

 tinued in a length of about 250 yards. The rock has been a calcareous sand- 

 stone, but is now mostly leached of the calcium content. Fossils occur in the 

 rock sparingly, and chiefly as impressions on the bedding planes. Towards the 

 southern end of this platform the Pliocene sandstone is entirely altered to a 

 highly ferruginous and cavernous rock. This change in the lithological char- 

 acter of the rock is maintained to the end of the platform area, and even beyond 

 the isolated fragment, or butte (pi. xxiii., fig. 2), which marks the termination of 

 the high cliffs to the southward. Ferruginous cappings occur still further to the 

 southward, together with some red rocks, which may be inliers of the Fresh- 

 water Series that underlie the fossiliferous Miocene beds that occur to the north- 

 ward of Witton Bluff. 



Near the butte, just mentioned, are two washouts in the form of canyons, 

 20 feet deep, that run back from the beach almost to the base of the butte. On 

 the southern side of these canyons is an isolated hill capped by the fossiliferous 

 Pliocene. It forms an outlier from the main body of the rocks of this age, but 

 has not been ferruginated, as in the case of the adjacent Pliocene sandstones. 

 The bed contains fossil impressions and an example of the characteristic 

 foraminifer, Orbitolites complanata, three-quarters of an inch in diameter, was 

 obtained at this spot. The fossiliferous bed is underlain by the white sandstone 

 found in the same position at other spots within the platform area. 



The outcrop of the Lower (fossiliferous) Pliocene within the limits of 

 Section C extends for a distance of about one and a half miles. 



Miocene Beds in Section C, including the Underlying Freshwater 



Beds. 



From the outlet of Morphett Vale Creek to near Witton Bluff the sea-cliffs 

 are composed exclusively of alluvial deposits which will be described later. Along 

 most of the beach between these two points large rounded stones derived from 

 the Miocene beds are packed up by wave action against the foot of the clay 

 cliffs, more particularly on the side towards the Bluff. It is not unlikely that 

 these well-worn stones may have been derived from a reef of this rock that 

 causes breakers about half a mile from the shore, although it is possible that, 

 as beach stones, they may have travelled northward from the Bluff. 



Witton (or, more correctly. Whiten) Bluff, situated on the northern side 

 of Port Noarlunga, is a prominent headland with a deep recess cut by the sea 

 on its northern side. The greater part of the headland is composed of beds of 

 Miocene age<^"^) which are highly fossiliferous and show a distinct dip to the 

 south-west. In consequence of this tilt of the strata the base of the series is 

 exposed on the northern side of the headland, and the upper portions pass below 



(2) The late Professor Ralph Tate and some other Australian geologists classified these 

 beds as Eocene, while Professor J. W. Gregory, F. Chapman, R. B. Newton, and others with 

 European experience, regard them as of Miocene (Janjukian) age. See Report Brit. Assoc. 

 Adv. Science, 1914, pp. 371-376. 



