299 



SUB-SECTION D. 



FROM THE MOUTH OF THE ONKAPARINGA RIVER TO THE 

 RED OCHRE COVE (4 MILES). 



Miocene Beds of Section D (including a small Outlier of 



FOSSILIFEROUS PlIOCENE). 



The estuary of the Onkaparinga has been excavated to base level in the 

 marine beds of the Miocene. The latter can be seen at, or below, sea level in the 

 broad entrance to the river and in cliffs on either side of the wide estuarine 

 flats ; they are exposed in the railway cutting and are banked up against the 

 Upper Cambrian purple slates on both sides of the Noarlunga township. On 

 the north side of the township the beds have a decided dip to the south-west 

 and exhibit shelvings below high-water mark. On the southern side, at the 

 convex bend of the "horseshoe," they form the cliff, bounded by the purple slates 

 on the one side and clay beds and gravels on the other. 



Fossiliferous beds of the same age occur in two railway cuttings near 

 Hackham, and also on the adjacent main road, about three miles to the north- 

 east of Noarlunga, at an elevation of 200 feet above sea level. Further again 

 to the northward highly glauconitic fossiliferous clays underlie Morphett Vale 

 and are exposed in the cuttings at Happy Valley reservoir. At about one mile 

 up the Onkaparinga River from Noarlunga, the junction of the Adelaide Series 

 and the Cambrian purple slates can again be studied, where the Brighton lime- 

 stone crosses the river in contact with the purple slates, and, about four miles 

 further up the gorge, the stream intersects the Cambrian tillite. 



Within half a mile of the sea the Onkaparinga narrows its bed with high 

 sandhills on its northern side, and on its southern side the older marine beds 

 (Miocene) make prominent and often vertical cliffs. The lowest exposed beds 

 in the series outcrop at the landward end of the cliffs. At that end the beds 

 consist of polyzoal rock, 2 feet to 3 feet in thickness, alternating with glauconitic 

 clays which are sparingly fossiliferous. The upper members consist of grey- 

 coloured argillaceous, varying to sandy, rocks, in which fossils are scarce, and 

 these beds are capped by a hard calcareous sandstone, also poor in fossils. 



At the southern head to the entrance of the river the marine beds are much 

 weathered, by the waves on the one side and the rain on the other, into hard 

 and bare terraces. Within the heads they have a thickness of about 30 feet 

 and are capped by Recent reddish clays and gravels. The newer marine series 

 (Pliocene) is not represented in this section and in positions higher up the 

 estuary, where the lower marine beds come to the surface, they are capped by 

 only a thin layer of travertine. The fossils mostly belong to the polyzoa. 

 Cellepora gamhierensis, Tennison Woods, is particularly abundant ; there also 

 occur examples of Reticulipora, Lichenopora, Pccten hochstetteri, Zittel, scat- 

 tered spines of Echinozoa, etc. 



On rounding the headland which forms the southern boundary to the 

 entrance of the Onkaparinga, going southward, the lower marine beds form low 

 cliffs and also platforms on the beach. Here they are richly fossiliferous in 

 certain forms, especially the large and massive cup-shaped Cellepora, and many 

 pectens, including P. eyerei, Tate; P. flindersi, Tate; P. peroni, Tate; and 

 P. hochstetteri, Zittel. 



The beds, both within the limits of the estuary and also along the beach to 

 the southward, roll in gentle and extended curves having a general dip to the 

 south-west, with an extreme inclination of about 4°. In consequence of this 

 pitch they gradually pass down to sea level and for some distance are confined 

 to the beach, between tide lines, and can be traced almost to the outlet of 



