ROCK PHOSPHATES OF S. AUSTRALIA. 239 



the formation to be quite analogous to South Australian occurrences of 

 Lower Cambrian till, though much more highly metamorphosed than 

 it in most instances. Underlying knotted mica schist is a considerable 

 thickness of micaceous schist containing fragments of schist quartz 

 and quartzite, and small boulders of granite. The inclusions are 

 largest in the lower portion of the bed, being sometimes 4 feet in 

 diameter. Intercalated in the series are lenticular beds of limestone 

 up to 20 feet in thickness. The lowest portions of the series observed 

 are alternating schist and quartzite, probably representing not the 

 basal bed of the series, but the phyllites — quartzites that occupy the 

 middle portion of the Glacial series as observed elsewhere. This occur- 

 rence is of interest as proving the identity of the ciystalline schist of 

 the Barrier Ranges with the slates and conglomerates of that area, 

 among which, as at Tarrowangie, Mr. Mawson, B. Sc, has discovered 

 Cambrian glacial till, and also affords confirmation of the assumption 

 by that author of a Lower Cambrian age for much of the Barrier 

 Eanges slates and schists. 



2.— NOTES ON THE ROCK PHOSPHATE DEPOSITS OF SOUTH 



AUSTRALIA. 



By B. T. L. BROWN, F.G.S., Government Geologist of South Australia. 



Clinton Rock PhospJiates. — Situated on the north end of Yorke 

 Peninsula, near the head of St. Vincent's Gulf. 



The existence of phosphate beneath the soil is indicated by 

 scattered fragments and blocks which have been upturned and brought 

 to the surface when the land was under cultivation. Some of these 

 fragments are white in colour, whilst others are brown, yellow, and 

 iron-stained : they are often associated with iron ore and manganese, 

 fragments of which are also scattered on the surface; they are em- 

 bedded with black earth, clay, loam, marl, &c., and occur in patches. 

 The soil generally contains nodules and lumps of phosphate rock, 

 beneath which lies the j-jhosphate deposit in situ. This consists of soft 

 yellow and grey clay, calcareous marl and sand}' clay, embedded in 

 which are segregated, rounded, and bedcled-like masses of phosphate 

 rock. 



The rock presents considerable variety in appearance, being 

 sometimes grey, white, and chalk-like, reticulated with thin veins of 

 denser composition, and at others a compact yellow, grey, and reddish- 

 coloured rock, with cellular spaces of various sizes, causing the whole 

 to have a brecciated appearance, and again compact and nodular. In 

 places earthy manganese fills the cellular spaces, particularly in the 

 case of the soft chalk-like rock, which is also stained with iron oxide. 



The deposit as a whole has no regular stratification, although 

 here and there appear traces of stratification, which, however, are not 

 persistent. The strata in which the deposits occur are Cambrian lime- 

 stones, eroded walls of which are to be seen in some of the excava- 

 tions, in some places vertical, and in others inclined, but they dip 

 generally at a much higher angle than the limestone strata. Froni 

 this and other facts relating to the exposed portion of the limestono 

 rock, it would appear that at one time caves and fissures, varying in 

 extent, were formed, and that at a later period these became filled 



