242 PROCEEDINGS OF SECTION C. 



at and near the surface to those mentioned above, on being followed 

 down appear to be interatratified with the argillaceous and arenaceous 

 beds, and, in some cases, to resemble lode formations filling fissures 

 and chasms in the "rock. 



The following deposits are described as examples of this : — 



Hu7idred of Willunga. — About 20 miles south of Adelaide. 



Phosphate is being rather extensively worked here. The country- 

 rock is Cambrian limestone with interstratified argillaceous, arena- 

 ceous, and calcareous beds. The workings extend north and south, 

 the lowest quarry being the most northern : here two bodies of 

 phosphate, separated by a wedge or " horse " of dolomitic limestone, 

 have been quarried out from the surface downwtxrd to a depth of about 

 40 ft. These bodies approach one another in going down as the lime- 

 stone wedge becomes narrower, and appear to unite in the bottom of 

 the quarry, being bounded on each side by argillaceous and arenaceous 

 beds having a vertical and sometimes contorted dip. The appeai-ance 

 presented is that of an irreg-ular shattered fissure, caused by upheaval 

 raid faulting, in which argillaceous material, broken bed rock, and 

 phosphate had been deposited ; blocks and boulders, chiefly of limer- 

 stone, are also contained, and manganese and iron oxides occur as 

 veins and coatings. At the bottom the phosphate rock is still under 

 foot. 



Going southward, towards rising ground, shallow quarries have 

 been made in clay and decomposed argillaceous and arenaceous rock, 

 limestone and slate mixed with phosphate, which is more widely 

 distributed, and apparently occupies hollows in the bed rock, being 

 disseminated in nodules, veins, and segregations for a considerable 

 width through them and the superincumbent clay and calcareous 

 material derived from their disintegration. 



Hundred of Noarlunga. — About 18 miles south of Adelaide. 



Phosphate rock occurs in clay and jointed broken argillaceous 

 strata in segregated nodular masses and lode-like bedded formations in 

 the dolomitic limestone. The deposit conforms to the north and south 

 strike of the containing rocks ; it has been worked by quames, and in 

 one place by a shaft which has been sunk to a depth of 40 ft., and a 

 drive made on a lode-like formation, which may be, however, a 

 stratified bed, the phosphate rock being confined between walls several 

 feet Jipart; manganese and iron oxide as small irregular veins and 

 stains are associated. At the bottom of this shaft and drive the phos- 

 phate still continues under foot, and further sinking should afford 

 valuable information as to the persistence in depth and true character 

 respecting- this and phosphate localities where the occurrence is under 

 similar conditions. 



Orroroo. — About 170 miles north of Adelaide. 



Phosphate rock has been quarried here, and also disclosed by 

 shallow pits at several points for a distance of about 1 mile along 

 the eastern boundary of the dolomitic limestone; it occurs along the 

 limestone boundary in irregular-shaped intermittent bands of varying 

 thickness and segregated masses in soft earthy argillaceous and arena- 

 ceous and calcareous rock dipping at high angles westward beneath 



