Park. — The Rock-phosphates of Otago. 397 



In the absence of rocks overlying the basalt it is impos- 

 sible to fix the date of its eruption even approximately. In 

 his work on the " Geology of Otago " (1875, p. 56), Captain 

 Hutton, F.E.S., considers the basalt at the head of Waihola 

 Lake, with which this basalt has probably some association, 

 to be contemporary with his Oamaru formation of Lower 

 Miocene age ; but the evidence on which this conclusion is 

 based is not given. 



At Cemetery Hill the flow rests on mica-schist, near Kiln 

 Point on the coal grits, and elsewhere in the Horseshoe 

 Estate on the brown sandstone overlying the limestone. This 

 shows that the Eocene strata were deposited, consolidated, 

 elevated, and denuded prior to the eruption of the basalt, 

 which may have taken place in Upper Miocene or Pliocene 

 times. 



EOCK-PHOSPHATE . 



This was first found at Discovery Point, at the head of 

 the bend, where it rests on the upper surface of the limestone. 

 Here it forms a massive outcrop from 12 ft. to 18 ft. high 

 and from 4 to 5 chains long. It consists of a very dense grey 

 or yellowish-grey rock-phosphate, very rich in calcium phos- 

 phates. In places it is nearly pure phosphorite, occurring in 

 narrow-banded pale-yellow and grey concretionary masses, 

 possessing a tendency to exfoliate in layers when struck with a 

 hammer. Cavities in this rock were found to be incrusted 

 with apatite possessing a mammillary structure. The extent 

 of the deposit at this place has not yet been determined. 



Another outcrop of rock-phosphate crops out on the side 

 of the valley opposite Discovery Point, and near it several 

 large masses of this mineral occur in a small depression in 

 the hill about 20 ft. above this outcrop. Eecent excavations 

 show that the phosphate-deposit here is of considerable ex- 

 tent. It has been exposed by open trenches for a distance of 

 4 chains along the side of the hill, and is found to rest on an 

 eroded surface of the greensands. Loose masses of rock- 

 phosphate, lying on the slopes to the north of this, point to 

 the presence of another deposit in that direction. 



At Kiln Point a considerable amount of stripping and 

 trenching has been effected, and here much interesting in- 

 formation was obtained concerning the mode of occurrence 

 of the rock-phosphate. At this place the outcrop has been 

 stripped for a distance of nearly 2 chains, exposing a very 

 clear vertical section of the phosphate - deposit and under- 

 lying limestone. The phosphate varies from 3 ft. to 12 ft. in 

 thickness, and rests in a series of pockets in a deeply eroded 

 surface of the limestone. In the face behind the old lime-kiln 

 there are three shallow pockets, the most southerly being 



