Park. — The Bock-phosphates of Otago. 



399 



stone presents the most marked irregularity. Under the 

 influence of both chemical and physical erosion it has been 

 formed into wide basins and deep well-like holes, surmounted 

 by overhanging knobs and spires of limestone. The basins 

 are filled with yellowish-brown sands, as shown in Sec- 

 tion III. below. 



Section III. 



Millburn Quarry, showing surface of limestone in present working-face. 

 A. Brown sands. B. Limestone. 



On the right side of the present quarry-face the upper 

 horizon of limestone has been eroded down to the lower more 

 sandy and glauconitic horizon, on the irregular surface of 

 which there rest two small patches of rock-phosphate, as 

 shown in Section IV. 



Section IV. 



Millburn Quarry, showing two patches of phosphate rock resting on lower 



horizon of limestone. 



On the right bank of a small stream near Sutherland's 

 limestone quarry there is a high face of rock-phosphate rest- 

 ing in a basin in the lower horizon of limestone, and a few 

 hundred yards south-west of Millburn quarry there is a similar 

 but smaller outcrop, which also appears to lie on the higher 

 part of the lower horizon. The surface contours and the 

 presence of basalt fragments in the phosphates at Kiln Point 

 tend to show that the formation of the deposits took place in 

 comparatively recent times — probably in the Post-Pliocene 

 period — and, obviously, since the present contours of the dis- 

 trict were determined.. Hence it seems probable that the 

 phosphate-deposits will be marginal, and follow the line of 

 limestone outcrop, contouring around the slopes of the hills 

 bounding the valleys and shallow basins. 



