Park. — The Rock-phosphates of Otago. 393 



but rises gently to the south-west, the inclination for the 

 most part being so gradual as to be perceptible only by 

 comparing the altitudes of the limestone outcrops over wide 

 intervals. The phosphate rock, to be more particularly 

 described hereafter, occurs in pockets in the limestone, and 

 is covered in most places with an overburden of brown- 

 coloured sands and clavs. 



A study of the topographical features of this area, when 

 considered in connection with the disposition of the rock 

 formations, shows that the present contours were determined 

 by denudation long after the eruption of the basalt cap. 



Classification of Eock Formations. 



For purposes of description and correlation the rock for- 

 mations present in this district may be classified according to 

 their respective ages as follows, excluding the recent alluvia 

 of the flats and swamps : — 



Post-Miocene .. ... Basalt flow. 



Oamaru series (Upper Eocene)... a. Brown sandstone. 



b. Limestone. 



c. Glauconitic sandstone. 



d. Quartz grits and conglo- 



merates. 

 Silurian ... ... ... Mica-schist. 



Silurian. 



The mica-schist crops out behind Cemetery Hill, about 

 45 ft. above the surface of Waihola Lake. It forms the base- 

 ment rock of this and surrounding districts, cropping out 

 along the western boundary of the Horseshoe Estate, whence 

 it extends westward and northward throughout Central 

 Otago. 



Near the cemetery, and all around, the schist lies in a 

 nearly horizontal position, but it would not be safe from this 

 to conclude that it had occupied this position from the time 

 of its formation until now. A rock of such antiquity must of 

 necessity have been subjected to all the stresses and foldings 

 which affected the younger formations in this region ; and it 

 is only reasonable to conclude that the direction of the later 

 secular movements has tended to flatten the Silurian strata, 

 which prior to these later movements were probably highly 

 inclined. 



Upper Eocene. 



(d.) Quartz Grits and Conglomerates. — These ride hard on 

 the mica-schist, from which the contained quartz grains and 

 pebbles were derived. Here, as elsewhere throughout 



