452 Transactions. 



Grits and Conglomerates. — The grits are tabloidal or flaggy in 

 structure, and are composed of angular grains of quartz cemented 

 by iron-oxide — limonite. Under the microscope the quartz- 

 grains are seen to possess the same characters as the quartz- 

 crystals of the subjacent chloritoid mica-schist — rutile needles, 

 chlorite inclusions, and sometimes undulose extinction ; musco- 

 vite is also seen in the grit. The quartz-grains of the grit have 

 been derived in past geological times from the disintegration of 

 the schist. In the conglomerate the quartz pebbles are well 

 rounded, and as much as 0-75 in. in diameter. No fossils have 

 been found in either grit or conglomerate. 



These beds are seen only occasionally, as the surface-soil 

 hides their outcrop ; it is unlikely, however, that they attain 

 any great thickness. They may be seen in two small cuttings 

 on the road near Sutherland's farm (west of the Millburn lime 

 quarry) ; they are also seen north-west from there on the hills 

 in the schist country, and again they are seen north of Kiln 

 Point. As seen at these places the thickness of the beds is never 

 more than 1 ft., but near Sutherland's farm there are surface 

 boulders of conglomerate 2 ft. and 3 ft. in diameter. These beds 

 are more extensively developed ten miles to the south of Mill- 

 burn, in association with the coal-seams of Fortification. 



The only evidence of the age of the grits in the district is 

 the fact that they underlie the calcareous limestone which is 

 part of the Oamaru formation. As in the case of the schist, 

 we must go outside the district to determine their age. In 

 1875 Hutton* considered the coal-grits, of which the Millburn 

 grits are part, to belong to his Oamaru formation, of supposed 

 Oligocene age. In 1880 Hectorf considered the " island sand- 

 stone, forming the cover of the most important coal-bearing 

 formations of New Zealand," as part of his Upper Greensand, 

 of Lower Eocene age. In 1886 Hectorf considered the island 

 sandstone as part of his Cretaceo-tertiary system, comprising 

 practically all the coal-measures of New Zealand. Professor 

 Park in 1902 referred the grits to the base of the Oamaru for- 

 mation, which he placed in the Upper Eocene. 



Calcareous Series. 



Occurrence. — The calcareous series follows the grits and con- 

 glomerates in conformable succession, the different members of 

 the series being quite conformable to one another. Over most of 



* Hutton, "Geology of Otago " (1875), p. 47. 



f Hector, " Corals and Bryozoa of the Neozoic Period in New Zea- 

 land" (1880), by J. E. Tenison- Woods : Pref., p. vi. 



% Hector, " Outline of New Zealand Geology " (1886), p. 59. 



