V.\ui)\:uAnsoi^.—7'/ie Platinum Gravels of OrepuJci. 457 



measuring tlie thickness. According to some of the miners who have 

 worked on the races, the thickness is about 15 ft. The formation is at a 

 height of 200 ft. above sea-level, covered by dark, tough shales, with a 

 floor of Ijrownish-coloured shales, and with a covering of soft green sand- 

 stone. These shales contain leaves of dicotyledonous plants, which have 

 not yet been identified with any degree of certainty. As the formation 

 nears the beach the coal has been washed away, and its place has been taken 

 by a thick deposit of sands and gravels of Pleistocene age. Associated 

 \\ath these Pleistocene gravels are also beds of lignite, some of which can 

 be distinctly seen on the sea-chffs. This lignite is muddy and very poor, 

 and has nothing whatever to do with the brown-coal formation. A section 

 through this Orepuki occurrence appears as follows : — 



a. Soft .sandstone, with lignite, b. Brown-coal formation (Oamaru), 

 c. Slates (Kaikoura). 



(6.) Oamaru Formation. — A reference to the map shows that in the dis- 

 trict this formation has a comparatively large development. Leaving out of 

 account the Orepuki portion, we may describe it thus : Beginning in the 

 south-west corner, to the north of the Pleistocene deposits, it stretches to 

 the northern boundary ; then away to the east ; crosses the Waiau Rivei- 

 about the neighbourhood of Clifden, whence a narrowing tongue extends 

 nearly to the mouth' of the river ; extends to the eastern boundary aftei' 

 skirting the outlying northern spurs of the Longwood Range ; and finally 

 pinches out just above the Jacob's Estuary, on the border of which Riverton 

 is built. The basaltic formation of Mount Pleasant stands surrounded by it. 



Viewed on a large scale, the strata seem to be nearly horizontal, but 

 rising slightly to the north. The rocks are almost wholly composed of 

 shelly limestone or calcareous sandstones. The limestone is in places very 

 fossiliferous. The following fossils have with certainty been recognized : 

 Hemipatagiis forrnosus, Waldheimia lenticular is, Terebratula gualteri, Pecten 

 hochstetteri, Pecten polymorpJioides. Others have been found, but theii- 

 identification is not yet complete. It will be seen that several of these 

 fossils are identical with those found in the limestone formation of Oamaru, 

 in Otago, and at the Weka Pass, in Canterbury. These fossils characterize 

 the oldest Tertiary and marine beds in New Zealand. 



The Umestone. which at places forms cliffs 30 ft. high on the banks of 

 the Waiau, is not pure, averaging usually between 60 and 70 per cent, of 

 CaO. 



Sir James Hector, in a map of this district prepared in 1864:, considers 

 this formation as belonging to the Pliocene period, and describes it as a 

 Pliocene marine tertiary. Undoubtedly it is marine, but the occurrence 

 of the fossils just mentioned would assign it rather to the Miocene than to 

 the Pliocene. 



