Uttley. — Volcanic Hocks of Oamaru. 107 



of the town of Oamaru. The pillow-lavas that occur in some localities 

 will be described, and a preliminary reference will be made to the micro- 

 scopic characters of some of the rocks, a detailed description of which must 

 be reserved for a future paper. I am much indebted to Dr. Thomson 

 and Mr. H. Suter for naming many of the fossils. Their determinations 

 are indicated by an asterisk placed in front of the name of the fossil. The 

 other determinations have been made by myself by comparison with forms 

 determined by these palaeontologists. 



II. The Succession of the Rocks of the Oamaru Series. 



It will be advisable at the outset to state briefly the detailed succession 

 of the Oamaru series as developed in the typical locality. The classification 

 of the upper rocks is based mainly on evidence to be brought forward in 

 this paper. 



To the west of Oamaru, in the basin of the Kakanui River, the lowest 

 Tertiary rocks are the grits, clays, and sandstones, sometimes associated 

 with lignite deposits, the whole forming the Ngaparan stage. These are 

 followed by a considerable thickness of greensands, and these in turn are 

 succeeded by a great thickness of breccias and tuffs, occurring in the Waia- 

 reka Valley. Towards the top these become fine-grained and tachylytic, 

 and are interbedded with deposits of diatomaceous earth, which, in addition 

 to the vegetable micro-organisms, contains an equal abundance of sponge- 

 remains and Radiolaria. Dykes and sills have intruded the tuffs and diatom- 

 aceous earth, and the siliceous rock has in many places been completely 

 metamorphosed into a flinty substance. These constitute the Waiarekan 

 stage. The Ototara limestone is the next succeeding rock. In its lower 

 portions it is interstratified with thin beds of marl, and occasional thin layers 

 of rolled volcanic pebbles. In its middle portion it is in some localities 

 intercalated with tufaceous bands, but these are probably detrital only. 

 In other localities the deposition of the limestone continued uninterruptedly ; 

 and it is free from volcanic material. Towards the end of the limestone 

 period volcanic activity was renewed in localities near the present coast- 

 line with the eruption of the breccia at Kakanui and the volcanic rocks 

 in the neighbourhood of Oamaru, the upper pillow-lava of the latter locality 

 being younger than the breccia. After volcanic action had ceased limestone 

 continued to be deposited, but in many places it contains large well-rounded 

 masses of volcanic rocks, and minerals similar to those occurring in the 

 breccia below. It is more than probable that the Kakanui breccia formed 

 small islands or submarine banks, for it is followed by limestone bands and 

 tuffs, the former containing rolled fragments of the breccia. In Oamaru 

 Creek these interstratified tuffs and calcareous bands are invaded by a 

 thick mass of dolerite which has overflowed to the north and formed the 

 upper pillow-lava near Grant's Creek. This in its turn is followed by 

 the limestone containing the large volcanic boulders. The latter disappear 

 towards the top of the limestone, which closes the Ototaran stage. The 

 greensands of the Hutchinsonian stage followed the limestone, and the 

 sequence closed with the mudstones of the Awamoan stage. 



III. Previous Opinion in regard to the Horizon of the Volcanic 



Rocks. 



Hector (1865) considered that the volcanic rocks near Hutchinson Quarry, 

 in the town of Oamaru, were submarine, but he based his conclusion on the 



