120 Transactions. 



II. Historical Summary. 



Although the older Geological Survey did a considerable amount of work 

 in the Oamaru and Waitaki districts of North Otago, little reference has been 

 made to the geology of the Papakaio district. 



In 1874 Traill collected fossils at Pukeuri, and Hector (1882, p. 123) 

 assigned the mudstones there to the horizon of the nummulitic beds of the 

 Upper Eocene — that is, he placed them below the Hutchinson Quarry beds. 

 McKay in 1876 made collections at the Devil's Bridge and at Ardgowan. 

 He also examined the limestone at Landon Creek and referred it to the 

 Cretaceo-Tertiary. The volcanic rocks in the watershed between Oamaru 

 and Landon Creek he referred to a horizon higher than the Waiareka tuffs, 

 and rightly ascribed them to the second period of vulcanicity. Park (1905, 

 p. 519), on palaeontological grounds, placed the Pukeuri beds below the 

 limestone, and stated that the limestone at the Devil's Bridge overlav the 

 Hutchinson Quarry beds. Marshall and Uttley (1913, p. 303), on palaeonto- 

 logical and stratigraphical evidence, placed the Pukeuri beds above the 

 limestone — that is, above the Oamaru beds — and the Hutchinson Quarry 

 beds at the Devil's Bridge also above the limestone. 



III. Aim of this Paper. 



In 1916, in a paper on the geology of the Kakanui district, I gave a 

 detailed succession of the beds of the Oamaru system east of the Waiareka 

 Valley, and that paper gave some of the observations on which the sequence 

 was based. The Waitaki stone of Professor Park was shown to be the 

 Ototara stone in the locality where he had described it. 



It is the aim of the present paper to produce further evidence of post- 

 Waiarekan volcanic activity, to give an account of some hitherto unde- 

 scribed sections in the Oamaru and Papakaio districts, and to show the 

 relationship of the beds to those in the south of the Oamaru district. 



IV. Description of the Sections. 



It has already been mentioned that gravel deposits form the surface 

 rock over a great part of the country, but the Tertiary beds crop out in 

 the basins of Oamaru and Landon Creeks, and at several places on the 

 Oamaru-Kurow Road. The sequence is usually clear, but at Papakaio 

 the beds are faulted, and the continuity of an otherwise excellent section is 

 broken. 



In the Devil's Bridge area the deposition of the limestone appears to 

 have been continuous from the close of the Waiarekan period to the com- 

 mencement of the Hutchinsonian ; in the other localities to be described, 

 deposition was interrupted by a recrudescence of vulcanicity. It is pro- 

 posed, therefore, to give an account of the Devil's Bridge section, to be 

 followed by descriptions of sections in the district that show important 

 departures from the normal sequence as represented in that area. 



1. Devil's Bridge. (Fig. 2.) 



Fig. 2 represents a section from the Devil's Bridge in a west-north-west 

 direction to a point about a mile beyond the area mapped, so as to include 

 the Waiarekan beds. 



The tuffs (a) are very fine and tachylytic, and are interbedded with 

 bands of diatomaceous earth. Dykes and sills intersect the tuffs and the 



