Morgan. — Unconformities in Stratified Rocks of West Coast. 275 



formable, since the former a short distance up the Fox River are nearly 

 horizontal, whilst the breccia in the same locality dips at 35° to the east- 

 north-east.* The unconformity was also observed by J. A. Bartrum in 

 December, 1912.| Since the Hawk's Crag breccia is a slope deposit, it 

 may be maintained that its dip at Brighton is partly or wholly original, 

 and not due to pre-Miocene earth-movement. Even were this admitted, 

 unconformity would still be deducible from the absence of the other mem- 

 bers of the bituminous-coal measures. 



C. Apparently Unconformable Contacts of Miocene and Eocene Strata. 



If it could be clearly shown that Miocene rocks were anywhere deposited 

 on the middle or lower beds of the bituminous-coal measures, or that the 

 upper part of the Miocene in any locality rests on any part of the bitu- 

 minous-coal measures, unconformity would in ordinary cases be considered 

 as proved. Such unconformable contacts seem to occur in a number of 

 places, but in most cases faulting introduces an element of doubt. 



Near the head of Patten's Creek, about two miles west of Seddonville, 

 steeply dipping sandstone, probably of Upper Miocene age, is in contact 

 with Brunner beds: On account of strong faulting here present, uncon- 

 formity cannot be considered as proved, but the entire absence of the 

 Kaiata beds from the section is significant. On the road to Denniston, 

 not far from Waimangaroa, sandstone, which contains fossils of Upper 

 Oamaru (Blue Bottom) age, is in contact with Kaiata mudstone. The 

 strata, owing to involvement in the great fault zone (Lower Buller or 

 Kongahu fault) at the western base of the Papahaua and Paparoa Ranges, 

 are dipping almost vertically, but only a slight movement is detectable at 

 the actual contact, which therefore practically represents a plane of deposi- 

 tion. Between Waimangaroa and the Buller River, Upper Miocene beds 

 are found in several places close to Eocene strata, but no actual contact 

 has been seen, and in each case the presence of the Kongahu fault renders 

 interpretation doubtful. For this latter reason uncertainty also applies to 

 a contact of bituminous-coal measures with Upper Miocene sandstone, seen 

 at Moran's water-race, two or three miles north-east of Addison's. 



At Kotuku, twenty-one miles from Greymouth, below Oamaru strata 

 occurs a conglomerate which lithologically resembles the Brunner con- 

 glomerate, and rests upon Aorere rocks. It is quite an open question 

 whether this rock was deposited at the base of the bituminous-coal 

 measures or at the base of the Oamaru series. J In the former case there 

 is unconformable contact. 



In the eastern part of the Lower Buller Gorge Miocene rocks are found 

 resting on Hawk's Crag breccia, the lowest member of the bituminous-coal 

 measures as developed in the Westport district. Near Hawk's Crag the 

 contact is obscured by faulting, so that details cannot be ascertained. In 

 the valley of Nada Creek, a tributary of the Blackwater River, contact of 

 Miocene and Eocene is again accompanied by faulting, but at one spot 

 in the bed of a small brook (Lily Creek) Miocene sandstone rests on an 

 irregular, apparently eroded surface of breccia. The exposure, however, is 

 so small that it must be deemed unsatisfactory, more particularly since the 



* " Reports relative to Collections of Fossils made on the West Coast District, 

 South Island." Rep. Geol. Surv. during 1873-74, No. 8, 1877, p. 109. 

 t Personal communication. 

 t See N.Z. Geol. Surv. Bull. No. 13 (n.s.), 1911, pp. 67, 138. 



