256 Transactions. 



above the general level of the great coastward expanse of more or less flat 

 open or " pakihi " country which, rises gradually from near sca-leVel to an 

 altitude of approximately 250 ft. at the base of the higher terraces near 

 Addison's. jj 



McKay* alone of many writers upon the geology of the Westport 

 district has given the elucidation of the geological history of these terraces 

 and flats any serious attention, and it is with the hope of enlarging upon 

 the foundation already laid by McKay that these notes have been written. 



Sketch of General Geology. 



The various geological formations encountered in the Westport- 

 Charleston district, which forms the area discussed in this paper, in 

 ascending order, are : — 



(a.) Folded argillites and greywackes of doubtful age, assigned by 

 McKayf on evidence from the vicinity of Reefton to his Carboniferous 

 " Maitai " formation, intruded by later granitic rocks and by quartz- 

 porphyries, the whole unconformably overlain by 



(6.) Bituminous coal-measures, commonly considered to be of Eocene 

 age. 



(c.) Above the coal-measures are Miocene beds. As developed at Cape 

 Foulwind and Charleston, where, as the writer believes, on account of 

 overlap and not unconformity (a question dealt with later), they rest 

 directly upon the old erosion surface of granite or gneiss, these consist 

 of sandstones with shaly bands and with lignite seams, which attain a 

 thickness of over 25 ft. at Charleston. They are followed by Cobden lime- 

 stone and then by a great thickness of fine-grained blue marine sandstones. 



(d.) Unconformably overlying the uppermost Miocene blue sandstones, 

 or " Blue Bottom " as the beds are commonly called on the West Coast, 

 are alluvial deposits of gravel and sand, chiefly the former, constituting 

 high-level terraces and beaches extending from sea-level to a height of 

 over 500 ft. Such gravels have no internal evidence of age, beyond the 

 fact that they are undecomposed, though since their formation they have 

 always been above water-level. As, however, there is apparent conformity 

 in the GreymouthJ and Reefton§ districts between rotten gravels commonly 

 regarded as Pliocene (" Moutere " or " Old Man " gravels) and the under- 

 lying " Blue Bottom," it can safely be asserted that these are younger 

 — -viz., post-Pliocene to Recent. They consist in part of reassorted fluvio- 

 glacial gravels, and hence are at least in part post-Glacial. 



The question of conformity or unconformity between the Eocene coal- 

 i leasures and the Miocene beds is much in debate; in the Westport, as 

 in the GreymouthJ district, there is strong evidence of widespread un- 

 conformity in water-worn fragments of coal present in mudstones and 

 sandstones immediately above the bituminous-coal measures. It is pro- 



* " Geology of the South-west Part of Nelson and the Northern Part of the West- 

 land District," Pari, paper C.-13, 1895 ; and see also McKay and Gordon, " Mining 

 Reserves, Westland and Nelson," Pari, paper C.-9, 1896. 



t See particularly " On the Geology of the Reefton District, Inangahua County," 

 Rep. Geol. Expl., 1882, pp. 91-153. 



X " The Geology of the Greymouth Subdivision, North Westland " (Morgan), N.Z. 

 Geol. Surv. Bull. No. 13, 1911, p. 42. 



§ Seventh Annual Report, N.Z. Geol. Surv. Department, Pari, paper C.-2, 1913, 

 p. 119 (Henderson). 



II See "The Geology of the Greymouth Subdivision, North Westland" (Morgan), 

 N.Z. Geol. Surv. Bull. No. 13, 1911, pp. 42, 65. 



