258 Transactions. 



the gravel cap is removed. At Cape Foulwind, and for many miles south- 

 wards from the mouth of the Waitakere River along the coast, uptilted 

 inliers of granitic or gneissic rock appear, but cover no great area. Close 

 above the old rock in these localities are the lignite-bearing beds prominent 

 near Charleston, and then again, above these latter, is a definite stratum 

 of Cobden limestone (see section AB). This is seen only as a narrow band 

 at Cape Foulwind, east of which it does not outcrop within the district 

 here described. After a gap of many miles in its southerly trend it re- 

 appears at the Totara River, not far above the mouth of this stream, and 

 thence thickens rapidly until near Charleston it attains a thickness of 

 approximately 600 ft. or 700 ft., and, forming a prominent cuesta, with a 

 steep and lofty escarpment facing the sea, continues southward outside 

 the limits of the district studied. 



The Eocene coal-measures are absent south of the Buller River from 

 the uplands of the area described, and reach the surface only in the up- 

 turned eda;es of the relatively downthrown coastal block at the base of the 

 Paparoa Mountains in outcrops up several branches of the Fox River, ten 

 miles south of Charleston, and at Omanu or Back Creek, about three miles 

 east of Addison's. 



Later Geological History. 



Since the date of the " Lower Buller " fault, which has involved the 

 Miocene beds, is evidently post-Miocene, the terraces and flats of the low- 

 lands of the Westport-Charleston district are thus indicative solely of 

 post-Miocene events. For convenience of description the physiographical 

 features of these lowlands may be classed thus : — 



(1.) An extended series of high-level terraces, ranging in height from 

 about 450 ft. at the seaward edges to 600 ft. against the mountain-slopes. 

 Such have been designated the " 500-foot " terraces. 



(2.) The lower-level terraces and flats, similar to Addison's Flat, north- 

 westward of the " 500-foot " terraces. 



(3.) High-level terraces south of the Little Totara River and east of 

 the limestone cuesta near Charleston. 



(1.) The "500-foot" Terraces (see Section CD). 



The terraces that have been designated the " 500-foot " terraces have 

 a remarkable development for thirteen or fourteen miles south-westwards 

 from Fairdown to the Little Totara River. They are almost perfect in 

 uniformity of level, regularity of surface, and marginal outline, and consist 

 of a substratum of " Blue Bottom " capped by gravels from 30 ft. to 60 ft 

 or more in depth. McKay* states that east of Addison's " black-sand 

 beach leads are contained by these gravels. These appear to be not far 

 above the floor of Miocene sandstone. Furthermore, beach leads are found 

 in terraces over 500 ft. above sea-level near Charleston, and again at Trig. 

 Station Uf (759 ft.), three miles south of Charleston, a typical wave-cut 

 platform is preserved in resistant gneiss. These facts all show that north 

 of the Little Totara River wave-action sculptured the surface of " Blue 

 Bottom " on which the gravels of the " 500-foot " terraces rest. South 



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

 land District," Parliamentary paper C.-13, 1895, p. 8. 



t Trig. Station U has an additional interest in that it represents a fossil monadnock 

 of the pre-Eocene cycle of erosion. 



»3 



