Page:Rambles on the Golden Coast of New Zealand.djvu/102

76 granites are full of rounded concretions of a blackish colour, and of a micaceous structure, exactly resembling the metamorphic schists which are observed near the hypogene rocks. These metamorphic rocks consist partly of micaceous schists and partly of granulites, and are intersected by occasional quartz veins. Their strike and dip are generally very irregular, their general strike is north and south, with a dip of sixty or eighty degrees towards the west. The cretaceous rocks which we meet with at the junction of the Inangahua and Buller extend to the coast, which they reach to the north of the Mohikinui stream. Here they consist of flaggy bluish and somewhat argillaceous limestone, intersected by large veins of calcspar, and in some places full of casts of fucoids. This rock extends, with only occasional intervals where granitoid rock crops out, to the mouth of the Wanganui, sometimes assuming the character of a chalk-marl, and sometimes that of a tabural whitish crystalline limestone, full of large oysters, pectens, terebratulas, and pieces of corals, in connection with the same fossils observed in the rocks between the Buller and Grey; but here also, as in the latter rocks, are no signs of belemnites or ammonites. The cretaceous cliffs at Otahu consist of bluish chalk marls from 8 to 12 ft. thick, of a white crystalline limestone, occasionally assuming a pale yellow colour, giving to the whole a ribbon-like appearance. In those sections where the limestone is found upon the granite we observe very interesting phenomena, indicating that during the deposition of the limestone great disturbances had taken place, either by earthquake or changes in the direction of great submarine currents. These sedimentary rocks frequently contain no fragments of hypogene rocks, and so continue for 20 or 30 ft., when they assume what at first blush would appear to be a granitoid appearance. In a calcareous base are disseminated quartz grains, crystals of feldspar, and scales of mica, in such abundance, that it is necessary to examine it closely in order to convince one’s self of its mechanical origin. In other places the granite is overlaid by a breccia, consisting of large angular pieces of granite and mica schists, embedded in a base of green semi-crystalline limestone, which is besides full of quartz grains and mica. The greater the interval between the sedimentary deposits and the granite, the smaller are the angular pieces, the limestone itself becoming more whitish. At a distance of 30 or 40 ft. from the granite, the angular pieces altogether cease, and mica scales are only occasionally found. The limestone itself begins to assume an earthy texture, and 80 ft. from the granite changes into a chalk-marl. In other places, above 20 or 30 ft. of quietly deposited matter, fresh revolutions appear to have taken place, and large beds of breccia, similar to those before described, again make their appearance. The cretaceous formation leaves the coast at the mouth of the Wanganui, and strikes in a north-easterly direction towards the Tasman mountains, the detritus of which gneiss granite and metamorphic schists is again brought to the sea by the larger streams.” As will be seen from this extract, to the geologist who has time at his disposal, and who makes preparations for a few days’ camp life on the Otahu range, the coast-line between the Mohikinui and Wanganui streams offers a splendid scope for the collection of specimens. Gold prospectors have also found