Page:Rambles on the Golden Coast of New Zealand.djvu/119

Rh towards the north. A very striking feature is, that these beds lie almost horizontally, forming near the sides of the granite wedge, vertical, and even in some places overhanging walls from 500 to 1500 ft. in height. These strata do not appear to have been upheaved by granite when in a soft state, but when this rock was in a solid condition, a proof of which we find near the sea, north of the Ngakawau stream. There large masses of porphyritic granite occur, resembling that which has protruded through the older syenitic granite. Near it we meet with a granitic breccia, consisting of large angular pieces of syenitic granite and micaceous rocks, embedded in a trappean granitic matrix, which could not have been formed by the rolling of the waves on the shore or by submarine currents, but only by friction, when the intruding masses upheaved the syenitic granite, and with it the coal bearing strata. In some other places, to the north of Mount Frederick, the porphyritic granite has itself intruded into the coal bearing strata, and many highly interesting rocks have been formed by alteration of the grits, coals, and shales. From the top of Mount Rochfort to the course of the Waimangaroa, which separates the last named mountain from Mount Frederick, the general strike of the carboniferous rocks, which attain here a thickness of 3500 ft., is from east to west, with a dip from 4 degrees to 7 degrees north, and the following is their succession in descending order, beginning at the top of Mount Rochfort:—

For the next 500 ft., the same attenuating succession of grits and shales continues, as observed in the gullies around Mount Rochfort, but without any apparent indications of coal. The shales, where not too micaceous, are replete with impressions of plants, all specifically the same as those in the Grey coal-fields, of which Voltzia is here the most conspicuous. Below them again for several hundred feet, slaty sandstones occur, succeeded by the grits and shales, amongst which I discovered a coal seam. In descending from Mount Rochfort, and crossing in an easterly direction the mountain plateau, intersected by innumerable streamlets, the rocky walls of which everywhere offer good sections, we again find ourselves, after having passed over all the strata before enumerated, amongst grits and shales. Having examined at least 80 ft. of these sandstones, the following strata, in descending order, are met with:—

The coal seam strikes regularly from north-north-east to south-south-west, with a dip of