C—lo,

34

On the west side the lode, together with the country-rock permeated with copper, is bounded by well-stratified red rocks, having a strike of 40° west of north, and a dip of 45° to the eastward. " The thickness of the bedding is about 4 in., and much twisted. The colour is lighter and the texture finer than the same rocks nearer the lode. Underlying these red rocks to the westward is a body of ordinary coarse sandstone of the Ruahine Range, interstratified in places with shales. The strike and dip coincide with the overlying rocks. The beds extend west until within 300 ft. of the ridge, where they are seen to overlie the parallel rib of red rocks belonging to the same belt, which continue to the top and cap the ridge without descending into the gully on the west. The strike of this second rib of red rock is 40° west of north, while the dip is to the eastward and at an angle of about 40°. This parallel rib shows no sign of iron or copper sulphides, neither does the rib in the gully outside the deposit examined. The rib on the ridge is peculiar, from the great amount of slickensiding characterising it. As mentioned before, these rocks do not descend on the western side of the ridge, and the rocks bounding them on the west are the ordinary coarse grey sandstones and dark shales. This rib is not associated with the other rocks of the mineral belt. The rocks to the westward, in the left branch of the Makaretu, are twisted and irregular. Their strike is east and west, and the dip nearly vertical and to the south. Going back, and continuing the section from the copper lode, and thence to the eastward down the valley of the Makaretu, the greenish rocks overlaying the jasperoid rocks are seen to be covered by very soft sandstones, shales, and sandstones, at a distance of about 200 yards from the outcrop, the strike of which is 20° west of north, and the dip is to the eastward at 40°. The Makaretu Valley is heavily timbered, and the outcrops of rock are few. More to the eastward, at a height of 2,500 ft., or 600 ft. below the copper lode, the very soft sandstone shales are lying almost horizontal, while three to four miles further down the creek, at a height of 1,625 ft., the rocks consist of sandstone, with black shale partings. The former is coarse, and grey in colour. The bedding is irregular, being from 2 ft. to 2 in. in thickness. The strike is 45° west of north, while the dip is to the south, at 40° from the horizontal. The creek now takes a turn and trends south, and the section now goes over a high range to the westward which rises to fully 3,000 ft. On the western slope of this range, at a height of 2,200 ft., the sandstones are seen to be much finer in grain. In strike they trend 10° west of north and are standing in a vertical position. The bedding is thin and very regular. Half a mile to the westward the strike and vertical position is just the same, but the rocks are coarse, thick-bedded irregularly stratified sandstones and shales. The shales and slaty partings disappear on the eastern slopes, and until the beds disappear under the Pleistocene terraces and low grounds the rocks continue as a coarse, thick-bedded, grey sandstone, standing almost vertical, with a general north and south strike, and a dip to the eastward. 25th May, 1901. W. A, McKay.

REPORT ON THE CORRESPONDENCE OF THE SHOOTS OF GOLD EAST AND WEST OF THE MOANATAIARI SLIDE, THAMES GOLDFIELD. By Alexander McKay, F.G.S., Government Geologist. As affecting the prosperity of the Thames Goldfield there is no problem of greater importance than the determining the correspondence of conditions that exist in the parts of the district east and west of the Moanataiari Fault or Slide. This is the principal and, at the same time, the best known of the different dislocations that affect the area over which gold-mining at the Thames is carried on. Two other principal faults have been mentioned by some writers, and are popularly understood to be present in this field—the Beach Slide, running along the flat between the foothills and the east shore of the Frith of Thames; and the Collarbone Fault, described as springing from the Moanataiari Fault at the point where it crosses Karaka Creek, and thence taking a somewhat sinuous course nearly north across Punga Flat, Tinker's Creek, and Ohio Creek (30 chains above where the latter joins Tararu Creek). With respect to the Beach Slide, there are no proofs other than to show that a steep shore-line suffered depression, and that subsequent deposits in the Frith of Thames tended rapidly to obliterate the inequality; so that this is of the nature of an unconformity separating deposits o different ages, and cannot be considered as a displacement by fracture. The Collarbone Slide probably consists of a number of minor displacements having no direct connection with each other. In the southern part, from the saddle at the head of Collarbone Creek to Karaka Creek, it shows all the evidences of a series of landslips moving down the gully and grinding against the solid rocks on the eastern side. Though the rocks in motion may have a considerable depth, the whole of this part is of a superficial character, and is a slide affecting the surface rather than a fault dislocation reaching to great depth. Recently proposals have been before the Government in which considerable stress is laid on the influence which the Moanataiari Slide has had in determining the position of the richer parts of the Thames Goldfield. In these it is contended that the displacement downwards and to the west of the rocks west of the line of fault makes it probable that the deep-seated continuations of the reefs west of the slide are to be found in the hills east of the slide in the neighbourhood of and even east of Punga Flat, and on this matter, my opinion being sought, the following is my reply to the question : — Re parts of the Hauraki Goldfield west of the Moanataiari Slide or line of fault, and the probability of tracing the reefs of the front lower hills and Grahamstown Flat in the country east of the slide, the following facts and the reasonable inferences therefrom have to be borne in mind :—