83

H.—34

the two series. The Mangles sandstones form the greater part of the high ridge between the Matiri and Buller valleys. The Owen has cut a gorge through 6,000 ft. of the steeply-dipping banded sandstones more or less characteristic of this series, and the sandstones forming the bluffs on the west bank of the Owen northward of the junction of that river with the Buller are believed to be the upper portion of the Mangles sandstones repeated by faulting. The massive sandstone immediately west of the Blackwater at its junction with the Mangles, together with banded sandstones which outcrop up the Blackwater valley, belong to the Mangles Series. In the lower valley of the Maruia fine-grained conglomerates and arkositic sandstones, decidedly more coarse-grained than the Mangles beds elsewhere, are referred to this series. In the upper valley of the Maruia, Mangles beds probably occupy a considerable extent of country, but it was impossible to determine the boundaries between these beds and the Longford beds, so the area in which either may be present has been indicated on the map by a combination of the rulings of the respective beds. Longford Series.—The Longford coal-measures and conglomerates comprise about 6,000 ft. of strata. The basal conglomerates, which are coarse-grained at the Owen but fine-grained or absent in some localities, are overlain by banded to massive sandstones and grits. They are succeeded by massive conglomerate bands alternating with sandstone or mudstone. The coal-seams, which appear to be lenticular, are at the Owen and Longford interbedded with the lower sandstones, grits, and conglomerates of this series, but carbonaceous layers also occur in the higher members. In localities where the seams are tilted at high angles or have been involved in faults they are crushed over the whole or part of their width. Occasionally shale or stone bands interrupt the continuity of a seam. The main mass of this series outcrops from the vicinity of the Owen to the upper valley of the Maruia. The conglomerates and sandstones occupying the synclinal basin in the upper Mangles do not appear to contain any coal-seams, though some of the Longford beds involved in the Tutaki fault (which separates the granite from the sedimentary rocks of this locality) are coal-bearing. Leafimpressions are abundant throughout these beds.

Sections AB, CD, EF, Murchison District.

Igneous Rocks. Plutonic rocks occupy considerable areas on each side of the Tertiary rocks. On the east they appear in plan as a wedge-shaped mass tapering from the northern boundary towards the south, where they become fault-involved in complex movements and appear as isolated blocks surrounded by sedimentary rocks. The rocks of this group of blocks range from acidic to basic composition. On the west igneous rocks underlie the Tertiaries of the Matiri Highlands, and are thence continuous with the granites and gneisses of Victoria Range. Few basic rocks, except as small dykes and xenoliths, occur among these rocks.