H.—34.

Economic Geology. Coal. —Although seams of lignite ancl sub-bituminous coals occur at many points throughout the coastal ranges, this material is mined in two places only—viz., at Herbert and Shag Point, there being two mines in the latter locality. The coal at Shag Point is of fair quality and, apart from household uses, can be employed for welding. Limestone.—A high-grade limestone or marble in the Kakanui Series occurs on the eastern wall of the Shag Valley at the Blue Mountains. The quarry at Inch Valley is served by rail, and several hundred tons of crushed and bulk stone are removed weekly for the manufacture of cement. A soft, coarse-grained limestone of good quality outcrops in the fault-angle at Green Valley, north-west of Dunback, and should be of great value in top-dressing. Gold. —In the past the river sediments in the subdivision have yielded much wealth ; but little interest in prospecting is shown to-day. Old workings and drives are common on the mica-schist country between Dunback and Macraes Flat. A rich alluvial claim was located at Yankee Gully near the head of Woolshed Creek. After heavy easterly gales " colours " are frequently reported on Hampden Beach, but no serious work is carried out in the search for the metal. Road Material. —No difficulty is experienced in roadmaking on the schist terrain and unlimited supplies of river gravels are available. The quartz conglomerates also make good surfacing material, whilst the tough, hard basalt at Smyler Peak, Palmerston, is used extensively by the Neuchatel Asphalte Co. as a base in their product. Building-stones. —Mica-schist is widely employed in the construction of bridge buttresses and approaches. The limonitic sandstone is displayed in the churches at Hampden and Palmerston, and weathers well. A fine-grained indurated facies of the Waiarekan tuffs was quarried at Herbert and used in the construction of the flourmill at Waianakarua. Roofing-slate. —Slate was quarried over sixty years ago in the north-west section of the Otepopo Survey District. Three factors combined to hinder the success of the project —viz., difficulty of access, dwindling of demand for such stone, and excessive waste occasioned by the presence of numerous quartz stringers throughout the rock. Greensands. —As in the neighbouring districts of South Canterbury, the Moeraki Subdivision abounds in greensands and glauconitic mudstones. The richest member of this type is the Otepopo greensand outcropping near Herbert, particularly well exposed in the railway-tunnel cutting. Samples of the higher-grade greensands have been collected in order to test their value for water-conditioning, but results are not yet to hand. Petroleum. —A sand smelling strongly of oil was discovered by Mr. A. Craig, of Hampden, at the extreme south end of Hampden Beach. The deposit is of small extent and occurs immediately on the beach, being involved in a huge slump which dislocates mudstones of the Moeraki Boulder Beds. The relation of the sand to the latter is not clear, and the opinion of the Dominion Laboratory that the oil is possibly a highly-refined one makes it appear that the local beach sand has been contaminated. A further examination will be made before the end of the season. Iron-ore. —West of Herbert, near Government Hill, a large deposit of rich lisematitic sandstone belonging to the Herbert Series is found outcropping on the hillsides. Analyses are not yet available, but McKay in 1887 reported that similar material contained up to 37 per cent, of iron. GLENORCHY SUBDIVISION. By J. Healy and R. W. Willett. During the 1937-38 field season approximately 120 square miles was mapped in detail, comprising parts of the Glenorchy and Earnslaw survey districts. The area, bounded on the east by the Richardson Mountains, extends north from Creighton Creek along the eastern shores of Lake Wakatipu to the Twenty-five Mile Creek near the headwaters of the Pees River, and on the west by Mount Alfred, together with the high ridge west of the Earnslaw Burn. It includes the Township of Glenorchy and the important scheelite-producing lodes of Mount Judali. The work in this subdivision was closed down for five weeks from Ist February to 7th March, in order to carry out geological work in the Martin Bay district. From November to the end of January Mr. A. G. Reid was employed as field assistant. Topography. The principal topographic feature of the district is the Richardson Mountains, which extend from the southern extremity, Mount Creighton, to the Forbes Range in the north. The. general summit level of these highlands is fairly even, ranging from Stone Peak. (7,222 ft.) and Mount Larkins (7,432 ft.) in the south to their highest point, the Centaur Peaks (8,284 ft.). The western slopes of the Richardson Mountains drain into the Rees River, which from its source in the Forbes Mountains flows south-south-west to discharge into the head of Lake Wakatipu. In the lower part of its course, from Lovers' Leap to its mouth, the Rees flows for about eight miles as a braided stream along a wide gravel-filled valley. This gravel-filled valley is roughly triangular in shape, having its apex at the head of Lake Wakatipu, its sides and

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