strip about a mile and a-quarter north-west of Trig. H. (See Section G. F., Text Fig. 2.) The other infaulted strip (see Section C. D. E., Text Fig. 2) extends from Wairaki River two and a-half miles to the south-east. The south-west margin is a fault boundary toward which the coal measures dip at 25°. These measures are well exposed on the bank of the Wairaki, where about 600 ft. of coal measures can be seen, consisting of brown and grey quartz sands containing several inter-bedded 1 ft. and 2 ft. seams of carbonaceous shale and dirty coal. Associated with the coal seams are calcareous concretionary beds with pyrite nodules, and sands that grade down into well-bedded, cemented, coarse quartz sandstones with some carbonaceous seams. Excellent leaf impressions were observed in the carbonaceous seams of the sandstone. The measures are sufficiently thin on the north margin to permit low mounds of basement rock to project through. An interesting point is the possibility of mapping the Tertiary strips by the type of vegetation, the Tertiary strips being covered with manuka scrub which is notably absent on the basement rocks.

Along the northern boundary of the area, Tertiary beds crop out in the terrace on the north bank of the Aparima. A fault brings the Tertiary beds on the north bank in contact with the Triassic to the south. The Tertiary beds here consist of blue-grey mudstone similar lithologically to the beds along Weydon Creek north of Centre Hill, of which they are probably the southward extension. Foraminiferal determinations by Dr. H. J. Finlay place the beds as Whaingaroan.

The coal measures in the Ohai basin have been examined and described in detail by Lillie (MS. report, 1945); and it is sufficient here to note that the northern boundary of the depression is a fault contact lying just south of Mount Linton and Mount Franklin.

3. Triassic. The Triassic beds make up the eastern part of Wairaki district, extending from Aparima River and Pleasant Creek in the north to Trig. H in the south, and westward from Aparima Valley to Letham Burn and Morley Stream. The strike of these beds swings from north-west in the south to north-east in the north, and they dip to the north-east and east. Irregular dips occur in faulted and disturbed areas, but the general picture is fairly regular.

The Triassic rocks consist of grey to grey-blue well-indurated mudstones, claystones, sandstones and conglomerates with here and there interbedded tuff beds similar to the greywackes and argillites of the other Mesozoic areas in Southland. The conglomerates are strongly cemented and consist of well-rounded cobbles and pebbles of the Fiordland complex, Te Anau Series, and the occasional porphyrite. The beds weather mechanically very rapidly, the fine-grained argillites frit into small angular fragments, a characteristic feature of the Mesozoic argillites in Southland, and many of the coarser greywackes break into flags. The mechanical weathering processes proceed much more rapidly than chemical weathering, with the result that the rock is usually well exposed and not obscured by clay. Talus slopes of angular scree material are a common feature, particularly below large bluffs.

The thickness represented by the Triassic beds (see Text Fig. 2) is 9,000 ft., but the repetition of beds by faulting may require this

amount to be reduced. In the absence of good indicator beds the extent of stratigraphic repetition cannot be gauged.

The conglomerate beds stand out strongly and are easily traced over long distances. Along the western margin of the Triassic rocks the conglomerate beds show the general trend of the strike swinging from west to north.

Fossils are found at many localities throughout the eastern part of the Wairaki area, being fairly plentiful at most points, and particularly so at some. Collections were made from the following localities and the specimens deposited in the Geological Survey collection. Dr. J. Marwick, of the Geological Survey, made the palaeontological determinations.

From all the above localities except k and l collections have been made by one of the writers (M. V. R.) and lodged in the Geological Survey collection, and are at present being examined in detail. Locality I was collected by Mr. R. A. S. Browne, and locality k by Messrs. Fraser Brothers, of Beaumont Station. All ammonite collections are being examined and described by Mr. R. A. S. Browne. Locality I had previously been collected by Dr. A. R. Lillie and Mr. M. Te Punga when working in the Ohai area.

The beds that make up the eastern part of the area, that is, lying to the east of Beaumont-Etal Ridge, are regarded as Carnic in age; to the west the narrow area of beds between the Carnic and the tuffs is Ladino-Carnic or older. Some of the ammonites are regarded as representing the upper part of the lower Triassic (personal communication, Mr. R. A. S. Browne).

4. (?) Permian. The Upper Palaeozoic (? Permian) beds are confined to a narrow strip ten chains wide and three miles long on the western scarp of the Letham Ridge. They crop out on the south in Productus Creek, a small tributary stream of Elbow Creek and end in the north at Coral Bluff near the headwaters of Letham Burn (Text Fig. 1).

The beds consist of a hard, fine-grained calcareous greywacke, almost black in colour. In places it is highly fossiliferous, particularly at Coral Bluff and Productus Creek. Between these two extreme points is a smaller fossiliferous outcrop; and detailed examination of the strip will probably reveal additional localities.