ir.—34.

The geological data from surface observations are so inadequate that no deductions as to subsurface structures can be made, and therefore no assistance can be obtained from this source. Consequently, if the potentialities of the south-western area are to be fully tested, geophysical prospecting and structure drilling are the only methods available in the search for oil at Kotuku The whole of the area cannot be regarded as fully prospected. The west flank of the Kotuku Anticline should be subjected to additional geophysical examination. Shallow refraction shooting to the surface of the Cobden Limestone would suffice to test the hypothesis of a meridional fault, which would account for the orientation of the seepages at Kotuku, but reflection shooting is required in the same area to determine the depth to greywacke basement, and likewise to determine the presence and thickness of the beds underlying the Cobden Limestone. It is advisable to combine refraction and reflection snooting with a test bore, to permit a correlation of theoretical and practical results, and to assure correct interpretation. The depth and position of the bore would be determined by the preliminary investigation. The extension of the topographical survey will also be necessary. General Gordon Area. This area is situated in the Reefton gold-belt, approximately half a mile east of the Progress Mine. Ihe survey was commenced on the 18th October, 1937, and occupied two months. The main object of the survey was the tracing of the General Gordon Reef northward across Union Creek, towards the Globe and Ballarat workings. The potential drop-ratio method was used, and the survey proceeded on standard lines previously adopted in the area. Anomalies were recorded and mapped and flagged on the ground for trenching. The results indicated the probable southward continuation of a reef known to exist near the Ballarat workings up to Union Creek, where it is dislocated by a crushed zone, probably a fault striking in a north-west direction. It does not appear as if the General Gordon Reef continues unbroken in a northerly direction, although the survey was not extensive enough to prove that its northward continuation is not farther to the east. Waiuta Area. Geological reconnaissance by E. 0. MacPherson and M. Gage showed that the Blackwater Reef is structurally controlled by an anticlinal fold. To determine its extent and position in a northerly direction from the known reef system, and to determine probable similar features, was the object of the geophysical investigation. The survey commenced on the 11th October, 1937, and is still in progress. Preliminary research was directed to the possible tracing of the diabasic dyke known to exist and to cross the Blackwater Reef at an oblique angle. The magnetic method was employed, but the observations showed that the magnetic properties of the dyke are not sufficiently active to have a decided influence on the magnetic balance, and the work was therefore discontinued. The potential drop-ratio method was next used, and is still in progress. While the study of the results during field observations has not been neglected, it was found difficult to interpret anomalies over a small area, and therefore it is intended to carry on with the observations until the survey reaches Big River, approximately one mile and a half north of the Prohibition bhaft. It is hoped that with the sum of this information it will be possible to interpret the results on a wider basis and to draw conclusions as to the desirability or otherwise of continuing the survey towards Merrijigs. Since the actual observations have, so far, only covered part of the area intended for study, only a tentative summary can be given at present. One major structural feature has been observed as continuous through the area. This is an a PPM§ntly small anticline, which enters the area in the south near Absolom's Mine, passes close to the Waiuta swimming-pool, crosses Blackwater and Krantz Creeks, and may connect with the fold previously observed near the junction of Big River and Sunderland Creek. This anticline has the Blackwater Reef on its left flank. The numerous anomalies observed north of the Prohibition Shaft appeared, at first, to be only associated with irregular fissures of no importance and no prevailing direction. Additional observations towards the north, however, permitted better interpretation of the results, and disclosed the existence of three major groujis of anomalies, of which their parallelism is a striking feature. The general strike of the anomalies is slightly east of north. In the majority of cases evidence of previous prospecting by trenching, driving, and shafting has been observed close to the recorded anomalies, which shows also that the survey has not yet been extended into an area which could be regarded as inaccessible to previous prospecting methods. Most of the early prospecting is confined to creeks and to the main ridge between Blackwater Creek and the Big River drainage system.. The area has been mapped and contoured. It is the intention of the survey to reconsider the recorded results during the winter months and to arrange the future programme accordingly. The field-work was in charge of W. E. Hall and F. A. MacNeill, who observed the. area north of Line 13. QUARTZ-SAND DEPOSITS AT MAUNGATI. By D. A. Bkown. Maungati is in Waimate County, about twenty miles south-west by good road from Timaru. The sand forms a 50 ft. band in the face of a cliff which extends for 60 chains north of the road past Maungati School. Mr. Bower, the lessee, has already shipped some 226 tons to different parts of New Zealand,

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