GEOLOGICAL SURVEY

Press, Volume XCIX, Issue 29240, 25 June 1960, Page 11

GEOLOGICAL SURVEY

Comprehensive Maps Of N.Z.

The New Zealand Geological Survey is at present engaged in its most ambitious project. It is pipping the whole of New Zeajjnd to show the distribution of jocks of different types and ages, punches of the survey doing the work are at Auckland, Lower Hutt, Rotorua, Christchurch, Greyjoouth and Dunedin. A large area in Canterbury hounded by Hanmer Springs to the north, Christchurch to the jouth and Rakaia Gorge to the vest is at present being mapped jn Christchurch. The field work, which includes the observation of outcrops, both natural and manjnide, was done during the summer. The results are now being collated. During this field work the Hope fault, a fault that forms the southern margin of the Hanmer plains, was found to extend over Harper's Pass and down through the Teremakau river to join the Alpine fault at Inchbonnie. A similar fault, the has also been mapped as far west as the Alpine fault at the head of the Grey river.

Confirmation that the Hope and Awatere faults meet the Alpine 'fault, largest in New Zealand, has posea a problem for geologists. They cannot understand why faulting can occur laterally for four miles in the Hope and Awatere areas without displacing the Alpine fault at the junction. Lateral faults are creating world-wide interest, because previous fault movements have been found to be mainly vertical. The maps are drawn in the branch offices on a scale of one inch to a mile. They are then sent to Lower Hutt for scaling down to four miles to one inch and are printed. Various colours and cross-hatchings are used to indicate the age and type of different rocks. The survey, from the completion of the field work to the printing of the maps, lasts about 18 months-

Because the maps indicate the types of rocks, the position of faults, they can be used by engineers to find sources of road metal and to discover where earthquakes are likely to occur. Soil scientists may obtain some idea of how certain rocks produce a particular soil.

Of the 28 maps to be printed, three are already completed. These are maps of the Wanganui, Fiordland and Christchurch areas. The project will be finished in 1964.