Magnetic Surveys of the Coasts of New Zealand

Abstract

A brief account is given of some early magnetic observations made on and around the coasts of New Zealand from Captain Cook's first visit (1769–1770) to 1873. The results of aerodeclinometer surveys made in 1955 over Foveaux and Cook Straits. at a height of 500 ft are shown by magnetic declination anomaly charts. From December 1959 to November 1961 the coasts of New Zealand were surveyed by means of a proton magnetometer measuring magnetic total force, towed behind various ships. The results cover traverses totalling more than 4,500 nautical miles and are displayed by magnetic profiles that can be related to position on the appropriate ship's track. Significant magnetic anomalies are revealed in Foveaux Strait, off the west coast north of Taranaki, off the coast of Fiordland between Breaksea Sound and Doubtful Inlet, and across the South Taranaki Bight from Nelson to Waitotara. Other lesser magnetic anomalies occur off Banks Peninsula and in the Bay of Plenty. A magnetic survey of the sea approaches to Tauranga airport is also included.