Scientists to study N.Z. marine ridge

Press, Volume CXI, Issue 32801, 29 December 1971, Page 15

Scientists to study N.Z. marine ridge

A 1 arge submarine ridge extending northwest from New Zealand, called the Lord Howe rise, is to be drilled and cored in an effort to discover if it was once dry land that subsequently sank thousands of feet below sea level millions of years ago.

In addition to drilling on this ridge, the Deep Sea Drilling Project drilling

vessel, the Glomar Challenger, will drill several other sites in the Melanesian region of the South Pacific after having sailed from Suva on November 16 for a two-month cruise to ‘Darwin, where it is due on January 11. This expedition, Leg 21 of the project, will attempt to provide information about the nature of the complex forces involved when two major plates of the ocean crust meet, as the vast Melanesian area lies at the junction at which the Pacific

crust moving to the west meets the Indian-Australian crust moving to the north. Two New Zealand members of the Leg 21 scientific staff are Dr G. van der Lingen, of the Geological Survey, Christchurch, who is a seismologist, and Mr A. R. Edwards, of the Geological Survey, Lower Hutt, a paleontologist. Specific answers will be sought to the following questions: (1) What is the oldest crust in the South Pacific? Drilling sites located immediately east of the Tonga-Kermadec Trench, which is an elongated area of very deep water separating the western limits of the true Pacific Ocean floor from the Melanesian region, should answer this question as well as examining any north-south variation in age which may exist along the edge of the trench. (2) What is the nature and history of the marginal basins of the Melanesian region? From drilling sites in the South Sea Basin, Lau Basin, New Caledonia Basin, the Tasman Basin, and the Coral Sea, the scientists will try to determine the ages of these basins, and also whether they represent small regions of sea-floor spreading. By studying these different basins, " the scientists hope not only to understand the mechanism of their formation, but also to integrate these data in an attempt to solve the larger problem of unravelling the relative movements between the Pacific and Indian crustal plates. Geophysical evidence gathered by other scientists in recent years indicates that the whole Melanesian region may have undergone considerable uplift in the last 10 million years, and that the configuration of the eastern part of this region could have developed within that time.

(3) What is the nature of the Lord Howe Rise, and how does it fit into the structural history of the Tasman Sea lying between Australia and New Zealand? This is the most interesting problem to be attacked,) because of the anomalous structure of the rise. The rise was named after an island which itself was named after its discoverer. Lord Howe. This feature is flat on top, is some 60 miles wide and more than 100 miles long, and lies about half a mile below sea level.

Scientists suggest that the rise is a foundered continental segment which at one time may have been mountainous, the valleys having since been filled with .sediments. Here the scientists may find rocks of Paleozoic age—which would be the oldest rocks found beneath the ocean to date.