Quick Dips

Mapping Rocks

Retired former head of the Geological Survey, Dr Pat Suggate, and Canterbury PhD student Tod Waight have been working to complete a geological map of the Hokitika area -- the only place in New Zealand where the relationship between the glacial advances and interglacial deposits can be recognised.

The map shows the sequence of glacial ice advances formed over the past 500,000 years. It also helps in the assessment of the economic potential of petroleum and alluvial gold in the area. The work itself has involved years of "low tech observation" by Suggate and his assistants -- hours of chipping away with the geology hammer and many more poring over contour maps and photos.

"It's a classic map and will be of much interest to the entire earth science community, says Dr Simon Nathan, of the Institute of Geological and Nuclear Sciences. The map production has been supported by a $10,000 grant from the Lottery Grants Board.

In the Wairarapa, retired Victoria University geologist Paul Vella has been undertaking similar work on a map which can provide a rich source of information on earthquake activity. This subject is most important, says Dr Nathan, because the Wairarapa fault ruptured in 1855 and plotting this Huangarua Fault can help predict the likelihood of a major earthquake.

"The whole of the area is actually forming a basin. Lake Wairarapa is filling a hole which is subsiding and the Aorangi Range is actually going up. Paul Vella's research in this area has identified several problems. In slowly working through efforts to answer them he has helped create a method of geological thinking which is used in the oil industry today for petrol exploration."

Vella began his research in the 1960s when the Wairarapa Geological Society was formed by "mostly rockhounds and interested people". The information they were collecting was recognised as valuable and so a map was started; it is now supported by a Lottery Grant.

"A lecturer in Victoria's Geology Department, John Collen, joined us -- there was no money for the work, which is sad. We continued it as a labour of love. "

Vella describes the Wairarapa as of especial interest because it is one of the very active areas in New Zealand tectonically. He says the area contains some very young geological deposits deformed by tectonic movements "which enables us to work out the rate of this activity -- there are not many plates where this can be done successfully. This information enables scientists to predict the speed with which seismic activity can happen in the future.