Local Focus: Valuable ventifacts protected

Ventifacts have been mistaken for everything from adzes to pieces of shattered asteroid. The rocks, stones, and sometimes boulders, get their interesting shapes from being sculpted and polished over thousands of years by exposure to wind-driven sand.

The study of the provenance and the shape of the rocks sheds light on the past but they are also worth something commercially.

In the '70s, the Geological Society of New Zealand became concerned that people were taking trailer loads of the ventifacts away and selling them, and wanted to put a stop to it to preserve them. It's now illegal to take ventifacts from the Nukumaru Domain, to protect them for future generations.

Professor Vince Neall, an expert on the geology of the Taranaki region, says studies of these sorts of materials will continually be enhanced with new methods of geochemical analysis of isotope ratios.

"I find it stunning that we can now figure out what people have been eating in the past by studying the isotope ratios in their bones as to whether they were eating fish or whether they were eating meat," Neall said.

Ventifacts can also be found among the dunes between Whanganui and Taranaki. Photo / Georgie Ormond

Although ventifacts are discovered in a lot of places where wind and certain rocks collide, the Waitotara ventifacts hold a little mystery.

"The real interest in these ventifacts is how they come to be here at Waitotara," Neall said.

"This particular rock type, as far as we know, is not known anywhere else in the North Island so the obvious question is ... how did they get to the North Island?"

The best explanation is they were pushed by the sea along a "marine bench" 120,000 years ago. The type of rock is the same as rock found south of Tākaka, at the top of the South Island. Their discovery in the North Island helps to explain a few things.

"Just as there are the land snails that occur in north-west Nelson and over here at Levin and in the Tararuas, and so there are these floral and faunal similarities, just as there are these geological similarities.

"During an ice age, sea levels would've fallen and you could've walked from north-west Nelson to Taranaki and this helps explain some commonalities in the flora between Mount Taranaki and north-west Nelson."

Neall is glad the ventifacts are protected, and says there is plenty more to learn from the study of these ventifacts.

While the ever-evolving science of studying rocks unlocks many mysteries of the past, there are other surprising applications.

If you want to see the ventifacts for yourself, some of the Whanganui Museum's collection is on display. The ventifacts can also be found amongst the dunes north of Waiinu Beach which lies between Whanganui and Taranaki.

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