The council has now granted consent for earthworks associated with scientific research at Foulden Maar, a decision celebrated yesterday by Dunedin’s scientific community.
The decision, provided by the council, said a group of 20 scientists, students and support staff would be permitted to access the site near Middlemarch once a month and excavate 0.5cum a month for up to five years.
The excavation would be done with hand tools and would not alter the floor of the pit on site.
"The Foulden Maar is large, but the works will be focused on a small previously excavated rimmed pit within the deposit.
"The works will involve the removal of thin layers of weathered material from outer faces of the pit’s rock walls to expose fresh surfaces of diatomite for research purposes."
University of Otago honorary professor of geology Dr Virginia Toy said returning to the site was an important step for scientists, but it was not one that was likely to leave much of a footprint.
Visitors to the site would not see that the natural environment had been disturbed by the proposed work, but researchers would have a window into the pre-historic past of New Zealand.
"Foulden Maar is a very significant site for understanding the paleoclimate record of New Zealand and the southern hemisphere, which is something that’s understudied so far.
"Foulden Maar has a lot of information about that and also about the biodiversity change over that time.
"It’s a really, really significant site. And it’s of interest not only to people in New Zealand, of course, but globally."
Prof Toy, who is also a professor at the University of Mainz, in Germany, said a volcanic eruption millions of years ago created a lake in the area "and it’s the stuff that fell into the lake, basically, that is of interest".
From its diverse record of plants and insect life to signs of changes in climate, there were a lot of answers the research could provide, she said.
University of Otago ancient DNA Associate Prof Nic Rawlence said getting resource consent meant paleontologists would be able to return to one of New Zealand’s "premier, most important" fossil sites from 23 million years ago "after years of limbo".
Mining company Plaman Resources had shut out researchers.
Then, after the company went into receivership in 2019, it took until last year when the council bought it before its future was secured.
Even then, it was not immediately clear when research would restart.
"Having the resource consent to be able to do excavations is fantastic.
"It's a window into the Miocene of New Zealand where there's very few other sites of that age and importance around," Assoc Prof Rawlence said.
"It’s plants and animals — there's the oldest examples of eels and galaxiids, what we fictionally call our whitebait.
"There are multitudes of insect fossils from there. And we've got lots and lots of different plant fossils have been discovered at Foulden Maar as well."
The fossils found there also provided an "exquisite climate record", he said.
It was not just local scientists who would be celebrating the return of researchers to the area but nationally and internationally it would be viewed as a victory for science, he said.
The council decision said the site had a consent for a small-scale mining activity, but it was unlikely to be used given the council ownership of the site and its stated aims.
"Following public opposition to a proposal to mine the diatomite on the site on a large scale, the site was purchased by the Dunedin City Council in 2023 to prevent mining of the site and preserve the site for environmental and scientific research," it said.
