Mining company Plaman Resources, which owns the internationally significant fossil site and diatomite mine near Middlemarch, was placed into voluntary receivership and liquidation on Tuesday.
Plaman's application to the Overseas Investment Office to buy a 430ha neighbouring farm is now on hold.
A petition by the group Save Foulden Maar has so far attracted more than 10,000 signatures.
Save Foulden Maar spokeswoman Kimberley Collins said it was clear from the petition there was both national and international support to have the site protected.
Ideally the group wanted either central or local government to purchase the land but crowd funding could also be an option, Ms Collins said.
While it was still unclear what the receiver intended to do with the ownership of the maar, if there was a possibility it could be sold into public ownership the group would do everything it could to make sure that happened, Ms Collins said.
That could include a public fundraising campaign, similar to the one which raised $2.3 million to buy Awaroa Beach in the Abel Tasman park in 2016, she said.
"We have set up a donation page already and it would be amazing to launch a crowdfunding campaign, but we are still assessing what the best way forward is.''
The group's main focus was a public meeting being held at the Otago Museum next Tuesday where the future of the maar would be discussed.
"We've really shifted our focus to figuring out how we can get this land and the land that surrounds it into public ownership so it can be protected in perpetuity.''
For the benefit of scientific research, the group would continue to pressure both the local and national governments to place protections on the maar and remove any mining permits, she said.
