The spectacular Cliefden Caves in central west NSW have been granted state heritage listing, almost certainly sparing them from a dam proposed for the region.

The caves, located on private land about 60 kilometres south-west of Bathurst, are known for their Ordovician-era fossils dating back about 460 million years, said Graham Quint, director of advocacy for the NSW division of the National Trust of Australia. The listing covers about 1550 hectares.

The Cliefden Caves, east of Canowindra, have been granted special heritage status. Credit:Alan Pryke/ Diimex

Wednesday's formal gazetting of the karst cave network on the state's register means it has "the highest level of protection you can have in NSW – it can't be destroyed", Mr Quint said.

"The caves contain fossils which are recognised not only in NSW but internationally," Gabrielle Upton, the environment minister, said. "It's great to be able to acknowledge the caves' significance with NSW heritage status."