Vandals have smashed dozens of headstones and memorials at a South Australian regional cemetery in what the local mayor has described as "desecration on a massive scale" and an "act of barbarity".

Locals in the small town of Auburn in the Clare Valley discovered 46 monuments at grave sites in the Moores Road cemetery had been knocked over and damaged.

The vandalism was reported on Saturday morning to police, who have labelled it "malicious and senseless" and believe it occurred in the past three days.

The damage bill has been estimated to be between $200,000 and $300,000.

"The extent of the damage is incomprehensible," Clare and Gilbert Valleys Mayor Allan Aughey said.

"I've got nothing else to compare it with. It's extensive and it's affected contemporary headstones, historic headstones.

"Monumental masonry on an epic scale has been damaged."

Mr Aughey said many in the community would not yet be aware of the violation.

"I'm standing here in front of a desecrated headstone and a beautiful angel on the top of it that's just been smashed completely," he said.

"[Cemeteries] are sacred places and they should be given the utmost respect and entirely the opposite has happened here. What has happened out here is an act of barbarity."

Mr Aughey said the council would notify families and "do what we can to assist those families and to assist in the rectification".

Clare police have asked anyone with information to contact Crime Stoppers on 1800 333 000.