Big storm unearths unusual rocks

Could Pourerere be the new Moeraki? If boulders stay visible they have tourism potential

Arecent storm has uncovered a series of boulders along beach which could rival the famous Moeraki attraction. The unusually spherical boulders were spotted by Pourerere resident Tracy Gay over the weekend. “They come and go,” she said. “I haven’t seen them for a few years.”

However, large swells during last week’s polar blast helped reveal the unusual looking rock formations.

“I saw them uncovered and thought, that’s cool.”

Gay estimated there were about a dozen or so boulders scattered along two locations at the beach.

“It changes out here all the time.” She said they reminded her of the Moeraki Boulders on Koekohe Beach, Otago.

Those were formed from calcite concretions about 65 million years ago and exposed by coastal erosion.

Geoscience Society president and Associate Professor of Geology at Otago University James Scott explained the rocks were the result of concretions in sedimentary rocks.

“They might look like giant cannonballs or something that has been rolling around on the sea floor, but they will be made of a type of mudstone. There will be something in that which forms an attraction point and it starts to accumulate and carbonate. It could have been a bone or a leaf.”

He estimated they were formed underwater between 25 million and 70 million years ago, before being lifted up to the surface by tectonic processes, then being uncovered as softer material around them eroded.

“We are talking about rocks that are millions of years old.”

Scott said previous concretions had even resulted in the discovery of several fossils, including a plesiosaur — a marine dinosaur — found near Shag Point, Otago, in 2002.

Though these types of formations were “pretty uncommon”, they can occur anywhere.

“Moeraki is a particularly striking example. It looks like there are more exposed at Pourerere than there are at Moeraki.”

If they were more regularly visible, he thought they could be a strong contender for a tourist attraction — high praise from a South Islander.

Associate Professor of Geology at the University of Otago, James Scott, explained the boulders were uncovered as softer material around them erodes.

Photos / Tracy Gay Significant swells which hit the east coast last week have helped uncover a series of spherical boulders along Pourerere Beach.

Pourerere resident Tracy Gay estimated there were about a dozen or so boulders scattered along two locations at the beach.

The boulders are estimated to be between 25-70 million years old.