On the way to the Opononi campsite we called in to see the Koutu boulders on the edge of Hokianger harbour. The boulders are perfectly spherical and very odd. Any budding geologist out there? How are they formed? Clues
We plodded through very sticky clay that stuck to our boots
They were sedimentary
They seemed to be in layers as some had a layer broken off showing fossils.
Nobody is sure how they have been formed. There are similar boulders on the south island east coast too.
My only idea is that they have formed by rolling in the clay like a large snow ball builds up when rolled in snow.