I have posted pictures of the strange 'beach' at Castlepoint a few time on the other blog with the following pictures. Apparently, there are similar coastlines near Wellington, too.
I searched many times trying to find out what it was made of but no success until now! It's called 'Miocene sandstone' on one page.
Here are some links if you are interested in how they are formed.
https://outtherelearning.co.nz/2012/04/whakataki/
