Modern limestone formation

Transcript

Professor Cam Nelson

In New Zealand, we can say the heyday of limestone formation was in the Oligocene. That doesn’t mean to say that we don’t have some limestone in the making around New Zealand at the modern day. We certainly don’t have it off the eastern and western sides of New Zealand in general, because there’s too much sand and mud being poured into the seas, the shallow seas, from the rugged countries, the mountains that we have forming a backbone of North Island and South Island.

But away to the north around Three Kings, and away to the south around Stewart Island and Snares Island, the shallow seafloor is covered in smashed up shelly material whose composition is exactly the same as we find in Oligocene limestones. The only difference is they’re loose and modern, forming today and are slowly accumulating, whereas Oligocene limestones have undergone diagenesis – they’ve been converted from loose sediments into hard rock as a consequence of burial. 

Acknowledgements: McDonald’s Lime Limited Dr Roger Grace