On a recent trip up to Karamea on the west coast of the South Island, I went to visit the Oparara Caves. These are a few kilometers inland, and not far from the end of the Heaphy Track. They are an amazing example of limestone erosion…
Huge archways have been cut through the limestone by the Oparara River. The limestone was laid down in the ocean during the Oligocene Epoch, about 34 million years ago.
The third photo shows the largest of the arches (the Oparara Arch). You can see the clear boundary between the limestone and the underlying Karamea Granite. This is about 350 million years old, much older than the limestone. The arch is an impressive 200 metres long and 50 metres across.
There are several accessible caves in the area. The unique geology and ecology is a ‘must see’ if you ever make the trip to Karamea.