After a conversation with James,, and armed with information from one of the chapters in the book, I recently visited a fossil locality near Murchison in the South Island. About 6.5 kms north of Longford on the main State Highway 6, there is a sign indicating Nuggety Creek Road.
A few hundred metres along the track there are some crumbling cliffs by the roadside. This is a fantastic place to collect fossil leaves from the Miocene (about 16 - 13 million years old). They were deposited in a river valley that was surrounded by a rainforest.
Boulders at the foot of the cliff are absolutely packed with leaves of different plants. There were large trees here as well as smaller plants such as ferns living beneath them. The rock is quite crumbly, so it can take a while to find a lump that is solid enough to stay in one piece.
As you can see from the last photo, some of the fossil leaves are superficially very similar in appearence to modern leaves found at the same locality today.