The findings could lead to more than 30 new species being identified from specimens up to 25million years old.
The Marsden-funded study, led by University of Otago and University of Gottingen researchers, was published in journal Gondwana Research this week.
It involved collecting and analysing amber deposits from more than 30 sites throughout New Zealand.
The small fossils are 15 to 25 million years old and include spiders, tiny carnivores such as pseudoscorpions, soil-dwelling mites, parasitoid wasps, ants, beetles and bark lice.
The hundreds of kilograms of amber were taken mostly from near Roxburgh, Hyde and Pomahaka.
The fossils were preserved in resin produced by a close relative of the kauri tree.
Associate Prof Daphne Lee said the paper was the culmination of seven years' work.
``This is an overview of what we've found so far, but each of the fossils needs more study.
``It's going to go on for a long time.''
Unlike much of the amber in the northern hemisphere, New Zealand's samples were not translucent, making the fossils more difficult to find, she said.
They had to be analysed at an amber lab under a high-powered microscope and special lights.
Researchers had not described any new species yet, but Prof Lee said there were likely to be about 30.
``This is really an important piece in the jigsaw of understanding Earth's history.''
The fossils showed a picture of ``busy forests'' with a diversity of life.
Prof Lee was leading the project with colleague Dr Uwe Kaulfuss and Prof Alexander Schmidt from the University of Gottingen, Germany.
The study involved 27 researchers from 16 institutions in eight countries.
