Fairfield Sand Quarry

The Fairfield Connection

Life just before a mass extinction

Late Cretaceous Period 70 million years ago

At the Fairfield sandquarry deposits of greensand preserve marine life existing before the mass extinction at the end of the Cretaceous period 65 million years ago. The fossils allow comparison of life before and after the event.

The rocks, chiefly muddy sandstone, were deposited in sheltered conditons. Concretions within the formation have produced a diverse range of marine fossils and plants from nearby land.

Among the invertebrate fauna, the most significant fossil in the ammonite Kossmaticeras bensoni. This was one of the last ammonite species on earth. Ammonites are cephalopods related to squid and octopus but equipped with external shells. They were abundant in the Late Cretaceous but died out along with many other groups. Kossmaticeras has been found in clusters of up to five indiduals. Incomplete specimens of another ammonite Maorites, have alos been found at Fairfield. Unlike ammonites, the nautiloids survived the mass extinction. The nautiloids Eutrephoceras, a rarer smooth-shelled cephalopod, has been found at Fairfield. Some specimens from Fairfield re over 250mm in diameter. The nautiloid group disappeared from New Zealand seas about five million years ago.

Other ancient marine groups represented in the Fairfield greensand include the bivalves and limpet-like gastropods.

Among the Fairfield foraminifera – minute animals of the sea Bathysiphon. Each individual occuoies a narrow white tube, about one millimetre in diameter, constructed of tiny quartz grains.

The plant fossils include leaves, kauri-like scales and bored wood.