Molluscan generic diversity of New Zealand Neogene stages: extinction and biostratigraphic events

Abstract

The Molluscan generic diversity histogram of New Zealand Neogene stages almost parallels the trend of published New Zealand paleotemperature curves. The major exception is very high diversity during the relatively cool Pliocene and Pleistocene stages, attributed to the good preservation at this time of near-shore, mollusc-rich facies. Diversity was lowest during Kapitean (Late Miocene) time, and probably particularly during late Kapitean (Messinian) time; 22.9% of molluscan genera became extinct at the end of the preceding Tongaporutuan Stage. Three major events can be recognised in the Neogene molluscan fauna: (1) a thermal maximum during late Early and early Middle Miocene (coeval around much of the Pacific); (2) the terminal Miocene event, when the most marked Neogene extinction occurred; and (3) the arrival of a cold-water subantarctic fauna in central North Island 2.4 m.y. ago, coeval with the onset of major Northern Hemisphere glaciation.