Lower miocene corals from the Waitakere Ranges, North Auckland, New Zealand

Abstract

Thirty-one species belonging to 23 genera of coral are recorded from upper Otaian and Altonian (lower Miocene) rocks of the Waitakere Ranges. The coral fauna consists of 12 species of hermatypic (reef) types in nine genera and 19 species of ahermatypic forms in 14 genera. Most specimens occur in redeposited rudites that flowed into bathyal seas from unstable areas around a line of active volcanoes. Several rich ahermatypic coral associations are thought to have been derived from areas of pebbly substrate near the top of a steepening submarine slope (50–350 m). Two hermatypic coral associations are inferred to have come from scattered communities growing on shallow-water boulder banks (0–90 m) around volcanic islands. Comparison of the hermatypic fauna with that of present-day reefs indicates that seasonal sea'temperature were 5°–7°C warmer than now and that a fauna of over 20 hermatypic genera may have been present. The hermatypic genus Goniastrea is recorded from New Zealand for the first time and at least 11 species are first records from lower Miocene rocks of North Auckland.