PALEOECOLOGY OF A LATE EOCENE MOBILE ROCKGROUND BIOTA FROM NORTH OTAGO, NEW-ZEALAND

A distinctive mobile pebble and cobble rockground biota of Late Eocene age is described from volcaniclastic sediments between Oamaru and Kak anui, North Otago, New Zealand. Thousands of subangular to subrounded basaltic pebbles and cobbles are encrusted with a diverse range of ver y well-preserved epibionts including crustose coralline algae, serpuli ds, bivalves, foraminifera, brachiopods, and more than 70 species of c yclostome and cheilostome bryozoans. The preservation of thin sediment layers beneath and between encrusting bryozoan colonies indicates the probable occurrence, during life, of agglutinating microbial mats. Th e abundance of subspherical rhodoliths, the diversity of epibionts, an d their occurrence on all faces of the volcanic clasts reflect interme diate levels of overturning and rolling in a moderately current-swept channel adjacent to small volcanic islands and seamounts. The occurren ce of large foraminifera (Asterocyclina), bryozoans (including two ext ant species), and brachiopods with warm-water affinities indicates sub tropical sea temperatures and water depths of 25-50 m for this communi ty, which represents one of the few described Cenozoic examples of a m obile rockground biota.