The Foraminifera of the Pitcairn Islands

Foraminifera were recovered from 18 samples collected in the Pitcairn Islands, 12 from Henderson Island (including the best and most comprehensive collections) and three each from Oeno Atoll and Pitcairn Island itself. Although both algae and sediment samples were collected, the living Foraminifera came, almost exclusively, from phytal (attached or clinging) habitats. Foraminifera in the sediment samples are mainly thanatocoenoses. The fauna is an exclusively calcareous, relatively low diversity assemblage, dominated by large soritids Marginopora, Amphisorus, Sorites) and Amphistegina , all of which are ubiquitous throughout the tropical Pacific. These larger Foraminifera are usually accompanied by small miliolids in particular, as well as by small attached Foraminifera (discorbids and the like). Typical reefal Foraminifera are generally under-represented. So far, no endemic species have been found. Of more significance, perhaps, is the apparent absence of Calcarina , small rotaliids, elphidiids and agglutinating species, so common in the western Pacific islands. One sample of fossil Foraminifera was analysed, from a shelly sand (c. 30 m above present sea-level) on Henderson Island. Though, for the most part, like the Recent assemblages, this was characterized by Archaias , a soritid which was not found in any of the modern collections made by the 1991– 92 Expedition. This could either be a sampling artifact or refer to a real environmental change since the Pleistocene.