Distribution of planktonic foraminifera in surface sediments of the South-West Pacific Ocean

Abstract

Abstract Twenty-six planktonic species have been recognised in a preliminary survey of surface sediment samples, mainly foraminiferal oozes, from the New Zealand sector (latitudes 18°–54°S) of the south-west Pacific Ocean. The following general trends in the distribution of the Foraminifera were noted: (a) the number of species decreased from a maximum of 23 at the northernmost stations to (j species at the southern limit of the area, and (b) many of the species showed a latitudinal distribution, primarily related to the hydrological conditions (mainly temperature) of the surface waters. The species with restricted latitudinal distribution are those with a limited temperature range: those with a cosmopolitan distribution have a wider temperature tolerance. Species in the former group are mainly warm-water forms restricted to the lower latitudes. Some of the more cosmopolitan species also tend to show latitudinal variation, with the greatest abundance in the faunas of the middle and higher latitudes. On the basis of occurrence and frequency distribution of the planktonic Foraminifera, the area was subdivided into five zones, each characterised by a distinct fauna. From north to south the faunal zones have been named: (1) Subequatorial, (2) Northern, (3) North-central, (4) Central, and (5) South-central. Their southern boundaries are at latitudes 26° S, 32° S, 37° S, 44° S, and south of 54° S.