Sedimentary record of radiolarian biogeography, offshore eastern New Zealand

Abstract

Examination of 38 surface sediment samples from offshore eastern New Zealand, between 33°S and 54°S, yielded 100 radiolarian taxa, which are common to abundant in sediments deposited at > 1000 m water depth but rare at shallower depths. In general, radiolarians are most abundant, most diverse, and best preserved in assemblages north of the Subtropical Front (STF). Multivariate analysis of census data for 29 radiolarian‐rich samples identifies six sample groups and eight species groups. The STF forms a major biogeographic barrier, separating three transitional zone (TR) and three subantarctic zone (SA) sample groups. The three primary sample groups (TR1, TR2, SA1) record a southward latitudinal trend of decreasing abundance of subtropical‐tropical or warm‐water taxa (species group 4) and increasing abundance of subantarctic ‐Antarctic or cool‐water taxa (species groups 7 and 8). Two secondary sample groups (TR3 and SA2) may record the influence of shallow‐water processes or strong surface currents on either side of the STF. A distinctive sample group (SA3), characterised by low abundance and diversity, records relatively shallow, stratified, and silica‐limited conditions of the central Campbell Plateau.

Key words:

• radiolarian
• Protista
• Subtropical Front
• transitional zone
• subantarctic zone
• multivariate analysis