Planktonic Foraminifera as Oceanographic Proxies: Comparison of Biogeographic Classifications Using Some Southwest Pacific Core-Top Faunas

G H Scott

doi:10.5402/2013/508184

Abstract

The distribution of planktonic foraminifera, as free-floating protists, is largely controlled by hydrography. Their death assemblages in surficial sediments provide proxy data on upper water mass properties for paleoceanography. Techniques for mapping faunal distributions for this purpose are compared in a study of 35 core-top samples that span the Subtropical Front in the Southwest Pacific. Faunas are analyzed by taxon composition, order of dominant taxa, and abundance. Taxon composition (presence-absence data) and dominant taxa (ordinal data) recognize groups of sites that approximate major water mass distributions (cool subtropical water, subantarctic water) and clearly define the location of the Subtropical Front. Quantitative data (relative abundances) more closely reflect the success of taxa in upper water mass niches. This information resolves groups of sites that reflect differences in intrawater mass hydrography. Comparisons suggest that abundance data should provide much better oceanographic resolution globally than the widely used ordinal biogeographic classification that identifies only Tropical, Subtropical Transitional, Subpolar and Polar provinces. As the data are strongly structured by variance in the abundance of Globigerina bulloides, Globorotalia inflata, Neogloboquadrina incompta, and Neogloboquadrina pachyderma, comparable classifications result from most clustering strategies. Principal coordinates analysis best represents the configuration of sites in two dimensions.

Highlights

The diversity of the Holocene planktonic foraminiferal fauna is modest, many taxa are distributed through the world ocean [1] and are exemplars for the interpretation of Cenozoic oceans [2]
The organization of sites according to their faunal content in a manner that is informative for paleoceanography is a more complex task that can be approached at several levels of analysis
Taxon presence-absence data form two high-level clusters (Figure 3(a)) that are partitioned about the Subtropical Front (STF)

Summary

Introduction

The diversity of the Holocene planktonic foraminiferal fauna is modest, many taxa are distributed through the world ocean [1] and are exemplars for the interpretation of Cenozoic oceans [2]. The organization of sites according to their faunal content in a manner that is informative for paleoceanography is a more complex task that can be approached at several levels of analysis. Seminal works in this field are those by Imbrie and Kipp [3] and Be [4]. They are widely applied and are focused on the distribution of dominant taxa, little attention has been given to their quite different methods and to their suitability for resolving faunal biogeographies [5]

Results

Discussion

Conclusion