Pollen distribution in marine surface sediments offshore Western Australia

Abstract

We have examined the pollen content in sediments from the top of 38 cores taken offshore Western Australia (WA). Water depth for these cores ranges between 81 and 4090 m. All samples are used to plot maps of total pollen and total Pteridophyta spore concentration. Only the 26 core tops that yielded sufficient pollen grains (>35) are used in the present study to plot percentage maps for individual pollen taxa, including that of the genus Pinus (recently introduced to Australia). Five major bioclimatic zones are recognised by the distribution of pollen assemblages offshore WA. These are related to the amount and seasonality of rainfall and vegetation distribution on land. They reflect: (1) the open Eucalyptus forests and woodlands of northern WA with high and summer rainfall; (2) the open Eucalyptus woodlands with Acacia and grasslands of northwestern WA with lower (400–600 mm) and summer rainfall; (3) the open Acacia shrublands with grasses and grasslands of northwestern WA with low (300–400 mm) and summer rainfall; (4) the open Acacia shrublands of central WA with low (<300 mm) and summer as well as winter rainfall; and (5) the open Eucalyptus forests and mixed shrublands of southwestern WA with lower (300–600 mm) and winter rainfall. The influence of Indonesian-derived waters via surficial currents such as the Leeuwin Current is recognised by the presence of Pteridophyta spores in the sediments at northern sites.