Distribution of recent benthic foraminifera along continental slope of the Sunda Shelf (South China Sea)

Abstract

The distribution of ‘live’ (Rose Bengal stained) and dead benthic foraminiferal distribution (> 150 µm) was investigated in sediment surface samples (0–1 cm) from the winter upwelling region off Borneo on the continental slope of the Sunda Shelf and from the continental slope of southern Vietnam Shelf. The benthic foraminiferal faunas of both areas are highly diverse ( H( S) 2.91–4.25 for living and 4.01–4.38 for dead). A canonical correspondence analysis proved that bathyal assemblages are most strongly influenced by the decreasing rates of organic carbon flux with increasing water depth, resulting in a pronounced depth-related succession of assemblages. Correlation between estimated C org-flux and factor 1 loadings of the CCA for modern, dead foraminiferal assemblages is very good ( r 2 = 0.96). Thus, a local transfer function ( y = 5.0289 x + 6.8142) for estimating paleo-C org-flux rates from the down-core samples has been successfully developed for the continental slope of the Sunda Shelf. Four benthic foraminiferal biofacies were recognised within the studied depth ranges: Upper Bathyal Biofacies ( Siphotextularia foliosa – Cibicidoides robertsonianus) well supplied and well oxygenated, Middle Bathyal Biofacies ( Uvigerina auberiana – Nuttallides rugosus) located within the oxygen minimum zone, uppermost Lower Bathyal Biofacies ( Lagenammina difflugiformis – Uvigerina peregrina) and Lower Bathyal Biofacies ( Paratrochammina challengeri – Parrelloides bradyi) from the relatively well oxygenated, but food limited environment.