Holocene Deep-Sea Benthic Foraminifera and Watermasses in the Indian Ocean and the Red Sea

The distribution of Holocene deep-sea benthic foraminifera in 19 core top samples from the Indian Ocean and the Red Sea is examined to understand the faunal-watermass associations. Relative percentages of significant taxa have enabled to identify distinct assemblages associated wth different watermasses in the Indian Ocean and the Red Sea. The first assemblage in the Indian Ocean is marked by the dominance of Nuttallides umbonifera. This assemblage is found below 4000 m where bottom water is highly carbonate-undersaturated and is influenced by Antarctic Bottom Water (AABW). The second assemblage is characterized by Uvigerina hispido-costata dominance with Cibiddes wuellerstorfi as a subsidiary species. This assemblage is associated with the lower tongue of North Indian Deep Water (NIDW) between 2500 and 4000 m water depths. U. hispido-costata has higher abundances at sites lying below upwelling zone off the Arabian coast in relatively high dissolved oxygen deep water. The third assemblage is dominated by Uvigerina proboscidea between 1500 and 2500 m depth. Globocassidulina pacifica/subglobosa, Pullenia bulloides and C. wuellerstorfi are secondary constituents. This assemblage characterizes high productivity regions (equatorial belt) with relatively low oxygen levels in deep water. The Red Sea Deep Water (RSDW) assemblage is dominated by Bolivina subreticulata and characterizes highly saline, warm, oxygen-poor deep water. Other species of this assemblage are Textularia agglutinans, Astrononion umbilicatulum, Miliolinella subrotunda and Ophthalmidium acutimargo.