Occurrence of the Biogenic Bloom in the Oligotrophic Southeastern Indian Ocean: Evidence from Late Neogene Deep-Sea Benthic Foraminifera (ODP Hole 752A)

We produced a 12.9 Ma census data of deep-sea benthic foraminifera from subtropical Ocean Drilling Program (ODP) Hole 752A, Broken Ridge, southeastern Indian Ocean to understand paleoceanographic and paleoclimatic changes and their relation to Southern Ocean climate variability as well as latitudinal shifts in the Subtropical Convergence Zone (SCZ). We employed knowledge of the ecology of Recent deep-sea benthic foraminifera from different ocean basins for environmental interpretations at Hole 752A. Benthic faunal data suggest a major transition in deep-sea environments of the southeastern Indian Ocean across 5.5-4.5 Ma roughly coinciding with the end of the Indo-Pacific "biogenic bloom". The benthic biofacies suggest well-oxygenated and nutrient poor deep waters from 12.9 to 10 Ma with variable flux of organic matter. The interval 10-5.5 Mais marked by high and sustainedflux of organic matter at the time when productivity increased many fold throughout the Indian and Pacific Oceans during which time the biogenic bloom peaked and the Indian summer monsoon intensified. Antarctic ice volume significantly increased and southern component deep-water formation enhanced during this time. This southern cooling in the late middle to late Miocene probably pushed the SCZ towards north above Hole 752A. Since 4.5 Ma, the organic flux was low to intermediate and pulsed.