Effect of Watermass Properties on the Distribution of Recent Deep-sea Benthic Foraminifera Across the Indian Ocean

De, Soma¹, Anil Kumar Gupta¹ (1) IIT Kharagpur, Kharagpur, India

In the Arabian Sea the distribution of benthic foraminifera is strongly related to the geochemistry of the sediments and thus to the depositional environments (Hermelin and Shimmield, 1990; Das and Gupta, 2006). The Holocene samples from Ocean Drilling Program (ODP) sites chosen in the present study are distributed all over the Indian Ocean (Leg 115, 116, 117 and 121). The data from GEOSECS Stations have been correlated with the Holocene Site locations.

The latest Holocene record from ODP Holes of the Indian Ocean was studied to understand the effect of different watermass properties on benthic foraminifera. The depth wise distribution of benthic foraminifera was correlated with the available GEOSECS (1983) data to understand the preference of abundant species (>10% abundance in at least one sample) to temperature, oxygen, phosphate and nitrate. Bolivinita quadrilatera, Epistominella exigua, Nuttallides umbonifera and Pyrgo murrhina prefer low temperature, high oxygen and low nutrient levels. Bulimina alazanensis and Uvigerina porrecta prefer low temperature and intermediate oxygen levels. Robulus nicobarensis, Textularia saggitula and Uvigerina peregrina are OMZ species favoring conditions of higher temperature and lower oxygen levels. Bulimina aculeata is suited to higher nutrient and intermediate temperature and oxygen conditions. Gyroidinoides cibaoensis and Uvigerina proboscidea are found in wider range of temperature and oxygen conditions. Globocassidulina subglobosa and Oridorsalis umbonatus are found in lower temperature and higher oxygen conditions. Cassidulina laevigata prefers high temperature, intermediate oxygen and nutrient conditions while Ehrenbergina carinata are suited to higher temperature, lower oxygen and higher nutrient levels.