Summary of Abstract Submission

Abstract Submission No. IO50-08-0024PresentationPoster

CHANGES IN THE DEPOSITIONAL ENVIRONMENT OF A SEDIMENT CORE FROM THE CENTRAL INDIAN BASIN (CIB), INDIAN OCEAN, FROM QUATERNARY TO PRE-QUATERNARY

Simontini Sensarma*1, Shyam Murti Gupta1, Ranadip Banerjee1, Subir Mukhopadhyay2

1 National Institute of Oceanography, India
2 Jadavpur University, India

ABSTRACT :

In this study an attempt has been taken to establish the biostratigraphy of a sediment core from Central Indian Basin (CIB), Indian Ocean, and its relation to the geochemical variation down the core. The core was located at a water depth much below the CCD (4935m), hence was devoid of calcareous fossils. Radiolarian index species were used to ascertain the Quaternary datum levels and an age upto 1.5Ma could be determined at about 100cm depth. The upper 0-50 cm section of the core exhibited higher sedimentation rate whereas lower 50-100cm exhibited lower sedimentation rate. Below 100cm depth radiolaria were sparse and had no identifiable index fossils, whereas sections from 200-500cm were completely devoid of radiolaria. From top of the core upto 185cm depth, the sediment colour was pale brown and light in nature, after which the colour changed to reddish brown and denser in nature, indicating a change in the litho-facies from radiolarian ooze to red clay zone. Geochemical data of 40 trace elements in 107 subsections of the core (at 5cm interval) were generated using an ICPMS. The elemental concentrations decreased gradually from the older to the younger sediments except Ba and Sr, indicating increasing bioproductivity in the area during the late Quaternary. Shale normalized REE pattern revealed middle REE enrichment in all the sections with a prominent negative Ce anomaly which became less pronounced in the younger sediments.