• Change of lithofacies in marine sediment core from Quaternary to Pre-Quaternary: A case study from the Central Indian Ocean Basin

• Fulltext

https://www.ias.ac.in/article/fulltext/jess/129/0054

• Keywords

Indian Ocean; sediment core; biostratigraphy; clay minerals; geochemistry

• Abstract

A distinct change in lithofacies was observed from red clay to siliceous ooze in a core from Indian Ocean. Radiolarian index species were used to ascertain the Quaternary datum levels and an age of 2.0 Ma is determined up to 125 cm depth from surface. Below 185 cm depth, the sediment core lacked radiolariantest completely. At about 50 cm from core top, the sedimentation rate decreased drastically from 0.18 to 0.05 cm/kyr with a corresponding age of 500 kyr, marking Marine Isotope Stage 13. The changes in lithofacies and sedimentation rate are further accompanied by the change in clay mineralogy from smectite rich older sediments to smectite depleted younger sediments and presence of higher amount of volcanogenic materials in the older sediments. Higher values of chemical index of alteration (CIA) and lower $\rm{K_{2}O/Al_{2}O_{3}}$ in older sediments indicate dominance of chemical weathering in the older sediments which decreased gradually towards core top. Ti normalized concentrations of elements like $\rm{Co}$, $\rm{V}$, $\rm{Cu}$, $\rm{Ni}$, $\rm{Ce}$, $\rm{Y}$ and $\Sigma\rm{REEs}$ exhibit lowest values at the transition zone above which the ratios increased steadily towards the core top. All these observations indicate a marked change in the climatic regime from late Quaternary onwards, prior to which the environment was less bio-productive.

• Author Affiliations

1. Geological Oceanography Division, CSIR–National Institute of Oceanography, Dona Paula, Goa 403 004, India.
2. Department of Geological Sciences, Jadavpur University, Kolkata, West Bengal 700 032, India.

• Journal of Earth System Science

Volume 129, 2020
All articles
Continuous Article Publishing mode

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019