Abstract
Multi-proxy approach for the reconstruction of paleo-redox conditions is attempted in a radiocarbon (14C) dated sediment core near the equatorial Indian Ocean. Based on behavior and distribution of redox sensitive and productivity proxies, the study demonstrates prevalence of anoxic bottom water conditions during LGM due to poorly ventilated bottom waters augmented by high surface productivity resulting in better preservation of organic carbon (OC). During early Holocene, the equatorial Indian Ocean witnessed high sedimentation rates resulting in high organic carbon (OC) with depleted redox sensitive element thereby causing better preservation of OC. The study underscores poor bottom water ventilation during LGM and preservation of OC as a result of high sedimentation rate in early Holocene.
Highlights
The depositional conditions in the marine environment can be oxic, suboxic and anoxic based on the presence or absence of oxygen at the sediment-water interface
The reconstructed age-depth model for the sediment core based on the calibrated radiocarbon dates of foraminifers at various depths provides paleoclimatic records for the last 25 ka years BP (Figure 2)
An average sedimentation rate of ∼8 cm.ka−1 was observed for the studied sediment core (Figure 2)
Summary
The depositional conditions in the marine environment can be oxic, suboxic and anoxic based on the presence or absence of oxygen at the sediment-water interface. Redox sensitive elements are often portrayed as classic tool to reconstruct the past depositional conditions in the bottom water (Brumsack, 1980, 2006; Calvert and Pedersen, 1993; Dean et al, 1999; Algeo and Tribovillard, 2009). The redox elements such as Mo, V, Cr, Mn have different solubilities in marine water depending on the redox conditions and has been commonly used to trace anoxic conditions near the sediment-water interface (Agnihotri et al, 2003; Rimmer, 2004; Algeo and Lyons, 2006; Tribovillard et al, 2006; Banerji et al, 2016).
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