Open AccessOrganic carbon preservation in S outheastern A rabian S ea sediments since mid‐ H olocene: I mplications to S outh A sian S ummer M onsoon variability
Author(s) -
Nagoji Siddhesh S.,
Tiwari Manish
Publication year - 2017
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2017gc006804
Subject(s) - terrigenous sediment , geology , total organic carbon , oceanography , organic matter , sediment , environmental chemistry , geomorphology , chemistry , organic chemistry
The earlier studies show a contrasting long‐term trend of the South Asian Summer Monsoon (SASM) after attaining the precessional forcing induced mid‐Holocene maximum. The increasing total organic carbon (TOC) concentration of marine sediments in the Southeastern Arabian Sea (SEAS) has been interpreted to imply strengthening SASM since mid‐Holocene by a few studies. However, TOC concentration is also influenced by redox conditions, sedimentation rate, and an influx of terrigenous matter depending on the regional settings. So, it needs to be ascertained whether the TOC concentration of the sediments in the SEAS is a signal of productivity related to the SASM strength or preservation. Therefore, we studied multiple proxies (TOC, total nitrogen, atomic C/N, δ 13 C org , CaCO 3 , and major and trace elements concentration) for determining the productivity, redox conditions, detrital supply, and provenance in a sediment core from the upper continental slope of the SEAS spanning the past ∼4700 years at centennial scale resolution. The present study shows that the observed increase in the TOC values since the mid‐Holocene is a result of better preservation caused by increased sedimentation rate and enhanced reducing conditions. We further show that the SASM has been declining since mid‐Holocene after attaining a precession‐forced maximum, which corroborates the earlier model ensemble studies.