Response of trace metal redox proxies in continental shelf environment: The Eastern Arabian Sea scenario

Acharya, Shiba Shankar; Panigrahi, M. K.; Gupta, Anil K.; Tripathy, Snehasis

doi:10.1016/j.csr.2015.07.008

Cited by 33 publications

(6 citation statements)

References 73 publications

(123 reference statements)

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“…So, in order to identify the origin (detrital, biogenic, or authigenic) of the studied elements in our core, correlation of aluminum and calcium carbonate with selected elements was determined using linear regression (least square method) for 36 samples using the statistical package—SigmaPlot 12.0. A high regression coefficient (r 2 ) value of these metals with Al indicates the detrital source (supporting information Figure 1) and with that of CaCO 3 indicates the biogenic source (supporting information Figure 2) [e.g., Acharya et al ., ]. The regression coefficient values (Table ) indicate that elements such as Ti, Fe Mn, Cr, and Co have a siliciclastic origin and their fluctuations in sediments can be explained in terms of the variation in the detrital influx.…”

Section: Resultsmentioning

confidence: 99%

Organic carbon preservation in Southeastern Arabian Sea sediments since mid‐Holocene: Implications to South Asian Summer Monsoon variability

Nagoji

Tiwari

2017

Geochem Geophys Geosyst

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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, δ13Corg, CaCO3, 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.

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Section: Resultsmentioning

confidence: 99%

Organic carbon preservation in Southeastern Arabian Sea sediments since mid‐Holocene: Implications to South Asian Summer Monsoon variability

Nagoji

Tiwari

2017

Geochem Geophys Geosyst

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“…Like PRT, LPD also serves as a best descriptor of the productivity of the system. Total lipids in the sediments (Fig.3c) varied from The proliferation of minerals may also in uence the degradation of lipids into other compounds(Cheriyan 2017). Better preservation of lipid constituents is also facilitated by frequent sedimentation, consequent sealing of OM in the deposited sediments and anoxic condition (Shibini et al 2019).Observed trends of biochemical composition in the study area were compared with previous studies data (Table3).…”

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confidence: 78%

Composition of sedimentary organic matter in Thrissur Kole wetland, southwest India

Vidya

Rajathy²,

Kumar³

2023

Environ Earth Sci

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Spatio-temporal distribution dynamics of various biochemical components in Thrissur Kole wetland were analysed to assess the quality of organic matter (OM) and trophic status. Thrissur Kole wetland forms the part of the Vembanad wetland system, located in the southwest coast of India. Surface sediment samples were collected from sixteen sites during non-monsoon (February 2019) and monsoon (August 2019) seasons. Concentration of biochemical parameters displayed a trend as follows: total carbohydrates > total protein > tannin & lignin > total lipids. Observed chlorophyll pigment concentration in sediments was as follows: Chl a > Chl b > Chl c (in both seasons). Intermediate values of C/N ratios indicated a mixed origin of OM. Majority of stations exhibited lower values of protein to carbohydrate ratios which revealed the occurrence of aged sedimentary OM. Lower values of lipid to carbohydrate ratio indicated lower nutritional value of the organic content. The lower content of labile OM, low biopolymeric carbon to total organic carbon ratio and low algal contribution to the biopolymeric carbon suggested that a bulk fraction of OM exist as refractory. Trophic state of the wetland system was evaluated as hypertrophic, based on protein and carbohydrate content, biopolymeric carbon and algal contribution to biopolymeric carbon.

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“…OM deposited in this period comprises freshwater organic matter, algae, and C3 vascular plant detritus (see Figure 3B), representing a typical terrestrial fluvial/lacustrine environment. Terrestrial components dominate in the region, which is indicated by the elevated C/N ratios (Hu et al, 2007;Acharya et al, 2015;Chen et al, 2015). The strong oxidation conditions also generate particularly low TS content in the freshwater environment.…”

Section: The Evolution Of Sulfur: Its Use As a Paleosalinity Archivementioning

confidence: 99%

Geochemical behavior of C, N, and S in sediments of Hangzhou Bay, Southeastern China: implications for the study of paleoclimate and sea-level changes

Gao,

Piotrowski,

et al. 2024

Front. Mar. Sci.

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The correlation between the amount of organic carbon (OC) and sulfur (S) in sediments has been widely used as a paleosalinity indicator to distinguish between marine and freshwater environments. However, whether the ratio of total OC to total S (TOC/TS) can be used to identify unsteady or dynamic marine environments across sedimentary strata is still contended. An HZW1907 sediment core of 80 m in length was successfully collected in the middle of Hangzhou Bay (HZB), serving as one of the few boreholes that are crucial for the study of geologic and geo-environment changes in the coastal regions of eastern China since the Last Glacial Maximum (LGM). Total OC (TOC), stable carbon isotope, and TS of 82 subsamples from the HZW1907 core were analyzed to reconstruct the history of the shallow water biological pump and sulfur preservation record in the bay since the Late Pleistocene. Our results indicate that the samples had low concentrations of TOC (0.21%) and total nitrogen (TN) (0.02%), high mass ratio of TOC/TN (10.8), low δ13C (−24.9‰), low TS content (0.06%), and a high ratio of TOC/TS (9.1) from 33.6 ka BP to 12.3 ka BP, implying that freshwater organic matter (OM), algae, and C3 plant fragments were the main sources of OM in a relatively cold environment. The abundances of TOC, TN, and TS increased to 0.56%, 0.07%, and 0.4%, respectively, while δ13C (−23.9‰) increased and TOC/TS (2.7) decreased in the Holocene sediments, suggesting that seawater began to influence the composition of the sediments of HZB. Climate warming, which is likely to have impacted the results, was experienced from 12.3 ka BP. An OC isotope mixing model indicated that since the Mid-late Holocene, more than 70% of riverine OM accounted for the total OM. The TOC/TS ratio was identified as an effective indicator of seawater intrusion, with C/S ratios of 1–6 being considered to indicate a “sea–land transitional zone” sedimentary environment, a C/S >6 indicating freshwater, and a C/S<1 indicating normal marine facies. These findings provide crucial evidence for using TOC/TS to distinguish freshwater from marine environments and enhance our understanding of past climate changes. Therefore, these geochemical indicators can be used in conjunction with other sedimentary records to obtain accurate results about sedimentary evolution.

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Response of trace metal redox proxies in continental shelf environment: The Eastern Arabian Sea scenario

Cited by 33 publications

References 73 publications

Organic carbon preservation in Southeastern Arabian Sea sediments since mid‐Holocene: Implications to South Asian Summer Monsoon variability

Organic carbon preservation in Southeastern Arabian Sea sediments since mid‐Holocene: Implications to South Asian Summer Monsoon variability

Composition of sedimentary organic matter in Thrissur Kole wetland, southwest India

Geochemical behavior of C, N, and S in sediments of Hangzhou Bay, Southeastern China: implications for the study of paleoclimate and sea-level changes

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