A critical evaluation of depositional parameters controlling the variability of organic carbon in Arabian Sea sediments

Paropkari, A.L.; Babu, C. Prakash; Mascarenhas, A.

doi:10.1016/0025-3227(92)90168-h

Cited by 135 publications

(44 citation statements)

References 20 publications

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“…The role of low-oxygenated bottom waters (Sarkar et al, 1993;Van der Weijden et al, 1999;Agnihotri et al, 2003;Pattan et al, 2003) and/or high productivity linked to the NE monsoon winds during LGM (Rostek et al, 1997;Schulte et al, 1999;von Rad et al, 1999;Thamban et al, 2001) were suggested for organic-rich sediments in the Eastern Arabian Sea. Since the organic matter content in sediments is also influenced by other factors (quality of organic matter, early diagenesis, rates of sedimentation and sediment type -see Paropkari et al, 1992), it may not serve as an independent proxy for productivity. Schnetger et al (2000) showed that the total organic carbon is not a tracer, but Ba/Al serves as a proxy for paleoproductivity in the sediments of deep Arabian Sea.…”

Section: Productivity and Redox Conditions 421 Glacial Sedimentsmentioning

confidence: 99%

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

et al. 2010

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The geochemical and rock-magnetic investigations were carried out on a sediment core collected from the SE Arabian Sea at 1420 m depth in oxygenated waters below the present day oxygen minimum zone. The top 250 cm sediments of the core represent the last 35 kaBP. The δ 18O values of Globigerinoides ruber are heaviest during the Last Glacial Maximum (LGM) and appear unaffected by low-saline waters transported from the Bay of Bengal by stronger northeast monsoon and West Indian coastal current. The signatures of Bφlling-Allerφd and Younger Dryas events are distinct in the records of magnetic susceptibility, organic carbon (OC) and δ 18O. Glacial sediments show higher OC, CaCO 3 , Ba, Mo, U and Cd, while the early to late Holocene sediments show increasing concentrations of OC, CaCO 3 , Ba, Cu, Ni and Zn and decreasing concentrations of Mo, U and Cd. Productivity induced lowoxygenated bottom waters and reducing sedimentary conditions during glaciation and, productivity and oxygenated bottom waters in Holocene are responsible for their variation. The core exhibits different stages of diagenesis at different sediment intervals. The occurrence of fine-grained, low-coercivity, ferrimagnetic mineral during glacial period is indicative of its formation in organic-rich, anoxic sediments, that may be analogous to the diagenetic magnetic enhancement known in sapropels of the Mediterranean Sea and Japan Sea. The glacial sediments exhibiting reductive diagenesis with anoxic sedimentary environment in this core correspond to reductive diagenesis and intermittent bioturbation (oxygenation) reported in another core in the vicinity. This suggests that the low-oxygenated bottom water conditions during glacial times should not be generalized, but are influenced locally by productivity, sedimentation rates and sediment reworking.

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Section: Productivity and Redox Conditions 421 Glacial Sedimentsmentioning

confidence: 99%

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

et al. 2010

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“…In addition, burial of C org (Kolla et al. , 1981;Paropkari et al, 1992;Van der Weijden et al, 1999) and formation of authigenic Ca-P (Schenau et al, 2000) are enhanced in sediments where the OMZ impinges on the sea floor. The latter has been attributed to an elevated input to the sediments of labile P phases such as OM and fish debris (Schenau et al, 2000;Schenau and De Lange, 2001).…”

Section: Introductionmentioning

confidence: 99%

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

et al. 2012

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Abstract. In this study, we investigate phosphorus (P) and iron (Fe) cycling in sediments along a depth transect from within to well below the oxygen minimum zone (OMZ) in the northern Arabian Sea (Murray Ridge). Pore-water and solid-phase analyses show that authigenic formation of calcium phosphate minerals (Ca-P) is largely restricted to where the OMZ intersects the seafloor topography, likely due to higher depositional fluxes of reactive P. Nonetheless, increased ratios of organic carbon to organic P (C org /P org ) and to total reactive P (C org /P reactive ) in surface sediments indicate that the overall burial efficiency of P relative to C org decreases under the low bottom water oxygen concentrations (BWO) in the OMZ. The relatively constant Fe/Al ratio in surface sediments along the depth transect suggest that corresponding changes in Fe burial are limited. Sedimentary pyrite contents are low throughout the ∼25 cm sediment cores at most stations, as commonly observed in the Arabian Sea OMZ. However, pyrite is an important sink for reactive Fe at one station in the OMZ. A reactive transport model (RTM) was applied to quantitatively investigate P and Fe diagenesis at an intermediate station at the lower boundary of the OMZ (bottom water O 2 : ∼ 14 µmol L −1 ). The RTM results contrast with earlier findings in showing that Fe redox cycling can control authigenic apatite formation and P burial in Arabian Sea sediment. In addition, results suggest that a large fraction of the sedimentary Ca-P is not authigenic, but is instead deposited from the water column and buried. Dust is likely a major source of this Ca-P. Inclusion of the unreactive Ca-P pool in the C org /P ratio leads to an overestimation of the burial efficiency of reactive P relative to C org along the depth transect. Moreover, the unreactive Ca-P accounts for ∼85 % of total Ca-P burial. In general, our results reveal large differences in P and Fe chemistry between stations in the OMZ, indicating dynamic sedimentary conditions under these oxygen-depleted waters.

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“…Generally, there are two schools of thought. One argues that the presence or absence of O 2 has little or no effect on organic matter preservation (e.g., Henrichs and Reeburgh, 1987;Pedersen and Calvert, 1990;, whereas the other school states the opposite (e.g., Demaison and Moore, 1980;Pratt, 1984;Canfield, 1989Canfield, , 1993Paropkari et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Changes in kerogen composition across an oxidation front in Madeira Abyssal Plain turbidites as revealed by pyrolysis GC-MS

Damsté¹,

Hoefs²,

Leeuw³

et al. 1998

Proceedings of the Ocean Drilling Program, 157 Scientific Results

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Isolated kerogens from Madeira Abyssal Plain turbidite samples were qualitatively and semiquantitatively studied by means of analytical pyrolysis for the effect of oxygen exposure on organic matter preservation. The initial organic matter in the turbidite is very homogeneous and relatively high and offers an ideal case for the study of oxygen effects on organic matter preservation without the usual complications of varying sources or sedimentation rates and bioturbation. From all four studied turbidites, one sample from the oxidized part of the turbidite was compared with two samples from the unoxidized part. The aliphatic character of the kerogens after postdepositional oxidation has increased significantly, as revealed by the abundance of the n-alkanes and n-alk-1-enes in the oxidized turbidite. At the same time, the contribution of the isoprenoid alkanes and alkenes and the alkylthiophenes to the pyrolysate has decreased significantly. The relative abundances of alkylbenzenes, alkylnaphthalenes, alkylphenols, alkylindenes, and alkan-2-ones in the pyrolysates have remained relatively constant upon oxidation. The alkylbenzene, alkylphenol, alkylnaphthalene, n-alkane, and n-alk-1-ene, isoprenoid alkane, and alkene internal distributions are substantially altered in the oxidized samples. This study shows that postdepositional oxidation of sedimentary organic matter by oxygen is far more severe than by sulfate alone. Furthermore, it is clear that oxidation of the organic matter is, to a significant degree, selective.

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A critical evaluation of depositional parameters controlling the variability of organic carbon in Arabian Sea sediments

Cited by 135 publications

References 20 publications

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

Changes in kerogen composition across an oxidation front in Madeira Abyssal Plain turbidites as revealed by pyrolysis GC-MS

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