High-resolution geochemical and micropalaeontological profiling of the most recent eastern Mediterranean sapropel

Mercone, D.; Thomson, J.; Abu-Zied, Ramadan H.; Croudace, Ian W.; Rohling, Eelco J.

doi:10.1016/s0025-3227(01)00122-0

Cited by 140 publications

(93 citation statements)

References 64 publications

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“…The general geochemistry of the sediment at all of these sites has been described extensively in the past (e.g. BC19: Slomp et al, 2002 ; SL60 (LC21-site) and MD90-917: Mercone et al, 2000Mercone et al, , 2001969E: Bosch et al, 1998;Passier and De Lange, 1998;Passier et al, 1999a,c;Nijenhuis and De Lange, 2000). Sapropels in the eastern Mediterranean Sea (including the SW-Aegean and Adriatic) are the result of climatic changes which led to periods of decreased circulation, increased surface water productivity, dysoxic or anoxic bottom waters and increased preservation of organic matter (Calvert et al, 1992;Rohling, 1994;Thomson et al, 1999).…”

Section: Methodsmentioning

confidence: 99%

“…That the bottom water was dysoxic or semi-euxinic during S1 formation has been deduced from, e.g. the trace metal, Fe and S geochemistry, abundances of benthic foraminifera, evidence for occasional bioturbation and preservation e⁄ciencies of C org in this sapropel (Passier et al, 1999c;Mercone et al, 2001;Slomp et al, 2002). There is a close linear relation between C org and water depth during sapropel S1, which has been explained as the result of a decrease in availability of oxygen in the water column with water depth (Murat and Got, 2000).…”

Section: Methodsmentioning

confidence: 99%

“…C org and CaCO 3 were determined coulometrically via the release of CO 2 . Further analytical details are given by Mercone et al (2001). Total concentrations of P of a selected number of samples (19) were determined after digestion in a mixture of HF, HNO 3 and HClO 4 and ¢nal solution in 1 M HCl using ICP-OES (Perkin Elmer Optima 3000).…”

Section: Methodsmentioning

confidence: 99%

“…In this paper, we use the C and P geochemistry for sapropels from four sites in the eastern Med- Slomp et al (2002); SL60: estimated from thickness of sapropel in core SL60 and radiocarbon dates for the S1 boundaries in core LC21 from the same site (Mercone et al, 2000(Mercone et al, , 2001; MD90-917: based on radiocarbon dates of Mercone et al (2000), taking into account that the Calypso corer extends upper core sections by an average factor of 2 without a¡ecting the stratigraphy (Thouveny et al, 2000); 969E: Emeis et al (1996). iterranean Sea to obtain more insight into the factors controlling P regeneration and burial in slowly accumulating sediments overlain by dysoxic or anoxic bottom waters.…”

Section: Introductionmentioning

confidence: 99%

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Controls on phosphorus regeneration and burial during formation of eastern Mediterranean sapropels

2004

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The carbon (C) and phosphorus (P) geochemistry of sapropels from four sites in the eastern Mediterranean Sea was determined to obtain more insight into the role of differences in sediment accumulation rates and bottom water anoxia on P regeneration and burial in sediments. Sediment C org /P org (with org = organic) ratios above Redfield indicate enhanced regeneration of P relative to C from organic matter during formation of the most recent sapropel S1 and a Pliocene sapropel (ODP-site 969E; i-282c). Release of P from Fe-oxides was relatively unimportant. Increased burial of Ca-P (authigenic carbonate fluorapatite and/or biogenic hydroxyapatite) occurred but was of minor importance compared to the enhanced P release from organic matter. For sapropel S1, C org /P org and C org /P reac , (with reac = reactive, defined as the sum of organic, Fe-bound, authigenic and biogenic Ca-P) ratios decreased with increasing sedimentation rate and oxygen exposure and decreasing water depth. Whether the water column in the deep basin was dysoxic/semi-euxinic (S1) or euxinic (Pliocene) does not appear to affect the estimated burial efficiencies of P org and P reac . Enhanced C org burial under the euxinic water column explains the much higher C org /P org and C org /P reac ratios in the Pliocene sapropel (on average V2860 and V760, respectively) compared to sapropel S1 (on average V530 and V160, respectively). ß

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controls on phosphorus regeneration and burial during formation of eastern Mediterranean sapropels

2004

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“…Presentday pelagic surface sediments have a range of TOC content of 0.2-0.6% only (see below). The higher TOC content (which is associated with faunal, floral, and geochemical changes) of sapropels has been attributed to either greatly enhanced surface productivity, which would suggest a different nutrient regime compared to recent conditions (Calvert et al, 1992;Kemp et al, 1999;Mercone et al, 2001), or to a better preservation of organic matter under oxygen-deficient bottom-water conditions at approximately equal productivity rates (Cheddadi and Rossignol-Strick, 1995;Sachs and Repeta, 1999;Moodley et al, 2005) or some combination of both. Based on stoichiometric calculations, several authors recently proposed that there is a causal link between anoxia and enhanced productivity via the enhanced recycling of phosphate from sediments/and sinking particles in the water column under anoxic conditions increasing N 2 -fixation (Tyrrell, 1999;Wallmann, 2003).…”

Section: Introductionmentioning

confidence: 99%

Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

2010

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Abstract. The enhanced accumulation of organic matter in Eastern Mediterranean sapropels and their unusually low δ 15 N values have been attributed to either enhanced nutrient availability which led to elevated primary production and carbon sequestration or to enhanced organic matter preservation under anoxic conditions. In order to evaluate these two hypothesis we have determined Ba/Al ratios, amino acid composition, N and organic C concentrations and δ 15 N in sinking particles, surface sediments, eight spatially distributed core records of the youngest sapropel S1 (10-6 ka) and older sapropels (S5, S6) from two locations. These data suggest that (i) temporal and spatial variations in δ 15 N of sedimentary N are driven by different degrees of diagenesis at different sites rather than by changes in N-sources or primary productivity and (ii) present day TOC export production would suffice to create a sapropel like S1 under conditions of deepwater anoxia. This implies that both enhanced TOC accumulation and 15 N depletion in sapropels were due to the absence of oxygen in deep waters. Thus preservation plays a major role for the accumulation of organic-rich sediments casting doubt on the need of enhanced primary production for sapropel formation.

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Matrix association effects on hydrodynamic sorting and degradation of terrestrial organic matter during cross‐shelf transport in the Laptev and East Siberian shelf seas

et al. 2016

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This study seeks an improved understanding of how matrix association affects the redistribution and degradation of terrigenous organic carbon (TerrOC) during cross-shelf transport in the Siberian margin. Sediments were collected at increasing distance from two river outlets (Lena and Kolyma Rivers) and one coastal region affected by erosion. Samples were fractionated according to density, size, and settling velocity. The chemical composition in each fraction was characterized using elemental analyses and terrigenous biomarkers. In addition, a dual-carbon-isotope mixing model (δ 13 C and Δ 14 C) was used to quantify the relative TerrOC contributions from active layer (Topsoil) and Pleistocene Ice Complex Deposits (ICD). Results indicate that physical properties of particles exert first-order control on the redistribution of different TerrOC pools. Because of its coarse nature, plant debris is hydraulically retained in the coastal region. With increasing distance from the coast, the OC is mainly associated with fine/ultrafine mineral particles. Furthermore, biomarkers indicate that the selective transport of fine-grained sediment results in mobilizing high-molecular weight (HMW) lipid-rich, diagenetically altered TerrOC while lignin-rich, less degraded TerrOC is retained near the coast. The loading (μg/m 2 ) of lignin and HMW wax lipids on the fine/ultrafine fraction drastically decreases with increasing distance from the coast (98% and 90%, respectively), which indicates extensive degradation during cross-shelf transport. Topsoil-C degrades more readily (90 ± 3.5%) compared to the ICD-C (60 ± 11%) during transport. Altogether, our results indicate that TerrOC is highly reactive and its accelerated remobilization from thawing permafrost followed by cross-shelf transport will likely represent a positive feedback to climate warming.Previous studies over this margin have exclusively focused on bulk (unfractionated) surface sediments. They have shown contrasting spatial trends for different classes of terrigenous biomarkers, suggesting that the TESI ET AL.SORTING AND DEGRADATION OF TERROC 731 PUBLICATIONS

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High-resolution geochemical and micropalaeontological profiling of the most recent eastern Mediterranean sapropel

Cited by 140 publications

References 64 publications

Controls on phosphorus regeneration and burial during formation of eastern Mediterranean sapropels

Controls on phosphorus regeneration and burial during formation of eastern Mediterranean sapropels

Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

Matrix association effects on hydrodynamic sorting and degradation of terrestrial organic matter during cross‐shelf transport in the Laptev and East Siberian shelf seas

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