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| Thomson, J; Crudeli, D; De Lange, Gj; Slomp, Cp; Erba, E; Corselli, C; Calvert, Se. |
| High relative concentrations of the lower photic zone nannofossil Florisphaera profunda have been reported in all recent eastern Mediterranean sapropels. In the most recent sapropel (S1), high bulk sediment Sr/Ca ratios occur along with high F. profunda contents toward the base of the unit, exemplified here in four cores from 1.5-3.5 km water depth. Co-occurring biogenic carbonates contain insufficient Sr to account for these high Sr concentrations, and X-ray diffraction and selective leaching show that the high Sr/Ca ratios are due to aragonite, the CaCO3 polymorph that is rarely preserved in deep marine sediments, with similar to1 wt % Sr. The possible sources of this aragonite include ( 1) precipitation with surface ocean production, ( 2) detrital input... |
| Tipo: Text |
Palavras-chave: Sapropel; Aragonite; Strontium. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/00229/33975/32412.pdf |
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| Mercone, D; Thomson, J; Croudace, Iw; Siani, G; Paterne, M; Troelstra, S. |
| Slowly accumulated (<5 cm kyr(-1)) and rapidly accumulated (5-20 cm kyr(-1)) sediments have been compared to define the initiation and termination times of the most recent sapropel (S1) in the eastern Mediterranean Sea. The Ba/Al ratio has been employed as a more persistent index of productivity than C-org. Accelerator mass spectrometry radiocarbon dating of pelagic foraminifera indicates a maximum duration for increased Ba/Al levels in S1 from similar to 9500-6000 (uncorrected radiocarbon convention years B.P.) in the rapidly accumulated sediments and similar to 9500-5300 years B.P. in the slowly accumulated sediments. This difference is ascribed to bioturbation affecting the slaver accumulated S1 sediments. In the two most rapidly accumulated S1... |
| Tipo: Text |
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| Ano: 2000 |
URL: https://archimer.ifremer.fr/doc/00220/33127/31650.pdf |
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| Slomp, Cp; Thomson, J; De Lange, Gj. |
| Phosphorus regeneration and burial fluxes during and after formation of the most recent sapropel Sl were determined for two deep-basin, low-sedimentation sites in the eastern Mediterranean Sea. Organic C/P ratios and burial fluxes indicate enhanced regeneration of P relative to C during deposition of sapropel S1. This is largely due to the enhanced release of P from organic matter during sulfate reduction. Release of P from Fe-bound P also increased, but this was only a relatively minor source of dissolved P. Pore-water HPO42- concentrations remained too low for carbonate fluorapatite formation. An increased burial of biogenic Ca-P (i.e., fish debris) was observed for one site. Estimated benthic fluxes of P during sapropel formation were elevated relative... |
| Tipo: Text |
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| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00223/33410/31854.pdf |
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